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Improvements to the MDXFileChunk() template function:

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- Remove unneeded fstat()/lseek() calls.
- Return NULL and set errno to EINVAL on negative length.
- Fix small style problems and expand variable names.

After this change, it is possible to use this code for some irregular
files. For example, 'md5 /dev/md0' should now succeed.

Differential Revision:	https://reviews.freebsd.org/D4748
Suggested by:	bde
Reviewed by:	bde, allanjude, delphij
This commit is contained in:
jtl 2016-01-14 21:08:23 +00:00
parent 61577b76c5
commit 71d3115e20
1 changed files with 31 additions and 29 deletions
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60
lib/libmd/mdXhl.c
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@ -1,4 +1,5 @@
/* mdXhl.c * ----------------------------------------------------------------------------
/* mdXhl.c
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* <phk@FreeBSD.org> wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
@ -52,43 +53,44 @@ MDXFileChunk(const char *filename, char *buf, off_t ofs, off_t len)
unsigned char buffer[16*1024];
MDX_CTX ctx;
struct stat stbuf;
int f, i, e;
off_t n;
int fd, readrv, e;
off_t remain;
if (len < 0) {
errno = EINVAL;
return NULL;
}
MDXInit(&ctx);
f = open(filename, O_RDONLY);
if (f < 0)
return 0;
if (fstat(f, &stbuf) < 0) {
i = -1;
goto error;
fd = open(filename, O_RDONLY);
if (fd < 0)
return NULL;
if (ofs != 0) {
errno = 0;
if (lseek(fd, ofs, SEEK_SET) != ofs ||
(ofs == -1 && errno != 0)) {
readrv = -1;
goto error;
}
}
if (ofs > stbuf.st_size)
ofs = stbuf.st_size;
if ((len == 0) || (len > stbuf.st_size - ofs))
len = stbuf.st_size - ofs;
if (lseek(f, ofs, SEEK_SET) < 0) {
i = -1;
goto error;
}
n = len;
i = 0;
while (n > 0) {
if (n > sizeof(buffer))
i = read(f, buffer, sizeof(buffer));
remain = len;
readrv = 0;
while (len == 0 || remain > 0) {
if (len == 0 || remain > sizeof(buffer))
readrv = read(fd, buffer, sizeof(buffer));
else
i = read(f, buffer, n);
if (i <= 0)
readrv = read(fd, buffer, remain);
if (readrv <= 0)
break;
MDXUpdate(&ctx, buffer, i);
n -= i;
MDXUpdate(&ctx, buffer, readrv);
remain -= readrv;
}
error:
e = errno;
close(f);
close(fd);
errno = e;
if (i < 0)
return 0;
if (readrv < 0)
return NULL;
return (MDXEnd(&ctx, buf));
}