GPXSee/src/map/IMG/subfile.cpp

#include <cstring>
#include "imgdata.h"
#include "subfile.h"

using namespace IMG;

#define mod2n(x, m) ((x) & ((m) - 1));

bool SubFile::seek(Handle &handle, quint32 pos) const
{
	if (_img) {
		quint32 blockBits = _img->blockBits();
		int blockNum = pos >> blockBits;

		if (handle._blockNum != blockNum) {
			if (blockNum >= _blocks->size())
				return false;
			if (!_img->readBlock(handle._file, _blocks->at(blockNum),
			  handle._data.data()))
				return false;
			handle._blockNum = blockNum;
		}

		handle._blockPos = mod2n(pos, 1U<<blockBits);
		handle._pos = pos;
	} else {
		int blockNum = pos >> BLOCK_BITS;

		if (handle._blockNum != blockNum) {
			if (!handle._file.seek((quint64)blockNum << BLOCK_BITS))
				return false;
			if (handle._file.read(handle._data.data(), (1<<BLOCK_BITS)) < 0)
				return false;
			handle._blockNum = blockNum;
		}

		handle._blockPos = mod2n(pos, 1U<<BLOCK_BITS);
		handle._pos = pos;
	}

	return true;
}

bool SubFile::readVUInt32(Handle &hdl, quint32 &val) const
{
	quint8 bytes, shift, b;

	if (!readByte(hdl, &b))
		return false;

	if ((b & 1) == 0) {
		if ((b & 2) == 0) {
			bytes = ((b >> 2) & 1) ^ 3;
			shift = 5;
		} else {
			shift = 6;
			bytes = 1;
		}
	} else {
		shift = 7;
		bytes = 0;
	}

	val = b >> (8 - shift);

	for (int i = 1; i <= bytes; i++) {
		if (!readByte(hdl, &b))
			return false;
		val |= (((quint32)b) << (i * 8)) >> (8 - shift);
	}

	return true;
}

bool SubFile::readVUInt32(Handle &hdl, quint32 bytes, quint32 &val) const
{
	switch (bytes) {
		case 1:
			return readUInt8(hdl, val);
		case 2:
			return readUInt16(hdl, val);
		case 3:
			return readUInt24(hdl, val);
		case 4:
			return readUInt32(hdl, val);
		default:
			return false;
	}
}

bool SubFile::readVBitfield32(Handle &hdl, quint32 &bitfield) const
{
	quint8 bits;

	if (!readByte(hdl, &bits))
		return false;

	if (!(bits & 1)) {
		seek(hdl, hdl._pos - 1);
		if (!((bits>>1) & 1)) {
			if (!((bits>>2) & 1)) {
				if (!readUInt32(hdl, bitfield))
					return false;
			} else {
				if (!readUInt24(hdl, bitfield))
					return false;
			}
			bitfield >>= 3;
		} else {
			if (!readUInt16(hdl, bitfield))
				return false;
			bitfield >>= 2;
		}
	} else
		bitfield = bits>>1;

	return true;
}

bool SubFile::read(Handle &handle, char *buff, quint32 size) const
{
	while (size) {
		quint32 remaining = handle._data.size() - handle._blockPos;
		if (size < remaining) {
			memcpy(buff, handle._data.constData() + handle._blockPos, size);
			handle._blockPos += size;
			handle._pos += size;
			return true;
		} else {
			memcpy(buff, handle._data.constData() + handle._blockPos,
			  remaining);
			buff += remaining;
			size -= remaining;
			handle._blockPos = 0;
			handle._pos += remaining;
			if (!seek(handle, handle._pos))
				return false;
		}
	}

	return true;
}