/******************************************************************************
Initialize HashTable - allocate the memory needed and clear it. *
******************************************************************************/
GifHashTableType *_InitHashTable(void)
{
GifHashTableType *HashTable;
if ((HashTable = (GifHashTableType *) malloc(sizeof(GifHashTableType)))
== NULL)
return NULL;
_ClearHashTable(HashTable);
return HashTable;
}
/******************************************************************************
* Initialize HashTable - allocate the memory needed and clear it. *
******************************************************************************/
GifHashTableType *_InitHashTable(void)
{
GifHashTableType *HashTable;
if ((HashTable = (GifHashTableType *) IMAGE_MALLOC(sizeof(GifHashTableType)))
== NULL)
return NULL;
_ClearHashTable(HashTable);
return HashTable;
}
/******************************************************************************
Setup the LZ compression for this image:
******************************************************************************/
static int
EGifSetupCompress(GifFileType *GifFile)
{
int BitsPerPixel;
GifByteType Buf;
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
/* Test and see what color map to use, and from it # bits per pixel: */
if (GifFile->Image.ColorMap)
BitsPerPixel = GifFile->Image.ColorMap->BitsPerPixel;
else if (GifFile->SColorMap)
BitsPerPixel = GifFile->SColorMap->BitsPerPixel;
else {
GifFile->Error = E_GIF_ERR_NO_COLOR_MAP;
return GIF_ERROR;
}
Buf = BitsPerPixel = (BitsPerPixel < 2 ? 2 : BitsPerPixel);
InternalWrite(GifFile, &Buf, 1); /* Write the Code size to file. */
Private->Buf[0] = 0; /* Nothing was output yet. */
Private->BitsPerPixel = BitsPerPixel;
Private->ClearCode = (1 << BitsPerPixel);
Private->EOFCode = Private->ClearCode + 1;
Private->RunningCode = Private->EOFCode + 1;
Private->RunningBits = BitsPerPixel + 1; /* Number of bits per code. */
Private->MaxCode1 = 1 << Private->RunningBits; /* Max. code + 1. */
Private->CrntCode = FIRST_CODE; /* Signal that this is first one! */
Private->CrntShiftState = 0; /* No information in CrntShiftDWord. */
Private->CrntShiftDWord = 0;
/* Clear hash table and send Clear to make sure the decoder do the same. */
_ClearHashTable(Private->HashTable);
if (EGifCompressOutput(GifFile, Private->ClearCode) == GIF_ERROR) {
GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
return GIF_OK;
}
/******************************************************************************
The LZ compression routine:
This version compresses the given buffer Line of length LineLen.
This routine can be called a few times (one per scan line, for example), in
order to complete the whole image.
******************************************************************************/
static int
EGifCompressLine(GifFileType *GifFile,
GifPixelType *Line,
const int LineLen)
{
int i = 0, CrntCode, NewCode;
unsigned long NewKey;
GifPixelType Pixel;
GifHashTableType *HashTable;
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
HashTable = Private->HashTable;
if (Private->CrntCode == FIRST_CODE) /* Its first time! */
CrntCode = Line[i++];
else
CrntCode = Private->CrntCode; /* Get last code in compression. */
while (i < LineLen) { /* Decode LineLen items. */
Pixel = Line[i++]; /* Get next pixel from stream. */
/* Form a new unique key to search hash table for the code combines
* CrntCode as Prefix string with Pixel as postfix char.
*/
NewKey = (((uint32_t) CrntCode) << 8) + Pixel;
if ((NewCode = _ExistsHashTable(HashTable, NewKey)) >= 0) {
/* This Key is already there, or the string is old one, so
* simple take new code as our CrntCode:
*/
CrntCode = NewCode;
} else {
/* Put it in hash table, output the prefix code, and make our
* CrntCode equal to Pixel.
*/
if (EGifCompressOutput(GifFile, CrntCode) == GIF_ERROR) {
GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
CrntCode = Pixel;
/* If however the HashTable if full, we send a clear first and
* Clear the hash table.
*/
if (Private->RunningCode >= LZ_MAX_CODE) {
/* Time to do some clearance: */
if (EGifCompressOutput(GifFile, Private->ClearCode)
== GIF_ERROR) {
GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
Private->RunningCode = Private->EOFCode + 1;
Private->RunningBits = Private->BitsPerPixel + 1;
Private->MaxCode1 = 1 << Private->RunningBits;
_ClearHashTable(HashTable);
} else {
/* Put this unique key with its relative Code in hash table: */
_InsertHashTable(HashTable, NewKey, Private->RunningCode++);
}
}
}
/* Preserve the current state of the compression algorithm: */
Private->CrntCode = CrntCode;
if (Private->PixelCount == 0) {
/* We are done - output last Code and flush output buffers: */
if (EGifCompressOutput(GifFile, CrntCode) == GIF_ERROR) {
GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
if (EGifCompressOutput(GifFile, Private->EOFCode) == GIF_ERROR) {
GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
if (EGifCompressOutput(GifFile, FLUSH_OUTPUT) == GIF_ERROR) {
GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
}
return GIF_OK;
}
