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ucptrie_impl.h (11336B)

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// © 2017 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html

// ucptrie_impl.h (modified from utrie2_impl.h)
// created: 2017dec29 Markus W. Scherer

#ifndef __UCPTRIE_IMPL_H__
#define __UCPTRIE_IMPL_H__

#include "unicode/ucptrie.h"
#ifdef UCPTRIE_DEBUG
#include "unicode/umutablecptrie.h"
#endif

// UCPTrie signature values, in platform endianness and opposite endianness.
// The UCPTrie signature ASCII byte values spell "Tri3".
#define UCPTRIE_SIG     0x54726933
#define UCPTRIE_OE_SIG  0x33697254

/**
* Header data for the binary, memory-mappable representation of a UCPTrie/CodePointTrie.
* @internal
*/
struct UCPTrieHeader {
   /** "Tri3" in big-endian US-ASCII (0x54726933) */
   uint32_t signature;

   /**
    * Options bit field:
    * Bits 15..12: Data length bits 19..16.
    * Bits 11..8: Data null block offset bits 19..16.
    * Bits 7..6: UCPTrieType
    * Bits 5..3: Reserved (0).
    * Bits 2..0: UCPTrieValueWidth
    */
   uint16_t options;

   /** Total length of the index tables. */
   uint16_t indexLength;

   /** Data length bits 15..0. */
   uint16_t dataLength;

   /** Index-3 null block offset, 0x7fff or 0xffff if none. */
   uint16_t index3NullOffset;

   /** Data null block offset bits 15..0, 0xfffff if none. */
   uint16_t dataNullOffset;

   /**
    * First code point of the single-value range ending with U+10ffff,
    * rounded up and then shifted right by UCPTRIE_SHIFT_2.
    */
   uint16_t shiftedHighStart;
};

// Constants for use with UCPTrieHeader.options.
constexpr uint16_t UCPTRIE_OPTIONS_DATA_LENGTH_MASK = 0xf000;
constexpr uint16_t UCPTRIE_OPTIONS_DATA_NULL_OFFSET_MASK = 0xf00;
constexpr uint16_t UCPTRIE_OPTIONS_RESERVED_MASK = 0x38;
constexpr uint16_t UCPTRIE_OPTIONS_VALUE_BITS_MASK = 7;

/**
* Value for index3NullOffset which indicates that there is no index-3 null block.
* Bit 15 is unused for this value because this bit is used if the index-3 contains
* 18-bit indexes.
*/
constexpr int32_t UCPTRIE_NO_INDEX3_NULL_OFFSET = 0x7fff;
constexpr int32_t UCPTRIE_NO_DATA_NULL_OFFSET = 0xfffff;

// Internal constants.

/** The length of the BMP index table. 1024=0x400 */
constexpr int32_t UCPTRIE_BMP_INDEX_LENGTH = 0x10000 >> UCPTRIE_FAST_SHIFT;

constexpr int32_t UCPTRIE_SMALL_LIMIT = 0x1000;
constexpr int32_t UCPTRIE_SMALL_INDEX_LENGTH = UCPTRIE_SMALL_LIMIT >> UCPTRIE_FAST_SHIFT;

/** Shift size for getting the index-3 table offset. */
constexpr int32_t UCPTRIE_SHIFT_3 = 4;

/** Shift size for getting the index-2 table offset. */
constexpr int32_t UCPTRIE_SHIFT_2 = 5 + UCPTRIE_SHIFT_3;

/** Shift size for getting the index-1 table offset. */
constexpr int32_t UCPTRIE_SHIFT_1 = 5 + UCPTRIE_SHIFT_2;

/**
* Difference between two shift sizes,
* for getting an index-2 offset from an index-3 offset. 5=9-4
*/
constexpr int32_t UCPTRIE_SHIFT_2_3 = UCPTRIE_SHIFT_2 - UCPTRIE_SHIFT_3;

/**
* Difference between two shift sizes,
* for getting an index-1 offset from an index-2 offset. 5=14-9
*/
constexpr int32_t UCPTRIE_SHIFT_1_2 = UCPTRIE_SHIFT_1 - UCPTRIE_SHIFT_2;

/**
* Number of index-1 entries for the BMP. (4)
* This part of the index-1 table is omitted from the serialized form.
*/
constexpr int32_t UCPTRIE_OMITTED_BMP_INDEX_1_LENGTH = 0x10000 >> UCPTRIE_SHIFT_1;

/** Number of entries in an index-2 block. 32=0x20 */
constexpr int32_t UCPTRIE_INDEX_2_BLOCK_LENGTH = 1 << UCPTRIE_SHIFT_1_2;

/** Mask for getting the lower bits for the in-index-2-block offset. */
constexpr int32_t UCPTRIE_INDEX_2_MASK = UCPTRIE_INDEX_2_BLOCK_LENGTH - 1;

/** Number of code points per index-2 table entry. 512=0x200 */
constexpr int32_t UCPTRIE_CP_PER_INDEX_2_ENTRY = 1 << UCPTRIE_SHIFT_2;

/** Number of entries in an index-3 block. 32=0x20 */
constexpr int32_t UCPTRIE_INDEX_3_BLOCK_LENGTH = 1 << UCPTRIE_SHIFT_2_3;

/** Mask for getting the lower bits for the in-index-3-block offset. */
constexpr int32_t UCPTRIE_INDEX_3_MASK = UCPTRIE_INDEX_3_BLOCK_LENGTH - 1;

/** Number of entries in a small data block. 16=0x10 */
constexpr int32_t UCPTRIE_SMALL_DATA_BLOCK_LENGTH = 1 << UCPTRIE_SHIFT_3;

/** Mask for getting the lower bits for the in-small-data-block offset. */
constexpr int32_t UCPTRIE_SMALL_DATA_MASK = UCPTRIE_SMALL_DATA_BLOCK_LENGTH - 1;


typedef UChar32
UCPTrieGetRange(const void *trie, UChar32 start,
               UCPMapValueFilter *filter, const void *context, uint32_t *pValue);

U_CFUNC UChar32
ucptrie_internalGetRange(UCPTrieGetRange *getRange,
                        const void *trie, UChar32 start,
                        UCPMapRangeOption option, uint32_t surrogateValue,
                        UCPMapValueFilter *filter, const void *context, uint32_t *pValue);

#ifdef UCPTRIE_DEBUG
U_CFUNC void
ucptrie_printLengths(const UCPTrie *trie, const char *which);

U_CFUNC void umutablecptrie_setName(UMutableCPTrie *builder, const char *name);
#endif

/*
* Format of the binary, memory-mappable representation of a UCPTrie/CodePointTrie.
* For overview information see https://icu.unicode.org/design/struct/utrie
*
* The binary trie data should be 32-bit-aligned.
* The overall layout is:
*
* UCPTrieHeader header; -- 16 bytes, see struct definition above
* uint16_t index[header.indexLength];
* uintXY_t data[header.dataLength];
*
* The trie data array is an array of uint16_t, uint32_t, or uint8_t,
* specified via the UCPTrieValueWidth when building the trie.
* The data array is 32-bit-aligned for uint32_t, otherwise 16-bit-aligned.
* The overall length of the trie data is a multiple of 4 bytes.
* (Padding is added at the end of the index array and/or near the end of the data array as needed.)
*
* The length of the data array (dataLength) is stored as an integer split across two fields
* of the header struct (high bits in header.options).
*
* The trie type can be "fast" or "small" which determines the index structure,
* specified via the UCPTrieType when building the trie.
*
* The type and valueWidth are stored in the header.options.
* There are reserved type and valueWidth values, and reserved header.options bits.
* They could be used in future format extensions.
* Code reading the trie structure must fail with an error when unknown values or options are set.
*
* Values for ASCII character (U+0000..U+007F) can always be found at the start of the data array.
*
* Values for code points below a type-specific fast-indexing limit are found via two-stage lookup.
* For a "fast" trie, the limit is the BMP/supplementary boundary at U+10000.
* For a "small" trie, the limit is UCPTRIE_SMALL_MAX+1=U+1000.
*
* All code points in the range highStart..U+10FFFF map to a single highValue
* which is stored at the second-to-last position of the data array.
* (See UCPTRIE_HIGH_VALUE_NEG_DATA_OFFSET.)
* The highStart value is header.shiftedHighStart<<UCPTRIE_SHIFT_2.
* (UCPTRIE_SHIFT_2=9)
*
* Values for code points fast_limit..highStart-1 are found via four-stage lookup.
* The data block size is smaller for this range than for the fast range.
* This together with more index stages with small blocks makes this range
* more easily compactable.
*
* There is also a trie error value stored at the last position of the data array.
* (See UCPTRIE_ERROR_VALUE_NEG_DATA_OFFSET.)
* It is intended to be returned for inputs that are not Unicode code points
* (outside U+0000..U+10FFFF), or in string processing for ill-formed input
* (unpaired surrogate in UTF-16, ill-formed UTF-8 subsequence).
*
* For a "fast" trie:
*
* The index array starts with the BMP index table for BMP code point lookup.
* Its length is 1024=0x400.
*
* The supplementary index-1 table follows the BMP index table.
* Variable length, for code points up to highStart-1.
* Maximum length 64=0x40=0x100000>>UCPTRIE_SHIFT_1.
* (For 0x100000 supplementary code points U+10000..U+10ffff.)
*
* After this index-1 table follow the variable-length index-3 and index-2 tables.
*
* The supplementary index tables are omitted completely
* if there is only BMP data (highStart<=U+10000).
*
* For a "small" trie:
*
* The index array starts with a fast-index table for lookup of code points U+0000..U+0FFF.
*
* The "supplementary" index tables are always stored.
* The index-1 table starts from U+0000, its maximum length is 68=0x44=0x110000>>UCPTRIE_SHIFT_1.
*
* For both trie types:
*
* The last index-2 block may be a partial block, storing indexes only for code points
* below highStart.
*
* Lookup for ASCII code point c:
*
* Linear access from the start of the data array.
*
* value = data[c];
*
* Lookup for fast-range code point c:
*
* Shift the code point right by UCPTRIE_FAST_SHIFT=6 bits,
* fetch the index array value at that offset,
* add the lower code point bits, index into the data array.
*
* value = data[index[c>>6] + (c&0x3f)];
*
* (This works for ASCII as well.)
*
* Lookup for small-range code point c below highStart:
*
* Split the code point into four bit fields using several sets of shifts & masks
* to read consecutive values from the index-1, index-2, index-3 and data tables.
*
* If all of the data block offsets in an index-3 block fit within 16 bits (up to 0xffff),
* then the data block offsets are stored directly as uint16_t.
*
* Otherwise (this is very unusual but possible), the index-2 entry for the index-3 block
* has bit 15 (0x8000) set, and each set of 8 index-3 entries is preceded by
* an additional uint16_t word. Data block offsets are 18 bits wide, with the top 2 bits stored
* in the additional word.
*
* See ucptrie_internalSmallIndex() for details.
*
* (In a "small" trie, this works for ASCII and below-fast_limit code points as well.)
*
* Compaction:
*
* Multiple code point ranges ("blocks") that are aligned on certain boundaries
* (determined by the shifting/bit fields of code points) and
* map to the same data values normally share a single subsequence of the data array.
* Data blocks can also overlap partially.
* (Depending on the builder code finding duplicate and overlapping blocks.)
*
* Iteration over same-value ranges:
*
* Range iteration (ucptrie_getRange()) walks the structure from a start code point
* until some code point is found that maps to a different value;
* the end of the returned range is just before that.
*
* The header.dataNullOffset (split across two header fields, high bits in header.options)
* is the offset of a widely shared data block filled with one single value.
* It helps quickly skip over large ranges of data with that value.
* The builder must ensure that if the start of any data block (fast or small)
* matches the dataNullOffset, then the whole block must be filled with the null value.
* Special care must be taken if there is no fast null data block
* but a small one, which is shorter, and it matches the *start* of some fast data block.
*
* Similarly, the header.index3NullOffset is the index-array offset of an index-3 block
* where all index entries point to the dataNullOffset.
* If there is no such data or index-3 block, then these offsets are set to
* values that cannot be reached (data offset out of range/reserved index offset),
* normally UCPTRIE_NO_DATA_NULL_OFFSET or UCPTRIE_NO_INDEX3_NULL_OFFSET respectively.
*/

#endif