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lzw: Add function for decoding multiple LZW codes at a time.

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This commit is contained in:
Michael Drake 2021-04-04 22:27:52 +01:00 committed by Michael Drake
parent ed3363b899
commit 5426e9b81a
2 changed files with 41 additions and 0 deletions
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26
libvips/foreign/libnsgif/lzw.c
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@ -437,3 +437,29 @@ lzw_result lzw_decode(struct lzw_ctx *ctx,
return lzw__decode(ctx, ctx->stack_base, sizeof(ctx->stack_base),
lzw__write_pixels, used);
}
/* Exported function, documented in lzw.h */
lzw_result lzw_decode_continuous(struct lzw_ctx *ctx,
const uint8_t ** const data,
uint32_t *restrict used)
{
*used = 0;
*data = ctx->stack_base;
if (ctx->output_left != 0) {
*used += lzw__write_pixels(ctx,
ctx->stack_base, sizeof(ctx->stack_base), *used,
ctx->output_code, ctx->output_left);
}
while (*used != sizeof(ctx->stack_base)) {
lzw_result res = lzw__decode(ctx,
ctx->stack_base, sizeof(ctx->stack_base),
lzw__write_pixels, used);
if (res != LZW_OK) {
return res;
}
}
return LZW_OK;
}

15
libvips/foreign/libnsgif/lzw.h
View File

@ -91,4 +91,19 @@ lzw_result lzw_decode(struct lzw_ctx *ctx,
const uint8_t *restrict *const restrict data,
uint32_t *restrict used);
/**
* Read input codes until end of lzw context owned output buffer.
*
* Ensure anything in output is used before calling this, as anything
* on the there before this call will be trampled.
*
* \param[in] ctx LZW reading context, updated.
* \param[out] data Returns pointer to array of output values.
* \param[out] used Returns the number of values written to data.
* \return LZW_OK on success, or appropriate error code otherwise.
*/
lzw_result lzw_decode_continuous(struct lzw_ctx *ctx,
const uint8_t ** const data,
uint32_t *restrict used);
#endif