aboutsummaryrefslogtreecommitdiff
path: root/deps/libchdr/huffman.c
diff options
context:
space:
mode:
Diffstat (limited to 'deps/libchdr/huffman.c')
-rw-r--r--deps/libchdr/huffman.c64
1 files changed, 39 insertions, 25 deletions
diff --git a/deps/libchdr/huffman.c b/deps/libchdr/huffman.c
index f48210e..a58b6be 100644
--- a/deps/libchdr/huffman.c
+++ b/deps/libchdr/huffman.c
@@ -125,11 +125,13 @@
struct huffman_decoder* create_huffman_decoder(int numcodes, int maxbits)
{
+ struct huffman_decoder* decoder = NULL;
+
/* limit to 24 bits */
if (maxbits > 24)
return NULL;
- struct huffman_decoder* decoder = (struct huffman_decoder*)malloc(sizeof(struct huffman_decoder));
+ decoder = (struct huffman_decoder*)malloc(sizeof(struct huffman_decoder));
decoder->numcodes = numcodes;
decoder->maxbits = maxbits;
decoder->lookup = (lookup_value*)malloc(sizeof(lookup_value) * (1 << maxbits));
@@ -167,8 +169,10 @@ uint32_t huffman_decode_one(struct huffman_decoder* decoder, struct bitstream* b
enum huffman_error huffman_import_tree_rle(struct huffman_decoder* decoder, struct bitstream* bitbuf)
{
+ int numbits, curnode;
+ enum huffman_error error;
+
/* bits per entry depends on the maxbits */
- int numbits;
if (decoder->maxbits >= 16)
numbits = 5;
else if (decoder->maxbits >= 8)
@@ -177,7 +181,6 @@ enum huffman_error huffman_import_tree_rle(struct huffman_decoder* decoder, stru
numbits = 3;
/* loop until we read all the nodes */
- int curnode;
for (curnode = 0; curnode < decoder->numcodes; )
{
/* a non-one value is just raw */
@@ -208,7 +211,7 @@ enum huffman_error huffman_import_tree_rle(struct huffman_decoder* decoder, stru
return HUFFERR_INVALID_DATA;
/* assign canonical codes for all nodes based on their code lengths */
- enum huffman_error error = huffman_assign_canonical_codes(decoder);
+ error = huffman_assign_canonical_codes(decoder);
if (error != HUFFERR_NONE)
return error;
@@ -228,12 +231,19 @@ enum huffman_error huffman_import_tree_rle(struct huffman_decoder* decoder, stru
enum huffman_error huffman_import_tree_huffman(struct huffman_decoder* decoder, struct bitstream* bitbuf)
{
+ int start;
+ int last = 0;
+ int count = 0;
+ int index;
+ int curcode;
+ uint8_t rlefullbits = 0;
+ uint32_t temp;
+ enum huffman_error error;
/* start by parsing the lengths for the small tree */
struct huffman_decoder* smallhuff = create_huffman_decoder(24, 6);
smallhuff->huffnode[0].numbits = bitstream_read(bitbuf, 3);
- int start = bitstream_read(bitbuf, 3) + 1;
- int count = 0;
- for (int index = 1; index < 24; index++)
+ start = bitstream_read(bitbuf, 3) + 1;
+ for (index = 1; index < 24; index++)
{
if (index < start || count == 7)
smallhuff->huffnode[index].numbits = 0;
@@ -245,20 +255,17 @@ enum huffman_error huffman_import_tree_huffman(struct huffman_decoder* decoder,
}
/* then regenerate the tree */
- enum huffman_error error = huffman_assign_canonical_codes(smallhuff);
+ error = huffman_assign_canonical_codes(smallhuff);
if (error != HUFFERR_NONE)
return error;
huffman_build_lookup_table(smallhuff);
/* determine the maximum length of an RLE count */
- uint32_t temp = decoder->numcodes - 9;
- uint8_t rlefullbits = 0;
+ temp = decoder->numcodes - 9;
while (temp != 0)
temp >>= 1, rlefullbits++;
/* now process the rest of the data */
- int last = 0;
- int curcode;
for (curcode = 0; curcode < decoder->numcodes; )
{
int value = huffman_decode_one(smallhuff, bitbuf);
@@ -298,14 +305,17 @@ enum huffman_error huffman_import_tree_huffman(struct huffman_decoder* decoder,
enum huffman_error huffman_compute_tree_from_histo(struct huffman_decoder* decoder)
{
+ int i;
+ uint32_t lowerweight;
+ uint32_t upperweight;
/* compute the number of data items in the histogram */
uint32_t sdatacount = 0;
- for (int i = 0; i < decoder->numcodes; i++)
+ for (i = 0; i < decoder->numcodes; i++)
sdatacount += decoder->datahisto[i];
/* binary search to achieve the optimum encoding */
- uint32_t lowerweight = 0;
- uint32_t upperweight = sdatacount * 2;
+ lowerweight = 0;
+ upperweight = sdatacount * 2;
while (1)
{
/* build a tree using the current weight */
@@ -359,11 +369,14 @@ static int huffman_tree_node_compare(const void *item1, const void *item2)
int huffman_build_tree(struct huffman_decoder* decoder, uint32_t totaldata, uint32_t totalweight)
{
+ int curcode;
+ int nextalloc;
+ int listitems = 0;
+ int maxbits = 0;
/* make a list of all non-zero nodes */
struct node_t** list = (struct node_t**)malloc(sizeof(struct node_t*) * decoder->numcodes * 2);
- int listitems = 0;
memset(decoder->huffnode, 0, decoder->numcodes * sizeof(decoder->huffnode[0]));
- for (int curcode = 0; curcode < decoder->numcodes; curcode++)
+ for (curcode = 0; curcode < decoder->numcodes; curcode++)
if (decoder->datahisto[curcode] != 0)
{
list[listitems++] = &decoder->huffnode[curcode];
@@ -395,7 +408,7 @@ int huffman_build_tree(struct huffman_decoder* decoder, uint32_t totaldata, uint
#endif
/* now build the tree */
- int nextalloc = decoder->numcodes;
+ nextalloc = decoder->numcodes;
while (listitems > 1)
{
/* remove lowest two items */
@@ -421,8 +434,7 @@ int huffman_build_tree(struct huffman_decoder* decoder, uint32_t totaldata, uint
}
/* compute the number of bits in each code, and fill in another histogram */
- int maxbits = 0;
- for (int curcode = 0; curcode < decoder->numcodes; curcode++)
+ for (curcode = 0; curcode < decoder->numcodes; curcode++)
{
struct node_t* node = &decoder->huffnode[curcode];
node->numbits = 0;
@@ -453,9 +465,11 @@ int huffman_build_tree(struct huffman_decoder* decoder, uint32_t totaldata, uint
enum huffman_error huffman_assign_canonical_codes(struct huffman_decoder* decoder)
{
+ int curcode, codelen;
+ uint32_t curstart = 0;
/* build up a histogram of bit lengths */
uint32_t bithisto[33] = { 0 };
- for (int curcode = 0; curcode < decoder->numcodes; curcode++)
+ for (curcode = 0; curcode < decoder->numcodes; curcode++)
{
struct node_t* node = &decoder->huffnode[curcode];
if (node->numbits > decoder->maxbits)
@@ -465,8 +479,7 @@ enum huffman_error huffman_assign_canonical_codes(struct huffman_decoder* decode
}
/* for each code length, determine the starting code number */
- uint32_t curstart = 0;
- for (int codelen = 32; codelen > 0; codelen--)
+ for (codelen = 32; codelen > 0; codelen--)
{
uint32_t nextstart = (curstart + bithisto[codelen]) >> 1;
if (codelen != 1 && nextstart * 2 != (curstart + bithisto[codelen]))
@@ -476,7 +489,7 @@ enum huffman_error huffman_assign_canonical_codes(struct huffman_decoder* decode
}
/* now assign canonical codes */
- for (int curcode = 0; curcode < decoder->numcodes; curcode++)
+ for (curcode = 0; curcode < decoder->numcodes; curcode++)
{
struct node_t* node = &decoder->huffnode[curcode];
if (node->numbits > 0)
@@ -493,8 +506,9 @@ enum huffman_error huffman_assign_canonical_codes(struct huffman_decoder* decode
void huffman_build_lookup_table(struct huffman_decoder* decoder)
{
+ int curcode;
/* iterate over all codes */
- for (int curcode = 0; curcode < decoder->numcodes; curcode++)
+ for (curcode = 0; curcode < decoder->numcodes; curcode++)
{
/* process all nodes which have non-zero bits */
struct node_t* node = &decoder->huffnode[curcode];
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-01 19:49:19 +0000