BlobIOSystem.h

/*
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Open Asset Import Library (assimp)
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  following disclaimer.
 
* Redistributions in binary form must reproduce the above
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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*/
 
#ifndef AI_BLOBIOSYSTEM_H_INCLUDED
#define AI_BLOBIOSYSTEM_H_INCLUDED
 
#include <assimp/cexport.h>
#include <stdint.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOStream.hpp>
#include <assimp/IOSystem.hpp>
#include <set>
#include <vector>
 
namespace Assimp {
class BlobIOSystem;
 
// --------------------------------------------------------------------------------------------
// --------------------------------------------------------------------------------------------
class BlobIOStream : public IOStream {
public:
    BlobIOStream(BlobIOSystem *creator, const std::string &file, size_t initial = 4096) :
            buffer(),
            cur_size(),
            file_size(),
            cursor(),
            initial(initial),
            file(file),
            creator(creator) {
        // empty
    }
 
    virtual ~BlobIOStream();
 
public:
    // -------------------------------------------------------------------
    aiExportDataBlob *GetBlob() {
        aiExportDataBlob *blob = new aiExportDataBlob();
        blob->size = file_size;
        blob->data = buffer;
 
        buffer = nullptr;
 
        return blob;
    }
 
    // -------------------------------------------------------------------
    virtual size_t Read(void *,
            size_t,
            size_t) {
        return 0;
    }
 
    // -------------------------------------------------------------------
    virtual size_t Write(const void *pvBuffer,
            size_t pSize,
            size_t pCount) {
        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;
    }
 
    // -------------------------------------------------------------------
    virtual aiReturn Seek(size_t pOffset,
            aiOrigin pOrigin) {
        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;
    }
 
    // -------------------------------------------------------------------
    virtual size_t Tell() const {
        return cursor;
    }
 
    // -------------------------------------------------------------------
    virtual size_t FileSize() const {
        return file_size;
    }
 
    // -------------------------------------------------------------------
    virtual void Flush() {
        // 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"
 
// --------------------------------------------------------------------------------------------
// --------------------------------------------------------------------------------------------
class BlobIOSystem : public IOSystem {
 
    friend class BlobIOStream;
    typedef std::pair<std::string, aiExportDataBlob *> BlobEntry;
 
public:
    BlobIOSystem() {
    }
 
    virtual ~BlobIOSystem() {
        for (BlobEntry &blobby : blobs) {
            delete blobby.second;
        }
    }
 
public:
    // -------------------------------------------------------------------
    const char *GetMagicFileName() const {
        return AI_BLOBIO_MAGIC;
    }
 
    // -------------------------------------------------------------------
    aiExportDataBlob *GetBlobChain() {
        // one must be the master
        aiExportDataBlob *master = nullptr, *cur;
        for (const BlobEntry &blobby : blobs) {
            if (blobby.first == AI_BLOBIO_MAGIC) {
                master = blobby.second;
                break;
            }
        }
        if (!master) {
            ASSIMP_LOG_ERROR("BlobIOSystem: no data written or master file was not closed properly.");
            return nullptr;
        }
 
        master->name.Set("");
 
        cur = master;
        for (const BlobEntry &blobby : blobs) {
            if (blobby.second == master) {
                continue;
            }
 
            cur->next = blobby.second;
            cur = cur->next;
 
            // 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:
    // -------------------------------------------------------------------
    virtual bool Exists(const char *pFile) const {
        return created.find(std::string(pFile)) != created.end();
    }
 
    // -------------------------------------------------------------------
    virtual char getOsSeparator() const {
        return '/';
    }
 
    // -------------------------------------------------------------------
    virtual IOStream *Open(const char *pFile,
            const char *pMode) {
        if (pMode[0] != 'w') {
            return nullptr;
        }
 
        created.insert(std::string(pFile));
        return new BlobIOStream(this, std::string(pFile));
    }
 
    // -------------------------------------------------------------------
    virtual void Close(IOStream *pFile) {
        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.push_back(BlobEntry(filename, child->GetBlob()));
    }
 
private:
    std::set<std::string> created;
    std::vector<BlobEntry> blobs;
};
 
// --------------------------------------------------------------------------------------------
BlobIOStream ::~BlobIOStream() {
    creator->OnDestruct(file, this);
    delete[] buffer;
}
 
} // namespace Assimp
 
#endif