55 lines
1.3 KiB
C
55 lines
1.3 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 <stdio.h>
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#include <sys/file.h>
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#include "loc_incl.h"
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int lseek(int d, int 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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int count, adjust = 0;
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long pos;
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#if (SEEK_CUR != L_INCR) || (SEEK_SET != L_SET) || (SEEK_END != L_XTND)
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int swhence; /* the real whence for lseek */
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switch(whence) { /* map to UNIX values */
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case SEEK_CUR: swhence = L_INCR; break;
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case SEEK_SET: swhence = L_SET; break;
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case SEEK_END: swhence = L_XTND; break;
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default: swhence = whence; break;
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}
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#else
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#define swhence whence
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#endif
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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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pos = lseek(fileno(stream), offset - adjust, swhence);
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stream->_count = 0;
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}
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else if (io_testflag(stream,_IOWRITING)) {
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fflush(stream);
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pos = lseek(fileno(stream), offset, swhence);
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}
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else /* neither reading nor writing. The buffer must be empty */
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pos = lseek(fileno(stream), offset, swhence);
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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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