fsetpos.c

来自「标准c库代码,可以应用于各个系统提供了大量的基本函数」· C语言 代码 · 共 55 行

/*
FUNCTION
<<fsetpos>>---restore position of a stream or file

INDEX
	fsetpos

ANSI_SYNOPSIS
	#include <stdio.h>
	int fsetpos(FILE *<[fp]>, const fpos_t *<[pos]>);

TRAD_SYNOPSIS
	#include <stdio.h>
	int fsetpos(<[fp]>, <[pos]>)
	FILE *<[fp]>;
	fpos_t *<[pos]>;

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 <<fsetpos>> to return the file identified by <[fp]> to a previous
position <<*<[pos]>>> (after first recording it with <<fgetpos>>).

See <<fseek>> for a similar facility.

RETURNS
<<fgetpos>> returns <<0>> when successful.  If <<fgetpos>> fails, the
result is <<1>>.  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 <<fsetpos>>, but does not specify the nature of
<<*<[pos]>>> beyond identifying it as written by <<fgetpos>>.

Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
<<lseek>>, <<read>>, <<sbrk>>, <<write>>.
*/

#include <stdio.h>

int
_DEFUN (fsetpos, (iop, pos),
	FILE * iop _AND
	_CONST fpos_t * pos)
{
  int x = fseek (iop, *pos, SEEK_SET);

  if (x != 0)
    return 1;
  return 0;
}