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scuffed-code/icu4c/source/common/ucnv_ext.h
Andy Heninger 04448b004f ICU-12764 UTF-8 source files, update file encoding comments. 
X-SVN-Rev: 39641
2017-02-03 18:57:23 +00:00

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// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
******************************************************************************
*
* Copyright (C) 2003-2013, International Business Machines
* Corporation and others. All Rights Reserved.
*
******************************************************************************
* file name: ucnv_ext.h
* encoding: UTF-8
* 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
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