1 Bug 1050342. Fix a case where the fast huffman decoder in libjpeg-turbo can produce different results depending on how data is fed to it.
3 This change comes from the blink repo https://codereview.appspot.com/229430043/ and is unlikely to be accepted upstream into libjpeg-turbo.
5 diff --git jdhuff.c jdhuff.c
8 @@ -674,9 +674,9 @@ decode_mcu_fast(j_decompress_ptr cinfo,
9 d_derived_tbl *dctbl = entropy->dc_cur_tbls[blkn];
10 d_derived_tbl *actbl = entropy->ac_cur_tbls[blkn];
11 register int s, k, r, l;
13 - HUFF_DECODE_FAST(s, l, dctbl);
14 + HUFF_DECODE_FAST(s, l, dctbl, slow_decode_mcu);
18 s = HUFF_EXTEND(r, s);
19 @@ -692,9 +692,9 @@ decode_mcu_fast(j_decompress_ptr cinfo,
21 if (entropy->ac_needed[blkn] && block) {
23 for (k = 1; k < DCTSIZE2; k++) {
24 - HUFF_DECODE_FAST(s, l, actbl);
25 + HUFF_DECODE_FAST(s, l, actbl, slow_decode_mcu);
30 @@ -711,9 +711,9 @@ decode_mcu_fast(j_decompress_ptr cinfo,
34 for (k = 1; k < DCTSIZE2; k++) {
35 - HUFF_DECODE_FAST(s, l, actbl);
36 + HUFF_DECODE_FAST(s, l, actbl, slow_decode_mcu);
41 @@ -728,8 +728,9 @@ decode_mcu_fast(j_decompress_ptr cinfo,
45 if (cinfo->unread_marker != 0) {
47 cinfo->unread_marker = 0;
51 diff --git jdhuff.h jdhuff.h
54 @@ -210,9 +210,9 @@ slowlabel: \
55 get_buffer = state.get_buffer; bits_left = state.bits_left; \
59 -#define HUFF_DECODE_FAST(s, nb, htbl) \
60 +#define HUFF_DECODE_FAST(s, nb, htbl, slowlabel) \
61 FILL_BIT_BUFFER_FAST; \
62 s = PEEK_BITS(HUFF_LOOKAHEAD); \
63 s = htbl->lookup[s]; \
64 nb = s >> HUFF_LOOKAHEAD; \
65 @@ -227,9 +227,11 @@ slowlabel: \
70 - s = htbl->pub->huffval[(int)(s + htbl->valoffset[nb]) & 0xFF]; \
73 + s = htbl->pub->huffval[ (int) (s + htbl->valoffset[nb]) ]; \
76 /* Out-of-line case for Huffman code fetching */
77 EXTERN(int) jpeg_huff_decode(bitread_working_state *state,