git.distorted.org.uk Git - u/mdw/putty/blob - charset/internal.h

   1 /*
   2  * internal.h - internal header stuff for the charset library.
   3  */
   4
   5 #ifndef charset_internal_h
   6 #define charset_internal_h
   7
   8 /* This invariably comes in handy */
   9 #define lenof(x) ( sizeof((x)) / sizeof(*(x)) )
  10
  11 /* This is an invalid Unicode value used to indicate an error. */
  12 #define ERROR 0xFFFFL                  /* Unicode value representing error */
  13
  14 typedef struct charset_spec charset_spec;
  15 typedef struct sbcs_data sbcs_data;
  16
  17 struct charset_spec {
  18     int charset;                       /* numeric identifier */
  19
  20     /*
  21      * A function to read the character set and output Unicode
  22      * characters. The `emit' function expects to get Unicode chars
  23      * passed to it; it should be sent ERROR for any encoding error
  24      * on the input.
  25      */
  26     void (*read)(charset_spec const *charset, long int input_chr,
  27                  charset_state *state,
  28                  void (*emit)(void *ctx, long int output), void *emitctx);
  29     /*
  30      * A function to read Unicode characters and output in this
  31      * character set. The `emit' function expects to get byte
  32      * values passed to it; it should be sent ERROR for any
  33      * non-representable characters on the input.
  34      */
  35     void (*write)(charset_spec const *charset, long int input_chr,
  36                   charset_state *state,
  37                   void (*emit)(void *ctx, long int output), void *emitctx);
  38     void const *data;
  39 };
  40
  41 /*
  42  * This is the format of `data' used by the SBCS read and write
  43  * functions; so it's the format used in all SBCS definitions.
  44  */
  45 struct sbcs_data {
  46     /*
  47      * This is a simple mapping table converting each SBCS position
  48      * to a Unicode code point. Some positions may contain ERROR,
  49      * indicating that that byte value is not defined in the SBCS
  50      * in question and its occurrence in input is an error.
  51      */
  52     unsigned long sbcs2ucs[256];
  53
  54     /*
  55      * This lookup table is used to convert Unicode back to the
  56      * SBCS. It consists of the valid byte values in the SBCS,
  57      * sorted in order of their Unicode translation. So given a
  58      * Unicode value U, you can do a binary search on this table
  59      * using the above table as a lookup: when testing the Xth
  60      * position in this table, you branch according to whether
  61      * sbcs2ucs[ucs2sbcs[X]] is less than, greater than, or equal
  62      * to U.
  63      *
  64      * Note that since there may be fewer than 256 valid byte
  65      * values in a particular SBCS, we must supply the length of
  66      * this table as well as the contents.
  67      */
  68     unsigned char ucs2sbcs[256];
  69     int nvalid;
  70 };
  71
  72 /*
  73  * Prototypes for internal library functions.
  74  */
  75 charset_spec const *charset_find_spec(int charset);
  76 void read_sbcs(charset_spec const *charset, long int input_chr,
  77                charset_state *state,
  78                void (*emit)(void *ctx, long int output), void *emitctx);
  79 void write_sbcs(charset_spec const *charset, long int input_chr,
  80                 charset_state *state,
  81                 void (*emit)(void *ctx, long int output), void *emitctx);
  82
  83 /*
  84  * Placate compiler warning about unused parameters, of which we
  85  * expect to have some in this library.
  86  */
  87 #define UNUSEDARG(x) ( (x) = (x) )
  88
  89 #endif /* charset_internal_h */