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- /*
- * Copyright 2011 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
- #include "include/private/SkTo.h"
- #include "src/effects/SkPackBits.h"
- #include <cstring>
- size_t SkPackBits::ComputeMaxSize8(size_t srcSize) {
- // worst case is the number of 8bit values + 1 byte per (up to) 128 entries.
- return ((srcSize + 127) >> 7) + srcSize;
- }
- static uint8_t* flush_same8(uint8_t dst[], uint8_t value, size_t count) {
- while (count > 0) {
- size_t n = count > 128 ? 128 : count;
- *dst++ = (uint8_t)(n - 1);
- *dst++ = (uint8_t)value;
- count -= n;
- }
- return dst;
- }
- static uint8_t* flush_diff8(uint8_t* SK_RESTRICT dst,
- const uint8_t* SK_RESTRICT src, size_t count) {
- while (count > 0) {
- size_t n = count > 128 ? 128 : count;
- *dst++ = (uint8_t)(n + 127);
- memcpy(dst, src, n);
- src += n;
- dst += n;
- count -= n;
- }
- return dst;
- }
- size_t SkPackBits::Pack8(const uint8_t* SK_RESTRICT src, size_t srcSize,
- uint8_t* SK_RESTRICT dst, size_t dstSize) {
- if (dstSize < ComputeMaxSize8(srcSize)) {
- return 0;
- }
- uint8_t* const origDst = dst;
- const uint8_t* stop = src + srcSize;
- for (intptr_t count = stop - src; count > 0; count = stop - src) {
- if (1 == count) {
- *dst++ = 0;
- *dst++ = *src;
- break;
- }
- unsigned value = *src;
- const uint8_t* s = src + 1;
- if (*s == value) { // accumulate same values...
- do {
- s++;
- if (s == stop) {
- break;
- }
- } while (*s == value);
- dst = flush_same8(dst, value, SkToInt(s - src));
- } else { // accumulate diff values...
- do {
- if (++s == stop) {
- goto FLUSH_DIFF;
- }
- // only stop if we hit 3 in a row,
- // otherwise we get bigger than compuatemax
- } while (*s != s[-1] || s[-1] != s[-2]);
- s -= 2; // back up so we don't grab the "same" values that follow
- FLUSH_DIFF:
- dst = flush_diff8(dst, src, SkToInt(s - src));
- }
- src = s;
- }
- return dst - origDst;
- }
- int SkPackBits::Unpack8(const uint8_t* SK_RESTRICT src, size_t srcSize,
- uint8_t* SK_RESTRICT dst, size_t dstSize) {
- uint8_t* const origDst = dst;
- uint8_t* const endDst = dst + dstSize;
- const uint8_t* stop = src + srcSize;
- while (src < stop) {
- unsigned n = *src++;
- if (n <= 127) { // repeat count (n + 1)
- n += 1;
- if (dst > (endDst - n) || src >= stop) {
- return 0;
- }
- memset(dst, *src++, n);
- } else { // same count (n - 127)
- n -= 127;
- if (dst > (endDst - n) || src > (stop - n)) {
- return 0;
- }
- memcpy(dst, src, n);
- src += n;
- }
- dst += n;
- }
- SkASSERT(src <= stop);
- SkASSERT(dst <= endDst);
- return SkToInt(dst - origDst);
- }
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