112 lines
3.0 KiB
C
112 lines
3.0 KiB
C
/* SPDX-License-Identifier: BSD-2-Clause */
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/* Contiguous-buffer LZ4 backend for EROFS FreeBSD. */
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/endian.h>
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#include "compress.h"
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#define EROFS_LZ4_TOKEN_LITERAL_SHIFT 4
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#define EROFS_LZ4_TOKEN_MATCH_MASK 0x0f
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#define EROFS_LZ4_MAX_RUN 15
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#define EROFS_LZ4_EXT_SENTINEL 255
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#define EROFS_LZ4_MIN_MATCH 4
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#define EROFS_LZ4_OFFSET_BYTES 2
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static int
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lz4_finish(const uint8_t *ip, const uint8_t *iend, int partial)
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{
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if (partial)
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return (0);
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while (ip < iend) {
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if (*ip++ != 0)
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return (EINTEGRITY);
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}
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return (0);
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}
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int
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z_erofs_lz4_buffer_decompress(const struct z_erofs_decompress_req *rq)
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{
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const uint8_t *input;
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uint8_t *output;
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unsigned int token;
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size_t length, copylen;
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size_t offset;
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size_t input_pos, output_pos;
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if (rq == NULL || (rq->inputsize != 0 && rq->in == NULL) ||
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(rq->outputsize != 0 && rq->out == NULL))
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return (EINTEGRITY);
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if (rq->inputsize == 0)
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return (rq->outputsize == 0 ? 0 : EINTEGRITY);
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/*
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* A length grows by at most 255 per input byte, so it cannot reach
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* SIZE_MAX however long the input is.
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*/
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input = rq->in;
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output = rq->out;
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input_pos = 0;
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output_pos = 0;
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while (input_pos < rq->inputsize) {
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token = input[input_pos++];
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length = token >> EROFS_LZ4_TOKEN_LITERAL_SHIFT;
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if (length == EROFS_LZ4_MAX_RUN) {
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unsigned int value;
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do {
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if (input_pos >= rq->inputsize)
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return (EINTEGRITY);
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value = input[input_pos++];
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length += value;
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} while (value == EROFS_LZ4_EXT_SENTINEL);
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}
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if (length > rq->inputsize - input_pos)
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return (EINTEGRITY);
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if (!rq->partial_decoding &&
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length > rq->outputsize - output_pos)
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return (EINTEGRITY);
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copylen = MIN(length, rq->outputsize - output_pos);
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memcpy(output + output_pos, input + input_pos, copylen);
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input_pos += length;
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output_pos += copylen;
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if (output_pos == rq->outputsize)
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return (lz4_finish(input + input_pos,
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input + rq->inputsize, rq->partial_decoding));
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if (input_pos >= rq->inputsize)
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break;
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if (EROFS_LZ4_OFFSET_BYTES > rq->inputsize - input_pos)
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return (EINTEGRITY);
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offset = le16dec(input + input_pos);
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input_pos += EROFS_LZ4_OFFSET_BYTES;
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if (offset == 0 || offset > output_pos)
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return (EINTEGRITY);
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length = token & EROFS_LZ4_TOKEN_MATCH_MASK;
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if (length == EROFS_LZ4_MAX_RUN) {
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unsigned int value;
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do {
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if (input_pos >= rq->inputsize)
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return (EINTEGRITY);
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value = input[input_pos++];
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length += value;
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} while (value == EROFS_LZ4_EXT_SENTINEL);
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}
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length += EROFS_LZ4_MIN_MATCH;
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if (!rq->partial_decoding &&
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length > rq->outputsize - output_pos)
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return (EINTEGRITY);
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copylen = MIN(length, rq->outputsize - output_pos);
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while (copylen-- != 0) {
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output[output_pos] = output[output_pos - offset];
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++output_pos;
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}
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if (output_pos == rq->outputsize)
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return (lz4_finish(input + input_pos,
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input + rq->inputsize, rq->partial_decoding));
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}
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return (output_pos == rq->outputsize ?
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lz4_finish(input + input_pos, input + rq->inputsize,
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rq->partial_decoding) : EINTEGRITY);
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}
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