lfgetmode.c

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/* lfgetmode.c - lfgetmode */

#include <xinu.h>

/*------------------------------------------------------------------------
 * lfgetmode  -  Parse mode argument and generate integer of mode bits
 *------------------------------------------------------------------------
 */
int32   lfgetmode (
     char   *mode           /* String of mode characters    */
    )
{
    int32   mbits;          /* Mode bits to return      */
    char    ch;         /* Next char in mode string */

    mbits = 0;

    /* Mode string specifies:                   */
    /*  r - read                        */
    /*  w - write                       */
    /*  o - old (file must exist)               */
    /*  n - new (create a new file)             */

    while ( (ch = *mode++) != NULLCH) {
        switch (ch) {

            case 'r':   if (mbits&LF_MODE_R) {
                    return SYSERR;
                }
                mbits |= LF_MODE_R;
                continue;

            case 'w':   if (mbits&LF_MODE_W) {
                    return SYSERR;
                }
                mbits |= LF_MODE_W;
                continue;

            case 'o':   if (mbits&LF_MODE_O || mbits&LF_MODE_N) {
                    return SYSERR;
                }
                mbits |= LF_MODE_O;
                break;

            case 'n':   if (mbits&LF_MODE_O || mbits&LF_MODE_N) {
                    return SYSERR;
                }
                mbits |= LF_MODE_N;
                break;

            default:    return SYSERR;
        }
    }

    /* If neither read nor write specified, allow both */

    if ( (mbits&LF_MODE_RW) == 0 ) {
        mbits |= LF_MODE_RW;
    }
    return mbits;
}