added load resource pack with offset feature

(cherry picked from commit c524d50444f98039faab75f7d701ca54a82e5848)

core/io/file_access_pack.cpp

@@ -34,11 +34,11 @@
 
 #include <stdio.h>
 
-Error PackedData::add_pack(const String &p_path, bool p_replace_files) {
+Error PackedData::add_pack(const String &p_path, bool p_replace_files, size_t p_offset) {
 
 	for (int i = 0; i < sources.size(); i++) {
 
-		if (sources[i]->try_open_pack(p_path, p_replace_files)) {
+		if (sources[i]->try_open_pack(p_path, p_replace_files, p_offset)) {
 
 			return OK;
 		};
@@ -132,15 +132,24 @@ PackedData::~PackedData() {
 
 //////////////////////////////////////////////////////////////////
 
-bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files) {
+bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset) {
 
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
 	if (!f)
 		return false;
 
+	f->seek(p_offset);
+
 	uint32_t magic = f->get_32();
 
 	if (magic != PACK_HEADER_MAGIC) {
+		// loading with offset feature not supported for self contained exe files
+		if (p_offset != 0) {
+			f->close();
+			memdelete(f);
+			ERR_FAIL_V_MSG(false, "Loading self-contained executable with offset not supported.");
+		}
+
 		//maybe at the end.... self contained exe
 		f->seek_end();
 		f->seek(f->get_position() - 4);
@@ -203,7 +212,7 @@ bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files)
 		uint64_t size = f->get_64();
 		uint8_t md5[16];
 		f->get_buffer(md5, 16);
-		PackedData::get_singleton()->add_path(p_path, path, ofs, size, md5, this, p_replace_files);
+		PackedData::get_singleton()->add_path(p_path, path, ofs + p_offset, size, md5, this, p_replace_files);
 	};
 
 	f->close();

core/io/file_access_pack.h

@@ -113,7 +113,7 @@ public:
 	_FORCE_INLINE_ bool is_disabled() const { return disabled; }
 
 	static PackedData *get_singleton() { return singleton; }
-	Error add_pack(const String &p_path, bool p_replace_files);
+	Error add_pack(const String &p_path, bool p_replace_files, size_t p_offset);
 
 	_FORCE_INLINE_ FileAccess *try_open_path(const String &p_path);
 	_FORCE_INLINE_ bool has_path(const String &p_path);
@@ -125,7 +125,7 @@ public:
 class PackSource {
 
 public:
-	virtual bool try_open_pack(const String &p_path, bool p_replace_files) = 0;
+	virtual bool try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset) = 0;
 	virtual FileAccess *get_file(const String &p_path, PackedData::PackedFile *p_file) = 0;
 	virtual ~PackSource() {}
 };
@@ -133,7 +133,7 @@ public:
 class PackedSourcePCK : public PackSource {
 
 public:
-	virtual bool try_open_pack(const String &p_path, bool p_replace_files);
+	virtual bool try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset);
 	virtual FileAccess *get_file(const String &p_path, PackedData::PackedFile *p_file);
 };
 

core/io/file_access_zip.cpp

@@ -160,9 +160,12 @@ unzFile ZipArchive::get_file_handle(String p_file) const {
 	return pkg;
 }
 
-bool ZipArchive::try_open_pack(const String &p_path, bool p_replace_files) {
+bool ZipArchive::try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset = 0) {
 
 	//printf("opening zip pack %ls, %i, %i\n", p_name.c_str(), p_name.extension().nocasecmp_to("zip"), p_name.extension().nocasecmp_to("pcz"));
+	// load with offset feature only supported for PCK files
+	ERR_FAIL_COND_V_MSG(p_offset != 0, false, "Invalid PCK data. Note that loading files with a non-zero offset isn't supported with ZIP archives.");
+
 	if (p_path.get_extension().nocasecmp_to("zip") != 0 && p_path.get_extension().nocasecmp_to("pcz") != 0)
 		return false;
 

core/io/file_access_zip.h

@@ -74,7 +74,7 @@ public:
 
 	bool file_exists(String p_name) const;
 
-	virtual bool try_open_pack(const String &p_path, bool p_replace_files);
+	virtual bool try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset);
 	FileAccess *get_file(const String &p_path, PackedData::PackedFile *p_file);
 
 	static ZipArchive *get_singleton();

core/project_settings.cpp

@@ -268,12 +268,12 @@ void ProjectSettings::_get_property_list(List<PropertyInfo> *p_list) const {
 	}
 }
 
-bool ProjectSettings::_load_resource_pack(const String &p_pack, bool p_replace_files) {
+bool ProjectSettings::_load_resource_pack(const String &p_pack, bool p_replace_files, int p_offset) {
 
 	if (PackedData::get_singleton()->is_disabled())
 		return false;
 
-	bool ok = PackedData::get_singleton()->add_pack(p_pack, p_replace_files) == OK;
+	bool ok = PackedData::get_singleton()->add_pack(p_pack, p_replace_files, p_offset) == OK;
 
 	if (!ok)
 		return false;
@@ -997,7 +997,7 @@ void ProjectSettings::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("localize_path", "path"), &ProjectSettings::localize_path);
 	ClassDB::bind_method(D_METHOD("globalize_path", "path"), &ProjectSettings::globalize_path);
 	ClassDB::bind_method(D_METHOD("save"), &ProjectSettings::save);
-	ClassDB::bind_method(D_METHOD("load_resource_pack", "pack", "replace_files"), &ProjectSettings::_load_resource_pack, DEFVAL(true));
+	ClassDB::bind_method(D_METHOD("load_resource_pack", "pack", "replace_files", "offset"), &ProjectSettings::_load_resource_pack, DEFVAL(true), DEFVAL(0));
 	ClassDB::bind_method(D_METHOD("property_can_revert", "name"), &ProjectSettings::property_can_revert);
 	ClassDB::bind_method(D_METHOD("property_get_revert", "name"), &ProjectSettings::property_get_revert);
 

core/project_settings.h

@@ -104,7 +104,7 @@ protected:
 
 	void _convert_to_last_version(int p_from_version);
 
-	bool _load_resource_pack(const String &p_pack, bool p_replace_files = true);
+	bool _load_resource_pack(const String &p_pack, bool p_replace_files = true, int p_offset = 0);
 
 	void _add_property_info_bind(const Dictionary &p_info);
 

doc/classes/ProjectSettings.xml

@@ -92,9 +92,12 @@
 			</argument>
 			<argument index="1" name="replace_files" type="bool" default="true">
 			</argument>
+			<argument index="2" name="offset" type="int" default="0">
+			</argument>
 			<description>
 				Loads the contents of the .pck or .zip file specified by [code]pack[/code] into the resource filesystem ([code]res://[/code]). Returns [code]true[/code] on success.
 				[b]Note:[/b] If a file from [code]pack[/code] shares the same path as a file already in the resource filesystem, any attempts to load that file will use the file from [code]pack[/code] unless [code]replace_files[/code] is set to [code]false[/code].
+				[b]Note:[/b] The optional [code]offset[/code] parameter can be used to specify the offset in bytes to the start of the resource pack. This is only supported for .pck files.
 			</description>
 		</method>
 		<method name="localize_path" qualifiers="const">