[PATCH] newlib: fix fseek optimization with SEEK_CUR

[Bastien Bouclet <bastien.bouclet@gmail.com>]

The call to fflush was invalidating the read buffer, preventing relative
seeks to positions that would have been inside the read buffer from
being optimized. The call to srefill would then re-read mostly the same
data that was initially in the read buffer.
---
 newlib/libc/stdio/fseeko.c     | 31 ++++++-------------------------
 newlib/libc/stdio64/fseeko64.c | 31 ++++++-------------------------
 2 files changed, 12 insertions(+), 50 deletions(-)

diff --git a/newlib/libc/stdio/fseeko.c b/newlib/libc/stdio/fseeko.c
index 3e0f9e90b..bbf1af43e 100644
--- a/newlib/libc/stdio/fseeko.c
+++ b/newlib/libc/stdio/fseeko.c
@@ -141,31 +141,12 @@ _fseeko_r (struct _reent *ptr,
   switch (whence)
     {
     case SEEK_CUR:
-      /*
-       * In order to seek relative to the current stream offset,
-       * we have to first find the current stream offset a la
-       * ftell (see ftell for details).
-       */
-      _fflush_r (ptr, fp);   /* may adjust seek offset on append stream */
-      if (fp->_flags & __SOFF)
-	curoff = fp->_offset;
-      else
-	{
-	  curoff = seekfn (ptr, fp->_cookie, (_fpos_t) 0, SEEK_CUR);
-	  if (curoff == -1L)
-	    {
-	      _newlib_flockfile_exit (fp);
-	      return EOF;
-	    }
-	}
-      if (fp->_flags & __SRD)
-	{
-	  curoff -= fp->_r;
-	  if (HASUB (fp))
-	    curoff -= fp->_ur;
-	}
-      else if (fp->_flags & __SWR && fp->_p != NULL)
-	curoff += fp->_p - fp->_bf._base;
+      curoff = _ftello_r(ptr, fp);
+      if (curoff == -1L)
+        {
+          _newlib_flockfile_exit (fp);
+          return EOF;
+        }
 
       offset += curoff;
       whence = SEEK_SET;
diff --git a/newlib/libc/stdio64/fseeko64.c b/newlib/libc/stdio64/fseeko64.c
index 0672086a3..f38005570 100644
--- a/newlib/libc/stdio64/fseeko64.c
+++ b/newlib/libc/stdio64/fseeko64.c
@@ -142,31 +142,12 @@ _fseeko64_r (struct _reent *ptr,
   switch (whence)
     {
     case SEEK_CUR:
-      /*
-       * In order to seek relative to the current stream offset,
-       * we have to first find the current stream offset a la
-       * ftell (see ftell for details).
-       */
-      _fflush_r (ptr, fp);   /* may adjust seek offset on append stream */
-      if (fp->_flags & __SOFF)
-	curoff = fp->_offset;
-      else
-	{
-	  curoff = seekfn (ptr, fp->_cookie, (_fpos64_t) 0, SEEK_CUR);
-	  if (curoff == -1L)
-	    {
-	      _newlib_flockfile_exit(fp);
-	      return EOF;
-	    }
-	}
-      if (fp->_flags & __SRD)
-	{
-	  curoff -= fp->_r;
-	  if (HASUB (fp))
-	    curoff -= fp->_ur;
-	}
-      else if (fp->_flags & __SWR && fp->_p != NULL)
-	curoff += fp->_p - fp->_bf._base;
+      curoff = _ftello64_r(ptr, fp);
+      if (curoff == -1L)
+        {
+          _newlib_flockfile_exit (fp);
+          return EOF;
+        }
 
       offset += curoff;
       whence = SEEK_SET;
-- 
2.24.0