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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) 2000-2013, International Business Machines
7 *   Corporation and others.  All Rights Reserved.
8 *
9 ******************************************************************************
10 *   file name:  ucnvmbcs.h
11 *   encoding:   UTF-8
12 *   tab size:   8 (not used)
13 *   indentation:4
14 *
15 *   created on: 2000jul07
16 *   created by: Markus W. Scherer
17 */
18 
19 #ifndef __UCNVMBCS_H__
20 #define __UCNVMBCS_H__
21 
22 #include "unicode/utypes.h"
23 
24 #if !UCONFIG_NO_CONVERSION
25 
26 #include "unicode/ucnv.h"
27 #include "ucnv_cnv.h"
28 #include "ucnv_ext.h"
29 
30 /**
31  * ICU conversion (.cnv) data file structure, following the usual UDataInfo
32  * header.
33  *
34  * Format version: 6.2
35  *
36  * struct UConverterStaticData -- struct containing the converter name, IBM CCSID,
37  *                                min/max bytes per character, etc.
38  *                                see ucnv_bld.h
39  *
40  * --------------------
41  *
42  * The static data is followed by conversionType-specific data structures.
43  * At the moment, there are only variations of MBCS converters. They all have
44  * the same toUnicode structures, while the fromUnicode structures for SBCS
45  * differ from those for other MBCS-style converters.
46  *
47  * _MBCSHeader.version 5 is optional and not backward-compatible
48  * (as usual for changes in the major version field).
49  *
50  * Versions 5.m work like versions 4.m except:
51  * - The _MBCSHeader has variable length (and is always longer than in version 4).
52  *   See the struct _MBCSHeader further description below.
53  * - There is a set of flags which indicate further incompatible changes.
54  *   (Reader code must reject the file if it does not recognize them all.)
55  * - In particular, one of these flags indicates that most of the fromUnicode
56  *   data is missing and must be reconstituted from the toUnicode data
57  *   and from the utf8Friendly mbcsIndex at load time.
58  *   (This only works with a utf8Friendly table.)
59  *   In this case, makeconv may increase maxFastUChar automatically to U+FFFF.
60  *
61  * The first of these versions is 5.3, which is like 4.3 except for the differences above.
62  *
63  * When possible, makeconv continues to generate version 4.m files.
64  *
65  * _MBCSHeader.version 5.4/4.4 supports "good one-way" mappings (|4)
66  * in the extension tables (fromUTableValues bit 30). See ucnv_ext.h for details.
67  *
68  * _MBCSHeader.version 4.3 optionally modifies the fromUnicode data structures
69  * slightly and optionally adds a table for conversion to MBCS (non-SBCS)
70  * charsets.
71  *
72  * The modifications are to make the data utf8Friendly. Not every 4.3 file
73  * file contains utf8Friendly data.
74  * It is utf8Friendly if _MBCSHeader.version[2]!=0.
75  * In this case, the data structures are utf8Friendly up to the code point
76  *   maxFastUChar=((_MBCSHeader.version[2]<<8)|0xff)
77  *
78  * A utf8Friendly file has fromUnicode stage 3 entries for code points up to
79  * maxFastUChar allocated in blocks of 64 for indexing with the 6 bits from
80  * a UTF-8 trail byte. ASCII is allocated linearly with 128 contiguous entries.
81  *
82  * In addition, a utf8Friendly MBCS file contains an additional
83  *   uint16_t mbcsIndex[(maxFastUChar+1)>>6];
84  * which replaces the stage 1 and 2 tables for indexing with bits from the
85  * UTF-8 lead byte and middle trail byte. Unlike the older MBCS stage 2 table,
86  * the mbcsIndex does not contain roundtrip flags. Therefore, all fallbacks
87  * from code points up to maxFastUChar (and roundtrips to 0x00) are moved to
88  * the extension data structure. This also allows for faster roundtrip
89  * conversion from UTF-16.
90  *
91  * SBCS files do not contain an additional sbcsIndex[] array because the
92  * proportional size increase would be noticeable, but the runtime
93  * code builds one for the code point range for which the runtime conversion
94  * code is optimized.
95  *
96  * For SBCS, maxFastUChar should be at least U+0FFF. The initial makeconv
97  * implementation sets it to U+1FFF. Because the sbcsIndex is not stored in
98  * the file, a larger maxFastUChar only affects stage 3 block allocation size
99  * and is free in empty blocks. (Larger blocks with sparse contents cause larger
100  * files.) U+1FFF includes almost all of the small scripts.
101  * U+0FFF covers UTF-8 two-byte sequences and three-byte sequences starting with
102  * 0xe0. This includes most scripts with legacy SBCS charsets.
103  * The initial runtime implementation using 4.3 files only builds an sbcsIndex
104  * for code points up to U+0FFF.
105  *
106  * For MBCS, maxFastUChar should be at least U+D7FF (=initial value).
107  * This boundary is convenient because practically all of the commonly used
108  * characters are below it, and because it is the boundary to surrogate
109  * code points, above which special handling is necessary anyway.
110  * (Surrogate pair assembly for UTF-16, validity checking for UTF-8.)
111  *
112  * maxFastUChar could be up to U+FFFF to cover the whole BMP, which could be
113  * useful especially for conversion from UTF-8 when the input can be assumed
114  * to be valid, because the surrogate range would then not have to be
115  * checked.
116  * (With maxFastUChar=0xffff, makeconv would have to check for mbcsIndex value
117  * overflow because with the all-unassigned block 0 and nearly full mappings
118  * from the BMP it is theoretically possible that an index into stage 3
119  * exceeds 16 bits.)
120  *
121  * _MBCSHeader.version 4.2 adds an optional conversion extension data structure.
122  * If it is present, then an ICU version reading header versions 4.0 or 4.1
123  * will be able to use the base table and ignore the extension.
124  *
125  * The unicodeMask in the static data is part of the base table data structure.
126  * Especially, the UCNV_HAS_SUPPLEMENTARY flag determines the length of the
127  * fromUnicode stage 1 array.
128  * The static data unicodeMask refers only to the base table's properties if
129  * a base table is included.
130  * In an extension-only file, the static data unicodeMask is 0.
131  * The extension data indexes have a separate field with the unicodeMask flags.
132  *
133  * MBCS-style data structure following the static data.
134  * Offsets are counted in bytes from the beginning of the MBCS header structure.
135  * Details about usage in comments in ucnvmbcs.c.
136  *
137  * struct _MBCSHeader (see the definition in this header file below)
138  * contains 32-bit fields as follows:
139  * 8 values:
140  *  0   uint8_t[4]  MBCS version in UVersionInfo format (currently 4.3.x.0)
141  *  1   uint32_t    countStates
142  *  2   uint32_t    countToUFallbacks
143  *  3   uint32_t    offsetToUCodeUnits
144  *  4   uint32_t    offsetFromUTable
145  *  5   uint32_t    offsetFromUBytes
146  *  6   uint32_t    flags, bits:
147  *                      31.. 8 offsetExtension -- _MBCSHeader.version 4.2 (ICU 2.8) and higher
148  *                                                0 for older versions and if
149  *                                                there is not extension structure
150  *                       7.. 0 outputType
151  *  7   uint32_t    fromUBytesLength -- _MBCSHeader.version 4.1 (ICU 2.4) and higher
152  *                  counts bytes in fromUBytes[]
153  *
154  * New and required in version 5:
155  *  8   uint32_t    options, bits:
156  *                      31..16 reserved for flags that can be added without breaking
157  *                                 backward compatibility
158  *                      15.. 6 reserved for flags whose addition will break
159  *                                 backward compatibility
160  *                           6 MBCS_OPT_FROM_U -- if set,
161  *                                 then most of the fromUnicode data is omitted;
162  *                                 fullStage2Length is present and the missing
163  *                                 bottom part of stage 2 must be reconstituted from
164  *                                 the toUnicode data;
165  *                                 stage 3 is missing completely as well;
166  *                                 not used for SBCS tables
167  *                       5.. 0 length of the _MBCSHeader (number of uint32_t)
168  *
169  * New and optional in version 5:
170  *  9   uint32_t    fullStage2Length: used if MBCS_OPT_FROM_U is set
171  *                                 specifies the full length of stage 2
172  *                                 including the omitted part
173  *
174  * if(outputType==MBCS_OUTPUT_EXT_ONLY) {
175  *     -- base table name for extension-only table
176  *     char baseTableName[variable]; -- with NUL plus padding for 4-alignment
177  *
178  *     -- all _MBCSHeader fields except for version and flags are 0
179  * } else {
180  *     -- normal base table with optional extension
181  *
182  *     int32_t stateTable[countStates][256];
183  *
184  *     struct _MBCSToUFallback { (fallbacks are sorted by offset)
185  *         uint32_t offset;
186  *         UChar32 codePoint;
187  *     } toUFallbacks[countToUFallbacks];
188  *
189  *     uint16_t unicodeCodeUnits[(offsetFromUTable-offsetToUCodeUnits)/2];
190  *                  (padded to an even number of units)
191  *
192  *     -- stage 1 tables
193  *     if(staticData.unicodeMask&UCNV_HAS_SUPPLEMENTARY) {
194  *         -- stage 1 table for all of Unicode
195  *         uint16_t fromUTable[0x440]; (32-bit-aligned)
196  *     } else {
197  *         -- BMP-only tables have a smaller stage 1 table
198  *         uint16_t fromUTable[0x40]; (32-bit-aligned)
199  *     }
200  *
201  *     -- stage 2 tables
202  *        length determined by top of stage 1 and bottom of stage 3 tables
203  *     if(outputType==MBCS_OUTPUT_1) {
204  *         -- SBCS: pure indexes
205  *         uint16_t stage 2 indexes[?];
206  *     } else {
207  *         -- DBCS, MBCS, EBCDIC_STATEFUL, ...: roundtrip flags and indexes
208  *         uint32_t stage 2 flags and indexes[?];
209  *         if(options&MBCS_OPT_NO_FROM_U) {
210  *             stage 2 really has length fullStage2Length
211  *             and the omitted lower part must be reconstituted from
212  *             the toUnicode data
213  *         }
214  *     }
215  *
216  *     -- stage 3 tables with byte results
217  *     if(outputType==MBCS_OUTPUT_1) {
218  *         -- SBCS: each 16-bit result contains flags and the result byte, see ucnvmbcs.c
219  *         uint16_t fromUBytes[fromUBytesLength/2];
220  *     } else if(!(options&MBCS_OPT_NO_FROM_U)) {
221  *         -- DBCS, MBCS, EBCDIC_STATEFUL, ... 2/3/4 bytes result, see ucnvmbcs.c
222  *         uint8_t fromUBytes[fromUBytesLength]; or
223  *         uint16_t fromUBytes[fromUBytesLength/2]; or
224  *         uint32_t fromUBytes[fromUBytesLength/4];
225  *     } else {
226  *         fromUBytes[] must be reconstituted from the toUnicode data
227  *     }
228  *
229  *     -- optional utf8Friendly mbcsIndex -- _MBCSHeader.version 4.3 (ICU 3.8) and higher
230  *     if(outputType!=MBCS_OUTPUT_1 &&
231  *        _MBCSHeader.version[1]>=3 &&
232  *        (maxFastUChar=_MBCSHeader.version[2])!=0
233  *     ) {
234  *         maxFastUChar=(maxFastUChar<<8)|0xff;
235  *         uint16_t mbcsIndex[(maxFastUChar+1)>>6];
236  *     }
237  * }
238  *
239  * -- extension table, details see ucnv_ext.h
240  * int32_t indexes[>=32]; ...
241  */
242 
243 /* MBCS converter data and state -------------------------------------------- */
244 
245 enum {
246     MBCS_MAX_STATE_COUNT=128
247 };
248 
249 /**
250  * MBCS action codes for conversions to Unicode.
251  * These values are in bits 23..20 of the state table entries.
252  */
253 enum {
254     MBCS_STATE_VALID_DIRECT_16,
255     MBCS_STATE_VALID_DIRECT_20,
256 
257     MBCS_STATE_FALLBACK_DIRECT_16,
258     MBCS_STATE_FALLBACK_DIRECT_20,
259 
260     MBCS_STATE_VALID_16,
261     MBCS_STATE_VALID_16_PAIR,
262 
263     MBCS_STATE_UNASSIGNED,
264     MBCS_STATE_ILLEGAL,
265 
266     MBCS_STATE_CHANGE_ONLY
267 };
268 
269 /* Macros for state table entries */
270 #define MBCS_ENTRY_TRANSITION(state, offset) (int32_t)(((int32_t)(state)<<24L)|(offset))
271 #define MBCS_ENTRY_TRANSITION_SET_OFFSET(entry, offset) (int32_t)(((entry)&0xff000000)|(offset))
272 #define MBCS_ENTRY_TRANSITION_ADD_OFFSET(entry, offset) (int32_t)((entry)+(offset))
273 
274 #define MBCS_ENTRY_FINAL(state, action, value) (int32_t)(0x80000000|((int32_t)(state)<<24L)|((action)<<20L)|(value))
275 #define MBCS_ENTRY_SET_FINAL(entry) (int32_t)((entry)|0x80000000)
276 #define MBCS_ENTRY_FINAL_SET_ACTION(entry, action) (int32_t)(((entry)&0xff0fffff)|((int32_t)(action)<<20L))
277 #define MBCS_ENTRY_FINAL_SET_VALUE(entry, value) (int32_t)(((entry)&0xfff00000)|(value))
278 #define MBCS_ENTRY_FINAL_SET_ACTION_VALUE(entry, action, value) (int32_t)(((entry)&0xff000000)|((int32_t)(action)<<20L)|(value))
279 
280 #define MBCS_ENTRY_SET_STATE(entry, state) (int32_t)(((entry)&0x80ffffff)|((int32_t)(state)<<24L))
281 
282 #define MBCS_ENTRY_STATE(entry) ((((uint32_t)entry)>>24)&0x7f)
283 
284 #define MBCS_ENTRY_IS_TRANSITION(entry) ((entry)>=0)
285 #define MBCS_ENTRY_IS_FINAL(entry) ((entry)<0)
286 
287 #define MBCS_ENTRY_TRANSITION_STATE(entry) (((uint32_t)entry)>>24)
288 #define MBCS_ENTRY_TRANSITION_OFFSET(entry) ((entry)&0xffffff)
289 
290 #define MBCS_ENTRY_FINAL_STATE(entry) ((((uint32_t)entry)>>24)&0x7f)
291 #define MBCS_ENTRY_FINAL_IS_VALID_DIRECT_16(entry) ((entry)<(int32_t)0x80100000)
292 #define MBCS_ENTRY_FINAL_ACTION(entry) ((((uint32_t)entry)>>20)&0xf)
293 #define MBCS_ENTRY_FINAL_VALUE(entry) ((entry)&0xfffff)
294 #define MBCS_ENTRY_FINAL_VALUE_16(entry) (uint16_t)(entry)
295 
296 #define IS_ASCII_ROUNDTRIP(b, asciiRoundtrips) (((asciiRoundtrips) & (1<<((b)>>2)))!=0)
297 
298 /* single-byte fromUnicode: get the 16-bit result word */
299 #define MBCS_SINGLE_RESULT_FROM_U(table, results, c) (results)[ (table)[ (table)[(c)>>10] +(((c)>>4)&0x3f) ] +((c)&0xf) ]
300 
301 /* single-byte fromUnicode using the sbcsIndex */
302 #define SBCS_RESULT_FROM_LOW_BMP(table, results, c) (results)[ (table)[(c)>>6] +((c)&0x3f) ]
303 
304 /* single-byte fromUTF8 using the sbcsIndex; l and t must be masked externally; can be l=0 and t<=0x7f */
305 #define SBCS_RESULT_FROM_UTF8(table, results, l, t) (results)[ (table)[l] +(t) ]
306 
307 /* multi-byte fromUnicode: get the 32-bit stage 2 entry */
308 #define MBCS_STAGE_2_FROM_U(table, c) ((const uint32_t *)(table))[ (table)[(c)>>10] +(((c)>>4)&0x3f) ]
309 #define MBCS_FROM_U_IS_ROUNDTRIP(stage2Entry, c) ( ((stage2Entry) & ((uint32_t)1<< (16+((c)&0xf)) )) !=0)
310 
311 #define MBCS_VALUE_2_FROM_STAGE_2(bytes, stage2Entry, c) ((uint16_t *)(bytes))[16*(uint32_t)(uint16_t)(stage2Entry)+((c)&0xf)]
312 #define MBCS_VALUE_4_FROM_STAGE_2(bytes, stage2Entry, c) ((uint32_t *)(bytes))[16*(uint32_t)(uint16_t)(stage2Entry)+((c)&0xf)]
313 
314 #define MBCS_POINTER_3_FROM_STAGE_2(bytes, stage2Entry, c) ((bytes)+(16*(uint32_t)(uint16_t)(stage2Entry)+((c)&0xf))*3)
315 
316 /* double-byte fromUnicode using the mbcsIndex */
317 #define DBCS_RESULT_FROM_MOST_BMP(table, results, c) (results)[ (table)[(c)>>6] +((c)&0x3f) ]
318 
319 /* double-byte fromUTF8 using the mbcsIndex; l and t1 combined into lt1; lt1 and t2 must be masked externally */
320 #define DBCS_RESULT_FROM_UTF8(table, results, lt1, t2) (results)[ (table)[lt1] +(t2) ]
321 
322 
323 /**
324  * MBCS output types for conversions from Unicode.
325  * These per-converter types determine the storage method in stage 3 of the lookup table,
326  * mostly how many bytes are stored per entry.
327  */
328 enum {
329     MBCS_OUTPUT_1,          /* 0 */
330     MBCS_OUTPUT_2,          /* 1 */
331     MBCS_OUTPUT_3,          /* 2 */
332     MBCS_OUTPUT_4,          /* 3 */
333 
334     MBCS_OUTPUT_3_EUC=8,    /* 8 */
335     MBCS_OUTPUT_4_EUC,      /* 9 */
336 
337     MBCS_OUTPUT_2_SISO=12,  /* c */
338     MBCS_OUTPUT_2_HZ,       /* d */
339 
340     MBCS_OUTPUT_EXT_ONLY,   /* e */
341 
342     MBCS_OUTPUT_COUNT,
343 
344     MBCS_OUTPUT_DBCS_ONLY=0xdb  /* runtime-only type for DBCS-only handling of SISO tables */
345 };
346 
347 /**
348  * Fallbacks to Unicode are stored outside the normal state table and code point structures
349  * in a vector of items of this type. They are sorted by offset.
350  */
351 typedef struct {
352     uint32_t offset;
353     UChar32 codePoint;
354 } _MBCSToUFallback;
355 
356 /** Constants for fast and UTF-8-friendly conversion. */
357 enum {
358     SBCS_FAST_MAX=0x0fff,               /* maximum code point with UTF-8-friendly SBCS runtime code, see makeconv SBCS_UTF8_MAX */
359     SBCS_FAST_LIMIT=SBCS_FAST_MAX+1,    /* =0x1000 */
360     MBCS_FAST_MAX=0xd7ff,               /* maximum code point with UTF-8-friendly MBCS runtime code, see makeconv MBCS_UTF8_MAX */
361     MBCS_FAST_LIMIT=MBCS_FAST_MAX+1     /* =0xd800 */
362 };
363 
364 /**
365  * This is the MBCS part of the UConverterTable union (a runtime data structure).
366  * It keeps all the per-converter data and points into the loaded mapping tables.
367  *
368  * utf8Friendly data structures added with _MBCSHeader.version 4.3
369  */
370 typedef struct UConverterMBCSTable {
371     /* toUnicode */
372     uint8_t countStates, dbcsOnlyState, stateTableOwned;
373     uint32_t countToUFallbacks;
374 
375     const int32_t (*stateTable)/*[countStates]*/[256];
376     int32_t (*swapLFNLStateTable)/*[countStates]*/[256]; /* for swaplfnl */
377     const uint16_t *unicodeCodeUnits/*[countUnicodeResults]*/;
378     const _MBCSToUFallback *toUFallbacks;
379 
380     /* fromUnicode */
381     const uint16_t *fromUnicodeTable;
382     const uint16_t *mbcsIndex;              /* for fast conversion from most of BMP to MBCS (utf8Friendly data) */
383     uint16_t sbcsIndex[SBCS_FAST_LIMIT>>6]; /* for fast conversion from low BMP to SBCS (utf8Friendly data) */
384     const uint8_t *fromUnicodeBytes;
385     uint8_t *swapLFNLFromUnicodeBytes;      /* for swaplfnl */
386     uint32_t fromUBytesLength;
387     uint8_t outputType, unicodeMask;
388     UBool utf8Friendly;                     /* for utf8Friendly data */
389     UChar maxFastUChar;                     /* for utf8Friendly data */
390 
391     /* roundtrips */
392     uint32_t asciiRoundtrips;
393 
394     /* reconstituted data that was omitted from the .cnv file */
395     uint8_t *reconstitutedData;
396 
397     /* converter name for swaplfnl */
398     char *swapLFNLName;
399 
400     /* extension data */
401     struct UConverterSharedData *baseSharedData;
402     const int32_t *extIndexes;
403 } UConverterMBCSTable;
404 
405 #define UCNV_MBCS_TABLE_INITIALIZER { \
406     /* toUnicode */ \
407     0, 0, 0, \
408     0, \
409      \
410     NULL, \
411     NULL, \
412     NULL, \
413     NULL, \
414      \
415     /* fromUnicode */ \
416     NULL, \
417     NULL, \
418     { 0 }, \
419     NULL, \
420     NULL, \
421     0, \
422     0, 0, \
423     FALSE, \
424     0, \
425      \
426     /* roundtrips */ \
427     0, \
428      \
429     /* reconstituted data that was omitted from the .cnv file */ \
430     NULL, \
431      \
432     /* converter name for swaplfnl */ \
433     NULL, \
434      \
435     /* extension data */ \
436     NULL, \
437     NULL \
438 }
439 
440 enum {
441     MBCS_OPT_LENGTH_MASK=0x3f,
442     MBCS_OPT_NO_FROM_U=0x40,
443     /*
444      * If any of the following options bits are set,
445      * then the file must be rejected.
446      */
447     MBCS_OPT_INCOMPATIBLE_MASK=0xffc0,
448     /*
449      * Remove bits from this mask as more options are recognized
450      * by all implementations that use this constant.
451      */
452     MBCS_OPT_UNKNOWN_INCOMPATIBLE_MASK=0xff80
453 };
454 
455 enum {
456     MBCS_HEADER_V4_LENGTH=8,
457     MBCS_HEADER_V5_MIN_LENGTH=9
458 };
459 
460 /**
461  * MBCS data header. See data format description above.
462  */
463 typedef struct {
464     UVersionInfo version;
465     uint32_t countStates,
466              countToUFallbacks,
467              offsetToUCodeUnits,
468              offsetFromUTable,
469              offsetFromUBytes,
470              flags,
471              fromUBytesLength;
472 
473     /* new and required in version 5 */
474     uint32_t options;
475 
476     /* new and optional in version 5; used if options&MBCS_OPT_NO_FROM_U */
477     uint32_t fullStage2Length;  /* number of 32-bit units */
478 } _MBCSHeader;
479 
480 #define UCNV_MBCS_HEADER_INITIALIZER { { 0 },  0, 0, 0, 0, 0, 0, 0,  0,  0 }
481 
482 /*
483  * This is a simple version of _MBCSGetNextUChar() that is used
484  * by other converter implementations.
485  * It only returns an "assigned" result if it consumes the entire input.
486  * It does not use state from the converter, nor error codes.
487  * It does not handle the EBCDIC swaplfnl option (set in UConverter).
488  * It handles conversion extensions but not GB 18030.
489  *
490  * Return value:
491  * U+fffe   unassigned
492  * U+ffff   illegal
493  * otherwise the Unicode code point
494  */
495 U_CFUNC UChar32
496 ucnv_MBCSSimpleGetNextUChar(UConverterSharedData *sharedData,
497                         const char *source, int32_t length,
498                         UBool useFallback);
499 
500 /**
501  * This version of _MBCSSimpleGetNextUChar() is optimized for single-byte, single-state codepages.
502  * It does not handle the EBCDIC swaplfnl option (set in UConverter).
503  * It does not handle conversion extensions (_extToU()).
504  */
505 U_CFUNC UChar32
506 ucnv_MBCSSingleSimpleGetNextUChar(UConverterSharedData *sharedData,
507                               uint8_t b, UBool useFallback);
508 
509 /**
510  * This macro version of _MBCSSingleSimpleGetNextUChar() gets a code point from a byte.
511  * It works for single-byte, single-state codepages that only map
512  * to and from BMP code points, and it always
513  * returns fallback values.
514  */
515 #define _MBCS_SINGLE_SIMPLE_GET_NEXT_BMP(sharedData, b) \
516     (UChar)MBCS_ENTRY_FINAL_VALUE_16((sharedData)->mbcs.stateTable[0][(uint8_t)(b)])
517 
518 /**
519  * This is an internal function that allows other converter implementations
520  * to check whether a byte is a lead byte.
521  */
522 U_CFUNC UBool
523 ucnv_MBCSIsLeadByte(UConverterSharedData *sharedData, char byte);
524 
525 /** This is a macro version of _MBCSIsLeadByte(). */
526 #define _MBCS_IS_LEAD_BYTE(sharedData, byte) \
527     (UBool)MBCS_ENTRY_IS_TRANSITION((sharedData)->mbcs.stateTable[0][(uint8_t)(byte)])
528 
529 /*
530  * This is another simple conversion function for internal use by other
531  * conversion implementations.
532  * It does not use the converter state nor call callbacks.
533  * It does not handle the EBCDIC swaplfnl option (set in UConverter).
534  * It handles conversion extensions but not GB 18030.
535  *
536  * It converts one single Unicode code point into codepage bytes, encoded
537  * as one 32-bit value. The function returns the number of bytes in *pValue:
538  * 1..4 the number of bytes in *pValue
539  * 0    unassigned (*pValue undefined)
540  * -1   illegal (currently not used, *pValue undefined)
541  *
542  * *pValue will contain the resulting bytes with the last byte in bits 7..0,
543  * the second to last byte in bits 15..8, etc.
544  * Currently, the function assumes but does not check that 0<=c<=0x10ffff.
545  */
546 U_CFUNC int32_t
547 ucnv_MBCSFromUChar32(UConverterSharedData *sharedData,
548                  UChar32 c, uint32_t *pValue,
549                  UBool useFallback);
550 
551 /**
552  * This version of _MBCSFromUChar32() is optimized for single-byte codepages.
553  * It does not handle the EBCDIC swaplfnl option (set in UConverter).
554  *
555  * It returns the codepage byte for the code point, or -1 if it is unassigned.
556  */
557 U_CFUNC int32_t
558 ucnv_MBCSSingleFromUChar32(UConverterSharedData *sharedData,
559                        UChar32 c,
560                        UBool useFallback);
561 
562 /**
563  * SBCS, DBCS, and EBCDIC_STATEFUL are replaced by MBCS, but
564  * we cheat a little about the type, returning the old types if appropriate.
565  */
566 U_CFUNC UConverterType
567 ucnv_MBCSGetType(const UConverter* converter);
568 
569 U_CFUNC void
570 ucnv_MBCSFromUnicodeWithOffsets(UConverterFromUnicodeArgs *pArgs,
571                             UErrorCode *pErrorCode);
572 U_CFUNC void
573 ucnv_MBCSToUnicodeWithOffsets(UConverterToUnicodeArgs *pArgs,
574                           UErrorCode *pErrorCode);
575 
576 /*
577  * Internal function returning a UnicodeSet for toUnicode() conversion.
578  * Currently only used for ISO-2022-CN, and only handles roundtrip mappings.
579  * In the future, if we add support for fallback sets, this function
580  * needs to be updated.
581  * Handles extensions.
582  * Does not empty the set first.
583  */
584 U_CFUNC void
585 ucnv_MBCSGetUnicodeSetForUnicode(const UConverterSharedData *sharedData,
586                                  const USetAdder *sa,
587                                  UConverterUnicodeSet which,
588                                  UErrorCode *pErrorCode);
589 
590 /*
591  * Same as ucnv_MBCSGetUnicodeSetForUnicode() but
592  * the set can be filtered by encoding scheme.
593  * Used by stateful converters which share regular conversion tables
594  * but only use a subset of their mappings.
595  */
596 U_CFUNC void
597 ucnv_MBCSGetFilteredUnicodeSetForUnicode(const UConverterSharedData *sharedData,
598                                          const USetAdder *sa,
599                                          UConverterUnicodeSet which,
600                                          UConverterSetFilter filter,
601                                          UErrorCode *pErrorCode);
602 
603 #endif
604 
605 #endif
606