61 lines
1.3 KiB
C
61 lines
1.3 KiB
C
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/*
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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;
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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,_IOREAD) ) {
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if ( whence < 2 && stream->_buf
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&& !io_testflag(stream,_IONBF) ) {
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count = stream->_count;
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pos = offset;
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if ( whence == SEEK_SET )
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pos +=
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count - lseek(fileno(stream), 0L, swhence);
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else
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offset -= count;
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if ( count > 0 && pos <= count
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&& pos >= stream->_buf - stream->_ptr ) {
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stream->_ptr += (int) pos;
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stream->_count -= (int) pos;
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return(0);
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}
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}
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pos = lseek(fileno(stream), offset, swhence);
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stream->_count = 0;
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} else if ( io_testflag(stream,_IOWRITE) ) {
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fflush(stream);
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pos = lseek(fileno(stream), offset, swhence);
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}
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return((pos == -1) ? -1 : 0 );
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}
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