/**
* @attention 本注释得到了"核高基"科技重大专项2012年课题“开源操作系统内核分析和安全性评估
*（课题编号：2012ZX01039-004）”的资助。
*
* @copyright 注释添加单位：清华大学——03任务（Linux内核相关通用基础软件包分析）承担单位
*
* @author 注释添加人员：谢文学
*
* @date 注释添加日期：2013年5月10日
*
* @note 注释详细内容:
*
* 本函数实现使用gunzip的解压缩读入的功能。
*/
int
gunzip_read (char *buf, int len)
{
int ret = 0;
compressed_file = 0;
gunzip_swap_values ();
/*
* Now "gzip_*" values refer to the uncompressed data.
*/
/* do we reset decompression to the beginning of the file? */
if (saved_filepos > gzip_filepos + WSIZE)
initialize_tables ();
/*
* This loop operates upon uncompressed data only. The only
* special thing it does is to make sure the decompression
* window is within the range of data it needs.
*/
while (len > 0 && !errnum)
{
register int size;
register char *srcaddr;
while (gzip_filepos >= saved_filepos)
inflate_window ();
srcaddr = (char *) ((gzip_filepos & (WSIZE - 1)) + slide);
size = saved_filepos - gzip_filepos;
if (size > len)
size = len;
memmove (buf, srcaddr, size);
buf += size;
len -= size;
gzip_filepos += size;
ret += size;
}
compressed_file = 1;
gunzip_swap_values ();
/*
* Now "gzip_*" values refer to the compressed data.
*/
if (errnum)
ret = 0;
return ret;
}
int
gunzip_test_header (void)
{
unsigned char buf[10];
/* "compressed_file" is already reset to zero by this point */
/*
* This checks if the file is gzipped. If a problem occurs here
* (other than a real error with the disk) then we don't think it
* is a compressed file, and simply mark it as such.
*/
if (no_decompression
|| grub_read (buf, 10) != 10
|| ((*((unsigned short *) buf) != GZIP_HDR_LE)
&& (*((unsigned short *) buf) != OLD_GZIP_HDR_LE)))
{
filepos = 0;
return ! errnum;
}
/*
* This does consistency checking on the header data. If a
* problem occurs from here on, then we have corrupt or otherwise
* bad data, and the error should be reported to the user.
*/
if (buf[2] != DEFLATED
|| (buf[3] & UNSUPP_FLAGS)
|| ((buf[3] & EXTRA_FIELD)
&& (grub_read (buf, 2) != 2
|| bad_field (*((unsigned short *) buf))))
|| ((buf[3] & ORIG_NAME) && bad_field (-1))
|| ((buf[3] & COMMENT) && bad_field (-1)))
{
if (! errnum)
errnum = ERR_BAD_GZIP_HEADER;
return 0;
}
gzip_data_offset = filepos;
filepos = filemax - 8;
if (grub_read (buf, 8) != 8)
{
if (! errnum)
errnum = ERR_BAD_GZIP_HEADER;
return 0;
}
gzip_crc = *((unsigned long *) buf);
gzip_fsmax = gzip_filemax = *((unsigned long *) (buf + 4));
initialize_tables ();
compressed_file = 1;
gunzip_swap_values ();
/*
* Now "gzip_*" values refer to the compressed data.
*/
filepos = 0;
return 1;
}
int
gunzip_test_header (void)
{
unsigned char buf[10];
/* "compressed_file" is already reset to zero by this point */
/*
* This checks if the file is gzipped. If a problem occurs here
* (other than a real error with the disk) then we don't think it
* is a compressed file, and simply mark it as such.
*/
if (no_decompression
|| grub_read (buf, 10) != 10
|| ((*((unsigned short *) buf) != GZIP_HDR_LE)
&& (*((unsigned short *) buf) != OLD_GZIP_HDR_LE)))
{
filepos = 0;
return ! errnum;
}
/*
* This does consistency checking on the header data. If a
* problem occurs from here on, then we have corrupt or otherwise
* bad data, and the error should be reported to the user.
*/
if (buf[2] != DEFLATED
|| (buf[3] & UNSUPP_FLAGS)
|| ((buf[3] & EXTRA_FIELD)
&& (grub_read (buf, 2) != 2
|| bad_field (*((unsigned short *) buf))))
|| ((buf[3] & ORIG_NAME) && bad_field (-1))
|| ((buf[3] & COMMENT) && bad_field (-1)))
{
if (! errnum)
errnum = ERR_BAD_GZIP_HEADER;
return 0;
}
gzip_data_offset = filepos;
/* We could read the last 8 bytes of the file to get the uncompressed
* size. Doing so under tftp would cause the file to be downloaded
* twice, which can be problem with large files. So we set it to
* MAXINT and correct it later when we get to the end of the file
* in get_byte().
*/
gzip_fsmax = gzip_filemax = MAXINT;
initialize_tables ();
compressed_file = 1;
gunzip_swap_values ();
/*
* Now "gzip_*" values refer to the compressed data.
*/
filepos = 0;
crc = (ulg)0xffffffffUL;
return 1;
}
int
gunzip_read (char *buf, int len)
{
int ret = 0;
int check_crc;
ulg crc_value = 0xffffffffUL;
compressed_file = 0;
gunzip_swap_values ();
/*
* Now "gzip_*" values refer to the uncompressed data.
*/
/* do we reset decompression to the beginning of the file? */
if (saved_filepos > gzip_filepos + WSIZE)
initialize_tables ();
/* perform CRC check only if reading the entire file */
check_crc = (saved_filepos == 0 && len == MAXINT);
/*
* This loop operates upon uncompressed data only. The only
* special thing it does is to make sure the decompression
* window is within the range of data it needs.
*/
while (len > 0 && !errnum)
{
register int size;
register char *srcaddr;
while (gzip_filepos >= saved_filepos && !errnum)
inflate_window ();
if (errnum)
break;
/* We could have started with an unknown gzip_filemax (MAXINT)
* which has been updated in get_byte(). If so, update len
* to avoid reading beyond the end.
*/
if (len > (gzip_filemax - gzip_filepos)) {
len = gzip_filemax - gzip_filepos;
if (len < 0) {
errnum = ERR_BAD_GZIP_DATA;
break;
}
}
srcaddr = (char *) ((gzip_filepos & (WSIZE - 1)) + slide);
size = saved_filepos - gzip_filepos;
if (size > len)
size = len;
memmove (buf, srcaddr, size);
/* do CRC calculation here! */
crc_value = updcrc(buf, (unsigned)size);
buf += size;
len -= size;
gzip_filepos += size;
ret += size;
}
/* check for CRC error if reading entire file */
if (!errnum && check_crc && gzip_crc != crc_value) {
#if 0
printf ("gunzip: crc value 0x%x, expected 0x%x\n", crc_value, gzip_crc);
#endif
errnum = ERR_BAD_GZIP_CRC;
}
compressed_file = 1;
gunzip_swap_values ();
/*
* Now "gzip_*" values refer to the compressed data.
*/
if (errnum)
ret = 0;
return ret;
}