Check in the pristine copy of ICU 4.6...

icu46/source/common/utf_impl.c

+/*
+******************************************************************************
+*
+*   Copyright (C) 1999-2006, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+******************************************************************************
+*   file name:  utf_impl.c
+*   encoding:   US-ASCII
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 1999sep13
+*   created by: Markus W. Scherer
+*
+*   This file provides implementation functions for macros in the utfXX.h
+*   that would otherwise be too long as macros.
+*/
+
+/* set import/export definitions */
+#ifndef U_UTF8_IMPL
+#   define U_UTF8_IMPL
+#endif
+
+#include "unicode/utypes.h"
+
+/*
+ * This table could be replaced on many machines by
+ * a few lines of assembler code using an
+ * "index of first 0-bit from msb" instruction and
+ * one or two more integer instructions.
+ *
+ * For example, on an i386, do something like
+ * - MOV AL, leadByte
+ * - NOT AL         (8-bit, leave b15..b8==0..0, reverse only b7..b0)
+ * - MOV AH, 0
+ * - BSR BX, AX     (16-bit)
+ * - MOV AX, 6      (result)
+ * - JZ finish      (ZF==1 if leadByte==0xff)
+ * - SUB AX, BX (result)
+ * -finish:
+ * (BSR: Bit Scan Reverse, scans for a 1-bit, starting from the MSB)
+ *
+ * In Unicode, all UTF-8 byte sequences with more than 4 bytes are illegal;
+ * lead bytes above 0xf4 are illegal.
+ * We keep them in this table for skipping long ISO 10646-UTF-8 sequences.
+ */
+U_EXPORT const uint8_t 
+utf8_countTrailBytes[256]={
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+
+    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+    3, 3, 3, 3, 3,
+    3, 3, 3,    /* illegal in Unicode */
+    4, 4, 4, 4, /* illegal in Unicode */
+    5, 5,       /* illegal in Unicode */
+    0, 0        /* illegal bytes 0xfe and 0xff */
+};
+
+static const UChar32
+utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };
+
+static const UChar32
+utf8_errorValue[6]={
+    UTF8_ERROR_VALUE_1, UTF8_ERROR_VALUE_2, UTF_ERROR_VALUE, 0x10ffff,
+    0x3ffffff, 0x7fffffff
+};
+
+/*
+ * Handle the non-inline part of the U8_NEXT() macro and its obsolete sibling
+ * UTF8_NEXT_CHAR_SAFE().
+ *
+ * The "strict" parameter controls the error behavior:
+ * <0  "Safe" behavior of U8_NEXT(): All illegal byte sequences yield a negative
+ *     code point result.
+ *  0  Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
+ *     All illegal byte sequences yield a positive code point such that this
+ *     result code point would be encoded with the same number of bytes as
+ *     the illegal sequence.
+ * >0  Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
+ *     Same as the obsolete "safe" behavior, but non-characters are also treated
+ *     like illegal sequences.
+ *
+ * The special negative (<0) value -2 is used for lenient treatment of surrogate
+ * code points as legal. Some implementations use this for roundtripping of
+ * Unicode 16-bit strings that are not well-formed UTF-16, that is, they
+ * contain unpaired surrogates.
+ *
+ * Note that a UBool is the same as an int8_t.
+ */
+U_CAPI UChar32 U_EXPORT2
+utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
+    int32_t i=*pi;
+    uint8_t count=UTF8_COUNT_TRAIL_BYTES(c);
+    if((i)+count<=(length)) {
+        uint8_t trail, illegal=0;
+
+        UTF8_MASK_LEAD_BYTE((c), count);
+        /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
+        switch(count) {
+        /* each branch falls through to the next one */
+        case 5:
+        case 4:
+            /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
+            illegal=1;
+            break;
+        case 3:
+            trail=s[(i)++];
+            (c)=((c)<<6)|(trail&0x3f);
+            if(c<0x110) {
+                illegal|=(trail&0xc0)^0x80;
+            } else {
+                /* code point>0x10ffff, outside Unicode */
+                illegal=1;
+                break;
+            }
+        case 2:
+            trail=s[(i)++];
+            (c)=((c)<<6)|(trail&0x3f);
+            illegal|=(trail&0xc0)^0x80;
+        case 1:
+            trail=s[(i)++];
+            (c)=((c)<<6)|(trail&0x3f);
+            illegal|=(trail&0xc0)^0x80;
+            break;
+        case 0:
+            if(strict>=0) {
+                return UTF8_ERROR_VALUE_1;
+            } else {
+                return U_SENTINEL;
+            }
+        /* no default branch to optimize switch()  - all values are covered */
+        }
+
+        /*
+         * All the error handling should return a value
+         * that needs count bytes so that UTF8_GET_CHAR_SAFE() works right.
+         *
+         * Starting with Unicode 3.0.1, non-shortest forms are illegal.
+         * Starting with Unicode 3.2, surrogate code points must not be
+         * encoded in UTF-8, and there are no irregular sequences any more.
+         *
+         * U8_ macros (new in ICU 2.4) return negative values for error conditions.
+         */
+
+        /* correct sequence - all trail bytes have (b7..b6)==(10)? */
+        /* illegal is also set if count>=4 */
+        if(illegal || (c)<utf8_minLegal[count] || (UTF_IS_SURROGATE(c) && strict!=-2)) {
+            /* error handling */
+            uint8_t errorCount=count;
+            /* don't go beyond this sequence */
+            i=*pi;
+            while(count>0 && UTF8_IS_TRAIL(s[i])) {
+                ++(i);
+                --count;
+            }
+            if(strict>=0) {
+                c=utf8_errorValue[errorCount-count];
+            } else {
+                c=U_SENTINEL;
+            }
+        } else if((strict)>0 && UTF_IS_UNICODE_NONCHAR(c)) {
+            /* strict: forbid non-characters like U+fffe */
+            c=utf8_errorValue[count];
+        }
+    } else /* too few bytes left */ {
+        /* error handling */
+        int32_t i0=i;
+        /* don't just set (i)=(length) in case there is an illegal sequence */
+        while((i)<(length) && UTF8_IS_TRAIL(s[i])) {
+            ++(i);
+        }
+        if(strict>=0) {
+            c=utf8_errorValue[i-i0];
+        } else {
+            c=U_SENTINEL;
+        }
+    }
+    *pi=i;
+    return c;
+}
+
+U_CAPI int32_t U_EXPORT2
+utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError) {
+    if((uint32_t)(c)<=0x7ff) {
+        if((i)+1<(length)) {
+            (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0);
+            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
+            return i;
+        }
+    } else if((uint32_t)(c)<=0xffff) {
+        /* Starting with Unicode 3.2, surrogate code points must not be encoded in UTF-8. */
+        if((i)+2<(length) && !U_IS_SURROGATE(c)) {
+            (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0);
+            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
+            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
+            return i;
+        }
+    } else if((uint32_t)(c)<=0x10ffff) {
+        if((i)+3<(length)) {
+            (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0);
+            (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80);
+            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
+            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
+            return i;
+        }
+    }
+    /* c>0x10ffff or not enough space, write an error value */
+    if(pIsError!=NULL) {
+        *pIsError=TRUE;
+    } else {
+        length-=i;
+        if(length>0) {
+            int32_t offset;
+            if(length>3) {
+                length=3;
+            }
+            s+=i;
+            offset=0;
+            c=utf8_errorValue[length-1];
+            UTF8_APPEND_CHAR_UNSAFE(s, offset, c);
+            i=i+offset;
+        }
+    }
+    return i;
+}
+
+U_CAPI UChar32 U_EXPORT2
+utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict) {
+    int32_t i=*pi;
+    uint8_t b, count=1, shift=6;
+
+    /* extract value bits from the last trail byte */
+    c&=0x3f;
+
+    for(;;) {
+        if(i<=start) {
+            /* no lead byte at all */
+            if(strict>=0) {
+                return UTF8_ERROR_VALUE_1;
+            } else {
+                return U_SENTINEL;
+            }
+            /*break;*/
+        }
+
+        /* read another previous byte */
+        b=s[--i];
+        if((uint8_t)(b-0x80)<0x7e) { /* 0x80<=b<0xfe */
+            if(b&0x40) {
+                /* lead byte, this will always end the loop */
+                uint8_t shouldCount=UTF8_COUNT_TRAIL_BYTES(b);
+
+                if(count==shouldCount) {
+                    /* set the new position */
+                    *pi=i;
+                    UTF8_MASK_LEAD_BYTE(b, count);
+                    c|=(UChar32)b<<shift;
+                    if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (UTF_IS_SURROGATE(c) && strict!=-2) || (strict>0 && UTF_IS_UNICODE_NONCHAR(c))) {
+                        /* illegal sequence or (strict and non-character) */
+                        if(count>=4) {
+                            count=3;
+                        }
+                        if(strict>=0) {
+                            c=utf8_errorValue[count];
+                        } else {
+                            c=U_SENTINEL;
+                        }
+                    } else {
+                        /* exit with correct c */
+                    }
+                } else {
+                    /* the lead byte does not match the number of trail bytes */
+                    /* only set the position to the lead byte if it would
+                       include the trail byte that we started with */
+                    if(count<shouldCount) {
+                        *pi=i;
+                        if(strict>=0) {
+                            c=utf8_errorValue[count];
+                        } else {
+                            c=U_SENTINEL;
+                        }
+                    } else {
+                        if(strict>=0) {
+                            c=UTF8_ERROR_VALUE_1;
+                        } else {
+                            c=U_SENTINEL;
+                        }
+                    }
+                }
+                break;
+            } else if(count<5) {
+                /* trail byte */
+                c|=(UChar32)(b&0x3f)<<shift;
+                ++count;
+                shift+=6;
+            } else {
+                /* more than 5 trail bytes is illegal */
+                if(strict>=0) {
+                    c=UTF8_ERROR_VALUE_1;
+                } else {
+                    c=U_SENTINEL;
+                }
+                break;
+            }
+        } else {
+            /* single-byte character precedes trailing bytes */
+            if(strict>=0) {
+                c=UTF8_ERROR_VALUE_1;
+            } else {
+                c=U_SENTINEL;
+            }
+            break;
+        }
+    }
+    return c;
+}
+
+U_CAPI int32_t U_EXPORT2
+utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i) {
+    /* i had been decremented once before the function call */
+    int32_t I=i, Z;
+    uint8_t b;
+
+    /* read at most the 6 bytes s[Z] to s[i], inclusively */
+    if(I-5>start) {
+        Z=I-5;
+    } else {
+        Z=start;
+    }
+
+    /* return I if the sequence starting there is long enough to include i */
+    do {
+        b=s[I];
+        if((uint8_t)(b-0x80)>=0x7e) { /* not 0x80<=b<0xfe */
+            break;
+        } else if(b>=0xc0) {
+            if(UTF8_COUNT_TRAIL_BYTES(b)>=(i-I)) {
+                return I;
+            } else {
+                break;
+            }
+        }
+    } while(Z<=--I);
+
+    /* return i itself to be consistent with the FWD_1 macro */
+    return i;
+}