4.3BSD - /usr/src/new/icon/functions/map.c

   1: #include "../h/rt.h"
   2: 
   3: /*
   4:  * map(s1,s2,s3) - map s1, using s2 and s3.
   5:  */
   6: Xmap(nargs, arg3, arg2, arg1, arg0)
   7: int nargs;
   8: struct descrip arg3, arg2, arg1, arg0;
   9:    {
  10:    register int i;
  11:    register char *s1, *s2, *s3;
  12:    char sbuf1[MAXSTRING], sbuf2[MAXSTRING], sbuf3[MAXSTRING];
  13:    static char maptab[MAXSTRING];
  14:    extern char *alcstr();
  15: 
  16:    /*
  17:     * s1 must be a string; s2 and s3 default to &ucase and &lcase,
  18:     *  respectively.
  19:     */
  20:    if (cvstr(&arg1, sbuf1) == NULL)
  21:       runerr(103, &arg1);
  22:    defany(&arg2, &ucase);
  23:    defany(&arg3, &lcase);
  24: 
  25:    /*
  26:     * If s2 and s3 are the same as for the last call of map,
  27:     *  the some old values, namely maps2, maps3, and maptab
  28:     *  can be reused.  Otherwise, the information must be
  29:     *  recomputed.
  30:     */
  31:    if (maps2.type != arg2.type || maps3.type != arg3.type ||
  32:        BLKLOC(maps2) != BLKLOC(arg2) || BLKLOC(maps3) != BLKLOC(arg3)) {
  33:       maps2 = arg2;
  34:       maps3 = arg3;
  35:       /*
  36:        * s2 and s3 must be strings and of the same length.
  37:        */
  38:       if (cvstr(&arg2, sbuf2) == NULL)
  39:          runerr(103, &arg2);
  40:       if (cvstr(&arg3, sbuf3) == NULL)
  41:          runerr(103, &arg3);
  42:       if (STRLEN(arg2) != STRLEN(arg3))
  43:          runerr(208, NULL);
  44:       /*
  45:        * The array maptab is used to perform the mapping.  First, maptab[i]
  46:        *  is initialized with i for i from 0 to MAXSTRING-1 (256).  Then,
  47:        *  the for each character in s2, the position in maptab corresponding
  48:        *  the value of the character is assigned the value of the character
  49:        *  in s3 that is in the same ordinal position as the character from s2.
  50:        *  For example, if s2 is "abc", and s3 is "123", the assignments are:
  51:        *   maptab['a'] = '1'
  52:        *   maptab['b'] = '2'
  53:        *   maptab['c'] = '3'
  54:        *  Note that the 0..256 (really should be 0..255!) initialization
  55:        *   causes unmapped characters to be themselves, for example,
  56:        *   maptab['d'] == 'd'.
  57:        */
  58:       s2 = STRLOC(arg2);
  59:       s3 = STRLOC(arg3);
  60:       for (i = MAXSTRING - 1; i >= 0; i--)
  61:          maptab[i] = i;
  62:       for (i = 0; i < STRLEN(arg2); i++)
  63:          maptab[s2[i]&0377] = s3[i];
  64:       }
  65: 
  66:    if (STRLEN(arg1) == 0) {
  67:       arg0.type = D_NULL;
  68:       INTVAL(arg0) = 1;
  69:       return;
  70:       }
  71: 
  72:    /*
  73:     * The result is a string the size of s1, so ensure that much space.
  74:     */
  75:    i = STRLEN(arg1);
  76:    sneed(i);
  77:    s1 = STRLOC(arg1);
  78: 
  79:    /*
  80:     * Create the result string, but specify no value for it.
  81:     */
  82:    STRLEN(arg0) = i;
  83:    STRLOC(arg0) = s2 = alcstr(NULL, i);
  84:    /*
  85:     * Buzz through the string using values in maptab to do the mapping.
  86:     */
  87:    while (i-- > 0)
  88:       *s2++ = maptab[(*s1++)&0377];
  89:    }
  90: 
  91: Procblock(map,3)

Defined functions