text: /*
  ******************************************************************************
  *
  *   Copyright (C) 2003-2013, International Business Machines
  *   Corporation and others.  All Rights Reserved.
  *
  ******************************************************************************
  *   file name:  ucnv_ext.h
  *   encoding:   US-ASCII
  *   tab size:   8 (not used)
  *   indentation:4
  *
  *   created on: 2003jun13
  *   created by: Markus W. Scherer
  *
  *   Conversion extensions
  */
  
  #ifndef __UCNV_EXT_H__
  #define __UCNV_EXT_H__
  
  #include "unicode/utypes.h"
  
  #if !UCONFIG_NO_CONVERSION
  
  #include "unicode/ucnv.h"
  #include "ucnv_cnv.h"
  
  /*
   * See icuhtml/design/conversion/conversion_extensions.html
   *
   * Conversion extensions serve three purposes:
   * 1. They support m:n mappings.
   * 2. They support extension-only conversion files that are used together
   *    with the regular conversion data in base files.
   * 3. They support mappings with more complicated meta data,
   *    for example "good one-way" mappings (|4).
   *
   * A base file may contain an extension table (explicitly requested or
   * implicitly generated for m:n mappings), but its extension table is not
   * used when an extension-only file is used.
   *
   * It is an error if a base file contains any regular (not extension) mapping
   * from the same sequence as a mapping in the extension file
   * because the base mapping would hide the extension mapping.
   *
   *
   * Data for conversion extensions:
   *
   * One set of data structures per conversion direction (to/from Unicode).
   * The data structures are sorted by input units to allow for binary search.
   * Input sequences of more than one unit are handled like contraction tables
   * in collation:
   * The lookup value of a unit points to another table that is to be searched
   * for the next unit, recursively.
   *
   * For conversion from Unicode, the initial code point is looked up in
   * a 3-stage trie for speed,
   * with an additional table of unique results to save space.
   *
   * Long output strings are stored in separate arrays, with length and index
   * in the lookup tables.
   * Output results also include a flag distinguishing roundtrip from
   * (reverse) fallback mappings.
   *
   * Input Unicode strings must not begin or end with unpaired surrogates
   * to avoid problems with matches on parts of surrogate pairs.
   *
   * Mappings from multiple characters (code points or codepage state
   * table sequences) must be searched preferring the longest match.
   * For this to work and be efficient, the variable-width table must contain
   * all mappings that contain prefixes of the multiple characters.
   * If an extension table is built on top of a base table in another file
   * and a base table entry is a prefix of a multi-character mapping, then
   * this is an error.
   *
   *
   * Implementation note:
   *
   * Currently, the parser and several checks in the code limit the number
   * of UChars or bytes in a mapping to
   * UCNV_EXT_MAX_UCHARS and UCNV_EXT_MAX_BYTES, respectively,
   * which are output value limits in the data structure.
   *
   * For input, this is not strictly necessary - it is a hard limit only for the
   * buffers in UConverter that are used to store partial matches.
   *
   * Input sequences could otherwise be arbitrarily long if partial matches
   * need not be stored (i.e., if a sequence does not span several buffers with too
   * many units before the last buffer), although then results would differ
   * depending on whether partial matches exceed the limits or not,
   * which depends on the pattern of buffer sizes.
   *
   *
   * Data structure:
   *
   * int32_t indexes[>=32];
   *
   *   Array of indexes and lengths etc. The length of the array is at least 32.
   *   The actual length is stored in indexes[0] to be forward compatible.
   *
   *   Each index to another array is the number of bytes from indexes[].
   *   Each length of an array is the number of array base units in that array.
   *
   *   Some of the structures may not be present, in which case their indexes
   *   and lengths are 0.
   *
   *   Usage of indexes[i]:
   *   [0]  length of indexes[]
   *
   *   // to Unicode table
   *   [1]  index of toUTable[] (array of uint32_t)
   *   [2]  length of toUTable[]
   *   [3]  index of toUUChars[] (array of UChar)
   *   [4]  length of toUUChars[]
   *
   *   // from Unicode table, not for the initial code point
   *   [5]  index of fromUTableUChars[] (array of UChar)
   *   [6]  index of fromUTableValues[] (array of uint32_t)
   *   [7]  length of fromUTableUChars[] and fromUTableValues[]
   *   [8]  index of fromUBytes[] (array of char)
   *   [9]  length of fromUBytes[]
   *
   *   // from Unicode trie for initial-code point lookup
   *   [10] index of fromUStage12[] (combined array of uint16_t for stages 1 & 2)
   *   [11] length of stage 1 portion of fromUStage12[]
   *   [12] length of fromUStage12[]
   *   [13] index of fromUStage3[] (array of uint16_t indexes into fromUStage3b[])
   *   [14] length of fromUStage3[]
   *   [15] index of fromUStage3b[] (array of uint32_t like fromUTableValues[])
   *   [16] length of fromUStage3b[]
   *
   *   [17] Bit field containing numbers of bytes:
   *        31..24 reserved, 0
   *        23..16 maximum input bytes
   *        15.. 8 maximum output bytes
   *         7.. 0 maximum bytes per UChar
   *
   *   [18] Bit field containing numbers of UChars:
   *        31..24 reserved, 0
   *        23..16 maximum input UChars
   *        15.. 8 maximum output UChars
   *         7.. 0 maximum UChars per byte
   *
   *   [19] Bit field containing flags:
   *               (extension table unicodeMask)
   *         1     UCNV_HAS_SURROGATES flag for the extension table
   *         0     UCNV_HAS_SUPPLEMENTARY flag for the extension table
   *
   *   [20]..[30] reserved, 0
   *   [31] number of bytes for the entire extension structure
   *   [>31] reserved; there are indexes[0] indexes
   *
   *
   * uint32_t toUTable[];
   *
   *   Array of byte/value pairs for lookups for toUnicode conversion.
   *   The array is partitioned into sections like collation contraction tables.
   *   Each section contains one word with the number of following words and
   *   a default value for when the lookup in this section yields no match.
   *
   *   A section is sorted in ascending order of input bytes,
   *   allowing for fast linear or binary searches.
   *   The builder may store entries for a contiguous range of byte values
   *   (compare difference between the first and last one with count),
   *   which then allows for direct array access.
   *   The builder should always do this for the initial table section.
   *
   *   Entries may have 0 values, see below.
   *   No two entries in a section have the same byte values.
   *
   *   Each uint32_t contains an input byte value in bits 31..24 and the
   *   corresponding lookup value in bits 23..0.
   *   Interpret the value as follows:
   *     if(value==0) {
   *       no match, see below
   *     } else if(value<0x1f0000) {
   *       partial match - use value as index to the next toUTable section
   *       and match the next unit; (value indexes toUTable[value])
   *     } else {
   *       if(bit 23 set) {
   *         roundtrip;
   *       } else {
   *         fallback;
   *       }
   *       unset value bit 23;
   *       if(value<=0x2fffff) {
   *         (value-0x1f0000) is a code point; (BMP: value<=0x1fffff)
   *       } else {
   *         bits 17..0 (value&0x3ffff) is an index to
   *           the result UChars in toUUChars[]; (0 indexes toUUChars[0])
   *         length of the result=((value>>18)-12); (length=0..19)
   *       }
   *     }
   *
   *   The first word in a section contains the number of following words in the
   *   input byte position (bits 31..24, number=1..0xff).
   *   The value of the initial word is used when the current byte is not found
   *   in this section.
   *   If the value is not 0, then it represents a result as above.
   *   If the value is 0, then the search has to return a shorter match with an
   *   earlier default value as the result, or result in "unmappable" even for the
   *   initial bytes.
   *   If the value is 0 for the initial toUTable entry, then the initial byte
   *   does not start any mapping input.
   *
   *
   * UChar toUUChars[];
   *
   *   Contains toUnicode mapping results, stored as sequences of UChars.
   *   Indexes and lengths stored in the toUTable[].
   *
   *
   * UChar fromUTableUChars[];
   * uint32_t fromUTableValues[];
   *
   *   The fromUTable is split into two arrays, but works otherwise much like
   *   the toUTable. The array is partitioned into sections like collation
   *   contraction tables and toUTable.
   *   A row in the table consists of same-index entries in fromUTableUChars[]
   *   and fromUTableValues[].
   *
   *   Interpret a value as follows:
   *     if(value==0) {
   *       no match, see below
   *     } else if(value<=0xffffff) { (bits 31..24 are 0)
   *       partial match - use value as index to the next fromUTable section
   *       and match the next unit; (value indexes fromUTable[value])
   *     } else {
   *       if(value==0x80000001) {
   *         return no mapping, but request for <subchar1>;
   *       }
   *       if(bit 31 set) {
   *         roundtrip (|0);
   *       } else if(bit 30 set) {
   *         "good one-way" mapping (|4); -- new in ICU4C 51, _MBCSHeader.version 5.4/4.4
   *       } else {
   *         normal fallback (|1);
   *       }
   *       // bit 29 reserved, 0
   *       length=(value>>24)&0x1f; (bits 28..24)
   *       if(length==1..3) {
   *         bits 23..0 contain 1..3 bytes, padded with 00s on the left;
   *       } else {
   *         bits 23..0 (value&0xffffff) is an index to
   *           the result bytes in fromUBytes[]; (0 indexes fromUBytes[0])
   *       }
   *     }
   *       
   *   The first pair in a section contains the number of following pairs in the
   *   UChar position (16 bits, number=1..0xffff).
   *   The value of the initial pair is used when the current UChar is not found
   *   in this section.
   *   If the value is not 0, then it represents a result as above.
   *   If the value is 0, then the search has to return a shorter match with an
   *   earlier default value as the result, or result in "unmappable" even for the
   *   initial UChars.
   *
   *   If the from Unicode trie is present, then the from Unicode search tables
   *   are not used for initial code points.
   *   In this case, the first entries (index 0) in the tables are not used
   *   (reserved, set to 0) because a value of 0 is used in trie results
   *   to indicate no mapping.
   *
   *
   * uint16_t fromUStage12[];
   *
   *   Stages 1 & 2 of a trie that maps an initial code point.
   *   Indexes in stage 1 are all offset by the length of stage 1 so that the
   *   same array pointer can be used for both stages.
   *   If (c>>10)>=(length of stage 1) then c does not start any mapping.
   *   Same bit distribution as for regular conversion tries.
   *
   *
   * uint16_t fromUStage3[];
   * uint32_t fromUStage3b[];
   *
   *   Stage 3 of the trie. The first array simply contains indexes to the second,
   *   which contains words in the same format as fromUTableValues[].
   *   Use a stage 3 granularity of 4, which allows for 256k stage 3 entries,
   *   and 16-bit entries in stage 3 allow for 64k stage 3b entries.
   *   The stage 3 granularity means that the stage 2 entry needs to be left-shifted.
   *
   *   Two arrays are used because it is expected that more than half of the stage 3
   *   entries will be zero. The 16-bit index stage 3 array saves space even
   *   considering storing a total of 6 bytes per non-zero entry in both arrays
   *   together.
   *   Using a stage 3 granularity of >1 diminishes the compactability in that stage
   *   but provides a larger effective addressing space in stage 2.
   *   All but the final result stage use 16-bit entries to save space.
   *
   *   fromUStage3b[] contains a zero for "no mapping" at its index 0,
   *   and may contain UCNV_EXT_FROM_U_SUBCHAR1 at index 1 for "<subchar1> SUB mapping"
   *   (i.e., "no mapping" with preference for <subchar1> rather than <subchar>),
   *   and all other items are unique non-zero results.
   *
   *   The default value of a fromUTableValues[] section that is referenced
   *   _directly_ from a fromUStage3b[] item may also be UCNV_EXT_FROM_U_SUBCHAR1,
   *   but this value must not occur anywhere else in fromUTableValues[]
   *   because "no mapping" is always a property of a single code point,
   *   never of multiple.
   *
   *
   * char fromUBytes[];
   *
   *   Contains fromUnicode mapping results, stored as sequences of chars.
   *   Indexes and lengths stored in the fromUTableValues[].
   */
  enum {
      UCNV_EXT_INDEXES_LENGTH,            /* 0 */
  
      UCNV_EXT_TO_U_INDEX,                /* 1 */
      UCNV_EXT_TO_U_LENGTH,
      UCNV_EXT_TO_U_UCHARS_INDEX,
      UCNV_EXT_TO_U_UCHARS_LENGTH,
  
      UCNV_EXT_FROM_U_UCHARS_INDEX,       /* 5 */
      UCNV_EXT_FROM_U_VALUES_INDEX,
      UCNV_EXT_FROM_U_LENGTH,
      UCNV_EXT_FROM_U_BYTES_INDEX,
      UCNV_EXT_FROM_U_BYTES_LENGTH,
  
      UCNV_EXT_FROM_U_STAGE_12_INDEX,     /* 10 */
      UCNV_EXT_FROM_U_STAGE_1_LENGTH,
      UCNV_EXT_FROM_U_STAGE_12_LENGTH,
      UCNV_EXT_FROM_U_STAGE_3_INDEX,
      UCNV_EXT_FROM_U_STAGE_3_LENGTH,
      UCNV_EXT_FROM_U_STAGE_3B_INDEX,
      UCNV_EXT_FROM_U_STAGE_3B_LENGTH,
  
      UCNV_EXT_COUNT_BYTES,               /* 17 */
      UCNV_EXT_COUNT_UCHARS,
      UCNV_EXT_FLAGS,
  
      UCNV_EXT_RESERVED_INDEX,            /* 20, moves with additional indexes */
  
      UCNV_EXT_SIZE=31,
      UCNV_EXT_INDEXES_MIN_LENGTH=32
  };
  
  /* get the pointer to an extension array from indexes[index] */
  #define UCNV_EXT_ARRAY(indexes, index, itemType) \
      ((const itemType *)((const char *)(indexes)+(indexes)[index]))
  
  #define UCNV_GET_MAX_BYTES_PER_UCHAR(indexes) \
      ((indexes)[UCNV_EXT_COUNT_BYTES]&0xff)
  
  /* internal API ------------------------------------------------------------- */
  
  U_CFUNC UBool
  ucnv_extInitialMatchToU(UConverter *cnv, const int32_t *cx,
                          int32_t firstLength,
                          const char **src, const char *srcLimit,
                          UChar **target, const UChar *targetLimit,
                          int32_t **offsets, int32_t srcIndex,
                          UBool flush,
                          UErrorCode *pErrorCode);
  
  U_CFUNC UChar32
  ucnv_extSimpleMatchToU(const int32_t *cx,
                         const char *source, int32_t length,
                         UBool useFallback);
  
  U_CFUNC void
  ucnv_extContinueMatchToU(UConverter *cnv,
                           UConverterToUnicodeArgs *pArgs, int32_t srcIndex,
                           UErrorCode *pErrorCode);
  
  
  U_CFUNC UBool
  ucnv_extInitialMatchFromU(UConverter *cnv, const int32_t *cx,
                            UChar32 cp,
                            const UChar **src, const UChar *srcLimit,
                            char **target, const char *targetLimit,
                            int32_t **offsets, int32_t srcIndex,
                            UBool flush,
                            UErrorCode *pErrorCode);
  
  U_CFUNC int32_t
  ucnv_extSimpleMatchFromU(const int32_t *cx,
                           UChar32 cp, uint32_t *pValue,
                           UBool useFallback);
  
  U_CFUNC void
  ucnv_extContinueMatchFromU(UConverter *cnv,
                             UConverterFromUnicodeArgs *pArgs, int32_t srcIndex,
                             UErrorCode *pErrorCode);
  
  /*
   * Add code points and strings to the set according to the extension mappings.
   * Limitation on the UConverterSetFilter:
   * The filters currently assume that they are used with 1:1 mappings.
   * They only apply to single input code points, and then they pass through
   * only mappings with single-charset-code results.
   * For example, the Shift-JIS filter only works for 2-byte results and tests
   * that those 2 bytes are in the JIS X 0208 range of Shift-JIS.
   */
  U_CFUNC void
  ucnv_extGetUnicodeSet(const UConverterSharedData *sharedData,
                        const USetAdder *sa,
                        UConverterUnicodeSet which,
                        UConverterSetFilter filter,
                        UErrorCode *pErrorCode);
  
  /* toUnicode helpers -------------------------------------------------------- */
  
  #define UCNV_EXT_TO_U_BYTE_SHIFT 24
  #define UCNV_EXT_TO_U_VALUE_MASK 0xffffff
  #define UCNV_EXT_TO_U_MIN_CODE_POINT 0x1f0000
  #define UCNV_EXT_TO_U_MAX_CODE_POINT 0x2fffff
  #define UCNV_EXT_TO_U_ROUNDTRIP_FLAG ((uint32_t)1<<23)
  #define UCNV_EXT_TO_U_INDEX_MASK 0x3ffff
  #define UCNV_EXT_TO_U_LENGTH_SHIFT 18
  #define UCNV_EXT_TO_U_LENGTH_OFFSET 12
  
  /* maximum number of indexed UChars */
  #define UCNV_EXT_MAX_UCHARS 19
  
  #define UCNV_EXT_TO_U_MAKE_WORD(byte, value) (((uint32_t)(byte)<<UCNV_EXT_TO_U_BYTE_SHIFT)|(value))
  
  #define UCNV_EXT_TO_U_GET_BYTE(word) ((word)>>UCNV_EXT_TO_U_BYTE_SHIFT)
  #define UCNV_EXT_TO_U_GET_VALUE(word) ((word)&UCNV_EXT_TO_U_VALUE_MASK)
  
  #define UCNV_EXT_TO_U_IS_PARTIAL(value) ((value)<UCNV_EXT_TO_U_MIN_CODE_POINT)
  #define UCNV_EXT_TO_U_GET_PARTIAL_INDEX(value) (value)
  
  #define UCNV_EXT_TO_U_IS_ROUNDTRIP(value) (((value)&UCNV_EXT_TO_U_ROUNDTRIP_FLAG)!=0)
  #define UCNV_EXT_TO_U_MASK_ROUNDTRIP(value) ((value)&~UCNV_EXT_TO_U_ROUNDTRIP_FLAG)
  
  /* use after masking off the roundtrip flag */
  #define UCNV_EXT_TO_U_IS_CODE_POINT(value) ((value)<=UCNV_EXT_TO_U_MAX_CODE_POINT)
  #define UCNV_EXT_TO_U_GET_CODE_POINT(value) ((value)-UCNV_EXT_TO_U_MIN_CODE_POINT)
  
  #define UCNV_EXT_TO_U_GET_INDEX(value) ((value)&UCNV_EXT_TO_U_INDEX_MASK)
  #define UCNV_EXT_TO_U_GET_LENGTH(value) (((value)>>UCNV_EXT_TO_U_LENGTH_SHIFT)-UCNV_EXT_TO_U_LENGTH_OFFSET)
  
  /* fromUnicode helpers ------------------------------------------------------ */
  
  /* most trie constants are shared with ucnvmbcs.h */
  
  /* see similar utrie.h UTRIE_INDEX_SHIFT and UTRIE_DATA_GRANULARITY */
  #define UCNV_EXT_STAGE_2_LEFT_SHIFT 2
  #define UCNV_EXT_STAGE_3_GRANULARITY 4
  
  /* trie access, returns the stage 3 value=index to stage 3b; s1Index=c>>10 */
  #define UCNV_EXT_FROM_U(stage12, stage3, s1Index, c) \
      (stage3)[ ((int32_t)(stage12)[ (stage12)[s1Index] +(((c)>>4)&0x3f) ]<<UCNV_EXT_STAGE_2_LEFT_SHIFT) +((c)&0xf) ]
  
  #define UCNV_EXT_FROM_U_LENGTH_SHIFT 24
  #define UCNV_EXT_FROM_U_ROUNDTRIP_FLAG ((uint32_t)1<<31)
  #define UCNV_EXT_FROM_U_GOOD_ONE_WAY_FLAG 0x40000000
  #define UCNV_EXT_FROM_U_STATUS_MASK 0xc0000000
  #define UCNV_EXT_FROM_U_RESERVED_MASK 0x20000000
  #define UCNV_EXT_FROM_U_DATA_MASK 0xffffff
  
  /* special value for "no mapping" to <subchar1> (impossible roundtrip to 0 bytes, value 01) */
  #define UCNV_EXT_FROM_U_SUBCHAR1 0x80000001
  
  /* at most 3 bytes in the lower part of the value */
  #define UCNV_EXT_FROM_U_MAX_DIRECT_LENGTH 3
  
  /* maximum number of indexed bytes */
  #define UCNV_EXT_MAX_BYTES 0x1f
  
  #define UCNV_EXT_FROM_U_IS_PARTIAL(value) (((value)>>UCNV_EXT_FROM_U_LENGTH_SHIFT)==0)
  #define UCNV_EXT_FROM_U_GET_PARTIAL_INDEX(value) (value)
  
  #define UCNV_EXT_FROM_U_IS_ROUNDTRIP(value) (((value)&UCNV_EXT_FROM_U_ROUNDTRIP_FLAG)!=0)
  #define UCNV_EXT_FROM_U_MASK_ROUNDTRIP(value) ((value)&~UCNV_EXT_FROM_U_ROUNDTRIP_FLAG)
  
  /* get length; masks away all other bits */
  #define UCNV_EXT_FROM_U_GET_LENGTH(value) (int32_t)(((value)>>UCNV_EXT_FROM_U_LENGTH_SHIFT)&UCNV_EXT_MAX_BYTES)
  
  /* get bytes or bytes index */
  #define UCNV_EXT_FROM_U_GET_DATA(value) ((value)&UCNV_EXT_FROM_U_DATA_MASK)
  
  #endif
  
  #endif
  