#include "common.hh"

#include "decompress.hh"

std::vector<uint8_t> decompressLZ(char const* data, size_t len)
{
  std::vector<uint8_t> ret;
  
  size_t pos = 0;
  while (pos < len) {
    uint8_t b = *(data+pos++);
    if (!((b&0xe0)==0xe0)) {
      unsigned size = 0, replSize = 0;
      unsigned replOfs = 0;
      if (!(b&0x80)) {
	if (pos >= len)
	  throw FormatException{"Compressed stream overrun"};
	
	uint8_t ofs = *(data+pos++);
	size = b&0x3;
	  
	replSize = ((b&0x1c)>>2) + 3;
	replOfs =  ((b&0x60)<<3)+ofs+1;
      } else if (!(b&0x40)) {
	if (pos+1 >= len)
	  throw FormatException{"Compressed stream overrun"};
	  
	uint8_t b1 = *(data+pos++);
	uint8_t b2 = *(data+pos++);

	size = (b1&0xc0)>>6;

	replSize = (b&0x3f)+4;
	replOfs = ((b1&0x3f)<<8)+b2+1;
      } else if (!(b&0x20)) {
	if (pos+2 >= len)
	  throw FormatException{"Compressed stream overrun"};
	  
	uint8_t b1 = *(data+pos++);
	uint8_t b2 = *(data+pos++);
	uint8_t b3 = *(data+pos++);

	size = b&0x3;

	replSize = b3+5+((b&0xc)<<6);
	replOfs = ((b&0x10)<<12)+1+(b1<<8)+b2;
      }
      if (pos+size >= len)
	throw FormatException{"Compressed stream overrun"};
      std::copy(data+pos, data+pos+size,
		std::back_inserter(ret));
      pos += size;

      if (replOfs > ret.size())
	throw FormatException{"Replication offset exceeds buffer"};
      unsigned start = ret.size()-replOfs;
      for (unsigned i = 0;i < replSize;++i)
	ret.push_back(ret[start+i]);
    } else {
      unsigned size = (b&0x1f)*4+4;
      if (size > 0x70) {
	if (pos+(b&0x3) > len)
	  throw FormatException{"Compressed stream overrun"};
	std::copy(data+pos, data+pos+(b&0x3),
		  std::back_inserter(ret));
	pos += (b&0x3);
#ifndef NDEBUG
	if (pos < len)
	  printf("%lu unparsed bytes in compressed data\n", len-pos);
#endif
	break;
      }
	
      if (pos+size > len)
	throw FormatException{"Compressed stream overrun"};
      std::copy(data+pos, data+pos+size,
		std::back_inserter(ret));
      pos += size;
    }
  }
  return ret;
}