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Annotation of 42BSD/ucb/gprof/hertz.c, revision 1.1

1.1     ! root        1: #ifndef lint
        !             2:     static     char *sccsid = "@(#)hertz.c     1.1 (Berkeley) 1/11/83";
        !             3: #endif lint
        !             4: 
        !             5:     /*
        !             6:      * discover the tick frequency of the machine
        !             7:      */
        !             8: #include <nlist.h>
        !             9: #include <stdio.h>
        !            10: 
        !            11: struct nlist   nl[] =  {{"_hz"},       /* clock ticks per second */
        !            12:                         {0}};
        !            13: 
        !            14: hertz()
        !            15: {
        !            16:     int                kmem;                   /* file descriptor for /dev/kmem */
        !            17:     long       lseek();
        !            18:     long       seeked;                 /* return value from lseek() */
        !            19:     long       hz;                     /* buffer for reading from system */
        !            20:     int                red;                    /* return value from read() */
        !            21:     int                closed;                 /* return value from close() */
        !            22: 
        !            23: #   define     VMUNIX  "/vmunix"       /* location of the system namelist */
        !            24:     nlist(VMUNIX, nl);
        !            25:     if (nl[0].n_type == 0) {
        !            26:        fprintf(stderr, "no %s namelist entry for _hz\n", VMUNIX);
        !            27:        return 0;
        !            28:     }
        !            29: #   define     KMEM    "/dev/kmem"     /* location of the system data space */
        !            30:     kmem = open(KMEM, 0);
        !            31:     if (kmem == -1) {
        !            32:        perror("hertz()");
        !            33:        fprintf(stderr, "open(\"%s\", 0)", KMEM);
        !            34:        return 0;
        !            35:     }
        !            36:     seeked = lseek(kmem, nl[0].n_value, 0);
        !            37:     if (seeked == -1) {
        !            38:        fprintf(stderr, "can't lseek(kmem, 0x%x, 0)\n", nl[0].n_value);
        !            39:        return 0;
        !            40:     }
        !            41:     red = read(kmem, &hz, sizeof hz);
        !            42:     if (red != sizeof hz) {
        !            43:        fprintf(stderr, "read(kmem, 0x%x, %d) returned %d\n",
        !            44:                &hz, sizeof hz, red);
        !            45:        return 0;
        !            46:     }
        !            47:     closed = close(kmem);
        !            48:     if (closed != 0) {
        !            49:        perror("hertz()");
        !            50:        fprintf(stderr, "close(\"%s\")", KMEM);
        !            51:        return 0;
        !            52:     }
        !            53:     return hz;
        !            54: }

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