290 lines
11 KiB
C++
290 lines
11 KiB
C++
// © 2017 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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// ucptrie_impl.h (modified from utrie2_impl.h)
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// created: 2017dec29 Markus W. Scherer
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#ifndef __UCPTRIE_IMPL_H__
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#define __UCPTRIE_IMPL_H__
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#include "unicode/ucptrie.h"
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#ifdef UCPTRIE_DEBUG
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#include "unicode/umutablecptrie.h"
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#endif
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// UCPTrie signature values, in platform endianness and opposite endianness.
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// The UCPTrie signature ASCII byte values spell "Tri3".
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#define UCPTRIE_SIG 0x54726933
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#define UCPTRIE_OE_SIG 0x33697254
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/**
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* Header data for the binary, memory-mappable representation of a UCPTrie/CodePointTrie.
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* @internal
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*/
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struct UCPTrieHeader {
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/** "Tri3" in big-endian US-ASCII (0x54726933) */
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uint32_t signature;
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/**
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* Options bit field:
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* Bits 15..12: Data length bits 19..16.
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* Bits 11..8: Data null block offset bits 19..16.
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* Bits 7..6: UCPTrieType
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* Bits 5..3: Reserved (0).
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* Bits 2..0: UCPTrieValueWidth
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*/
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uint16_t options;
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/** Total length of the index tables. */
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uint16_t indexLength;
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/** Data length bits 15..0. */
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uint16_t dataLength;
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/** Index-3 null block offset, 0x7fff or 0xffff if none. */
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uint16_t index3NullOffset;
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/** Data null block offset bits 15..0, 0xfffff if none. */
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uint16_t dataNullOffset;
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/**
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* First code point of the single-value range ending with U+10ffff,
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* rounded up and then shifted right by UCPTRIE_SHIFT_2.
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*/
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uint16_t shiftedHighStart;
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};
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/**
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* Constants for use with UCPTrieHeader.options.
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* @internal
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*/
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enum {
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UCPTRIE_OPTIONS_DATA_LENGTH_MASK = 0xf000,
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UCPTRIE_OPTIONS_DATA_NULL_OFFSET_MASK = 0xf00,
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UCPTRIE_OPTIONS_RESERVED_MASK = 0x38,
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UCPTRIE_OPTIONS_VALUE_BITS_MASK = 7,
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/**
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* Value for index3NullOffset which indicates that there is no index-3 null block.
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* Bit 15 is unused for this value because this bit is used if the index-3 contains
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* 18-bit indexes.
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*/
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UCPTRIE_NO_INDEX3_NULL_OFFSET = 0x7fff,
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UCPTRIE_NO_DATA_NULL_OFFSET = 0xfffff
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};
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// Internal constants.
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enum {
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/** The length of the BMP index table. 1024=0x400 */
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UCPTRIE_BMP_INDEX_LENGTH = 0x10000 >> UCPTRIE_FAST_SHIFT,
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UCPTRIE_SMALL_LIMIT = 0x1000,
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UCPTRIE_SMALL_INDEX_LENGTH = UCPTRIE_SMALL_LIMIT >> UCPTRIE_FAST_SHIFT,
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/** Shift size for getting the index-3 table offset. */
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UCPTRIE_SHIFT_3 = 4,
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/** Shift size for getting the index-2 table offset. */
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UCPTRIE_SHIFT_2 = 5 + UCPTRIE_SHIFT_3,
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/** Shift size for getting the index-1 table offset. */
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UCPTRIE_SHIFT_1 = 5 + UCPTRIE_SHIFT_2,
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/**
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* Difference between two shift sizes,
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* for getting an index-2 offset from an index-3 offset. 5=9-4
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*/
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UCPTRIE_SHIFT_2_3 = UCPTRIE_SHIFT_2 - UCPTRIE_SHIFT_3,
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/**
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* Difference between two shift sizes,
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* for getting an index-1 offset from an index-2 offset. 5=14-9
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*/
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UCPTRIE_SHIFT_1_2 = UCPTRIE_SHIFT_1 - UCPTRIE_SHIFT_2,
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/**
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* Number of index-1 entries for the BMP. (4)
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* This part of the index-1 table is omitted from the serialized form.
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*/
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UCPTRIE_OMITTED_BMP_INDEX_1_LENGTH = 0x10000 >> UCPTRIE_SHIFT_1,
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/** Number of entries in an index-2 block. 32=0x20 */
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UCPTRIE_INDEX_2_BLOCK_LENGTH = 1 << UCPTRIE_SHIFT_1_2,
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/** Mask for getting the lower bits for the in-index-2-block offset. */
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UCPTRIE_INDEX_2_MASK = UCPTRIE_INDEX_2_BLOCK_LENGTH - 1,
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/** Number of code points per index-2 table entry. 512=0x200 */
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UCPTRIE_CP_PER_INDEX_2_ENTRY = 1 << UCPTRIE_SHIFT_2,
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/** Number of entries in an index-3 block. 32=0x20 */
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UCPTRIE_INDEX_3_BLOCK_LENGTH = 1 << UCPTRIE_SHIFT_2_3,
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/** Mask for getting the lower bits for the in-index-3-block offset. */
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UCPTRIE_INDEX_3_MASK = UCPTRIE_INDEX_3_BLOCK_LENGTH - 1,
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/** Number of entries in a small data block. 16=0x10 */
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UCPTRIE_SMALL_DATA_BLOCK_LENGTH = 1 << UCPTRIE_SHIFT_3,
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/** Mask for getting the lower bits for the in-small-data-block offset. */
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UCPTRIE_SMALL_DATA_MASK = UCPTRIE_SMALL_DATA_BLOCK_LENGTH - 1
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};
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typedef UChar32
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UCPTrieGetRange(const void *trie, UChar32 start,
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UCPMapValueFilter *filter, const void *context, uint32_t *pValue);
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U_CFUNC UChar32
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ucptrie_internalGetRange(UCPTrieGetRange *getRange,
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const void *trie, UChar32 start,
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UCPMapRangeOption option, uint32_t surrogateValue,
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UCPMapValueFilter *filter, const void *context, uint32_t *pValue);
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#ifdef UCPTRIE_DEBUG
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U_CFUNC void
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ucptrie_printLengths(const UCPTrie *trie, const char *which);
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U_CFUNC void umutablecptrie_setName(UMutableCPTrie *builder, const char *name);
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#endif
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/*
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* Format of the binary, memory-mappable representation of a UCPTrie/CodePointTrie.
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* For overview information see https://icu.unicode.org/design/struct/utrie
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*
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* The binary trie data should be 32-bit-aligned.
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* The overall layout is:
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*
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* UCPTrieHeader header; -- 16 bytes, see struct definition above
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* uint16_t index[header.indexLength];
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* uintXY_t data[header.dataLength];
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*
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* The trie data array is an array of uint16_t, uint32_t, or uint8_t,
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* specified via the UCPTrieValueWidth when building the trie.
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* The data array is 32-bit-aligned for uint32_t, otherwise 16-bit-aligned.
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* The overall length of the trie data is a multiple of 4 bytes.
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* (Padding is added at the end of the index array and/or near the end of the data array as needed.)
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*
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* The length of the data array (dataLength) is stored as an integer split across two fields
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* of the header struct (high bits in header.options).
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*
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* The trie type can be "fast" or "small" which determines the index structure,
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* specified via the UCPTrieType when building the trie.
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*
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* The type and valueWidth are stored in the header.options.
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* There are reserved type and valueWidth values, and reserved header.options bits.
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* They could be used in future format extensions.
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* Code reading the trie structure must fail with an error when unknown values or options are set.
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*
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* Values for ASCII character (U+0000..U+007F) can always be found at the start of the data array.
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*
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* Values for code points below a type-specific fast-indexing limit are found via two-stage lookup.
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* For a "fast" trie, the limit is the BMP/supplementary boundary at U+10000.
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* For a "small" trie, the limit is UCPTRIE_SMALL_MAX+1=U+1000.
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*
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* All code points in the range highStart..U+10FFFF map to a single highValue
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* which is stored at the second-to-last position of the data array.
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* (See UCPTRIE_HIGH_VALUE_NEG_DATA_OFFSET.)
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* The highStart value is header.shiftedHighStart<<UCPTRIE_SHIFT_2.
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* (UCPTRIE_SHIFT_2=9)
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*
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* Values for code points fast_limit..highStart-1 are found via four-stage lookup.
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* The data block size is smaller for this range than for the fast range.
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* This together with more index stages with small blocks makes this range
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* more easily compactable.
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*
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* There is also a trie error value stored at the last position of the data array.
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* (See UCPTRIE_ERROR_VALUE_NEG_DATA_OFFSET.)
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* It is intended to be returned for inputs that are not Unicode code points
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* (outside U+0000..U+10FFFF), or in string processing for ill-formed input
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* (unpaired surrogate in UTF-16, ill-formed UTF-8 subsequence).
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*
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* For a "fast" trie:
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*
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* The index array starts with the BMP index table for BMP code point lookup.
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* Its length is 1024=0x400.
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*
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* The supplementary index-1 table follows the BMP index table.
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* Variable length, for code points up to highStart-1.
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* Maximum length 64=0x40=0x100000>>UCPTRIE_SHIFT_1.
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* (For 0x100000 supplementary code points U+10000..U+10ffff.)
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*
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* After this index-1 table follow the variable-length index-3 and index-2 tables.
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*
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* The supplementary index tables are omitted completely
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* if there is only BMP data (highStart<=U+10000).
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*
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* For a "small" trie:
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*
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* The index array starts with a fast-index table for lookup of code points U+0000..U+0FFF.
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*
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* The "supplementary" index tables are always stored.
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* The index-1 table starts from U+0000, its maximum length is 68=0x44=0x110000>>UCPTRIE_SHIFT_1.
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*
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* For both trie types:
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*
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* The last index-2 block may be a partial block, storing indexes only for code points
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* below highStart.
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*
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* Lookup for ASCII code point c:
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*
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* Linear access from the start of the data array.
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*
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* value = data[c];
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*
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* Lookup for fast-range code point c:
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*
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* Shift the code point right by UCPTRIE_FAST_SHIFT=6 bits,
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* fetch the index array value at that offset,
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* add the lower code point bits, index into the data array.
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*
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* value = data[index[c>>6] + (c&0x3f)];
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*
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* (This works for ASCII as well.)
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*
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* Lookup for small-range code point c below highStart:
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*
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* Split the code point into four bit fields using several sets of shifts & masks
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* to read consecutive values from the index-1, index-2, index-3 and data tables.
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*
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* If all of the data block offsets in an index-3 block fit within 16 bits (up to 0xffff),
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* then the data block offsets are stored directly as uint16_t.
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*
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* Otherwise (this is very unusual but possible), the index-2 entry for the index-3 block
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* has bit 15 (0x8000) set, and each set of 8 index-3 entries is preceded by
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* an additional uint16_t word. Data block offsets are 18 bits wide, with the top 2 bits stored
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* in the additional word.
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*
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* See ucptrie_internalSmallIndex() for details.
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*
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* (In a "small" trie, this works for ASCII and below-fast_limit code points as well.)
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*
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* Compaction:
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*
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* Multiple code point ranges ("blocks") that are aligned on certain boundaries
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* (determined by the shifting/bit fields of code points) and
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* map to the same data values normally share a single subsequence of the data array.
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* Data blocks can also overlap partially.
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* (Depending on the builder code finding duplicate and overlapping blocks.)
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*
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* Iteration over same-value ranges:
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*
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* Range iteration (ucptrie_getRange()) walks the structure from a start code point
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* until some code point is found that maps to a different value;
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* the end of the returned range is just before that.
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*
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* The header.dataNullOffset (split across two header fields, high bits in header.options)
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* is the offset of a widely shared data block filled with one single value.
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* It helps quickly skip over large ranges of data with that value.
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* The builder must ensure that if the start of any data block (fast or small)
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* matches the dataNullOffset, then the whole block must be filled with the null value.
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* Special care must be taken if there is no fast null data block
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* but a small one, which is shorter, and it matches the *start* of some fast data block.
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*
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* Similarly, the header.index3NullOffset is the index-array offset of an index-3 block
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* where all index entries point to the dataNullOffset.
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* If there is no such data or index-3 block, then these offsets are set to
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* values that cannot be reached (data offset out of range/reserved index offset),
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* normally UCPTRIE_NO_DATA_NULL_OFFSET or UCPTRIE_NO_INDEX3_NULL_OFFSET respectively.
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*/
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#endif
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