mdw@git.distorted.org.uk Git - sgt/charset/blob - sbcs.c

   1 /*
   2  * sbcs.c - routines to handle single-byte character sets.
   3  */
   4
   5 #include "charset.h"
   6 #include "internal.h"
   7
   8 /*
   9  * The charset_spec for any single-byte character set should
  10  * provide read_sbcs() as its read function, and its `data' field
  11  * should be a wchar_t string constant containing the 256 entries
  12  * of the translation table.
  13  */
  14
  15 void read_sbcs(charset_spec const *charset, long int input_chr,
  16                charset_state *state,
  17                void (*emit)(void *ctx, long int output), void *emitctx)
  18 {
  19     const struct sbcs_data *sd = charset->data;
  20
  21     UNUSEDARG(state);
  22
  23     emit(emitctx, sd->sbcs2ucs[input_chr]);
  24 }
  25
  26 int write_sbcs(charset_spec const *charset, long int input_chr,
  27                charset_state *state,
  28                void (*emit)(void *ctx, long int output), void *emitctx)
  29 {
  30     const struct sbcs_data *sd = charset->data;
  31     int i, j, k, c;
  32
  33     UNUSEDARG(state);
  34
  35     if (input_chr == -1)
  36         return TRUE;                   /* stateless; no cleanup required */
  37
  38     /*
  39      * Binary-search in the ucs2sbcs table.
  40      */
  41     i = -1;
  42     j = sd->nvalid;
  43     while (i+1 < j) {
  44         k = (i+j)/2;
  45         c = sd->ucs2sbcs[k];
  46         if (input_chr < sd->sbcs2ucs[c])
  47             j = k;
  48         else if (input_chr > sd->sbcs2ucs[c])
  49             i = k;
  50         else {
  51             emit(emitctx, c);
  52             return TRUE;
  53         }
  54     }
  55     return FALSE;
  56 }