CompressedFileAdapter.cc

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#include "CompressedFileAdapter.hh"
#include "FileException.hh"
#include "hash_set.hh"
#include "xxhash.hh"
#include <cstring>
 
namespace openmsx {
 
struct GetURLFromDecompressed {
        template<typename Ptr> [[nodiscard]] const std::string& operator()(const Ptr& p) const {
                return p->cachedURL;
        }
};
static hash_set<std::unique_ptr<CompressedFileAdapter::Decompressed>,
                GetURLFromDecompressed, XXHasher> decompressCache;
 
 
CompressedFileAdapter::CompressedFileAdapter(std::unique_ptr<FileBase> file_)
        : file(std::move(file_))
{
}
 
CompressedFileAdapter::~CompressedFileAdapter()
{
        if (decompressed) {
                auto it = decompressCache.find(getURL());
                assert(it != end(decompressCache));
                assert(it->get() == decompressed);
                --(*it)->useCount;
                if ((*it)->useCount == 0) {
                        // delete last user of Decompressed, remove from cache
                        decompressCache.erase(it);
                }
        }
}
 
void CompressedFileAdapter::decompress()
{
        if (decompressed) return;
 
        const std::string& url = getURL();
        auto it = decompressCache.find(url);
        if (it == end(decompressCache)) {
                auto d = std::make_unique<Decompressed>();
                decompress(*file, *d);
                d->cachedModificationDate = getModificationDate();
                d->cachedURL = url;
                it = decompressCache.insert_noDuplicateCheck(std::move(d));
        }
        ++(*it)->useCount;
        decompressed = it->get();
 
        // close original file after successful 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");
}
 
std::span<const 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
}
 
const std::string& CompressedFileAdapter::getURL() const
{
        return file ? file->getURL() : decompressed->cachedURL;
}
 
std::string_view CompressedFileAdapter::getOriginalName()
{
        decompress();
        return decompressed->originalName;
}
 
bool CompressedFileAdapter::isReadOnly() const
{
        return true;
}
 
time_t CompressedFileAdapter::getModificationDate()
{
        return file ? file->getModificationDate()
                    : decompressed->cachedModificationDate;
}
 
} // namespace openmsx