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rune.c

/*
 * The authors of this software are Rob Pike and Ken Thompson.
 *              Copyright (c) 2002 by Lucent Technologies.
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
 * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 */
#include <stdarg.h>
#include <string.h>
#include "plan9.h"
#include "utf.h"

enum
{
      Bit1  = 7,
      Bitx  = 6,
      Bit2  = 5,
      Bit3  = 4,
      Bit4  = 3,

      T1    = ((1<<(Bit1+1))-1) ^ 0xFF,   /* 0000 0000 */
      Tx    = ((1<<(Bitx+1))-1) ^ 0xFF,   /* 1000 0000 */
      T2    = ((1<<(Bit2+1))-1) ^ 0xFF,   /* 1100 0000 */
      T3    = ((1<<(Bit3+1))-1) ^ 0xFF,   /* 1110 0000 */
      T4    = ((1<<(Bit4+1))-1) ^ 0xFF,   /* 1111 0000 */

      Rune1 = (1<<(Bit1+0*Bitx))-1,       /* 0000 0000 0111 1111 */
      Rune2 = (1<<(Bit2+1*Bitx))-1,       /* 0000 0111 1111 1111 */
      Rune3 = (1<<(Bit3+2*Bitx))-1,       /* 1111 1111 1111 1111 */

      Maskx = (1<<Bitx)-1,                /* 0011 1111 */
      Testx = Maskx ^ 0xFF,               /* 1100 0000 */

      Bad   = Runeerror,
};

int
chartorune(Rune *rune, char *str)
{
      int c, c1, c2;
      long l;

      /*
       * one character sequence
       *    00000-0007F => T1
       */
      c = *(uchar*)str;
      if(c < Tx) {
            *rune = c;
            return 1;
      }

      /*
       * two character sequence
       *    0080-07FF => T2 Tx
       */
      c1 = *(uchar*)(str+1) ^ Tx;
      if(c1 & Testx)
            goto bad;
      if(c < T3) {
            if(c < T2)
                  goto bad;
            l = ((c << Bitx) | c1) & Rune2;
            if(l <= Rune1)
                  goto bad;
            *rune = l;
            return 2;
      }

      /*
       * three character sequence
       *    0800-FFFF => T3 Tx Tx
       */
      c2 = *(uchar*)(str+2) ^ Tx;
      if(c2 & Testx)
            goto bad;
      if(c < T4) {
            l = ((((c << Bitx) | c1) << Bitx) | c2) & Rune3;
            if(l <= Rune2)
                  goto bad;
            *rune = l;
            return 3;
      }

      /*
       * bad decoding
       */
bad:
      *rune = Bad;
      return 1;
}

int
runetochar(char *str, Rune *rune)
{
      long c;

      /*
       * one character sequence
       *    00000-0007F => 00-7F
       */
      c = *rune;
      if(c <= Rune1) {
            str[0] = c;
            return 1;
      }

      /*
       * two character sequence
       *    0080-07FF => T2 Tx
       */
      if(c <= Rune2) {
            str[0] = T2 | (c >> 1*Bitx);
            str[1] = Tx | (c & Maskx);
            return 2;
      }

      /*
       * three character sequence
       *    0800-FFFF => T3 Tx Tx
       */
      str[0] = T3 |  (c >> 2*Bitx);
      str[1] = Tx | ((c >> 1*Bitx) & Maskx);
      str[2] = Tx |  (c & Maskx);
      return 3;
}

int
runelen(long c)
{
      Rune rune;
      char str[10];

      rune = c;
      return runetochar(str, &rune);
}

int
runenlen(Rune *r, int nrune)
{
      int nb, c;

      nb = 0;
      while(nrune--) {
            c = *r++;
            if(c <= Rune1)
                  nb++;
            else
            if(c <= Rune2)
                  nb += 2;
            else
                  nb += 3;
      }
      return nb;
}

int
fullrune(char *str, int n)
{
      int c;

      if(n > 0) {
            c = *(uchar*)str;
            if(c < Tx)
                  return 1;
            if(n > 1)
                  if(c < T3 || n > 2)
                        return 1;
      }
      return 0;
}

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