Reapply #15336.

[p5sagit/p5-mst-13.2.git] / ext / Encode / encode.h

#ifndef ENCODE_H
#define ENCODE_H

#ifndef U8
/* A tad devious this:
   perl normally has a #define for U8 - if that isn't present
   then we typedef it - leaving it #ifndef so we can do data parts without
   getting extern references to the code parts
 */
typedef unsigned char U8;
#endif

typedef struct encpage_s encpage_t;


struct encpage_s
{
 /* fields ordered to pack nicely on 32-bit machines */
 const U8   *seq;       /* Packed output sequences we generate if we match */
 encpage_t  *next;      /* Page to go to if we match */
 U8         min;        /* Min value of octet to match this entry */
 U8         max;        /* Max value of octet to match this entry */
 U8         dlen;       /* destination length - size of entries in seq */
 U8         slen;       /* source length - number of source octets needed */
};

/*
   At any point in a translation there is a page pointer which points at an array
   of the above structures.

   Basic operation :
   get octet from source stream.
   if (octet >= min && octet < max) {
      if slen is 0 then we cannot represent this character.
      if we have less than slen octets (including this one) then we have a partial character.
      otherwise
       copy dlen octets from seq + dlen*(octet-min) to output
       (dlen may be zero if we don't know yet.)
       load page pointer with next to continue.
       (is slen is one this is end of a character)
       get next octet.
   }
   else {
      increment the page pointer to look at next slot in the array
   }

   arrays SHALL be constructed so there is an entry which matches ..0xFF at the end,
   and either maps it or indicates no representation.

   if MSB of slen is set then mapping is an approximate "FALLBACK" entry.

*/


typedef struct encode_s encode_t;
struct encode_s
{
 encpage_t  *t_utf8;    /* Starting table for translation from the encoding to UTF-8 form */
 encpage_t  *f_utf8;    /* Starting table for translation from UTF-8 to the encoding */
 const U8   *rep;       /* Replacement character in this encoding e.g. "?" */
 int        replen;     /* Number of octets to represent replacement character */
 U8         min_el;     /* Minimum octets to represent a character */
 U8         max_el;     /* Maximum octets to represent a character */
 const char *name[2];   /* name(s) of this encoding */
};

#ifdef U8
/* See comment at top of file for deviousness */

extern int do_encode(encpage_t *enc, const U8 *src, STRLEN *slen,
                     U8 *dst, STRLEN dlen, STRLEN *dout, int approx);

extern void Encode_DefineEncoding(encode_t *enc);

#endif

#define ENCODE_NOSPACE  1
#define ENCODE_PARTIAL  2
#define ENCODE_NOREP    3
#define ENCODE_FALLBACK 4
#endif