CompressedFileAdapter.cc

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#include "CompressedFileAdapter.hh"
#include "FileException.hh"
#include "hash_set.hh"
#include "xxhash.hh"
#include <cstring>

using std::string;

namespace openmsx {

struct GetURLFromDecompressed {
        template<typename Ptr> const string& operator()(const Ptr& p) const {
                return p->cachedURL;
        }
};
static hash_set<std::shared_ptr<CompressedFileAdapter::Decompressed>,
                GetURLFromDecompressed, XXHasher> decompressCache;


CompressedFileAdapter::CompressedFileAdapter(std::unique_ptr<FileBase> file_)
        : file(std::move(file_)), pos(0)
{
}

CompressedFileAdapter::~CompressedFileAdapter()
{
        auto it = decompressCache.find(getURL());
        decompressed.reset();
        if (it != end(decompressCache) && it->unique()) {
                // delete last user of Decompressed, remove from cache
                decompressCache.erase(it);
        }
}

void CompressedFileAdapter::decompress()
{
        if (decompressed) return;

        string url = getURL();
        auto it = decompressCache.find(url);
        if (it != end(decompressCache)) {
                decompressed = *it;
        } else {
                decompressed = std::make_shared<Decompressed>();
                decompress(*file, *decompressed);
                decompressed->cachedModificationDate = getModificationDate();
                decompressed->cachedURL = std::move(url);
                decompressCache.insert_noDuplicateCheck(decompressed);
        }

        // close original file after succesful decompress
        file.reset();
}

void CompressedFileAdapter::read(void* buffer, size_t num)
{
        decompress();
        if (decompressed->size < (pos + num)) {
                throw FileException("Read beyond end of file");
        }
        const auto& buf = decompressed->buf;
        memcpy(buffer, buf.data() + pos, num);
        pos += num;
}

void CompressedFileAdapter::write(const void* /*buffer*/, size_t /*num*/)
{
        throw FileException("Writing to compressed files not yet supported");
}

span<uint8_t> CompressedFileAdapter::mmap()
{
        decompress();
        return { decompressed->buf.data(), decompressed->size };
}

void CompressedFileAdapter::munmap()
{
        // nothing
}

size_t CompressedFileAdapter::getSize()
{
        decompress();
        return decompressed->size;
}

void CompressedFileAdapter::seek(size_t newpos)
{
        pos = newpos;
}

size_t CompressedFileAdapter::getPos()
{
        return pos;
}

void CompressedFileAdapter::truncate(size_t /*size*/)
{
        throw FileException("Truncating compressed files not yet supported.");
}

void CompressedFileAdapter::flush()
{
        // nothing because writing is not supported
}

string CompressedFileAdapter::getURL() const
{
        return file ? file->getURL() : decompressed->cachedURL;
}

string CompressedFileAdapter::getOriginalName()
{
        decompress();
        return decompressed->originalName;
}

bool CompressedFileAdapter::isReadOnly() const
{
        return true;
}

time_t CompressedFileAdapter::getModificationDate()
{
        return file ? file->getModificationDate()
                    : decompressed->cachedModificationDate;
}

} // namespace openmsx