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Implement seeking to earlier offsets in gzipfs. This allows my loader

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to e.g. correctly load all .ko.gz's I've tried, as opposed to messing
up trying to read section headers on some of them.
This commit is contained in:
Brian Feldman 2003-12-10 16:10:34 +00:00
parent c53a5d8fb8
commit e083cf16d9
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=123392
1 changed files with 30 additions and 15 deletions
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45
lib/libstand/gzipfs.c
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@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
struct z_file
{
int zf_rawfd;
off_t zf_dataoffset;
z_stream zf_zstream;
char zf_buf[Z_BUFSIZE];
};
@ -98,11 +99,12 @@ zf_fill(struct z_file *zf)
* Returns 0 if the header is OK, nonzero if not.
*/
static int
get_byte(struct z_file *zf)
get_byte(struct z_file *zf, off_t *curoffp)
{
if ((zf->zf_zstream.avail_in == 0) && (zf_fill(zf) == -1))
return(-1);
zf->zf_zstream.avail_in--;
++*curoffp;
return(*(zf->zf_zstream.next_in)++);
}
@ -124,36 +126,37 @@ check_header(struct z_file *zf)
uInt len;
int c;
zf->zf_dataoffset = 0;
/* Check the gzip magic header */
for (len = 0; len < 2; len++) {
c = get_byte(zf);
c = get_byte(zf, &zf->zf_dataoffset);
if (c != gz_magic[len]) {
return(1);
}
}
method = get_byte(zf);
flags = get_byte(zf);
method = get_byte(zf, &zf->zf_dataoffset);
flags = get_byte(zf, &zf->zf_dataoffset);
if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
return(1);
}
/* Discard time, xflags and OS code: */
for (len = 0; len < 6; len++) (void)get_byte(zf);
for (len = 0; len < 6; len++) (void)get_byte(zf, &zf->zf_dataoffset);
if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
len = (uInt)get_byte(zf);
len += ((uInt)get_byte(zf))<<8;
len = (uInt)get_byte(zf, &zf->zf_dataoffset);
len += ((uInt)get_byte(zf, &zf->zf_dataoffset))<<8;
/* len is garbage if EOF but the loop below will quit anyway */
while (len-- != 0 && get_byte(zf) != -1) ;
while (len-- != 0 && get_byte(zf, &zf->zf_dataoffset) != -1) ;
}
if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
while ((c = get_byte(zf)) != 0 && c != -1) ;
while ((c = get_byte(zf, &zf->zf_dataoffset)) != 0 && c != -1) ;
}
if ((flags & COMMENT) != 0) { /* skip the .gz file comment */
while ((c = get_byte(zf)) != 0 && c != -1) ;
while ((c = get_byte(zf, &zf->zf_dataoffset)) != 0 && c != -1) ;
}
if ((flags & HEAD_CRC) != 0) { /* skip the header crc */
for (len = 0; len < 2; len++) c = get_byte(zf);
for (len = 0; len < 2; len++) c = get_byte(zf, &zf->zf_dataoffset);
}
/* if there's data left, we're in business */
return((c == -1) ? 1 : 0);
@ -274,6 +277,20 @@ zf_read(struct open_file *f, void *buf, size_t size, size_t *resid)
return(0);
}
static int
zf_rewind(struct open_file *f)
{
struct z_file *zf = (struct z_file *)f->f_fsdata;
if (lseek(zf->zf_rawfd, zf->zf_dataoffset, SEEK_SET) == -1)
return -1;
zf->zf_zstream.avail_in = 0;
zf->zf_zstream.next_in = NULL;
(void)inflateReset(&zf->zf_zstream);
return 0;
}
static off_t
zf_seek(struct open_file *f, off_t offset, int where)
{
@ -292,11 +309,9 @@ zf_seek(struct open_file *f, off_t offset, int where)
target = -1;
}
/* Can we get there from here? */
if (target < zf->zf_zstream.total_out) {
errno = EOFFSET;
/* rewind if required */
if (target < zf->zf_zstream.total_out && zf_rewind(f) != 0)
return -1;
}
/* skip forwards if required */
while (target > zf->zf_zstream.total_out) {