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stb_image: Make 'fast' table contain code size and value directly.

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This commit is contained in:
Fabian Giesen 2014-12-13 18:48:37 -08:00
parent 007de5eb6e
commit 3d6dccf0c4
1 changed files with 6 additions and 5 deletions
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11
stb_image.h
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@ -2036,7 +2036,7 @@ static int stbi__zbuild_huffman(stbi__zhuffman *z, stbi_uc *sizelist, int num)
// DEFLATE spec for generating codes // DEFLATE spec for generating codes
memset(sizes, 0, sizeof(sizes)); memset(sizes, 0, sizeof(sizes));
memset(z->fast, 255, sizeof(z->fast)); memset(z->fast, 0, sizeof(z->fast));
for (i=0; i < num; ++i) for (i=0; i < num; ++i)
++sizes[sizelist[i]]; ++sizes[sizelist[i]];
sizes[0] = 0; sizes[0] = 0;
@ -2059,12 +2059,13 @@ static int stbi__zbuild_huffman(stbi__zhuffman *z, stbi_uc *sizelist, int num)
int s = sizelist[i]; int s = sizelist[i];
if (s) { if (s) {
int c = next_code[s] - z->firstcode[s] + z->firstsymbol[s]; int c = next_code[s] - z->firstcode[s] + z->firstsymbol[s];
stbi__uint16 fastv = (stbi__uint16) ((s << 9) | i);
z->size [c] = (stbi_uc ) s; z->size [c] = (stbi_uc ) s;
z->value[c] = (stbi__uint16) i; z->value[c] = (stbi__uint16) i;
if (s <= STBI__ZFAST_BITS) { if (s <= STBI__ZFAST_BITS) {
int k = stbi__bit_reverse(next_code[s],s); int k = stbi__bit_reverse(next_code[s],s);
while (k < (1 << STBI__ZFAST_BITS)) { while (k < (1 << STBI__ZFAST_BITS)) {
z->fast[k] = (stbi__uint16) c; z->fast[k] = fastv;
k += (1 << s); k += (1 << s);
} }
} }
@ -2142,11 +2143,11 @@ stbi_inline static int stbi__zhuffman_decode(stbi__zbuf *a, stbi__zhuffman *z)
int b,s; int b,s;
if (a->num_bits < 16) stbi__fill_bits(a); if (a->num_bits < 16) stbi__fill_bits(a);
b = z->fast[a->code_buffer & STBI__ZFAST_MASK]; b = z->fast[a->code_buffer & STBI__ZFAST_MASK];
if (b < 0xffff) { if (b) {
s = z->size[b]; s = b >> 9;
a->code_buffer >>= s; a->code_buffer >>= s;
a->num_bits -= s; a->num_bits -= s;
return z->value[b]; return b & 511;
} }
return stbi__zhuffman_decode_slowpath(a, z); return stbi__zhuffman_decode_slowpath(a, z);
} }