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Fix ftell() bug: It was not accounting for data buffered in memory. From Macs N

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This commit is contained in:
Gregory Nutt 2014-03-31 09:47:28 -06:00
parent cd135fe3a8
commit 68025784b0
2 changed files with 41 additions and 3 deletions
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3
ChangeLog
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@ -7092,3 +7092,6 @@
* libc/stdio/lib_ferror.c, lib_fread.c, lib_libfflush.c,
lib_libfread.c, and lib_libfwrite.c: Finish incomplete support
for ferror(). From Macs N (2014-3-14).
* libc/stdio/lib_ftell.c: Fix a logic error in ftell(). It was
simply using the file offset and did not take into account data
buffered in memory. From Macs N (2013-3-31).

41
libc/stdio/lib_ftell.c
View File

@ -52,7 +52,7 @@
#include "lib_internal.h"
/****************************************************************************
* Definitions
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
@ -83,6 +83,41 @@
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: lib_getrdoffset
*
* Description:
* It is insufficient to simply use the file offset; we must also account
* for the data offset in the any buffered data. This function calculates
* that offset.
*
* Returned Value:
* The file position offset due to buffered data.
*
****************************************************************************/
#if CONFIG_STDIO_BUFFER_SIZE > 0
static off_t lib_getrdoffset(FAR FILE *stream)
{
off_t rdoffset = 0;
lib_take_semaphore(stream);
if (stream->fs_bufread != stream->fs_bufstart)
{
#if CONFIG_NUNGET_CHARS > 0
rdoffset = stream->fs_bufread - stream->fs_bufpos + stream->fs_nungotten;
#else
rdoffset = stream->fs_bufread - stream->fs_bufpos;
#endif
}
lib_give_semaphore(stream);
return rdoffset;
}
#else
# define lib_getrdoffset(stream) (0)
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
@ -95,7 +130,7 @@
* stream pointed to by stream.
*
* Returned Value:
* Zero on succes; -1 on failure with errno set appropriately.
* Zero on success; -1 on failure with errno set appropriately.
*
****************************************************************************/
@ -118,7 +153,7 @@ long ftell(FAR FILE *stream)
position = lseek(stream->fs_fd, 0, SEEK_CUR);
if (position != (off_t)-1)
{
return (long)position;
return (long)(position - lib_getrdoffset(stream));
}
else
{