icuSources/tools/makeconv/genmbcs.h

   1 // © 2016 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3 /*
   4 *******************************************************************************
   5 *
   6 *   Copyright (C) 2000-2008, International Business Machines
   7 *   Corporation and others.  All Rights Reserved.
   8 *
   9 *******************************************************************************
  10 *   file name:  genmbcs.h
  11 *   encoding:   UTF-8
  12 *   tab size:   8 (not used)
  13 *   indentation:4
  14 *
  15 *   created on: 2000jul10
  16 *   created by: Markus W. Scherer
  17 */
  18
  19 #ifndef __GENMBCS_H__
  20 #define __GENMBCS_H__
  21
  22 #include "makeconv.h"
  23
  24 enum {
  25     /*
  26      * TODO: Consider using ucnvmbcs.h constants.
  27      * However, not all values need to be exactly the same, for example
  28      * the xxx_UTF8_MAX values may be different. (Especially SBCS_UTF8_MAX
  29      * may be higher in makeconv than in the runtime code because that
  30      * affects only a small number of .cnv files [if any] but all
  31      * runtime UConverterSharedData objects.
  32      */
  33     MBCS_STAGE_2_SHIFT=4,
  34     MBCS_STAGE_2_BLOCK_SIZE=0x40,       /* =64=1<<6 for 6 bits in stage 2 */
  35     MBCS_STAGE_2_BLOCK_SIZE_SHIFT=6,    /* log2(MBCS_STAGE_2_BLOCK_SIZE) */
  36     MBCS_STAGE_2_BLOCK_MASK=0x3f,       /* for after shifting by MBCS_STAGE_2_SHIFT */
  37     MBCS_STAGE_1_SHIFT=10,
  38     MBCS_STAGE_1_BMP_SIZE=0x40, /* 0x10000>>MBCS_STAGE_1_SHIFT, or 16 for one entry per 1k code points on the BMP */
  39     MBCS_STAGE_1_SIZE=0x440,    /* 0x110000>>MBCS_STAGE_1_SHIFT, or 17*64 for one entry per 1k code points */
  40     MBCS_STAGE_2_SIZE=0xfbc0,   /* 0x10000-MBCS_STAGE_1_SIZE: stages 1 & 2 share a 16-bit-indexed array */
  41     MBCS_MAX_STAGE_2_TOP=MBCS_STAGE_2_SIZE,
  42     MBCS_STAGE_2_MAX_BLOCKS=MBCS_STAGE_2_SIZE>>MBCS_STAGE_2_BLOCK_SIZE_SHIFT,
  43
  44     MBCS_STAGE_2_ALL_UNASSIGNED_INDEX=0, /* stage 1 entry for the all-unassigned stage 2 block */
  45     MBCS_STAGE_2_FIRST_ASSIGNED=MBCS_STAGE_2_BLOCK_SIZE, /* start of the first stage 2 block after the all-unassigned one */
  46
  47     MBCS_STAGE_3_BLOCK_SIZE=16,         /* =16=1<<4 for 4 bits in stage 3 */
  48     MBCS_STAGE_3_BLOCK_MASK=0xf,
  49     MBCS_STAGE_3_FIRST_ASSIGNED=MBCS_STAGE_3_BLOCK_SIZE, /* start of the first stage 3 block after the all-unassigned one */
  50
  51     MBCS_STAGE_3_GRANULARITY=16,        /* =1<<4: MBCS stage 2 indexes are shifted left 4 */
  52     MBCS_STAGE_3_SBCS_SIZE=0x10000,     /* max 64k mappings for SBCS */
  53     MBCS_STAGE_3_MBCS_SIZE=0x10000*MBCS_STAGE_3_GRANULARITY, /* max mappings for MBCS */
  54
  55     /*
  56      * SBCS_UTF8_MAX: Maximum code point with UTF-8-friendly SBCS data structures.
  57      * Possible values are 0x01ff..0xffff, in steps of 0x100.
  58      *
  59      * Unlike for MBCS, this constant only affects the stage 3 block allocation size;
  60      * there is no additional stage 1/2 table stored in the .cnv file.
  61      * The max value should be at least 0x7ff to cover 2-byte UTF-8.
  62      * 0xfff also covers a number other small scripts which have legacy charsets
  63      * (like Thai).
  64      * Higher values up to 0x1fff are harmless and potentially useful because
  65      * that covers small-script blocks which usually have either dense mappings
  66      * or no mappings at all.
  67      * Starting at U+2000, there are mostly symbols and format characters
  68      * with a low density of SBCS mappings, which would result in more wasted
  69      * stage 3 entries with the larger block size.
  70      */
  71     SBCS_UTF8_MAX=0x1fff,
  72
  73     /*
  74      * MBCS_UTF8_MAX: Maximum code point with UTF-8-friendly MBCS data structures.
  75      * Possible values are 0x01ff..0xffff, in steps of 0x100.
  76      *
  77      * Note that with 0xffff, MBCSAddFromUnicode() may overflow the additional UTF-8 stage table
  78      * with extreme input data. The function checks for this overflow.
  79      *
  80      * 0xd7ff is chosen for the majority of common characters including Unihan and Hangul.
  81      * At U+d800 there are mostly surrogates, private use codes, compatibility characters, etc.
  82      * Larger values cause slightly larger MBCS .cnv files.
  83      */
  84     MBCS_UTF8_MAX=0xd7ff,
  85     MBCS_UTF8_LIMIT=MBCS_UTF8_MAX+1,    /* =0xd800 */
  86
  87     MBCS_UTF8_STAGE_SHIFT=6,
  88     MBCS_UTF8_STAGE_3_BLOCK_SIZE=0x40,  /* =64=1<<6 for 6 bits from last trail byte */
  89     MBCS_UTF8_STAGE_3_BLOCK_MASK=0x3f,
  90
  91     /* size of the single-stage table for up to U+d7ff (used instead of stage1/2) */
  92     MBCS_UTF8_STAGE_SIZE=MBCS_UTF8_LIMIT>>MBCS_UTF8_STAGE_SHIFT, /* =0x360 */
  93
  94     MBCS_FROM_U_EXT_FLAG=0x10,          /* UCMapping.f bit for base table mappings that fit into the base toU table */
  95     MBCS_FROM_U_EXT_MASK=0x0f,          /* but need to go into the extension fromU table */
  96
  97     /* =4 number of regular stage 3 blocks for final UTF-8 trail byte */
  98     MBCS_UTF8_STAGE_3_BLOCKS=MBCS_UTF8_STAGE_3_BLOCK_SIZE/MBCS_STAGE_3_BLOCK_SIZE,
  99
 100     MBCS_MAX_FALLBACK_COUNT=8192
 101 };
 102
 103 U_CFUNC NewConverter *
 104 MBCSOpen(UCMFile *ucm);
 105
 106 struct MBCSData;
 107 typedef struct MBCSData MBCSData;
 108
 109 /*
 110  * Get a dummy MBCSData for use with MBCSOkForBaseFromUnicode()
 111  * for creating an extension-only file.
 112  * Assume maxCharLength>1.
 113  */
 114 U_CFUNC const MBCSData *
 115 MBCSGetDummy(void);
 116
 117 /* Test if a 1:1 mapping fits into the MBCS base table's fromUnicode structure. */
 118 U_CFUNC UBool
 119 MBCSOkForBaseFromUnicode(const MBCSData *mbcsData,
 120                          const uint8_t *bytes, int32_t length,
 121                          UChar32 c, int8_t flag);
 122
 123 U_CFUNC NewConverter *
 124 CnvExtOpen(UCMFile *ucm);
 125
 126 #endif /* __GENMBCS_H__ */