// Returns a buffer filled with the bitmap file header in little endian:
// Signature 2 bytes 'BM'
// FileSize 4 bytes File size in bytes
// reserved 4 bytes unused (=0)
// DataOffset 4 bytes File offset to Raster Data
// Returns true if successful
bool nsICODecoder::FillBitmapFileHeaderBuffer(PRInt8 *bfh)
{
memset(bfh, 0, 14);
bfh[0] = 'B';
bfh[1] = 'M';
PRInt32 dataOffset = 0;
PRInt32 fileSize = 0;
dataOffset = BFH_LENGTH + BITMAPINFOSIZE;
// The color table is present only if BPP is <= 8
if (mDirEntry.mBitCount <= 8) {
PRUint16 numColors = GetNumColors();
if (numColors == (PRUint16)-1) {
return false;
}
dataOffset += 4 * numColors;
fileSize = dataOffset + GetRealWidth() * GetRealHeight();
} else {
fileSize = dataOffset + (mDirEntry.mBitCount * GetRealWidth() *
GetRealHeight()) / 8;
}
fileSize = NATIVE32_TO_LITTLE(fileSize);
memcpy(bfh + 2, &fileSize, sizeof(fileSize));
dataOffset = NATIVE32_TO_LITTLE(dataOffset);
memcpy(bfh + 10, &dataOffset, sizeof(dataOffset));
return true;
}
// A BMP inside of an ICO has *2 height because of the AND mask
// that follows the actual bitmap. The BMP shouldn't know about
// this difference though.
bool
nsICODecoder::FixBitmapHeight(PRInt8 *bih)
{
// Get the height from the BMP file information header
PRInt32 height;
memcpy(&height, bih + 8, sizeof(height));
height = LITTLE_TO_NATIVE32(height);
// The bitmap height is by definition * 2 what it should be to account for
// the 'AND mask'. It is * 2 even if the `AND mask` is not present.
height /= 2;
if (height > 256) {
return false;
}
// We should always trust the height from the bitmap itself instead of
// the ICO height. So fix the ICO height.
if (height == 256) {
mDirEntry.mHeight = 0;
} else {
mDirEntry.mHeight = (PRInt8)height;
}
// Fix the BMP height in the BIH so that the BMP decoder can work properly
height = NATIVE32_TO_LITTLE(height);
memcpy(bih + 8, &height, sizeof(height));
return true;
}
// A BMP inside of an ICO has *2 height because of the AND mask
// that follows the actual bitmap. The BMP shouldn't know about
// this difference though.
void
nsICODecoder::FillBitmapInformationBufferHeight(PRInt8 *bih)
{
PRInt32 height = GetRealHeight();
height = NATIVE32_TO_LITTLE(height);
memcpy(bih + 8, &height, sizeof(height));
}
