import newlib-2000-02-17 snapshot

1 files changed, 310 insertions, 0 deletions

diff --git a/newlib/libc/stdio/fseek.c b/newlib/libc/stdio/fseek.c
new file mode 100644
index 0000000..d22292e
--- /dev/null
+++ b/newlib/libc/stdio/fseek.c
@@ -0,0 +1,310 @@
+/*
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted
+ * provided that the above copyright notice and this paragraph are
+ * duplicated in all such forms and that any documentation,
+ * advertising materials, and other materials related to such
+ * distribution and use acknowledge that the software was developed
+ * by the University of California, Berkeley.  The name of the
+ * University may not be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+/*
+FUNCTION
+<<fseek>>---set file position
+
+INDEX
+	fseek
+
+ANSI_SYNOPSIS
+	#include <stdio.h>
+	int fseek(FILE *<[fp]>, long <[offset]>, int <[whence]>)
+
+TRAD_SYNOPSIS
+	#include <stdio.h>
+	int fseek(<[fp]>, <[offset]>, <[whence]>)
+	FILE *<[fp]>;
+	long <[offset]>;
+	int <[whence]>;
+
+DESCRIPTION
+Objects of type <<FILE>> can have a ``position'' that records how much
+of the file your program has already read.  Many of the <<stdio>> functions
+depend on this position, and many change it as a side effect.
+
+You can use <<fseek>> to set the position for the file identified by
+<[fp]>.  The value of <[offset]> determines the new position, in one
+of three ways selected by the value of <[whence]> (defined as macros
+in `<<stdio.h>>'):
+
+<<SEEK_SET>>---<[offset]> is the absolute file position (an offset
+from the beginning of the file) desired.  <[offset]> must be positive.
+
+<<SEEK_CUR>>---<[offset]> is relative to the current file position.
+<[offset]> can meaningfully be either positive or negative.
+
+<<SEEK_END>>---<[offset]> is relative to the current end of file.
+<[offset]> can meaningfully be either positive (to increase the size
+of the file) or negative.
+
+See <<ftell>> to determine the current file position.
+
+RETURNS
+<<fseek>> returns <<0>> when successful.  If <<fseek>> fails, the
+result is <<EOF>>.  The reason for failure is indicated in <<errno>>:
+either <<ESPIPE>> (the stream identified by <[fp]> doesn't support
+repositioning) or <<EINVAL>> (invalid file position).
+
+PORTABILITY
+ANSI C requires <<fseek>>.
+
+Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
+<<lseek>>, <<read>>, <<sbrk>>, <<write>>.
+*/
+
+#include <stdio.h>
+#include <time.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include "local.h"
+
+#define	POS_ERR	(-(fpos_t)1)
+
+/*
+ * Seek the given file to the given offset.
+ * `Whence' must be one of the three SEEK_* macros.
+ */
+
+int
+fseek (fp, offset, whence)
+     register FILE *fp;
+     long offset;
+     int whence;
+{
+  struct _reent *ptr;
+  fpos_t _EXFUN ((*seekfn), (void *, fpos_t, int));
+  fpos_t target, curoff;
+  size_t n;
+  struct stat st;
+  int havepos;
+
+  /* Make sure stdio is set up.  */
+
+  CHECK_INIT (fp);
+  ptr = fp->_data;
+
+  /* If we've been doing some writing, and we're in append mode
+     then we don't really know where the filepos is.  */
+
+  if (fp->_flags & __SAPP && fp->_flags & __SWR)
+    {
+      /* So flush the buffer and seek to the end.  */
+      fflush (fp);
+    }
+
+  /* Have to be able to seek.  */
+
+  if ((seekfn = fp->_seek) == NULL)
+    {
+      ptr->_errno = ESPIPE;	/* ??? */
+      return EOF;
+    }
+
+  /*
+   * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
+   * After this, whence is either SEEK_SET or SEEK_END.
+   */
+
+  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(fp);   /* may adjust seek offset on append stream */
+      if (fp->_flags & __SOFF)
+	curoff = fp->_offset;
+      else
+	{
+	  curoff = (*seekfn) (fp->_cookie, (fpos_t) 0, SEEK_CUR);
+	  if (curoff == -1L)
+	    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;
+
+      offset += curoff;
+      whence = SEEK_SET;
+      havepos = 1;
+      break;
+
+    case SEEK_SET:
+    case SEEK_END:
+      havepos = 0;
+      break;
+
+    default:
+      ptr->_errno = EINVAL;
+      return (EOF);
+    }
+
+  /*
+   * Can only optimise if:
+   *	reading (and not reading-and-writing);
+   *	not unbuffered; and
+   *	this is a `regular' Unix file (and hence seekfn==__sseek).
+   * We must check __NBF first, because it is possible to have __NBF
+   * and __SOPT both set.
+   */
+
+  if (fp->_bf._base == NULL)
+    __smakebuf (fp);
+  if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT))
+    goto dumb;
+  if ((fp->_flags & __SOPT) == 0)
+    {
+      if (seekfn != __sseek
+	  || fp->_file < 0
+	  || _fstat_r (ptr, fp->_file, &st)
+	  || (st.st_mode & S_IFMT) != S_IFREG)
+	{
+	  fp->_flags |= __SNPT;
+	  goto dumb;
+	}
+#ifdef	HAVE_BLKSIZE
+      fp->_blksize = st.st_blksize;
+#else
+      fp->_blksize = 1024;
+#endif
+      fp->_flags |= __SOPT;
+    }
+
+  /*
+   * We are reading; we can try to optimise.
+   * Figure out where we are going and where we are now.
+   */
+
+  if (whence == SEEK_SET)
+    target = offset;
+  else
+    {
+      if (_fstat_r (ptr, fp->_file, &st))
+	goto dumb;
+      target = st.st_size + offset;
+    }
+
+  if (!havepos)
+    {
+      if (fp->_flags & __SOFF)
+	curoff = fp->_offset;
+      else
+	{
+	  curoff = (*seekfn) (fp->_cookie, 0L, SEEK_CUR);
+	  if (curoff == POS_ERR)
+	    goto dumb;
+	}
+      curoff -= fp->_r;
+      if (HASUB (fp))
+	curoff -= fp->_ur;
+    }
+
+  /*
+   * Compute the number of bytes in the input buffer (pretending
+   * that any ungetc() input has been discarded).  Adjust current
+   * offset backwards by this count so that it represents the
+   * file offset for the first byte in the current input buffer.
+   */
+
+  if (HASUB (fp))
+    {
+      curoff += fp->_r;       /* kill off ungetc */
+      n = fp->_up - fp->_bf._base;
+      curoff -= n;
+      n += fp->_ur;
+    }
+  else
+    {
+      n = fp->_p - fp->_bf._base;
+      curoff -= n;
+      n += fp->_r;
+    }
+
+  /*
+   * If the target offset is within the current buffer,
+   * simply adjust the pointers, clear EOF, undo ungetc(),
+   * and return.  (If the buffer was modified, we have to
+   * skip this; see fgetline.c.)
+   */
+
+  if ((fp->_flags & __SMOD) == 0 &&
+      target >= curoff && target < curoff + n)
+    {
+      register int o = target - curoff;
+
+      fp->_p = fp->_bf._base + o;
+      fp->_r = n - o;
+      if (HASUB (fp))
+	FREEUB (fp);
+      fp->_flags &= ~__SEOF;
+      return 0;
+    }
+
+  /*
+   * The place we want to get to is not within the current buffer,
+   * but we can still be kind to the kernel copyout mechanism.
+   * By aligning the file offset to a block boundary, we can let
+   * the kernel use the VM hardware to map pages instead of
+   * copying bytes laboriously.  Using a block boundary also
+   * ensures that we only read one block, rather than two.
+   */
+
+  curoff = target & ~(fp->_blksize - 1);
+  if ((*seekfn) (fp->_cookie, curoff, SEEK_SET) == POS_ERR)
+    goto dumb;
+  fp->_r = 0;
+  if (HASUB (fp))
+    FREEUB (fp);
+  fp->_flags &= ~__SEOF;
+  n = target - curoff;
+  if (n)
+    {
+      if (__srefill (fp) || fp->_r < n)
+	goto dumb;
+      fp->_p += n;
+      fp->_r -= n;
+    }
+  return 0;
+
+  /*
+   * We get here if we cannot optimise the seek ... just
+   * do it.  Allow the seek function to change fp->_bf._base.
+   */
+
+dumb:
+  if (fflush (fp) || (*seekfn) (fp->_cookie, offset, whence) == POS_ERR)
+    return EOF;
+  /* success: clear EOF indicator and discard ungetc() data */
+  if (HASUB (fp))
+    FREEUB (fp);
+  fp->_p = fp->_bf._base;
+  fp->_r = 0;
+  /* fp->_w = 0; *//* unnecessary (I think...) */
+  fp->_flags &= ~__SEOF;
+  return 0;
+}