APR's handling of seeks to APR_END in buffered files has a sign error.
I've included a patch (see the end), and a test case.
I verified that nothing in Subversion or httpd uses APR_END, so it
seems likely that nothing is relying on the sign error. And the
documentation of apr_file_seek is very clear:
* APR_END -- add the offset to the current file size
I have tested the fix on Unix. I can't test the change to the Windows
or OS/2 code, but it's a pretty obvious fix.
---- Test case ---
#include <apr.h>
#include <apr_pools.h>
#include <apr_file_io.h>
int main()
{
apr_pool_t *pool;
apr_file_t *file;
char buf[128];
apr_size_t len;
apr_off_t off;
apr_initialize();
apr_pool_create(&pool, NULL);
apr_file_open(&file, "testfile", APR_READ|APR_BUFFERED, 0, pool);
off = -5;
apr_file_seek(file, APR_END, &off);
len = sizeof(buf) - 1;
apr_file_read(file, buf, &len);
buf[len] = 0;
printf("%s", buf);
return 0;
}
To see the problem, echo something like "1234567890" into the file
"testfile" and then compile and run the test case. You will see no
output. If you remove the APR_BUFFERED flag, you will see "7890\n" as
expected.
Index: os2/seek.c
===================================================================
RCS file: /home/cvspublic/apr/file_io/os2/seek.c,v
retrieving revision 1.26
diff -u -r1.26 seek.c
--- os2/seek.c 13 Feb 2004 09:38:24 -0000 1.26
+++ os2/seek.c 29 Apr 2004 14:01:40 -0000
@@ -70,7 +70,7 @@
case APR_END:
rc = apr_file_info_get(&finfo, APR_FINFO_NORM, thefile);
if (rc == APR_SUCCESS)
- rc = setptr(thefile, finfo.size - *offset);
+ rc = setptr(thefile, finfo.size + *offset);
break;
}
Index: unix/seek.c
===================================================================
RCS file: /home/cvspublic/apr/file_io/unix/seek.c,v
retrieving revision 1.34
diff -u -r1.34 seek.c
--- unix/seek.c 27 Mar 2004 13:11:17 -0000 1.34
+++ unix/seek.c 29 Apr 2004 14:01:40 -0000
@@ -69,7 +69,7 @@
case APR_END:
rc = apr_file_info_get(&finfo, APR_FINFO_SIZE, thefile);
if (rc == APR_SUCCESS)
- rc = setptr(thefile, finfo.size - *offset);
+ rc = setptr(thefile, finfo.size + *offset);
break;
}
Index: win32/seek.c
===================================================================
RCS file: /home/cvspublic/apr/file_io/win32/seek.c,v
retrieving revision 1.28
diff -u -r1.28 seek.c
--- win32/seek.c 13 Feb 2004 09:38:27 -0000 1.28
+++ win32/seek.c 29 Apr 2004 14:01:40 -0000
@@ -73,7 +73,7 @@
case APR_END:
rc = apr_file_info_get(&finfo, APR_FINFO_SIZE, thefile);
if (rc == APR_SUCCESS)
- rc = setptr(thefile, finfo.size - *offset);
+ rc = setptr(thefile, finfo.size + *offset);
break;
default:
