105 lines
2.5 KiB
C
105 lines
2.5 KiB
C
/* SPDX-License-Identifier: BSD-2-Clause */
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/* Minimal LZ4 decompressor for EROFS FreeBSD */
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#include <sys/param.h>
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#include <sys/endian.h>
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#include <sys/systm.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_decompress(const struct z_erofs_decompress_req *rq)
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{
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const uint8_t *ip, *iend;
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uint8_t *op, *oend;
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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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ip = rq->in;
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iend = ip + rq->inputsize;
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op = rq->out;
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oend = op + rq->outputsize;
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if (iend < ip || oend < op)
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return (EINTEGRITY);
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while (ip < iend) {
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token = *ip++;
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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 (ip >= iend)
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return (EINTEGRITY);
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value = *ip++;
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if (length > SIZE_MAX - value)
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return (EINTEGRITY);
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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 > (size_t)(iend - ip))
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return (EINTEGRITY);
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if (!rq->partial_decoding && length > (size_t)(oend - op))
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return (EINTEGRITY);
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copylen = MIN(length, (size_t)(oend - op));
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memcpy(op, ip, copylen);
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ip += length;
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op += copylen;
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if (op == oend)
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return (lz4_finish(ip, iend, rq->partial_decoding));
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if (ip >= iend)
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break;
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if (ip + EROFS_LZ4_OFFSET_BYTES > iend)
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return (EINTEGRITY);
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offset = le16dec(ip);
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ip += EROFS_LZ4_OFFSET_BYTES;
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if (offset == 0 || offset >
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(size_t)(op - (uint8_t *)rq->out))
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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 (ip >= iend)
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return (EINTEGRITY);
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value = *ip++;
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if (length > SIZE_MAX - value)
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return (EINTEGRITY);
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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 > SIZE_MAX - EROFS_LZ4_MIN_MATCH)
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return (EINTEGRITY);
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length += EROFS_LZ4_MIN_MATCH;
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if (!rq->partial_decoding && length > (size_t)(oend - op))
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return (EINTEGRITY);
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copylen = MIN(length, (size_t)(oend - op));
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while (copylen-- != 0) {
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*op = *(op - offset);
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++op;
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}
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if (op == oend)
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return (lz4_finish(ip, iend, rq->partial_decoding));
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}
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return (op == oend ?
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lz4_finish(ip, iend, rq->partial_decoding) : EINTEGRITY);
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}
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