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icu46/source/common/ucnv_ext.h

+/*
+******************************************************************************
+*
+*   Copyright (C) 2003-2007, 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 two 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.
+ *
+ * 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;
+ *       } else {
+ *         fallback;
+ *       }
+ *       // bits 30..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_RESERVED_MASK 0x60000000
+#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