initial import

1 files changed, 177 insertions, 0 deletions

diff --git a/stdio/fseek.c b/stdio/fseek.c
new file mode 100644
index 0000000000..a5abfe4866
--- /dev/null
+++ b/stdio/fseek.c
@@ -0,0 +1,177 @@
+/* Copyright (C) 1991, 1992, 1993, 1995 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <ansidecl.h>
+#include <errno.h>
+#include <stdio.h>
+
+
+/* Move the file position of STREAM to OFFSET
+   bytes from the beginning of the file if WHENCE
+   is SEEK_SET, the end of the file is it is SEEK_END,
+   or the current position if it is SEEK_CUR.  */
+int
+DEFUN(fseek, (stream, offset, whence),
+      register FILE *stream AND long int offset AND int whence)
+{
+  long int o;
+
+  if (!__validfp (stream))
+    {
+      errno = EINVAL;
+      return EOF;
+    }
+
+  /* Write out any pending data.  */
+  if (stream->__mode.__write && __flshfp (stream, EOF) == EOF)
+    return EOF;
+
+  /* Make sure we know the current offset info.  */
+  if (__stdio_check_offset (stream) == EOF)
+    return EOF;
+
+  /* We are moving the file position, so we are no longer at EOF.  */
+  stream->__eof = 0;
+
+  if (stream->__pushed_back)
+    {
+      /* Discard the character pushed back by ungetc.  */
+      stream->__bufp = stream->__pushback_bufp;
+      stream->__pushed_back = 0;
+    }
+
+  /* Check the WHENCE argument for validity, and process OFFSET
+     into an absolute position in O.  By the end of this switch,
+     either we have returned, or O contains an absolute position.  */
+  o = offset;
+  switch (whence)
+    {
+    default:
+      errno = EINVAL;
+      return EOF;
+
+    case SEEK_END:
+      /* We don't know where the end of the file is,
+	 so seek to the position in the file the user asked
+	 for, and then look where that is.  */
+      if (stream->__io_funcs.__seek == NULL)
+	{
+	  errno = ESPIPE;
+	  return EOF;
+	}
+      else
+	{
+	  fpos_t pos = (fpos_t) o;
+	  if ((*stream->__io_funcs.__seek)
+	      (stream->__cookie, &pos, SEEK_END) < 0)
+	    {
+	      if (errno == ESPIPE)
+		stream->__io_funcs.__seek = NULL;
+	      return EOF;
+	    }
+	  stream->__offset = pos;
+	  /* Make O be absolute, rather than
+	     relative to the end of the file.  */
+	  o = pos;
+	}
+
+      /* Fall through to try an absolute seek.  */
+
+    case SEEK_SET:
+      /* Make O be relative to the buffer.  */
+      o -= stream->__target;
+      /* Make O be relative to the current position in the buffer.  */
+      o -= stream->__bufp - stream->__buffer;
+
+      /* Fall through to see if we can do it by
+	 moving the pointer around in the buffer.  */
+
+    case SEEK_CUR:
+      /* If the offset is small enough, we can just
+	 move the pointer around in the buffer.  */
+
+#if 0	/* Why did I think this would ever work???  */
+      if (stream->__put_limit > stream->__buffer)
+	{
+	  /* We are writing.  */
+	  if (stream->__bufp + o >= stream->__buffer &&
+	      stream->__put_limit > stream->__bufp + o &&
+	      stream->__get_limit > stream->__bufp + o)
+	    {
+	      /* We have read all the data we will change soon.
+		 We can just move the pointer around.  */
+	      stream->__bufp += o;
+	      return 0;
+	    }
+	  else
+	    {
+	      /* Flush the buffer.  */
+	      if (__flshfp(stream, EOF) == EOF)
+		return EOF;
+	    }
+	} else
+#endif
+      if (o < 0 ?
+	  (-o <= stream->__bufp - stream->__buffer) :
+	  (o <= stream->__get_limit - stream->__bufp))
+	{
+	  stream->__bufp += o;
+	  return 0;
+	}
+
+      /* Turn it into an absolute seek.  */
+      o += stream->__bufp - stream->__buffer;
+      o += stream->__target;
+      break;
+    }
+
+  if (o < 0)
+    {
+      /* Negative file position is meaningless.  */
+      errno = EINVAL;
+      return -1;
+    }
+
+  /* O is now an absolute position, the new target.  */
+  stream->__target = o;
+
+  /* Set bufp and both end pointers to the beginning of the buffer.
+     The next i/o will force a call to the input/output room function.  */
+  stream->__bufp
+    = stream->__get_limit = stream->__put_limit = stream->__buffer;
+
+  /* Make sure __flshfp doesn't think the put_limit is at the beginning
+     of the buffer because of line-buffering magic.  */
+  stream->__linebuf_active = 0;
+
+  /* If there is no seek function, seeks always fail.  */
+  if (stream->__io_funcs.__seek == NULL)
+    {
+      /* This is preemptive, since we don't actually do the seeking.
+	 But it makes more sense for fseek to to fail with ESPIPE
+	 than for the next reading or writing operation to fail
+	 that way.  */
+      errno = ESPIPE;
+      return EOF;
+    }
+
+  /* Don't actually seek.  The next reading or writing operation
+     will force a call to the input or output room function,
+     which will move to the target file position before reading or writing.  */
+  return 0;
+}