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/*
* uzlib - tiny deflate/inflate library (deflate, gzip, zlib)
*
* Copyright (c) 2003 by Joergen Ibsen / Jibz
* All Rights Reserved
*
* http://www.ibsensoftware.com/
*
* Copyright (c) 2014-2018 by Paul Sokolovsky
*
* Optimised for MicroPython:
* Copyright (c) 2023 by Jim Mussared
*
* 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 "uzlib.h"
#define FTEXT 1
#define FHCRC 2
#define FEXTRA 4
#define FNAME 8
#define FCOMMENT 16
void tinf_skip_bytes(uzlib_uncomp_t *d, int num);
uint16_t tinf_get_uint16(uzlib_uncomp_t *d);
void tinf_skip_bytes(uzlib_uncomp_t *d, int num)
{
while (num--) uzlib_get_byte(d);
}
uint16_t tinf_get_uint16(uzlib_uncomp_t *d)
{
unsigned int v = uzlib_get_byte(d);
v = (uzlib_get_byte(d) << 8) | v;
return v;
}
int uzlib_parse_zlib_gzip_header(uzlib_uncomp_t *d, int *wbits)
{
/* -- check format -- */
unsigned char cmf = uzlib_get_byte(d);
unsigned char flg = uzlib_get_byte(d);
/* check for gzip id bytes */
if (cmf == 0x1f && flg == 0x8b) {
/* check method is deflate */
if (uzlib_get_byte(d) != 8) return UZLIB_DATA_ERROR;
/* get flag byte */
flg = uzlib_get_byte(d);
/* check that reserved bits are zero */
if (flg & 0xe0) return UZLIB_DATA_ERROR;
/* -- find start of compressed data -- */
/* skip rest of base header of 10 bytes */
tinf_skip_bytes(d, 6);
/* skip extra data if present */
if (flg & FEXTRA)
{
unsigned int xlen = tinf_get_uint16(d);
tinf_skip_bytes(d, xlen);
}
/* skip file name if present */
if (flg & FNAME) { while (uzlib_get_byte(d)); }
/* skip file comment if present */
if (flg & FCOMMENT) { while (uzlib_get_byte(d)); }
/* check header crc if present */
if (flg & FHCRC)
{
/*unsigned int hcrc =*/ tinf_get_uint16(d);
// TODO: Check!
// if (hcrc != (tinf_crc32(src, start - src) & 0x0000ffff))
// return UZLIB_DATA_ERROR;
}
/* initialize for crc32 checksum */
d->checksum_type = UZLIB_CHKSUM_CRC;
d->checksum = ~0;
/* gzip does not include the window size in the header, as it is expected that a
compressor will use wbits=15 (32kiB).*/
*wbits = 15;
return UZLIB_HEADER_GZIP;
} else {
/* check checksum */
if ((256*cmf + flg) % 31) return UZLIB_DATA_ERROR;
/* check method is deflate */
if ((cmf & 0x0f) != 8) return UZLIB_DATA_ERROR;
/* check window size is valid */
if ((cmf >> 4) > 7) return UZLIB_DATA_ERROR;
/* check there is no preset dictionary */
if (flg & 0x20) return UZLIB_DATA_ERROR;
/* initialize for adler32 checksum */
d->checksum_type = UZLIB_CHKSUM_ADLER;
d->checksum = 1;
*wbits = (cmf >> 4) + 8;
return UZLIB_HEADER_ZLIB;
}
}
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