limine/common/compress/gzip.c

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/*
* originally from tinfgzip - tiny gzip decompressor
*
* Copyright (c) 2003-2019 Joergen Ibsen
* Copyright (c) 2023 mintsuki and contributors to the Limine project
*
* This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any damages
* arising from the use of this software.
*
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
*
* 1. The origin of this software must not be misrepresented; you must
* not claim that you wrote the original software. If you use this
* software in a product, an acknowledgment in the product
* documentation would be appreciated but is not required.
*
* 2. Altered source versions must be plainly marked as such, and must
* not be misrepresented as being the original software.
*
* 3. This notice may not be removed or altered from any source
* distribution.
*/
#include <stdint.h>
#include <stb/stb_image.h>
typedef enum {
FTEXT = 1,
FHCRC = 2,
FEXTRA = 4,
FNAME = 8,
FCOMMENT = 16
} gzip_flag;
void *gzip_uncompress(const void *source, uint64_t sourceLen, uint64_t *outsize) {
const uint8_t *src = (const uint8_t *) source;
const uint8_t *start;
int res;
uint8_t flg;
/* -- Check header -- */
/* Check room for at least 10 byte header and 8 byte trailer */
if (sourceLen < 18) {
return NULL;
}
/* Check id bytes */
if (src[0] != 0x1F || src[1] != 0x8B) {
return NULL;
}
/* Check method is deflate */
if (src[2] != 8) {
return NULL;
}
/* Get flag byte */
flg = src[3];
/* Check that reserved bits are zero */
if (flg & 0xE0) {
return NULL;
}
/* -- Find start of compressed data -- */
/* Skip base header of 10 bytes */
start = src + 10;
/* Skip extra data if present */
if (flg & FEXTRA) {
uint64_t xlen = *((uint16_t *)start);
if (xlen > sourceLen - 12) {
return NULL;
}
start += xlen + 2;
}
/* Skip file name if present */
if (flg & FNAME) {
do {
if (((uint64_t)(start - src)) >= sourceLen) {
return NULL;
}
} while (*start++);
}
/* Skip file comment if present */
if (flg & FCOMMENT) {
do {
if (((uint64_t)(start - src)) >= sourceLen) {
return NULL;
}
} while (*start++);
}
if (flg & FHCRC) {
start += 2;
}
/* -- Get decompressed length -- */
uint32_t dlen = *((uint32_t *)&src[sourceLen - 4]);
/* -- Decompress data -- */
if ((src + sourceLen) - start < 8) {
return NULL;
}
void *buf = ext_mem_alloc(dlen);
res = stbi_zlib_decode_noheader_buffer(buf, dlen, (const char *)start, (src + sourceLen) - start - 8);
if (res == -1) {
pmm_free(buf, dlen);
return NULL;
}
*outsize = (uint64_t)dlen;
return buf;
}