Add support for delta encoding to patch PCKs

core/io/delta_encoding.cpp

@@ -0,0 +1,110 @@
+/**************************************************************************/
+/*  delta_encoding.cpp                                                    */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#include "delta_encoding.h"
+
+#include <zstd.h>
+
+#define ERR_FAIL_ZSTD_V_MSG(m_result, m_retval, m_msg) \
+	ERR_FAIL_COND_V_MSG(ZSTD_isError(m_result), m_retval, vformat("%s Zstandard reported error code %d: \"%s\".", m_msg, ZSTD_getErrorCode(m_result), ZSTD_getErrorString(ZSTD_getErrorCode(m_result))))
+
+struct ZstdCompressionContext {
+	ZSTD_CCtx *context = ZSTD_createCCtx();
+	~ZstdCompressionContext() { ZSTD_freeCCtx(context); }
+	operator ZSTD_CCtx *() { return context; }
+};
+
+struct ZstdDecompressionContext {
+	ZSTD_DCtx *context = ZSTD_createDCtx();
+	~ZstdDecompressionContext() { ZSTD_freeDCtx(context); }
+	operator ZSTD_DCtx *() { return context; }
+};
+
+static constexpr uint8_t DELTA_MAGIC[4] = { 'G', 'D', 'D', 'L' };
+static constexpr uint8_t DELTA_VERSION_NUMBER = 1;
+static constexpr size_t DELTA_HEADER_SIZE = 5;
+
+Error DeltaEncoding::encode_delta(Span<uint8_t> p_old_data, Span<uint8_t> p_new_data, Vector<uint8_t> &r_delta, int p_compression_level) {
+	size_t zstd_result = ZSTD_compressBound(p_new_data.size());
+	ERR_FAIL_ZSTD_V_MSG(zstd_result, FAILED, "Failed to encode delta. Calculating compression bounds failed.");
+
+	r_delta.reserve_exact(DELTA_HEADER_SIZE + zstd_result);
+	r_delta.resize(DELTA_HEADER_SIZE + zstd_result);
+
+	memcpy(r_delta.ptrw(), DELTA_MAGIC, 4);
+	r_delta.write[4] = DELTA_VERSION_NUMBER;
+
+	ZstdCompressionContext zstd_context;
+
+	ZSTD_parameters zstd_params = ZSTD_getParams(p_compression_level, p_new_data.size(), p_old_data.size());
+	zstd_params.fParams.contentSizeFlag = 1;
+	zstd_params.fParams.checksumFlag = 1;
+
+	zstd_result = ZSTD_CCtx_setParams(zstd_context, zstd_params);
+	ERR_FAIL_ZSTD_V_MSG(zstd_result, FAILED, "Failed to encode delta. Setting compression parameters failed.");
+
+	zstd_result = ZSTD_CCtx_refPrefix(zstd_context, p_old_data.ptr(), p_old_data.size());
+	ERR_FAIL_ZSTD_V_MSG(zstd_result, FAILED, "Failed to encode delta. Setting prefix dictionary failed.");
+
+	zstd_result = ZSTD_compress2(zstd_context, r_delta.ptrw() + DELTA_HEADER_SIZE, r_delta.size() - DELTA_HEADER_SIZE, p_new_data.ptr(), p_new_data.size());
+	ERR_FAIL_ZSTD_V_MSG(zstd_result, FAILED, "Failed to encode delta. Compression failed.");
+
+	r_delta.resize(DELTA_HEADER_SIZE + zstd_result);
+
+	return OK;
+}
+
+Error DeltaEncoding::decode_delta(Span<uint8_t> p_old_data, Span<uint8_t> p_delta, Vector<uint8_t> &r_new_data) {
+	ERR_FAIL_COND_V_MSG(p_delta.size() < DELTA_HEADER_SIZE, ERR_INVALID_DATA, vformat("Failed to decode delta. File size (%d) is too small.", p_delta.size()));
+
+	uint8_t magic[4];
+	memcpy(magic, p_delta.ptr(), sizeof(magic));
+	uint8_t version = p_delta[4];
+
+	ERR_FAIL_COND_V_MSG(memcmp(magic, DELTA_MAGIC, 4) != 0, ERR_FILE_CORRUPT, "Failed to decode delta. Header is invalid.");
+	ERR_FAIL_COND_V_MSG(version != DELTA_VERSION_NUMBER, ERR_FILE_UNRECOGNIZED, vformat("Failed to decode delta. Expected version %d but found %d.", DELTA_VERSION_NUMBER, version));
+
+	size_t zstd_result = ZSTD_findDecompressedSize(p_delta.ptr() + DELTA_HEADER_SIZE, p_delta.size() - DELTA_HEADER_SIZE);
+	ERR_FAIL_ZSTD_V_MSG(zstd_result, FAILED, "Failed to decode delta. Unable to find decompressed size.");
+
+	r_new_data.reserve_exact(zstd_result);
+	r_new_data.resize(zstd_result);
+
+	ZstdDecompressionContext zstd_context;
+
+	zstd_result = ZSTD_DCtx_refPrefix(zstd_context, p_old_data.ptr(), p_old_data.size());
+	ERR_FAIL_ZSTD_V_MSG(zstd_result, FAILED, "Failed to decode delta. Setting prefix dictionary failed.");
+
+	zstd_result = ZSTD_decompressDCtx(zstd_context, r_new_data.ptrw(), r_new_data.size(), p_delta.ptr() + DELTA_HEADER_SIZE, p_delta.size() - DELTA_HEADER_SIZE);
+	ERR_FAIL_ZSTD_V_MSG(zstd_result, FAILED, "Failed to decode delta. Decompression failed.");
+	ERR_FAIL_COND_V(zstd_result != (size_t)r_new_data.size(), ERR_FILE_CORRUPT);
+
+	return OK;
+}

core/io/delta_encoding.h

@@ -0,0 +1,39 @@
+/**************************************************************************/
+/*  delta_encoding.h                                                      */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#pragma once
+
+#include "core/io/file_access.h"
+
+class DeltaEncoding {
+public:
+	static Error encode_delta(Span<uint8_t> p_old_data, Span<uint8_t> p_new_data, Vector<uint8_t> &r_delta, int p_compression_level = 19);
+	static Error decode_delta(Span<uint8_t> p_old_data, Span<uint8_t> p_delta, Vector<uint8_t> &r_new_data);
+};

core/io/file_access_pack.cpp

@@ -31,6 +31,7 @@
 #include "file_access_pack.h"
 
 #include "core/io/file_access_encrypted.h"
+#include "core/io/file_access_patched.h"
 #include "core/object/script_language.h"
 #include "core/os/os.h"
 #include "core/version.h"
@@ -45,7 +46,7 @@ Error PackedData::add_pack(const String &p_path, bool p_replace_files, uint64_t
 	return ERR_FILE_UNRECOGNIZED;
 }
 
-void PackedData::add_path(const String &p_pkg_path, const String &p_path, uint64_t p_ofs, uint64_t p_size, const uint8_t *p_md5, PackSource *p_src, bool p_replace_files, bool p_encrypted, bool p_bundle) {
+void PackedData::add_path(const String &p_pkg_path, const String &p_path, uint64_t p_ofs, uint64_t p_size, const uint8_t *p_md5, PackSource *p_src, bool p_replace_files, bool p_encrypted, bool p_bundle, bool p_delta) {
 	String simplified_path = p_path.simplify_path().trim_prefix("res://");
 	PathMD5 pmd5(simplified_path.md5_buffer());
 
@@ -54,6 +55,7 @@ void PackedData::add_path(const String &p_pkg_path, const String &p_path, uint64
 	PackedFile pf;
 	pf.encrypted = p_encrypted;
 	pf.bundle = p_bundle;
+	pf.delta = p_delta;
 	pf.pack = p_pkg_path;
 	pf.offset = p_ofs;
 	pf.size = p_size;
@@ -62,8 +64,11 @@ void PackedData::add_path(const String &p_pkg_path, const String &p_path, uint64
 	}
 	pf.src = p_src;
 
-	if (!exists || p_replace_files) {
+	if (p_delta) {
+		delta_patches[pmd5].push_back(pf);
+	} else if (!exists || p_replace_files) {
 		files[pmd5] = pf;
+		delta_patches[pmd5].clear();
 	}
 
 	if (!exists) {
@@ -137,6 +142,28 @@ uint8_t *PackedData::get_file_hash(const String &p_path) {
 	return E->value.md5;
 }
 
+Vector<PackedData::PackedFile> PackedData::get_delta_patches(const String &p_path) const {
+	String simplified_path = p_path.simplify_path().trim_prefix("res://");
+	PathMD5 pmd5(simplified_path.md5_buffer());
+	HashMap<PathMD5, Vector<PackedFile>, PathMD5>::ConstIterator E = delta_patches.find(pmd5);
+	if (!E) {
+		return Vector<PackedFile>();
+	}
+
+	return E->value;
+}
+
+bool PackedData::has_delta_patches(const String &p_path) const {
+	String simplified_path = p_path.simplify_path().trim_prefix("res://");
+	PathMD5 pmd5(simplified_path.md5_buffer());
+	HashMap<PathMD5, Vector<PackedFile>, PathMD5>::ConstIterator E = delta_patches.find(pmd5);
+	if (!E) {
+		return false;
+	}
+
+	return !E->value.is_empty();
+}
+
 HashSet<String> PackedData::get_file_paths() const {
 	HashSet<String> file_paths;
 	_get_file_paths(root, root->name, file_paths);
@@ -155,6 +182,7 @@ void PackedData::_get_file_paths(PackedDir *p_dir, const String &p_parent_dir, H
 
 void PackedData::clear() {
 	files.clear();
+	delta_patches.clear();
 	_free_packed_dirs(root);
 	root = memnew(PackedDir);
 }
@@ -322,7 +350,7 @@ bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files,
 		if (flags & PACK_FILE_REMOVAL) { // The file was removed.
 			PackedData::get_singleton()->remove_path(path);
 		} else {
-			PackedData::get_singleton()->add_path(p_path, path, file_base + ofs, size, md5, this, p_replace_files, (flags & PACK_FILE_ENCRYPTED), sparse_bundle);
+			PackedData::get_singleton()->add_path(p_path, path, file_base + ofs, size, md5, this, p_replace_files, (flags & PACK_FILE_ENCRYPTED), sparse_bundle, (flags & PACK_FILE_DELTA));
 		}
 	}
 
@@ -330,7 +358,17 @@ bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files,
 }
 
 Ref<FileAccess> PackedSourcePCK::get_file(const String &p_path, PackedData::PackedFile *p_file) {
-	return memnew(FileAccessPack(p_path, *p_file));
+	Ref<FileAccess> file(memnew(FileAccessPack(p_path, *p_file)));
+
+	if (PackedData::get_singleton()->has_delta_patches(p_path)) {
+		Ref<FileAccessPatched> file_patched;
+		file_patched.instantiate();
+		Error err = file_patched->open_custom(file);
+		ERR_FAIL_COND_V(err != OK, Ref<FileAccess>());
+		file = file_patched;
+	}
+
+	return file;
 }
 
 //////////////////////////////////////////////////////////////////
@@ -362,7 +400,7 @@ void PackedSourceDirectory::add_directory(const String &p_path, bool p_replace_f
 	for (const String &file_name : da->get_files()) {
 		String file_path = p_path.path_join(file_name);
 		uint8_t md5[16] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
-		PackedData::get_singleton()->add_path(p_path, file_path, 0, 0, md5, this, p_replace_files, false, false);
+		PackedData::get_singleton()->add_path(p_path, file_path, 0, 0, md5, this, p_replace_files, false, false, false);
 	}
 
 	for (const String &sub_dir_name : da->get_directories()) {
@@ -470,6 +508,7 @@ void FileAccessPack::close() {
 }
 
 FileAccessPack::FileAccessPack(const String &p_path, const PackedData::PackedFile &p_file) {
+	path = p_path;
 	pf = p_file;
 	if (pf.bundle) {
 		String simplified_path = p_path.simplify_path();

core/io/file_access_pack.h

@@ -54,6 +54,7 @@ enum PackFlags {
 enum PackFileFlags {
 	PACK_FILE_ENCRYPTED = 1 << 0,
 	PACK_FILE_REMOVAL = 1 << 1,
+	PACK_FILE_DELTA = 1 << 2,
 };
 
 class PackSource;
@@ -72,6 +73,7 @@ public:
 		PackSource *src = nullptr;
 		bool encrypted;
 		bool bundle;
+		bool delta;
 	};
 
 private:
@@ -103,6 +105,7 @@ private:
 	};
 
 	HashMap<PathMD5, PackedFile, PathMD5> files;
+	HashMap<PathMD5, Vector<PackedFile>, PathMD5> delta_patches;
 
 	Vector<PackSource *> sources;
 
@@ -116,9 +119,11 @@ private:
 
 public:
 	void add_pack_source(PackSource *p_source);
-	void add_path(const String &p_pkg_path, const String &p_path, uint64_t p_ofs, uint64_t p_size, const uint8_t *p_md5, PackSource *p_src, bool p_replace_files, bool p_encrypted = false, bool p_bundle = false); // for PackSource
+	void add_path(const String &p_pkg_path, const String &p_path, uint64_t p_ofs, uint64_t p_size, const uint8_t *p_md5, PackSource *p_src, bool p_replace_files, bool p_encrypted = false, bool p_bundle = false, bool p_delta = false); // for PackSource
 	void remove_path(const String &p_path);
 	uint8_t *get_file_hash(const String &p_path);
+	Vector<PackedFile> get_delta_patches(const String &p_path) const;
+	bool has_delta_patches(const String &p_path) const;
 	HashSet<String> get_file_paths() const;
 
 	void set_disabled(bool p_disabled) { disabled = p_disabled; }
@@ -166,6 +171,7 @@ class FileAccessPack : public FileAccess {
 	GDSOFTCLASS(FileAccessPack, FileAccess);
 	PackedData::PackedFile pf;
 
+	String path;
 	mutable uint64_t pos;
 	mutable bool eof;
 	uint64_t off;
@@ -186,6 +192,9 @@ class FileAccessPack : public FileAccess {
 public:
 	virtual bool is_open() const override;
 
+	virtual String get_path() const override { return path; }
+	virtual String get_path_absolute() const override { return path; }
+
 	virtual void seek(uint64_t p_position) override;
 	virtual void seek_end(int64_t p_position = 0) override;
 	virtual uint64_t get_position() const override;

core/io/file_access_patched.cpp

@@ -0,0 +1,203 @@
+/**************************************************************************/
+/*  file_access_patched.cpp                                               */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#include "file_access_patched.h"
+
+#include "file_access_pack.h"
+
+#include "core/io/delta_encoding.h"
+#include "core/os/os.h"
+
+Error FileAccessPatched::_apply_patch() const {
+	ERR_FAIL_COND_V(!is_open(), FAILED);
+
+	String path = old_file->get_path();
+	Vector<PackedData::PackedFile> delta_patches = PackedData::get_singleton()->get_delta_patches(path);
+	Vector<uint8_t> old_file_data = old_file->get_buffer(old_file->get_length());
+
+	for (int i = 0; i < delta_patches.size(); ++i) {
+		const PackedData::PackedFile &delta_patch = delta_patches[i];
+		ERR_FAIL_COND_V(delta_patch.bundle, FAILED);
+
+		Error err = OK;
+
+		uint64_t total_usec_start = OS::get_singleton()->get_ticks_usec();
+		uint64_t io_usec_start = OS::get_singleton()->get_ticks_usec();
+
+		Ref<FileAccess> patch_file = FileAccess::open(delta_patch.pack, FileAccess::READ, &err);
+		ERR_FAIL_COND_V(err != OK, err);
+
+		patch_file->seek(delta_patch.offset);
+		ERR_FAIL_COND_V(patch_file->get_error() != OK, patch_file->get_error());
+
+		Vector<uint8_t> patch_data = patch_file->get_buffer(delta_patch.size);
+		ERR_FAIL_COND_V(patch_data.is_empty(), ERR_FILE_CANT_READ);
+
+		uint64_t io_usec_end = OS::get_singleton()->get_ticks_usec();
+		uint64_t decode_usec_start = OS::get_singleton()->get_ticks_usec();
+
+		Vector<uint8_t> new_file_data;
+		err = DeltaEncoding::decode_delta(old_file_data, patch_data, new_file_data);
+		ERR_FAIL_COND_V_MSG(err != OK, err, vformat("Failed to apply delta patch (%d of %d) to \"%s\".", i + 1, delta_patches.size(), path));
+
+		uint64_t decode_usec_end = OS::get_singleton()->get_ticks_usec();
+
+		old_file_data = new_file_data;
+
+		uint64_t total_usec_end = OS::get_singleton()->get_ticks_usec();
+
+		print_verbose(vformat(U"Applied delta patch to \"%s\" from \"%s\" in %d μs (%d μs I/O, %d μs decoding).", path, delta_patch.pack.get_file(), total_usec_end - total_usec_start, io_usec_end - io_usec_start, decode_usec_end - decode_usec_start));
+	}
+
+	patched_file_data = old_file_data;
+	patched_file.instantiate();
+	return patched_file->open_custom(patched_file_data.ptr(), patched_file_data.size());
+}
+
+bool FileAccessPatched::_try_apply_patch() const {
+	if (last_error != OK) {
+		return false;
+	}
+
+	if (patched_file.is_valid()) {
+		return true;
+	}
+
+	last_error = _apply_patch();
+	return last_error == OK;
+}
+
+Error FileAccessPatched::open_custom(const Ref<FileAccess> &p_old_file) {
+	close();
+
+	if (!p_old_file->is_open()) {
+		last_error = ERR_FILE_CANT_OPEN;
+		return last_error;
+	}
+
+	old_file = p_old_file;
+
+	return OK;
+}
+
+bool FileAccessPatched::is_open() const {
+	return old_file.is_valid() && old_file->is_open();
+}
+
+void FileAccessPatched::seek(uint64_t p_position) {
+	if (!_try_apply_patch()) {
+		return;
+	}
+
+	patched_file->seek(p_position);
+}
+
+void FileAccessPatched::seek_end(int64_t p_position) {
+	if (!_try_apply_patch()) {
+		return;
+	}
+
+	patched_file->seek_end(p_position);
+}
+
+uint64_t FileAccessPatched::get_position() const {
+	if (!_try_apply_patch()) {
+		return 0;
+	}
+
+	return patched_file->get_position();
+}
+
+uint64_t FileAccessPatched::get_length() const {
+	if (!_try_apply_patch()) {
+		return 0;
+	}
+
+	return patched_file->get_length();
+}
+
+bool FileAccessPatched::eof_reached() const {
+	if (!_try_apply_patch()) {
+		return true;
+	}
+
+	return patched_file->eof_reached();
+}
+
+Error FileAccessPatched::get_error() const {
+	if (last_error != OK) {
+		return last_error;
+	}
+
+	if (patched_file.is_valid()) {
+		Error inner_error = patched_file->get_error();
+		if (inner_error != OK) {
+			return inner_error;
+		}
+	}
+
+	return last_error;
+}
+
+bool FileAccessPatched::store_buffer(const uint8_t *p_src, uint64_t p_length) {
+	if (!_try_apply_patch()) {
+		return false;
+	}
+
+	return patched_file->store_buffer(p_src, p_length);
+}
+
+uint64_t FileAccessPatched::get_buffer(uint8_t *p_dst, uint64_t p_length) const {
+	if (!_try_apply_patch()) {
+		return 0;
+	}
+
+	return patched_file->get_buffer(p_dst, p_length);
+}
+
+void FileAccessPatched::flush() {
+	if (!_try_apply_patch()) {
+		return;
+	}
+
+	patched_file->flush();
+}
+
+void FileAccessPatched::close() {
+	old_file = Ref<FileAccess>();
+	patched_file = Ref<FileAccessMemory>();
+	patched_file_data.clear();
+	last_error = OK;
+}
+
+bool FileAccessPatched::file_exists(const String &p_name) {
+	ERR_FAIL_COND_V(old_file.is_null(), false);
+	return old_file->file_exists(p_name);
+}

core/io/file_access_patched.h

@@ -0,0 +1,84 @@
+/**************************************************************************/
+/*  file_access_patched.h                                                 */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#pragma once
+
+#include "file_access.h"
+#include "file_access_memory.h"
+
+class FileAccessPatched : public FileAccess {
+	GDSOFTCLASS(FileAccessPatched, FileAccess);
+
+	Ref<FileAccess> old_file;
+	mutable Vector<uint8_t> patched_file_data;
+	mutable Ref<FileAccessMemory> patched_file;
+	mutable Error last_error = OK;
+
+	Error _apply_patch() const;
+	bool _try_apply_patch() const;
+
+protected:
+	virtual BitField<UnixPermissionFlags> _get_unix_permissions(const String &p_file) override { return 0; }
+	virtual Error _set_unix_permissions(const String &p_file, BitField<UnixPermissionFlags> p_permissions) override { return FAILED; }
+
+	virtual bool _get_hidden_attribute(const String &p_file) override { return false; }
+	virtual Error _set_hidden_attribute(const String &p_file, bool p_hidden) override { return ERR_UNAVAILABLE; }
+
+	virtual bool _get_read_only_attribute(const String &p_file) override { return false; }
+	virtual Error _set_read_only_attribute(const String &p_file, bool p_ro) override { return ERR_UNAVAILABLE; }
+
+	virtual uint64_t _get_modified_time(const String &p_file) override { return 0; }
+	virtual uint64_t _get_access_time(const String &p_file) override { return 0; }
+	virtual int64_t _get_size(const String &p_file) override { return -1; }
+
+	virtual Error open_internal(const String &p_path, int p_mode_flags) override { return ERR_UNAVAILABLE; }
+
+public:
+	Error open_custom(const Ref<FileAccess> &p_old_file);
+
+	virtual bool is_open() const override;
+
+	virtual void seek(uint64_t p_position) override;
+	virtual void seek_end(int64_t p_position = 0) override;
+
+	virtual uint64_t get_position() const override;
+	virtual uint64_t get_length() const override;
+	virtual bool eof_reached() const override;
+	virtual Error get_error() const override;
+
+	virtual bool store_buffer(const uint8_t *p_src, uint64_t p_length) override;
+	virtual uint64_t get_buffer(uint8_t *p_dst, uint64_t p_length) const override;
+	virtual Error resize(int64_t p_length) override { return ERR_UNAVAILABLE; }
+
+	virtual void flush() override;
+	virtual void close() override;
+
+	virtual bool file_exists(const String &p_name) override;
+};

editor/export/editor_export.cpp

@@ -83,7 +83,13 @@ void EditorExport::_save() {
 		config->set_value(section, "include_filter", preset->get_include_filter());
 		config->set_value(section, "exclude_filter", preset->get_exclude_filter());
 		config->set_value(section, "export_path", preset->get_export_path());
+
 		config->set_value(section, "patches", preset->get_patches());
+		config->set_value(section, "patch_delta_encoding", preset->is_patch_delta_encoding_enabled());
+		config->set_value(section, "patch_delta_compression_level_zstd", preset->get_patch_delta_zstd_level());
+		config->set_value(section, "patch_delta_min_reduction", preset->get_patch_delta_min_reduction());
+		config->set_value(section, "patch_delta_include_filters", preset->get_patch_delta_include_filter());
+		config->set_value(section, "patch_delta_exclude_filters", preset->get_patch_delta_exclude_filter());
 
 		config->set_value(section, "encryption_include_filters", preset->get_enc_in_filter());
 		config->set_value(section, "encryption_exclude_filters", preset->get_enc_ex_filter());
@@ -332,6 +338,22 @@ void EditorExport::load_config() {
 		preset->set_script_export_mode(config->get_value(section, "script_export_mode", EditorExportPreset::MODE_SCRIPT_BINARY_TOKENS_COMPRESSED));
 		preset->set_patches(config->get_value(section, "patches", Vector<String>()));
 
+		if (config->has_section_key(section, "patch_delta_encoding")) {
+			preset->set_patch_delta_encoding_enabled(config->get_value(section, "patch_delta_encoding"));
+		}
+		if (config->has_section_key(section, "patch_delta_compression_level_zstd")) {
+			preset->set_patch_delta_zstd_level(config->get_value(section, "patch_delta_compression_level_zstd"));
+		}
+		if (config->has_section_key(section, "patch_delta_min_reduction")) {
+			preset->set_patch_delta_min_reduction(config->get_value(section, "patch_delta_min_reduction"));
+		}
+		if (config->has_section_key(section, "patch_delta_include_filters")) {
+			preset->set_patch_delta_include_filter(config->get_value(section, "patch_delta_include_filters"));
+		}
+		if (config->has_section_key(section, "patch_delta_exclude_filters")) {
+			preset->set_patch_delta_exclude_filter(config->get_value(section, "patch_delta_exclude_filters"));
+		}
+
 		if (config->has_section_key(section, "seed")) {
 			preset->set_seed(config->get_value(section, "seed"));
 		}

editor/export/editor_export_platform.cpp

@@ -35,6 +35,7 @@
 #include "core/config/project_settings.h"
 #include "core/crypto/crypto_core.h"
 #include "core/extension/gdextension.h"
+#include "core/io/delta_encoding.h"
 #include "core/io/dir_access.h"
 #include "core/io/file_access_encrypted.h"
 #include "core/io/file_access_pack.h" // PACK_HEADER_MAGIC, PACK_FORMAT_VERSION
@@ -66,12 +67,12 @@ class EditorExportSaveProxy {
 public:
 	bool has_saved(const String &p_path) const { return saved_paths.has(p_path); }
 
-	Error save_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
+	Error save_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
 		if (tracking_saves) {
 			saved_paths.insert(p_path.simplify_path().trim_prefix("res://"));
 		}
 
-		return save_func(p_userdata, p_path, p_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed);
+		return save_func(p_preset, p_userdata, p_path, p_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, p_delta);
 	}
 
 	EditorExportSaveProxy(EditorExportPlatform::EditorExportSaveFunction p_save_func, bool p_track_saves) :
@@ -218,26 +219,6 @@ bool EditorExportPlatform::fill_log_messages(RichTextLabel *p_log, Error p_err)
 	return has_messages;
 }
 
-bool EditorExportPlatform::_check_hash(const uint8_t *p_hash, const Vector<uint8_t> &p_data) {
-	if (p_hash == nullptr) {
-		return false;
-	}
-
-	unsigned char hash[16];
-	Error err = CryptoCore::md5(p_data.ptr(), p_data.size(), hash);
-	if (err != OK) {
-		return false;
-	}
-
-	for (int i = 0; i < 16; i++) {
-		if (p_hash[i] != hash[i]) {
-			return false;
-		}
-	}
-
-	return true;
-}
-
 Error EditorExportPlatform::_load_patches(const Vector<String> &p_patches) {
 	Error err = OK;
 	if (!p_patches.is_empty()) {
@@ -310,7 +291,7 @@ Error EditorExportPlatform::_encrypt_and_store_data(Ref<FileAccess> p_fd, const
 	return OK;
 }
 
-Error EditorExportPlatform::_save_pack_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
+Error EditorExportPlatform::_save_pack_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
 	ERR_FAIL_COND_V_MSG(p_total < 1, ERR_PARAMETER_RANGE_ERROR, "Must select at least one file to export.");
 
 	PackData *pd = (PackData *)p_userdata;
@@ -328,6 +309,7 @@ Error EditorExportPlatform::_save_pack_file(void *p_userdata, const String &p_pa
 	sd.path_utf8 = simplified_path.trim_prefix("res://").utf8();
 	sd.ofs = (pd->use_sparse_pck) ? 0 : pd->f->get_position();
 	sd.size = p_data.size();
+	sd.delta = p_delta;
 	Error err = _encrypt_and_store_data(ftmp, simplified_path, p_data, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, sd.encrypted);
 	if (err != OK) {
 		return err;
@@ -363,15 +345,67 @@ Error EditorExportPlatform::_save_pack_file(void *p_userdata, const String &p_pa
 	return OK;
 }
 
-Error EditorExportPlatform::_save_pack_patch_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
-	if (_check_hash(PackedData::get_singleton()->get_file_hash(p_path), p_data)) {
-		return OK;
+Error EditorExportPlatform::_save_pack_patch_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
+	Ref<FileAccess> old_file = PackedData::get_singleton()->try_open_path(p_path);
+	if (old_file.is_null()) {
+		return _save_pack_file(p_preset, p_userdata, p_path, p_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, false);
+	}
+
+	Vector<uint8_t> old_data = old_file->get_buffer(old_file->get_length());
+
+	// We can't rely on the MD5 as stored in the PCKs, since delta patches could have made it stale.
+	if (p_data == old_data) {
+		return OK; // Do nothing if the file hasn't changed.
 	}
 
-	return _save_pack_file(p_userdata, p_path, p_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed);
+	if (!p_preset->is_patch_delta_encoding_enabled()) {
+		return _save_pack_file(p_preset, p_userdata, p_path, p_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, false);
+	}
+
+	bool delta = false;
+
+	for (const String &filter : p_preset->get_patch_delta_include_filter().split(",", false)) {
+		String filter_stripped = filter.strip_edges();
+		if (p_path.matchn(filter_stripped) || p_path.trim_prefix("res://").matchn(filter_stripped)) {
+			delta = true;
+			break;
+		}
+	}
+
+	for (const String &filter : p_preset->get_patch_delta_exclude_filter().split(",", false)) {
+		String filter_stripped = filter.strip_edges();
+		if (p_path.matchn(filter_stripped) || p_path.trim_prefix("res://").matchn(filter_stripped)) {
+			delta = false;
+			break;
+		}
+	}
+
+	Vector<uint8_t> patch_data = p_data;
+
+	if (delta) {
+		Error err = DeltaEncoding::encode_delta(old_data, p_data, patch_data, p_preset->get_patch_delta_zstd_level());
+		if (err != OK) {
+			return err;
+		}
+
+		int64_t reduction_bytes = MAX(0, p_data.size() - patch_data.size());
+		double reduction_ratio = reduction_bytes / (double)p_data.size();
+
+		if (reduction_ratio >= p_preset->get_patch_delta_min_reduction()) {
+			print_verbose(vformat("Used delta encoding for patch of \"%s\", resulting in a patch of %d bytes, which reduced the size by %.1f%% (%d bytes) compared to the actual file.", p_path, patch_data.size(), reduction_ratio * 100, reduction_bytes));
+		} else {
+			print_verbose(vformat("Skipped delta encoding for patch of \"%s\", as it resulted in a patch of %d bytes, which only reduced the size by %.1f%% (%d bytes) compared to the actual file.", p_path, patch_data.size(), reduction_ratio * 100, reduction_bytes));
+			patch_data = p_data;
+			delta = false;
+		}
+	} else {
+		print_verbose(vformat("Skipped delta encoding for patch of \"%s\", due to include/exclude filters.", p_path));
+	}
+
+	return _save_pack_file(p_preset, p_userdata, p_path, patch_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, delta);
 }
 
-Error EditorExportPlatform::_save_zip_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
+Error EditorExportPlatform::_save_zip_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
 	ERR_FAIL_COND_V_MSG(p_total < 1, ERR_PARAMETER_RANGE_ERROR, "Must select at least one file to export.");
 
 	const String path = simplify_path(p_path).replace_first("res://", "");
@@ -403,12 +437,18 @@ Error EditorExportPlatform::_save_zip_file(void *p_userdata, const String &p_pat
 	return OK;
 }
 
-Error EditorExportPlatform::_save_zip_patch_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
-	if (_check_hash(PackedData::get_singleton()->get_file_hash(p_path), p_data)) {
-		return OK;
+Error EditorExportPlatform::_save_zip_patch_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
+	Ref<FileAccess> old_file = PackedData::get_singleton()->try_open_path(p_path);
+	if (old_file.is_valid()) {
+		Vector<uint8_t> old_data = old_file->get_buffer(old_file->get_length());
+
+		// We can't rely on the MD5 as stored in the PCKs, since delta patches could have made it stale.
+		if (p_data == old_data) {
+			return OK; // Do nothing if the file hasn't changed.
+		}
 	}
 
-	return _save_zip_file(p_userdata, p_path, p_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed);
+	return _save_zip_file(p_preset, p_userdata, p_path, p_data, p_file, p_total, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, p_delta);
 }
 
 Ref<Texture2D> EditorExportPlatform::get_option_icon(int p_index) const {
@@ -1036,7 +1076,7 @@ Vector<String> EditorExportPlatform::get_forced_export_files(const Ref<EditorExp
 	return files;
 }
 
-Error EditorExportPlatform::_script_save_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
+Error EditorExportPlatform::_script_save_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
 	Callable cb = ((ScriptCallbackData *)p_userdata)->file_cb;
 	ERR_FAIL_COND_V(!cb.is_valid(), FAILED);
 
@@ -1060,7 +1100,7 @@ Error EditorExportPlatform::_script_save_file(void *p_userdata, const String &p_
 	return (Error)ret.operator int();
 }
 
-Error EditorExportPlatform::_script_add_shared_object(void *p_userdata, const SharedObject &p_so) {
+Error EditorExportPlatform::_script_add_shared_object(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so) {
 	Callable cb = ((ScriptCallbackData *)p_userdata)->so_cb;
 	if (!cb.is_valid()) {
 		return OK; // Optional.
@@ -1216,14 +1256,14 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 		for (int i = 0; i < export_plugins.size(); i++) {
 			if (p_so_func) {
 				for (int j = 0; j < export_plugins[i]->shared_objects.size(); j++) {
-					err = p_so_func(p_udata, export_plugins[i]->shared_objects[j]);
+					err = p_so_func(p_preset, p_udata, export_plugins[i]->shared_objects[j]);
 					if (err != OK) {
 						return err;
 					}
 				}
 			}
 			for (int j = 0; j < export_plugins[i]->extra_files.size(); j++) {
-				err = save_proxy.save_file(p_udata, export_plugins[i]->extra_files[j].path, export_plugins[i]->extra_files[j].data, 0, paths.size(), enc_in_filters, enc_ex_filters, key, seed);
+				err = save_proxy.save_file(p_preset, p_udata, export_plugins[i]->extra_files[j].path, export_plugins[i]->extra_files[j].data, 0, paths.size(), enc_in_filters, enc_ex_filters, key, seed, false);
 				if (err != OK) {
 					return err;
 				}
@@ -1315,9 +1355,8 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 	// for continue statements without accidentally skipping an increment.
 	int idx = total > 0 ? -1 : 0;
 
-	for (const String &E : paths) {
+	for (const String &path : paths) {
 		idx++;
-		String path = E;
 		String type = ResourceLoader::get_resource_type(path);
 
 		bool has_import_file = FileAccess::exists(path + ".import");
@@ -1347,7 +1386,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 			}
 			if (p_so_func) {
 				for (int j = 0; j < export_plugins[i]->shared_objects.size(); j++) {
-					err = p_so_func(p_udata, export_plugins[i]->shared_objects[j]);
+					err = p_so_func(p_preset, p_udata, export_plugins[i]->shared_objects[j]);
 					if (err != OK) {
 						return err;
 					}
@@ -1355,7 +1394,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 			}
 
 			for (int j = 0; j < export_plugins[i]->extra_files.size(); j++) {
-				err = save_proxy.save_file(p_udata, export_plugins[i]->extra_files[j].path, export_plugins[i]->extra_files[j].data, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+				err = save_proxy.save_file(p_preset, p_udata, export_plugins[i]->extra_files[j].path, export_plugins[i]->extra_files[j].data, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 				if (err != OK) {
 					return err;
 				}
@@ -1385,7 +1424,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 			if (importer_type == "keep") {
 				// Just keep file as-is.
 				Vector<uint8_t> array = FileAccess::get_file_as_bytes(path);
-				err = save_proxy.save_file(p_udata, path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+				err = save_proxy.save_file(p_preset, p_udata, path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 
 				if (err != OK) {
 					return err;
@@ -1427,13 +1466,13 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 				sarr.resize(cs.size());
 				memcpy(sarr.ptrw(), cs.ptr(), sarr.size());
 
-				err = save_proxy.save_file(p_udata, path + ".import", sarr, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+				err = save_proxy.save_file(p_preset, p_udata, path + ".import", sarr, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 				if (err != OK) {
 					return err;
 				}
 				// Now actual remapped file:
 				sarr = FileAccess::get_file_as_bytes(export_path);
-				err = save_proxy.save_file(p_udata, export_path, sarr, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+				err = save_proxy.save_file(p_preset, p_udata, export_path, sarr, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 				if (err != OK) {
 					return err;
 				}
@@ -1461,14 +1500,14 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 					if (remap == "path") {
 						String remapped_path = config->get_value("remap", remap);
 						Vector<uint8_t> array = FileAccess::get_file_as_bytes(remapped_path);
-						err = save_proxy.save_file(p_udata, remapped_path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+						err = save_proxy.save_file(p_preset, p_udata, remapped_path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 					} else if (remap.begins_with("path.")) {
 						String feature = remap.get_slicec('.', 1);
 
 						if (remap_features.has(feature)) {
 							String remapped_path = config->get_value("remap", remap);
 							Vector<uint8_t> array = FileAccess::get_file_as_bytes(remapped_path);
-							err = save_proxy.save_file(p_udata, remapped_path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+							err = save_proxy.save_file(p_preset, p_udata, remapped_path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 						} else {
 							// Remove paths if feature not enabled.
 							config->erase_section_key("remap", remap);
@@ -1494,7 +1533,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 				sarr.resize(cs.size());
 				memcpy(sarr.ptrw(), cs.ptr(), sarr.size());
 
-				err = save_proxy.save_file(p_udata, path + ".import", sarr, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+				err = save_proxy.save_file(p_preset, p_udata, path + ".import", sarr, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 
 				if (err != OK) {
 					return err;
@@ -1515,7 +1554,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 			}
 
 			Vector<uint8_t> array = FileAccess::get_file_as_bytes(export_path);
-			err = save_proxy.save_file(p_udata, export_path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+			err = save_proxy.save_file(p_preset, p_udata, export_path, array, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 			if (err != OK) {
 				return err;
 			}
@@ -1584,7 +1623,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 				new_file.write[j] = utf8[j];
 			}
 
-			err = save_proxy.save_file(p_udata, from + ".remap", new_file, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+			err = save_proxy.save_file(p_preset, p_udata, from + ".remap", new_file, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 			if (err != OK) {
 				return err;
 			}
@@ -1602,7 +1641,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 		} else {
 			array = FileAccess::get_file_as_bytes(forced_export[i]);
 		}
-		err = save_proxy.save_file(p_udata, forced_export[i], array, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+		err = save_proxy.save_file(p_preset, p_udata, forced_export[i], array, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 		if (err != OK) {
 			return err;
 		}
@@ -1611,7 +1650,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 	Dictionary int_export = get_internal_export_files(p_preset, p_debug);
 	for (const KeyValue<Variant, Variant> &int_export_kv : int_export) {
 		const PackedByteArray &array = int_export_kv.value;
-		err = save_proxy.save_file(p_udata, int_export_kv.key, array, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+		err = save_proxy.save_file(p_preset, p_udata, int_export_kv.key, array, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 		if (err != OK) {
 			return err;
 		}
@@ -1624,7 +1663,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 	Vector<uint8_t> data = FileAccess::get_file_as_bytes(engine_cfb);
 	DirAccess::remove_file_or_error(engine_cfb);
 
-	err = save_proxy.save_file(p_udata, "res://" + config_file, data, idx, total, enc_in_filters, enc_ex_filters, key, seed);
+	err = save_proxy.save_file(p_preset, p_udata, "res://" + config_file, data, idx, total, enc_in_filters, enc_ex_filters, key, seed, false);
 	if (err != OK) {
 		return err;
 	}
@@ -1633,7 +1672,7 @@ Error EditorExportPlatform::export_project_files(const Ref<EditorExportPreset> &
 		HashSet<String> currently_loaded_paths = PackedData::get_singleton()->get_file_paths();
 		for (const String &path : currently_loaded_paths) {
 			if (!save_proxy.has_saved(path)) {
-				err = p_remove_func(p_udata, path);
+				err = p_remove_func(p_preset, p_udata, path);
 				if (err != OK) {
 					return err;
 				}
@@ -1660,7 +1699,7 @@ Vector<uint8_t> EditorExportPlatform::_filter_extension_list_config_file(const S
 	return data;
 }
 
-Error EditorExportPlatform::_pack_add_shared_object(void *p_userdata, const SharedObject &p_so) {
+Error EditorExportPlatform::_pack_add_shared_object(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so) {
 	PackData *pack_data = (PackData *)p_userdata;
 	if (pack_data->so_files) {
 		pack_data->so_files->push_back(p_so);
@@ -1669,7 +1708,7 @@ Error EditorExportPlatform::_pack_add_shared_object(void *p_userdata, const Shar
 	return OK;
 }
 
-Error EditorExportPlatform::_remove_pack_file(void *p_userdata, const String &p_path) {
+Error EditorExportPlatform::_remove_pack_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path) {
 	PackData *pd = (PackData *)p_userdata;
 
 	SavedData sd;
@@ -1691,7 +1730,7 @@ Error EditorExportPlatform::_remove_pack_file(void *p_userdata, const String &p_
 	return OK;
 }
 
-Error EditorExportPlatform::_zip_add_shared_object(void *p_userdata, const SharedObject &p_so) {
+Error EditorExportPlatform::_zip_add_shared_object(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so) {
 	ZipData *zip_data = (ZipData *)p_userdata;
 	if (zip_data->so_files) {
 		zip_data->so_files->push_back(p_so);
@@ -1996,6 +2035,9 @@ bool EditorExportPlatform::_encrypt_and_store_directory(Ref<FileAccess> p_fd, Pa
 		if (p_pack_data.file_ofs[i].removal) {
 			flags |= PACK_FILE_REMOVAL;
 		}
+		if (p_pack_data.file_ofs[i].delta) {
+			flags |= PACK_FILE_DELTA;
+		}
 		fhead->store_32(flags);
 	}
 

editor/export/editor_export_platform.h

@@ -53,9 +53,9 @@ protected:
 	static void _bind_methods();
 
 public:
-	typedef Error (*EditorExportSaveFunction)(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
-	typedef Error (*EditorExportRemoveFunction)(void *p_userdata, const String &p_path);
-	typedef Error (*EditorExportSaveSharedObject)(void *p_userdata, const SharedObject &p_so);
+	typedef Error (*EditorExportSaveFunction)(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
+	typedef Error (*EditorExportRemoveFunction)(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path);
+	typedef Error (*EditorExportSaveSharedObject)(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so);
 
 	enum DebugFlags {
 		DEBUG_FLAG_DUMB_CLIENT = 1,
@@ -83,6 +83,7 @@ public:
 		uint64_t size = 0;
 		bool encrypted = false;
 		bool removal = false;
+		bool delta = false;
 		Vector<uint8_t> md5;
 		CharString path_utf8;
 
@@ -119,25 +120,23 @@ private:
 	void _export_find_customized_resources(const Ref<EditorExportPreset> &p_preset, EditorFileSystemDirectory *p_dir, EditorExportPreset::FileExportMode p_mode, HashSet<String> &p_paths);
 	void _export_find_dependencies(const String &p_path, HashSet<String> &p_paths);
 
-	static bool _check_hash(const uint8_t *p_hash, const Vector<uint8_t> &p_data);
+	static Error _save_pack_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
+	static Error _save_pack_patch_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
+	static Error _pack_add_shared_object(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so);
 
-	static Error _save_pack_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
-	static Error _save_pack_patch_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
-	static Error _pack_add_shared_object(void *p_userdata, const SharedObject &p_so);
+	static Error _remove_pack_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path);
 
-	static Error _remove_pack_file(void *p_userdata, const String &p_path);
-
-	static Error _save_zip_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
-	static Error _save_zip_patch_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
-	static Error _zip_add_shared_object(void *p_userdata, const SharedObject &p_so);
+	static Error _save_zip_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
+	static Error _save_zip_patch_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
+	static Error _zip_add_shared_object(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so);
 
 	struct ScriptCallbackData {
 		Callable file_cb;
 		Callable so_cb;
 	};
 
-	static Error _script_save_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
-	static Error _script_add_shared_object(void *p_userdata, const SharedObject &p_so);
+	static Error _script_save_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
+	static Error _script_add_shared_object(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so);
 
 	void _edit_files_with_filter(Ref<DirAccess> &da, const Vector<String> &p_filters, HashSet<String> &r_list, bool exclude);
 	void _edit_filter_list(HashSet<String> &r_list, const String &p_filter, bool exclude);

editor/export/editor_export_preset.cpp

@@ -28,10 +28,11 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
 /**************************************************************************/
 
-#include "editor_export.h"
+#include "editor_export_preset.h"
 
 #include "core/config/project_settings.h"
 #include "core/io/dir_access.h"
+#include "editor/export/editor_export.h"
 #include "editor/settings/editor_settings.h"
 
 bool EditorExportPreset::_set(const StringName &p_name, const Variant &p_value) {
@@ -440,6 +441,51 @@ Vector<String> EditorExportPreset::get_patches() const {
 	return patches;
 }
 
+void EditorExportPreset::set_patch_delta_encoding_enabled(bool p_enable) {
+	patch_delta_encoding_enabled = p_enable;
+	EditorExport::singleton->save_presets();
+}
+
+bool EditorExportPreset::is_patch_delta_encoding_enabled() const {
+	return patch_delta_encoding_enabled;
+}
+
+void EditorExportPreset::set_patch_delta_zstd_level(int p_level) {
+	patch_delta_zstd_level = p_level;
+	EditorExport::singleton->save_presets();
+}
+
+int EditorExportPreset::get_patch_delta_zstd_level() const {
+	return patch_delta_zstd_level;
+}
+
+void EditorExportPreset::set_patch_delta_min_reduction(double p_ratio) {
+	patch_delta_min_reduction = p_ratio;
+	EditorExport::singleton->save_presets();
+}
+
+double EditorExportPreset::get_patch_delta_min_reduction() const {
+	return patch_delta_min_reduction;
+}
+
+void EditorExportPreset::set_patch_delta_include_filter(const String &p_filter) {
+	patch_delta_include_filter = p_filter;
+	EditorExport::singleton->save_presets();
+}
+
+String EditorExportPreset::get_patch_delta_include_filter() const {
+	return patch_delta_include_filter;
+}
+
+void EditorExportPreset::set_patch_delta_exclude_filter(const String &p_filter) {
+	patch_delta_exclude_filter = p_filter;
+	EditorExport::singleton->save_presets();
+}
+
+String EditorExportPreset::get_patch_delta_exclude_filter() const {
+	return patch_delta_exclude_filter;
+}
+
 void EditorExportPreset::set_custom_features(const String &p_custom_features) {
 	custom_features = p_custom_features;
 	EditorExport::singleton->save_presets();

editor/export/editor_export_preset.h

@@ -73,6 +73,11 @@ private:
 	bool dedicated_server = false;
 
 	Vector<String> patches;
+	bool patch_delta_encoding_enabled = false;
+	int patch_delta_zstd_level = 19;
+	double patch_delta_min_reduction = 0.1;
+	String patch_delta_include_filter = "*";
+	String patch_delta_exclude_filter;
 
 	friend class EditorExport;
 	friend class EditorExportPlatform;
@@ -148,11 +153,28 @@ public:
 
 	void add_patch(const String &p_path, int p_at_pos = -1);
 	void set_patch(int p_index, const String &p_path);
+
 	String get_patch(int p_index);
 	void remove_patch(int p_index);
+
 	void set_patches(const Vector<String> &p_patches);
 	Vector<String> get_patches() const;
 
+	void set_patch_delta_encoding_enabled(bool p_enable);
+	bool is_patch_delta_encoding_enabled() const;
+
+	void set_patch_delta_zstd_level(int p_level);
+	int get_patch_delta_zstd_level() const;
+
+	void set_patch_delta_min_reduction(double p_ratio);
+	double get_patch_delta_min_reduction() const;
+
+	void set_patch_delta_include_filter(const String &p_filter);
+	String get_patch_delta_include_filter() const;
+
+	void set_patch_delta_exclude_filter(const String &p_filter);
+	String get_patch_delta_exclude_filter() const;
+
 	void set_custom_features(const String &p_custom_features);
 	String get_custom_features() const;
 

editor/export/project_export.cpp

@@ -51,11 +51,14 @@
 #include "scene/gui/option_button.h"
 #include "scene/gui/popup_menu.h"
 #include "scene/gui/rich_text_label.h"
+#include "scene/gui/spin_box.h"
 #include "scene/gui/split_container.h"
 #include "scene/gui/tab_container.h"
 #include "scene/gui/texture_rect.h"
 #include "scene/gui/tree.h"
 
+#include <zstd.h>
+
 void ProjectExportTextureFormatError::_on_fix_texture_format_pressed() {
 	export_dialog->hide();
 	ProjectSettingsEditor *project_settings = EditorNode::get_singleton()->get_project_settings();
@@ -301,6 +304,19 @@ void ProjectExportDialog::_edit_preset(int p_index) {
 	exclude_filters->set_text(current->get_exclude_filter());
 	server_strip_message->set_visible(current->get_export_filter() == EditorExportPreset::EXPORT_CUSTOMIZED);
 
+	bool patch_delta_encoding_enabled = current->is_patch_delta_encoding_enabled();
+	patch_delta_encoding->set_pressed(patch_delta_encoding_enabled);
+	patch_delta_zstd_level->set_editable(patch_delta_encoding_enabled);
+	patch_delta_zstd_level->set_value(current->get_patch_delta_zstd_level());
+	patch_delta_min_reduction->set_editable(patch_delta_encoding_enabled);
+	patch_delta_min_reduction->set_value(current->get_patch_delta_min_reduction() * 100);
+	patch_delta_include_filter->set_editable(patch_delta_encoding_enabled);
+	patch_delta_exclude_filter->set_editable(patch_delta_encoding_enabled);
+	if (!updating_patch_delta_filters) {
+		patch_delta_include_filter->set_text(current->get_patch_delta_include_filter());
+		patch_delta_exclude_filter->set_text(current->get_patch_delta_exclude_filter());
+	}
+
 	patches->clear();
 	TreeItem *patch_root = patches->create_item();
 	Vector<String> patch_list = current->get_patches();
@@ -745,6 +761,11 @@ void ProjectExportDialog::_duplicate_preset() {
 	preset->set_include_filter(current->get_include_filter());
 	preset->set_exclude_filter(current->get_exclude_filter());
 	preset->set_patches(current->get_patches());
+	preset->set_patch_delta_encoding_enabled(current->is_patch_delta_encoding_enabled());
+	preset->set_patch_delta_zstd_level(current->get_patch_delta_zstd_level());
+	preset->set_patch_delta_min_reduction(current->get_patch_delta_min_reduction());
+	preset->set_patch_delta_include_filter(current->get_patch_delta_include_filter());
+	preset->set_patch_delta_exclude_filter(current->get_patch_delta_exclude_filter());
 	preset->set_custom_features(current->get_custom_features());
 	preset->set_enc_in_filter(current->get_enc_in_filter());
 	preset->set_enc_ex_filter(current->get_enc_ex_filter());
@@ -1201,6 +1222,75 @@ void ProjectExportDialog::_set_file_export_mode(int p_id) {
 	_propagate_file_export_mode(include_files->get_root(), EditorExportPreset::MODE_FILE_NOT_CUSTOMIZED);
 }
 
+void ProjectExportDialog::_patch_delta_encoding_changed(bool p_pressed) {
+	if (updating) {
+		return;
+	}
+
+	Ref<EditorExportPreset> current = get_current_preset();
+	ERR_FAIL_COND(current.is_null());
+
+	current->set_patch_delta_encoding_enabled(p_pressed);
+
+	_update_current_preset();
+}
+
+void ProjectExportDialog::_patch_delta_include_filter_changed(const String &p_filter) {
+	if (updating) {
+		return;
+	}
+
+	Ref<EditorExportPreset> current = get_current_preset();
+	ERR_FAIL_COND(current.is_null());
+
+	current->set_patch_delta_include_filter(patch_delta_include_filter->get_text());
+
+	updating_patch_delta_filters = true;
+	_update_current_preset();
+	updating_patch_delta_filters = false;
+}
+
+void ProjectExportDialog::_patch_delta_exclude_filter_changed(const String &p_filter) {
+	if (updating) {
+		return;
+	}
+
+	Ref<EditorExportPreset> current = get_current_preset();
+	ERR_FAIL_COND(current.is_null());
+
+	current->set_patch_delta_exclude_filter(patch_delta_exclude_filter->get_text());
+
+	updating_patch_delta_filters = true;
+	_update_current_preset();
+	updating_patch_delta_filters = false;
+}
+
+void ProjectExportDialog::_patch_delta_zstd_level_changed(double p_value) {
+	if (updating) {
+		return;
+	}
+
+	Ref<EditorExportPreset> current = get_current_preset();
+	ERR_FAIL_COND(current.is_null());
+
+	current->set_patch_delta_zstd_level((int)p_value);
+
+	_update_current_preset();
+}
+
+void ProjectExportDialog::_patch_delta_min_reduction_changed(double p_value) {
+	if (updating) {
+		return;
+	}
+
+	Ref<EditorExportPreset> current = get_current_preset();
+	ERR_FAIL_COND(current.is_null());
+
+	current->set_patch_delta_min_reduction(p_value / 100.0);
+
+	_update_current_preset();
+}
+
 void ProjectExportDialog::_patch_tree_button_clicked(Object *p_item, int p_column, int p_id, int p_mouse_button_index) {
 	TreeItem *ti = Object::cast_to<TreeItem>(p_item);
 
@@ -1657,11 +1747,52 @@ ProjectExportDialog::ProjectExportDialog() {
 			exclude_filters);
 	exclude_filters->connect(SceneStringName(text_changed), callable_mp(this, &ProjectExportDialog::_filter_changed));
 
-	// Patch packages.
+	// Patching.
 
 	VBoxContainer *patch_vb = memnew(VBoxContainer);
 	sections->add_child(patch_vb);
-	patch_vb->set_name(TTR("Patches"));
+	patch_vb->set_name(TTRC("Patching"));
+
+	patch_delta_encoding = memnew(CheckButton);
+	patch_delta_encoding->connect(SceneStringName(toggled), callable_mp(this, &ProjectExportDialog::_patch_delta_encoding_changed));
+	patch_delta_encoding->set_text(TTRC("Enable Delta Encoding"));
+	patch_delta_encoding->set_tooltip_text(TTRC("If checked, any change to a file already present in the base packs will be exported as the difference between the old file and the new file.\n"
+												"Enabling this comes at the cost of longer export times as well as longer load times for patched resources."));
+	patch_vb->add_child(patch_delta_encoding);
+
+	patch_delta_zstd_level = memnew(SpinBox);
+	patch_delta_zstd_level->set_min(ZSTD_minCLevel());
+	patch_delta_zstd_level->set_max(ZSTD_maxCLevel());
+	patch_delta_zstd_level->set_step(1);
+	patch_delta_zstd_level->set_tooltip_text(
+			vformat(TTR("The Zstandard compression level to use when generating delta-encoded patches.\n"
+						"Higher positive levels will reduce patch sizes, at the cost of longer export time, but do not affect the time it takes to apply patches.\n"
+						"Negative levels will reduce the time it takes to apply patches, at the cost of worse compression.\n"
+						"Levels above 19 require more memory both during export and when applying patches, usually for very little benefit.\n"
+						"Level 0 will cause Zstandard to use its default compression level, which is currently level %d."),
+					ZSTD_CLEVEL_DEFAULT));
+	patch_delta_zstd_level->connect(SceneStringName(value_changed), callable_mp(this, &ProjectExportDialog::_patch_delta_zstd_level_changed));
+	patch_vb->add_margin_child(TTRC("Delta Encoding Compression Level"), patch_delta_zstd_level);
+
+	patch_delta_min_reduction = memnew(SpinBox);
+	patch_delta_min_reduction->set_min(0.0);
+	patch_delta_min_reduction->set_max(100.0);
+	patch_delta_min_reduction->set_step(1.0);
+	patch_delta_min_reduction->set_suffix("%");
+	patch_delta_min_reduction->set_tooltip_text(TTRC("How much smaller, when compared to the new file, a delta-encoded patch needs to be for it to be exported.\n"
+													 "If the patch is not at least this much smaller, the new file will be exported as-is."));
+	patch_delta_min_reduction->connect(SceneStringName(value_changed), callable_mp(this, &ProjectExportDialog::_patch_delta_min_reduction_changed));
+	patch_vb->add_margin_child(TTRC("Delta Encoding Minimum Size Reduction"), patch_delta_min_reduction);
+
+	patch_delta_include_filter = memnew(LineEdit);
+	patch_delta_include_filter->set_accessibility_name(TTRC("Delta Encoding Include Filters"));
+	patch_delta_include_filter->connect(SceneStringName(text_changed), callable_mp(this, &ProjectExportDialog::_patch_delta_include_filter_changed));
+	patch_vb->add_margin_child(TTRC("Filters to include files/folders from being delta-encoded\n(comma-separated, e.g: *.gdc, scripts/*)"), patch_delta_include_filter);
+
+	patch_delta_exclude_filter = memnew(LineEdit);
+	patch_delta_exclude_filter->set_accessibility_name(TTRC("Delta Encoding Exclude Filters"));
+	patch_delta_exclude_filter->connect(SceneStringName(text_changed), callable_mp(this, &ProjectExportDialog::_patch_delta_exclude_filter_changed));
+	patch_vb->add_margin_child(TTRC("Filters to exclude files/folders from being delta-encoded\n(comma-separated, e.g: *.ctex, textures/*)"), patch_delta_exclude_filter);
 
 	patches = memnew(Tree);
 	patches->set_v_size_flags(Control::SIZE_EXPAND_FILL);

editor/export/project_export.h

@@ -46,6 +46,7 @@ class OptionButton;
 class PopupMenu;
 class ProjectExportDialog;
 class RichTextLabel;
+class SpinBox;
 class TabContainer;
 class Tree;
 class TreeItem;
@@ -107,6 +108,11 @@ class ProjectExportDialog : public ConfirmationDialog {
 
 	RBSet<String> feature_set;
 
+	CheckButton *patch_delta_encoding = nullptr;
+	SpinBox *patch_delta_zstd_level = nullptr;
+	SpinBox *patch_delta_min_reduction = nullptr;
+	LineEdit *patch_delta_include_filter = nullptr;
+	LineEdit *patch_delta_exclude_filter = nullptr;
 	Tree *patches = nullptr;
 	int patch_index = -1;
 	EditorFileDialog *patch_dialog = nullptr;
@@ -158,6 +164,12 @@ class ProjectExportDialog : public ConfirmationDialog {
 	void _tree_popup_edited(bool p_arrow_clicked);
 	void _set_file_export_mode(int p_id);
 
+	bool updating_patch_delta_filters = false;
+	void _patch_delta_encoding_changed(bool p_pressed);
+	void _patch_delta_include_filter_changed(const String &p_filter);
+	void _patch_delta_exclude_filter_changed(const String &p_filter);
+	void _patch_delta_zstd_level_changed(double p_value);
+	void _patch_delta_min_reduction_changed(double p_value);
 	void _patch_tree_button_clicked(Object *p_item, int p_column, int p_id, int p_mouse_button_index);
 	void _patch_tree_item_edited();
 	void _patch_file_selected(const String &p_path);

platform/android/export/export_plugin.cpp

@@ -767,7 +767,7 @@ Error EditorExportPlatformAndroid::store_in_apk(APKExportData *ed, const String
 	return OK;
 }
 
-Error EditorExportPlatformAndroid::save_apk_so(void *p_userdata, const SharedObject &p_so) {
+Error EditorExportPlatformAndroid::save_apk_so(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so) {
 	if (!p_so.path.get_file().begins_with("lib")) {
 		String err = "Android .so file names must start with \"lib\", but got: " + p_so.path;
 		ERR_PRINT(err);
@@ -801,14 +801,14 @@ Error EditorExportPlatformAndroid::save_apk_so(void *p_userdata, const SharedObj
 	return OK;
 }
 
-Error EditorExportPlatformAndroid::save_apk_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
+Error EditorExportPlatformAndroid::save_apk_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
 	APKExportData *ed = static_cast<APKExportData *>(p_userdata);
 
 	const String simplified_path = simplify_path(p_path);
 
 	Vector<uint8_t> enc_data;
 	EditorExportPlatform::SavedData sd;
-	Error err = _store_temp_file(simplified_path, p_data, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, enc_data, sd);
+	Error err = _store_temp_file(simplified_path, p_data, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, p_delta, enc_data, sd);
 	if (err != OK) {
 		return err;
 	}
@@ -822,11 +822,11 @@ Error EditorExportPlatformAndroid::save_apk_file(void *p_userdata, const String
 	return OK;
 }
 
-Error EditorExportPlatformAndroid::ignore_apk_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
+Error EditorExportPlatformAndroid::ignore_apk_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
 	return OK;
 }
 
-Error EditorExportPlatformAndroid::copy_gradle_so(void *p_userdata, const SharedObject &p_so) {
+Error EditorExportPlatformAndroid::copy_gradle_so(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so) {
 	ERR_FAIL_COND_V_MSG(!p_so.path.get_file().begins_with("lib"), FAILED,
 			"Android .so file names must start with \"lib\", but got: " + p_so.path);
 	Vector<ABI> abis = get_abis();

platform/android/export/export_plugin.h

@@ -151,13 +151,13 @@ class EditorExportPlatformAndroid : public EditorExportPlatform {
 
 	static Error store_in_apk(APKExportData *ed, const String &p_path, const Vector<uint8_t> &p_data, int compression_method = Z_DEFLATED);
 
-	static Error save_apk_so(void *p_userdata, const SharedObject &p_so);
+	static Error save_apk_so(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so);
 
-	static Error save_apk_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
+	static Error save_apk_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
 
-	static Error ignore_apk_file(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
+	static Error ignore_apk_file(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
 
-	static Error copy_gradle_so(void *p_userdata, const SharedObject &p_so);
+	static Error copy_gradle_so(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const SharedObject &p_so);
 
 	bool _has_read_write_storage_permission(const Vector<String> &p_permissions);
 

platform/android/export/gradle_export_util.cpp

@@ -170,14 +170,14 @@ Error store_string_at_path(const String &p_path, const String &p_data) {
 // It is used by the export_project_files method to save all the asset files into the gradle project.
 // It's functionality mirrors that of the method save_apk_file.
 // This method will be called ONLY when gradle build is enabled.
-Error rename_and_store_file_in_gradle_project(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed) {
+Error rename_and_store_file_in_gradle_project(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta) {
 	CustomExportData *export_data = static_cast<CustomExportData *>(p_userdata);
 
 	const String simplified_path = EditorExportPlatform::simplify_path(p_path);
 
 	Vector<uint8_t> enc_data;
 	EditorExportPlatform::SavedData sd;
-	Error err = _store_temp_file(simplified_path, p_data, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, enc_data, sd);
+	Error err = _store_temp_file(simplified_path, p_data, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, p_delta, enc_data, sd);
 	if (err != OK) {
 		return err;
 	}
@@ -398,7 +398,7 @@ String _get_application_tag(const Ref<EditorExportPlatform> &p_export_platform,
 	return manifest_application_text;
 }
 
-Error _store_temp_file(const String &p_simplified_path, const Vector<uint8_t> &p_data, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, Vector<uint8_t> &r_enc_data, EditorExportPlatform::SavedData &r_sd) {
+Error _store_temp_file(const String &p_simplified_path, const Vector<uint8_t> &p_data, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta, Vector<uint8_t> &r_enc_data, EditorExportPlatform::SavedData &r_sd) {
 	Error err = OK;
 	Ref<FileAccess> ftmp = FileAccess::create_temp(FileAccess::WRITE_READ, "export", "tmp", false, &err);
 	if (err != OK) {
@@ -407,6 +407,7 @@ Error _store_temp_file(const String &p_simplified_path, const Vector<uint8_t> &p
 	r_sd.path_utf8 = p_simplified_path.trim_prefix("res://").utf8();
 	r_sd.ofs = 0;
 	r_sd.size = p_data.size();
+	r_sd.delta = p_delta;
 	err = EditorExportPlatform::_encrypt_and_store_data(ftmp, p_simplified_path, p_data, p_enc_in_filters, p_enc_ex_filters, p_key, p_seed, r_sd.encrypted);
 	if (err != OK) {
 		return err;

platform/android/export/gradle_export_util.h

@@ -85,7 +85,7 @@ int _get_app_category_value(int category_index);
 
 String _get_app_category_label(int category_index);
 
-Error _store_temp_file(const String &p_simplified_path, const Vector<uint8_t> &p_data, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, Vector<uint8_t> &r_enc_data, EditorExportPlatform::SavedData &r_sd);
+Error _store_temp_file(const String &p_simplified_path, const Vector<uint8_t> &p_data, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta, Vector<uint8_t> &r_enc_data, EditorExportPlatform::SavedData &r_sd);
 
 // Utility method used to create a directory.
 Error create_directory(const String &p_dir);
@@ -103,7 +103,7 @@ Error store_string_at_path(const String &p_path, const String &p_data);
 // It is used by the export_project_files method to save all the asset files into the gradle project.
 // It's functionality mirrors that of the method save_apk_file.
 // This method will be called ONLY when gradle build is enabled.
-Error rename_and_store_file_in_gradle_project(void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed);
+Error rename_and_store_file_in_gradle_project(const Ref<EditorExportPreset> &p_preset, void *p_userdata, const String &p_path, const Vector<uint8_t> &p_data, int p_file, int p_total, const Vector<String> &p_enc_in_filters, const Vector<String> &p_enc_ex_filters, const Vector<uint8_t> &p_key, uint64_t p_seed, bool p_delta);
 
 // Creates strings.xml files inside the gradle project for different locales.
 Error _create_project_name_strings_files(const Ref<EditorExportPreset> &p_preset, const String &p_project_name, const String &p_gradle_build_dir, const Dictionary &p_appnames);