Have hand-written decode_huffman_fast copy history
This makes it pass "wuffs test -skipgen std/deflate".
@@ -92,6 +92,7 @@ index c570e34..0d080d8 100644
#include <stddef.h>
#include <stdio.h> // For manual printf debugging.
+extern const char* wuffs_deflate__error__internal_error_inconsistent_distance;
extern const char*
wuffs_deflate__error__internal_error_inconsistent_huffman_decoder_state;
@@ -190,7 +191,7 @@ wuffs_base__status c_wuffs_deflate__decoder__decode_huffman_fast(
uint32_t n_bits = self->private_impl.f_n_bits;
// Initialize other local variables.
- uint8_t* pdst0 = pdst;
+ uint8_t* pdst_mark = a_dst.private_impl.mark ? a_dst.private_impl.mark : pdst;
uint32_t lmask = MASK(self->private_impl.f_n_huffs_bits[0]);
uint32_t dmask = MASK(self->private_impl.f_n_huffs_bits[1]);
@@ -321,12 +322,50 @@ outer_loop:
n_bits -= n;
}
- // TODO: look at a sliding window, not just output written so far to dst.
- if ((ptrdiff_t)(dist_minus_1 + 1) > (pdst - pdst0)) {
- status = wuffs_base__error__bad_argument;
+ // Copy from the history buffer, if necessary.
+ if ((ptrdiff_t)(dist_minus_1 + 1) > (pdst - pdst_mark)) {
+ // Set (hlen, hdist) to be the length-distance pair to copy from
+ // this.history, and (length, distance) to be the remaining
+ // length-distance pair to copy from args.dst.
+ uint32_t hlen = 0;
+ uint32_t hdist = ((dist_minus_1 + 1) - (pdst - pdst_mark));
+ if (length > hdist) {
+ length -= hdist;
+ hlen = hdist;
+ } else {
+ hlen = length;
+ length = 0;
+ }
+ if (self->private_impl.f_history_index < hdist) {
+ status = wuffs_deflate__error__bad_distance;
goto end;
}
+ // Copy up to the right edge of the f_history array.
+ uint32_t history_index =
+ (self->private_impl.f_history_index - hdist) & 0x7FFF;
+ uint32_t available = 0x8000 - history_index;
+ uint32_t n_copied = (hlen < available) ? hlen : available;
+ memmove(pdst, self->private_impl.f_history + history_index, n_copied);
+ pdst += n_copied;
+
+ // Copy from the left edge of the f_history array.
+ if (hlen > n_copied) {
+ hlen -= n_copied;
+ memmove(pdst, self->private_impl.f_history, hlen);
+ pdst += hlen;
+ }
+
+ if (length == 0) {
+ goto outer_loop;
+ }
+
+ if ((ptrdiff_t)(dist_minus_1 + 1) > (pdst - pdst_mark)) {
+ status = wuffs_deflate__error__internal_error_inconsistent_distance;
+ goto end;
+ }
+ }
+
uint8_t* pback = pdst - (dist_minus_1 + 1);
#if defined(WUFFS_DEFLATE__HAVE_64_BIT_UNALIGNED_LITTLE_ENDIAN_LOADS)
