788 ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
789
790 bits[codesize[i]]++;
791 }
792 }
793
794 /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
795 * Huffman procedure assigned any such lengths, we must adjust the coding.
796 * Here is what the JPEG spec says about how this next bit works:
797 * Since symbols are paired for the longest Huffman code, the symbols are
798 * removed from this length category two at a time. The prefix for the pair
799 * (which is one bit shorter) is allocated to one of the pair; then,
800 * skipping the BITS entry for that prefix length, a code word from the next
801 * shortest nonzero BITS entry is converted into a prefix for two code words
802 * one bit longer.
803 */
804
805 for (i = MAX_CLEN; i > 16; i--) {
806 while (bits[i] > 0) {
807 j = i - 2; /* find length of new prefix to be used */
808 while (bits[j] == 0)
809 j--;
810
811 bits[i] -= 2; /* remove two symbols */
812 bits[i-1]++; /* one goes in this length */
813 bits[j+1] += 2; /* two new symbols in this length */
814 bits[j]--; /* symbol of this length is now a prefix */
815 }
816 }
817
818 /* Remove the count for the pseudo-symbol 256 from the largest codelength */
819 while (bits[i] == 0) /* find largest codelength still in use */
820 i--;
821 bits[i]--;
822
823 /* Return final symbol counts (only for lengths 0..16) */
824 MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits));
825
826 /* Return a list of the symbols sorted by code length */
827 /* It's not real clear to me why we don't need to consider the codelength
828 * changes made above, but the JPEG spec seems to think this works.
829 */
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788 ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
789
790 bits[codesize[i]]++;
791 }
792 }
793
794 /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
795 * Huffman procedure assigned any such lengths, we must adjust the coding.
796 * Here is what the JPEG spec says about how this next bit works:
797 * Since symbols are paired for the longest Huffman code, the symbols are
798 * removed from this length category two at a time. The prefix for the pair
799 * (which is one bit shorter) is allocated to one of the pair; then,
800 * skipping the BITS entry for that prefix length, a code word from the next
801 * shortest nonzero BITS entry is converted into a prefix for two code words
802 * one bit longer.
803 */
804
805 for (i = MAX_CLEN; i > 16; i--) {
806 while (bits[i] > 0) {
807 j = i - 2; /* find length of new prefix to be used */
808 while (bits[j] == 0) {
809 if (j == 0)
810 ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
811 j--;
812 }
813
814 bits[i] -= 2; /* remove two symbols */
815 bits[i-1]++; /* one goes in this length */
816 bits[j+1] += 2; /* two new symbols in this length */
817 bits[j]--; /* symbol of this length is now a prefix */
818 }
819 }
820
821 /* Remove the count for the pseudo-symbol 256 from the largest codelength */
822 while (bits[i] == 0) /* find largest codelength still in use */
823 i--;
824 bits[i]--;
825
826 /* Return final symbol counts (only for lengths 0..16) */
827 MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits));
828
829 /* Return a list of the symbols sorted by code length */
830 /* It's not real clear to me why we don't need to consider the codelength
831 * changes made above, but the JPEG spec seems to think this works.
832 */
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