Check in the pristine copy of ICU 4.6...

icu46/source/i18n/bocsu.c

+/*
+*******************************************************************************
+*   Copyright (C) 2001-2003, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*******************************************************************************
+*   file name:  bocsu.c
+*   encoding:   US-ASCII
+*   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 "bocsu.h"
+
+/*
+ * encode one difference value -0x10ffff..+0x10ffff in 1..3 bytes,
+ * preserving lexical order
+ */
+U_CFUNC 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;
+}
+
+/* How many bytes would writeDiff() write? */
+static int32_t
+lengthOfDiff(int32_t diff) {
+    if(diff>=SLOPE_REACH_NEG_1) {
+        if(diff<=SLOPE_REACH_POS_1) {
+            return 1;
+        } else if(diff<=SLOPE_REACH_POS_2) {
+            return 2;
+        } else if(diff<=SLOPE_REACH_POS_3) {
+            return 3;
+        } else {
+            return 4;
+        }
+    } else {
+        if(diff>=SLOPE_REACH_NEG_2) {
+            return 2;
+        } else if(diff>=SLOPE_REACH_NEG_3) {
+            return 3;
+        } else {
+            return 4;
+        }
+    }
+}
+
+/*
+ * 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 int32_t
+u_writeIdenticalLevelRun(const UChar *s, int32_t length, uint8_t *p) {
+    uint8_t *p0;
+    int32_t c, prev;
+    int32_t i;
+
+    prev=0;
+    p0=p;
+    i=0;
+    while(i<length) {
+        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;
+        }
+
+        UTF_NEXT_CHAR(s, i, length, c);
+        p=u_writeDiff(c-prev, p);
+        prev=c;
+    }
+    return (int32_t)(p-p0);
+}
+
+U_CFUNC int32_t
+u_writeIdenticalLevelRunTwoChars(UChar32 first, UChar32 second, uint8_t *p) {
+    uint8_t *p0 = p;
+    if(first<0x4e00 || first>=0xa000) {
+        first=(first&~0x7f)-SLOPE_REACH_NEG_1;
+    } else {
+        /*
+         * Unihan U+4e00..U+9fa5:
+         * double-bytes down from the upper end
+         */
+        first=0x9fff-SLOPE_REACH_POS_2;
+    }
+
+    p=u_writeDiff(second-first, p);
+    return (int32_t)(p-p0);
+}
+
+/* How many bytes would writeIdenticalLevelRun() write? */
+U_CFUNC int32_t
+u_lengthOfIdenticalLevelRun(const UChar *s, int32_t length) {
+    int32_t c, prev;
+    int32_t i, runLength;
+
+    prev=0;
+    runLength=0;
+    i=0;
+    while(i<length) {
+        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;
+        }
+
+        UTF_NEXT_CHAR(s, i, length, c);
+        runLength+=lengthOfDiff(c-prev);
+        prev=c;
+    }
+    return runLength;
+}
+
+#endif /* #if !UCONFIG_NO_COLLATION */