145 lines
4.8 KiB
C++
145 lines
4.8 KiB
C++
// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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/*
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*******************************************************************************
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* Copyright (C) 2001-2014, International Business Machines
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* Corporation and others. All Rights Reserved.
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*******************************************************************************
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* file name: bocsu.cpp
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* encoding: UTF-8
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* tab size: 8 (not used)
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* indentation:4
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*
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* Author: Markus W. Scherer
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*
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* Modification history:
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* 05/18/2001 weiv Made into separate module
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*/
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#include "unicode/utypes.h"
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#if !UCONFIG_NO_COLLATION
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#include "unicode/bytestream.h"
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#include "unicode/utf16.h"
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#include "bocsu.h"
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/*
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* encode one difference value -0x10ffff..+0x10ffff in 1..4 bytes,
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* preserving lexical order
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*/
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static uint8_t *
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u_writeDiff(int32_t diff, uint8_t *p) {
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if(diff>=SLOPE_REACH_NEG_1) {
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if(diff<=SLOPE_REACH_POS_1) {
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*p++=(uint8_t)(SLOPE_MIDDLE+diff);
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} else if(diff<=SLOPE_REACH_POS_2) {
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*p++=(uint8_t)(SLOPE_START_POS_2+(diff/SLOPE_TAIL_COUNT));
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*p++=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
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} else if(diff<=SLOPE_REACH_POS_3) {
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p[2]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
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diff/=SLOPE_TAIL_COUNT;
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p[1]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
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*p=(uint8_t)(SLOPE_START_POS_3+(diff/SLOPE_TAIL_COUNT));
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p+=3;
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} else {
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p[3]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
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diff/=SLOPE_TAIL_COUNT;
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p[2]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
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diff/=SLOPE_TAIL_COUNT;
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p[1]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
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*p=SLOPE_MAX;
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p+=4;
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}
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} else {
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int32_t m;
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if(diff>=SLOPE_REACH_NEG_2) {
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NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
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*p++=(uint8_t)(SLOPE_START_NEG_2+diff);
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*p++=(uint8_t)(SLOPE_MIN+m);
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} else if(diff>=SLOPE_REACH_NEG_3) {
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NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
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p[2]=(uint8_t)(SLOPE_MIN+m);
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NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
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p[1]=(uint8_t)(SLOPE_MIN+m);
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*p=(uint8_t)(SLOPE_START_NEG_3+diff);
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p+=3;
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} else {
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NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
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p[3]=(uint8_t)(SLOPE_MIN+m);
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NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
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p[2]=(uint8_t)(SLOPE_MIN+m);
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NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
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p[1]=(uint8_t)(SLOPE_MIN+m);
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*p=SLOPE_MIN;
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p+=4;
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}
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}
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return p;
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}
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/*
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* Encode the code points of a string as
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* a sequence of byte-encoded differences (slope detection),
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* preserving lexical order.
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*
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* Optimize the difference-taking for runs of Unicode text within
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* small scripts:
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*
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* Most small scripts are allocated within aligned 128-blocks of Unicode
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* code points. Lexical order is preserved if "prev" is always moved
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* into the middle of such a block.
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*
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* Additionally, "prev" is moved from anywhere in the Unihan
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* area into the middle of that area.
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* Note that the identical-level run in a sort key is generated from
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* NFD text - there are never Hangul characters included.
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*/
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U_CFUNC UChar32
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u_writeIdenticalLevelRun(UChar32 prev, const UChar *s, int32_t length, icu::ByteSink &sink) {
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char scratch[64];
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int32_t capacity;
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int32_t i=0;
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while(i<length) {
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char *buffer=sink.GetAppendBuffer(1, length*2, scratch, (int32_t)sizeof(scratch), &capacity);
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uint8_t *p;
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// We must have capacity>=SLOPE_MAX_BYTES in case u_writeDiff() writes that much,
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// but we do not want to force the sink.GetAppendBuffer() to allocate
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// for a large min_capacity because we might actually only write one byte.
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if(capacity<16) {
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buffer=scratch;
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capacity=(int32_t)sizeof(scratch);
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}
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p=reinterpret_cast<uint8_t *>(buffer);
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uint8_t *lastSafe=p+capacity-SLOPE_MAX_BYTES;
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while(i<length && p<=lastSafe) {
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if(prev<0x4e00 || prev>=0xa000) {
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prev=(prev&~0x7f)-SLOPE_REACH_NEG_1;
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} else {
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/*
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* Unihan U+4e00..U+9fa5:
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* double-bytes down from the upper end
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*/
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prev=0x9fff-SLOPE_REACH_POS_2;
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}
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UChar32 c;
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U16_NEXT(s, i, length, c);
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if(c==0xfffe) {
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*p++=2; // merge separator
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prev=0;
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} else {
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p=u_writeDiff(c-prev, p);
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prev=c;
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}
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}
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sink.Append(buffer, (int32_t)(p-reinterpret_cast<uint8_t *>(buffer)));
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}
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return prev;
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}
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#endif /* #if !UCONFIG_NO_COLLATION */
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