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 long int sbcs_to_unicode(const struct sbcs_data *sd, long int input_chr)
  16 {
  17     return sd->sbcs2ucs[input_chr];
  18 }
  19
  20 void read_sbcs(charset_spec const *charset, long int input_chr,
  21                charset_state *state,
  22                void (*emit)(void *ctx, long int output), void *emitctx)
  23 {
  24     const struct sbcs_data *sd = charset->data;
  25
  26     UNUSEDARG(state);
  27
  28     emit(emitctx, sbcs_to_unicode(sd, input_chr));
  29 }
  30
  31 long int sbcs_from_unicode(const struct sbcs_data *sd, long int input_chr)
  32 {
  33     int i, j, k, c;
  34
  35     /*
  36      * Binary-search in the ucs2sbcs table.
  37      */
  38     i = -1;
  39     j = sd->nvalid;
  40     while (i+1 < j) {
  41         k = (i+j)/2;
  42         c = sd->ucs2sbcs[k];
  43         if (input_chr < (long int)sd->sbcs2ucs[c])
  44             j = k;
  45         else if (input_chr > (long int)sd->sbcs2ucs[c])
  46             i = k;
  47         else {
  48             return c;
  49         }
  50     }
  51     return ERROR;
  52 }
  53
  54 int write_sbcs(charset_spec const *charset, long int input_chr,
  55                charset_state *state,
  56                void (*emit)(void *ctx, long int output), void *emitctx)
  57 {
  58     const struct sbcs_data *sd = charset->data;
  59     long int ret;
  60
  61     UNUSEDARG(state);
  62
  63     if (input_chr == -1)
  64         return TRUE;                   /* stateless; no cleanup required */
  65
  66     ret = sbcs_from_unicode(sd, input_chr);
  67     if (ret == ERROR)
  68         return FALSE;
  69
  70     emit(emitctx, ret);
  71     return TRUE;
  72 }