ZlibInflate.cc

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#include "ZlibInflate.hh"
#include "FileException.hh"
#include "MemBuffer.hh"
#include "narrow.hh"
#include "xrange.hh"
#include <limits>
 
namespace openmsx {
 
ZlibInflate::ZlibInflate(std::span<const uint8_t> input)
{
        if (input.size() > std::numeric_limits<decltype(s.avail_in)>::max()) {
                throw FileException(
                        "Error while decompressing: input file too big");
        }
        auto inputLen = static_cast<decltype(s.avail_in)>(input.size());
 
        s.zalloc = nullptr;
        s.zfree  = nullptr;
        s.opaque = nullptr;
        s.next_in  = const_cast<uint8_t*>(input.data());
        s.avail_in = inputLen;
        wasInit = false;
}
 
ZlibInflate::~ZlibInflate()
{
        if (wasInit) {
                inflateEnd(&s);
        }
}
 
void ZlibInflate::skip(size_t num)
{
        repeat(num, [&] { (void)getByte(); });
}
 
uint8_t ZlibInflate::getByte()
{
        if (s.avail_in <= 0) {
                throw FileException(
                        "Error while decompressing: unexpected end of file.");
        }
        --s.avail_in;
        return *(s.next_in++);
}
 
unsigned ZlibInflate::get16LE()
{
        unsigned result = getByte();
        result += getByte() << 8;
        return result;
}
 
unsigned ZlibInflate::get32LE()
{
        unsigned result = getByte();
        result += getByte() <<  8;
        result += getByte() << 16;
        result += getByte() << 24;
        return result;
}
 
std::string ZlibInflate::getString(size_t len)
{
        std::string result;
        result.reserve(len);
        repeat(len, [&] { result.push_back(narrow_cast<char>(getByte())); });
        return result;
}
 
std::string ZlibInflate::getCString()
{
        std::string result;
        while (auto c = narrow_cast<char>(getByte())) {
                result.push_back(c);
        }
        return result;
}
 
size_t ZlibInflate::inflate(MemBuffer<uint8_t>& output, size_t sizeHint)
{
        if (int err = inflateInit2(&s, -MAX_WBITS);
            err != Z_OK) {
                throw FileException(
                        "Error initializing inflate struct: ", zError(err));
        }
        wasInit = true;
 
        size_t outSize = sizeHint;
        output.resize(outSize);
        s.avail_out = uInt(outSize); // TODO overflow?
        while (true) {
                s.next_out = output.data() + s.total_out;
                int err = ::inflate(&s, Z_NO_FLUSH);
                if (err == Z_STREAM_END) {
                        break;
                }
                if (err != Z_OK) {
                        throw FileException("Error decompressing gzip: ", zError(err));
                }
                auto oldSize = outSize;
                outSize = oldSize * 2; // double buffer size
                output.resize(outSize);
                s.avail_out = uInt(outSize - oldSize); // TODO overflow?
        }
 
        // set actual size
        output.resize(s.total_out);
        return s.total_out;
}
 
} // namespace openmsx