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shiftjis.c

/*
 * shiftjis.c - multibyte encoding of Shift-JIS
 */

#ifndef ENUM_CHARSETS

#include "charset.h"
#include "internal.h"

/*
 * Shift-JIS has no associated data, so `charset' may be ignored.
 */

static void read_sjis(charset_spec const *charset, long int input_chr,
                  charset_state *state,
                  void (*emit)(void *ctx, long int output), void *emitctx)
{
    UNUSEDARG(charset);

    /*
     * For reading Shift-JIS, state->s0 simply contains the single
     * stored lead byte when we are half way through a double-byte
     * character, or 0 if we aren't.
     */

    if (state->s0 == 0) {
      if ((input_chr >= 0x81 && input_chr <= 0x9F) ||
          (input_chr >= 0xE0 && input_chr <= 0xEF)) {
          /*
           * Lead byte. Just store it.
           */
          state->s0 = input_chr;
      } else {
          /*
           * Anything else we translate through JIS X 0201.
           */
          if (input_chr == 0x5C)
            input_chr = 0xA5;
          else if (input_chr == 0x7E)
            input_chr = 0x203E;
          else if (input_chr >= 0xA1 && input_chr <= 0xDF)
            input_chr += 0xFF61 - 0xA1;
          else if (input_chr < 0x80)
            /* do nothing */;
          else
            input_chr = ERROR;
          emit(emitctx, input_chr);
      }
    } else {
      /*
       * We have a stored lead byte. We expect a valid followup
       * byte.
       */
      if (input_chr >= 0x40 && input_chr <= 0xFC && input_chr != 0x7F) {
          int r, c;
          r = state->s0;
          if (r >= 0xE0) r -= (0xE0 - 0xA0);
          r -= 0x81;
          c = input_chr;
          if (c > 0x7F) c--;
          c -= 0x40;
          r *= 2;
          if (c >= 94)
            r++, c -= 94;
          emit(emitctx, jisx0208_to_unicode(r, c));
      } else {
          emit(emitctx, ERROR);
      }
      state->s0 = 0;
    }
}

/*
 * Shift-JIS is a stateless multi-byte encoding (in the sense that
 * just after any character has been completed, the state is always
 * the same); hence when writing it, there is no need to use the
 * charset_state.
 */

static int write_sjis(charset_spec const *charset, long int input_chr,
                  charset_state *state,
                  void (*emit)(void *ctx, long int output), void *emitctx)
{
    UNUSEDARG(charset);
    UNUSEDARG(state);

    if (input_chr == -1)
      return TRUE;                   /* stateless; no cleanup required */

    if (input_chr < 0x80 && input_chr != 0x5C && input_chr != 0x7E) {
      emit(emitctx, input_chr);
      return TRUE;
    } else if (input_chr == 0xA5) {
      emit(emitctx, 0x5C);
      return TRUE;
    } else if (input_chr == 0x203E) {
      emit(emitctx, 0x7E);
      return TRUE;
    } else if (input_chr >= 0xFF61 && input_chr <= 0xFF9F) {
      emit(emitctx, input_chr - (0xFF61 - 0xA1));
      return TRUE;
    } else {
      int r, c;
      if (unicode_to_jisx0208(input_chr, &r, &c)) {
          c += 94 * (r % 2);
          r /= 2;
          r += 0x81;
          if (r >= 0xA0) r += 0xE0 - 0xA0;
          c += 0x40;
          if (c >= 0x7F) c++;
          emit(emitctx, r);
          emit(emitctx, c);
          return TRUE;
      } else {
          return FALSE;
      }
    }
}

const charset_spec charset_CS_SHIFT_JIS = {
    CS_SHIFT_JIS, read_sjis, write_sjis, NULL
};

#else /* ENUM_CHARSETS */

ENUM_CHARSET(CS_SHIFT_JIS)

#endif /* ENUM_CHARSETS */

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