assimp.assimp/include/assimp/BlobIOSystem.h

/*
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Open Asset Import Library (assimp)
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/** @file Provides cheat implementations for IOSystem and IOStream to
 *  redirect exporter output to a blob chain.*/

#pragma once
#ifndef AI_BLOBIOSYSTEM_H_INCLUDED
#define AI_BLOBIOSYSTEM_H_INCLUDED

#ifdef __GNUC__
#pragma GCC system_header
#endif

#include <assimp/cexport.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOStream.hpp>
#include <assimp/IOSystem.hpp>
#include <cstdint>
#include <set>
#include <vector>

namespace Assimp {
class BlobIOSystem;

// --------------------------------------------------------------------------------------------
/** Redirect IOStream to a blob */
// --------------------------------------------------------------------------------------------
class BlobIOStream : public IOStream {
public:
    /// @brief The class constructor with all needed parameters
    /// @param creator  Pointer to the creator instance
    /// @param file     The filename
    /// @param initial  The initial size
    BlobIOStream(BlobIOSystem *creator, const std::string &file, size_t initial = 4096) :
            buffer(),
            cur_size(),
            file_size(),
            cursor(),
            initial(initial),
            file(file),
            creator(creator) {
        // empty
    }

    ///	@brief  The class destructor.
    ~BlobIOStream() override;

public:
    // -------------------------------------------------------------------
    aiExportDataBlob *GetBlob() {
        aiExportDataBlob *blob = new aiExportDataBlob();
        blob->size = file_size;
        blob->data = buffer;

        buffer = nullptr;

        return blob;
    }

    // -------------------------------------------------------------------
    size_t Read(void *, size_t, size_t) override {
        return 0;
    }

    // -------------------------------------------------------------------
    size_t Write(const void *pvBuffer, size_t pSize, size_t pCount) override {
        pSize *= pCount;
        if (cursor + pSize > cur_size) {
            Grow(cursor + pSize);
        }

        memcpy(buffer + cursor, pvBuffer, pSize);
        cursor += pSize;

        file_size = std::max(file_size, cursor);
        return pCount;
    }

    // -------------------------------------------------------------------
    aiReturn Seek(size_t pOffset, aiOrigin pOrigin) override {
        switch (pOrigin) {
            case aiOrigin_CUR:
                cursor += pOffset;
                break;

            case aiOrigin_END:
                cursor = file_size - pOffset;
                break;

            case aiOrigin_SET:
                cursor = pOffset;
                break;

            default:
                return AI_FAILURE;
        }

        if (cursor > file_size) {
            Grow(cursor);
        }

        file_size = std::max(cursor, file_size);

        return AI_SUCCESS;
    }

    // -------------------------------------------------------------------
    size_t Tell() const override {
        return cursor;
    }

    // -------------------------------------------------------------------
    size_t FileSize() const override {
        return file_size;
    }

    // -------------------------------------------------------------------
    void Flush() override {
        // ignore
    }

private:
    // -------------------------------------------------------------------
    void Grow(size_t need = 0) {
        // 1.5 and phi are very heap-friendly growth factors (the first
        // allows for frequent re-use of heap blocks, the second
        // forms a fibonacci sequence with similar characteristics -
        // since this heavily depends on the heap implementation
        // and other factors as well, i'll just go with 1.5 since
        // it is quicker to compute).
        size_t new_size = std::max(initial, std::max(need, cur_size + (cur_size >> 1)));

        const uint8_t *const old = buffer;
        buffer = new uint8_t[new_size];

        if (old) {
            memcpy(buffer, old, cur_size);
            delete[] old;
        }

        cur_size = new_size;
    }

private:
    uint8_t *buffer;
    size_t cur_size, file_size, cursor, initial;

    const std::string file;
    BlobIOSystem *const creator;
};

#define AI_BLOBIO_MAGIC "$blobfile"

// --------------------------------------------------------------------------------------------
/** Redirect IOSystem to a blob */
// --------------------------------------------------------------------------------------------
class BlobIOSystem : public IOSystem {

    friend class BlobIOStream;
    typedef std::pair<std::string, aiExportDataBlob *> BlobEntry;


public:
    /// @brief The default class constructor.
    BlobIOSystem() :
            baseName{AI_BLOBIO_MAGIC} {
    }

    ///	@brief  The class constructor with the base name.
    /// @param baseName     The base name.
    BlobIOSystem(const std::string &baseName) :
            baseName(baseName) {
        // empty
    }

    ~BlobIOSystem() override {
        for (BlobEntry &blobby : blobs) {
            delete blobby.second;
        }
    }

public:
    // -------------------------------------------------------------------
    const char *GetMagicFileName() const {
        return baseName.c_str();
    }

    // -------------------------------------------------------------------
    aiExportDataBlob *GetBlobChain() {
        const auto magicName = std::string(this->GetMagicFileName());
        const bool hasBaseName = baseName != AI_BLOBIO_MAGIC;

        // one must be the master
        aiExportDataBlob *master = nullptr, *cur;

        for (const BlobEntry &blobby : blobs) {
            if (blobby.first == magicName) {
                master = blobby.second;
                master->name.Set(hasBaseName ? blobby.first : "");
                break;
            }
        }

        if (!master) {
            ASSIMP_LOG_ERROR("BlobIOSystem: no data written or master file was not closed properly.");
            return nullptr;
        }

        cur = master;

        for (const BlobEntry &blobby : blobs) {
            if (blobby.second == master) {
                continue;
            }

            cur->next = blobby.second;
            cur = cur->next;

            if (hasBaseName) {
                cur->name.Set(blobby.first);
            } else {
                // extract the file extension from the file written
                const std::string::size_type s = blobby.first.find_first_of('.');
                cur->name.Set(s == std::string::npos ? blobby.first : blobby.first.substr(s + 1));
            }
        }

        // give up blob ownership
        blobs.clear();
        return master;
    }

public:
    // -------------------------------------------------------------------
    bool Exists(const char *pFile) const override {
        return created.find(std::string(pFile)) != created.end();
    }

    // -------------------------------------------------------------------
    char getOsSeparator() const override {
        return '/';
    }

    // -------------------------------------------------------------------
    IOStream *Open(const char *pFile, const char *pMode) override {
        if (pMode[0] != 'w') {
            return nullptr;
        }

        created.insert(std::string(pFile));
        return new BlobIOStream(this, std::string(pFile));
    }

    // -------------------------------------------------------------------
    void Close(IOStream *pFile) override {
        delete pFile;
    }

private:
    // -------------------------------------------------------------------
    void OnDestruct(const std::string &filename, BlobIOStream *child) {
        // we don't know in which the files are closed, so we
        // can't reliably say that the first must be the master
        // file ...
        blobs.emplace_back(filename, child->GetBlob());
    }

private:
    std::string baseName;
    std::set<std::string> created;
    std::vector<BlobEntry> blobs;
};

// --------------------------------------------------------------------------------------------
BlobIOStream::~BlobIOStream() {
    if (nullptr != creator) {
        creator->OnDestruct(file, this);
    }
    delete[] buffer;
}

} // namespace Assimp

#endif