53 lines
1.1 KiB
C
53 lines
1.1 KiB
C
/*
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* fseek.c - perform an fseek
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*/
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/* $Header$ */
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#include <assert.h>
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#include <stdio.h>
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#if (SEEK_CUR != 1) || (SEEK_END != 2) || (SEEK_SET != 0)
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#error SEEK_* values are wrong
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#endif
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#include "loc_incl.h"
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#include <sys/types.h>
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off_t _lseek(int fildes, off_t offset, int whence);
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int
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fseek(FILE *stream, long int offset, int whence)
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{
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assert(sizeof(offset) == sizeof(off_t));
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return fseeko(stream, (off_t) offset, whence);
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}
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int
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fseeko(FILE *stream, off_t offset, int whence)
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{
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int adjust = 0;
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long pos;
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stream->_flags &= ~(_IOEOF | _IOERR);
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/* Clear both the end of file and error flags */
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if (io_testflag(stream, _IOREADING)) {
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if (whence == SEEK_CUR
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&& stream->_buf
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&& !io_testflag(stream,_IONBF))
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adjust = stream->_count;
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stream->_count = 0;
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} else if (io_testflag(stream,_IOWRITING)) {
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fflush(stream);
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} else /* neither reading nor writing. The buffer must be empty */
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/* EMPTY */ ;
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pos = _lseek(fileno(stream), offset - adjust, whence);
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if (io_testflag(stream, _IOREAD) && io_testflag(stream, _IOWRITE))
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stream->_flags &= ~(_IOREADING | _IOWRITING);
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stream->_ptr = stream->_buf;
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return ((pos == -1) ? -1 : 0);
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}
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