64lseek.c

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C语言 代码 · 共 74 行

/****************************************************************************
*
*                            Open Watcom Project
*
*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
*
*  ========================================================================
*
*    This file contains Original Code and/or Modifications of Original
*    Code as defined in and that are subject to the Sybase Open Watcom
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*    except in compliance with the License. BY USING THIS FILE YOU AGREE TO
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*    provided with the Original Code and Modifications, and is also
*    available at www.sybase.com/developer/opensource.
*
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* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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****************************************************************************/


/*
 * This file is not indirected with an #include so we can compile this code
 * for multiple platforms without duplicating it in multiple files.
 */

#include "variety.h"
#define __INT64__
#include "int64.h"
#include <limits.h>
#include <unistd.h>


_WCRTLINK __int64 _lseeki64( int hid, __int64 _offset, int origin )
{
    long                rc;
    INT_TYPE            offset = GET_INT64(_offset);
    INT_TYPE            minoff, maxoff;
    INT_TYPE            minusone;
    INT_TYPE            retval;
    INT_TYPE            negminoff, negoffset;
    long                offset32;

    /*** Fail if offset isn't in the interval [LONG_MIN,LONG_MAX] ***/
    _clib_I32ToI64( -1L, minusone );
    _clib_I32ToI64( LONG_MAX, maxoff );
    if( _clib_U64Cmp( offset, maxoff )  >  0 ) {
        RETURN_INT64(minusone);         /* offset > LONG_MAX */
    }
    _clib_I32ToI64( LONG_MIN, minoff );
    _clib_I64Neg( minoff, negminoff );
    _clib_I64Neg( offset, negoffset );
    if( _clib_U64Cmp( offset, maxoff )  >  0 ) {
        RETURN_INT64(minusone);         /* offset < LONG_MIN */
    }

    /*** Ok, now call lseek ***/
    _clib_I64ToLong( offset, offset32 );
    rc = lseek( hid, offset32, origin );
    _clib_I32ToI64( rc, retval );
    RETURN_INT64(retval);
}