170 lines
4.8 KiB
C
170 lines
4.8 KiB
C
/*
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*******************************************************************************
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* Copyright (C) 2001, International Business Machines
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* Corporation and others. All Rights Reserved.
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*******************************************************************************
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* file name: bocsu.c
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* encoding: US-ASCII
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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 "bocsu.h"
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/*
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* encode one difference value -0x10ffff..+0x10ffff in 1..3 bytes,
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* preserving lexical order
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*/
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U_CFUNC 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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/* How many bytes would writeDiff() write? */
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static int32_t
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lengthOfDiff(int32_t diff) {
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if(diff>=SLOPE_REACH_NEG_1) {
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if(diff<=SLOPE_REACH_POS_1) {
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return 1;
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} else if(diff<=SLOPE_REACH_POS_2) {
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return 2;
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} else if(diff<=SLOPE_REACH_POS_3) {
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return 3;
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} else {
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return 4;
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}
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} else {
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if(diff>=SLOPE_REACH_NEG_2) {
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return 2;
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} else if(diff>=SLOPE_REACH_NEG_3) {
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return 3;
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} else {
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return 4;
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}
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}
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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 int32_t
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u_writeIdenticalLevelRun(const UChar *s, int32_t length, uint8_t *p) {
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uint8_t *p0;
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int32_t c, prev;
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int32_t i;
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prev=0;
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p0=p;
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i=0;
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while(i<length) {
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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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UTF_NEXT_CHAR(s, i, length, c);
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p=u_writeDiff(c-prev, p);
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prev=c;
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}
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return p-p0;
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}
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/* How many bytes would writeIdenticalLevelRun() write? */
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U_CFUNC int32_t
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u_lengthOfIdenticalLevelRun(const UChar *s, int32_t length) {
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int32_t c, prev;
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int32_t i, runLength;
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prev=0;
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runLength=0;
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i=0;
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while(i<length) {
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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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UTF_NEXT_CHAR(s, i, length, c);
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runLength+=lengthOfDiff(c-prev);
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prev=c;
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}
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return runLength;
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}
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