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// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
* Copyright (C) 2001-2014, International Business Machines
* Corporation and others. All Rights Reserved.
*******************************************************************************
* file name: bocsu.cpp
* encoding: UTF-8
* tab size: 8 (not used)
* indentation:4
*
* Author: Markus W. Scherer
*
* Modification history:
* 05/18/2001 weiv Made into separate module
*/
#include "unicode/utypes.h"
#if !UCONFIG_NO_COLLATION
#include "unicode/bytestream.h"
#include "unicode/utf16.h"
#include "bocsu.h"
/*
* encode one difference value -0x10ffff..+0x10ffff in 1..4 bytes,
* preserving lexical order
*/
static uint8_t *
u_writeDiff(int32_t diff, uint8_t *p) {
if(diff>=SLOPE_REACH_NEG_1) {
if(diff<=SLOPE_REACH_POS_1) {
*p++=(uint8_t)(SLOPE_MIDDLE+diff);
} else if(diff<=SLOPE_REACH_POS_2) {
*p++=(uint8_t)(SLOPE_START_POS_2+(diff/SLOPE_TAIL_COUNT));
*p++=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
} else if(diff<=SLOPE_REACH_POS_3) {
p[2]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
diff/=SLOPE_TAIL_COUNT;
p[1]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
*p=(uint8_t)(SLOPE_START_POS_3+(diff/SLOPE_TAIL_COUNT));
p+=3;
} else {
p[3]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
diff/=SLOPE_TAIL_COUNT;
p[2]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
diff/=SLOPE_TAIL_COUNT;
p[1]=(uint8_t)(SLOPE_MIN+diff%SLOPE_TAIL_COUNT);
*p=SLOPE_MAX;
p+=4;
}
} else {
int32_t m;
if(diff>=SLOPE_REACH_NEG_2) {
NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
*p++=(uint8_t)(SLOPE_START_NEG_2+diff);
*p++=(uint8_t)(SLOPE_MIN+m);
} else if(diff>=SLOPE_REACH_NEG_3) {
NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
p[2]=(uint8_t)(SLOPE_MIN+m);
NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
p[1]=(uint8_t)(SLOPE_MIN+m);
*p=(uint8_t)(SLOPE_START_NEG_3+diff);
p+=3;
} else {
NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
p[3]=(uint8_t)(SLOPE_MIN+m);
NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
p[2]=(uint8_t)(SLOPE_MIN+m);
NEGDIVMOD(diff, SLOPE_TAIL_COUNT, m);
p[1]=(uint8_t)(SLOPE_MIN+m);
*p=SLOPE_MIN;
p+=4;
}
}
return p;
}
/*
* Encode the code points of a string as
* a sequence of byte-encoded differences (slope detection),
* preserving lexical order.
*
* Optimize the difference-taking for runs of Unicode text within
* small scripts:
*
* Most small scripts are allocated within aligned 128-blocks of Unicode
* code points. Lexical order is preserved if "prev" is always moved
* into the middle of such a block.
*
* Additionally, "prev" is moved from anywhere in the Unihan
* area into the middle of that area.
* Note that the identical-level run in a sort key is generated from
* NFD text - there are never Hangul characters included.
*/
U_CFUNC UChar32
u_writeIdenticalLevelRun(UChar32 prev, const char16_t *s, int32_t length, icu::ByteSink &sink) {
char scratch[64];
int32_t capacity;
int32_t i=0;
while(i<length) {
char *buffer=sink.GetAppendBuffer(1, length*2, scratch, (int32_t)sizeof(scratch), &capacity);
uint8_t *p;
// We must have capacity>=SLOPE_MAX_BYTES in case u_writeDiff() writes that much,
// but we do not want to force the sink.GetAppendBuffer() to allocate
// for a large min_capacity because we might actually only write one byte.
if(capacity<16) {
buffer=scratch;
capacity=(int32_t)sizeof(scratch);
}
p=reinterpret_cast<uint8_t *>(buffer);
uint8_t *lastSafe=p+capacity-SLOPE_MAX_BYTES;
while(i<length && p<=lastSafe) {
if(prev<0x4e00 || prev>=0xa000) {
prev=(prev&~0x7f)-SLOPE_REACH_NEG_1;
} else {
/*
* Unihan U+4e00..U+9fa5:
* double-bytes down from the upper end
*/
prev=0x9fff-SLOPE_REACH_POS_2;
}
UChar32 c;
U16_NEXT(s, i, length, c);
if(c==0xfffe) {
*p++=2; // merge separator
prev=0;
} else {
p=u_writeDiff(c-prev, p);
prev=c;
}
}
sink.Append(buffer, (int32_t)(p-reinterpret_cast<uint8_t *>(buffer)));
}
return prev;
}
#endif /* #if !UCONFIG_NO_COLLATION */
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