// © 2016 and later: Unicode, Inc. and others.

// License & terms of use: http://www.unicode.org/copyright.html

/*

******************************************************************************

*

*   Copyright (C) 1999-2012, International Business Machines

*   Corporation and others.  All Rights Reserved.

*

******************************************************************************

*   file name:  utf_impl.c

*   encoding:   UTF-8

*   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"

#include "unicode/utf.h"

#include "unicode/utf8.h"

#include "unicode/utf_old.h"

#include "uassert.h"

/*

 * Table of the number of utf8 trail bytes, indexed by the lead byte.

 * Used by the deprecated macro UTF8_COUNT_TRAIL_BYTES, defined in utf_old.h

 *

 * The current macro, U8_COUNT_TRAIL_BYTES, does _not_ use this table.

 *

 * Note that this table cannot be removed, even if UTF8_COUNT_TRAIL_BYTES were

 * changed to no longer use it. References to the table from expansions of UTF8_COUNT_TRAIL_BYTES

 * may exist in old client code that must continue to run with newer icu library versions.

 *

 * 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.

 */

extern "C" 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

};

static UChar32

errorValue(int32_t count, int8_t strict) {

    if(strict>=0) {

        return utf8_errorValue[count];

    } else if(strict==-3) {

        return 0xfffd;

    } else {

        return U_SENTINEL;

    }

}

/*

 * Handle the non-inline part of the U8_NEXT() and U8_NEXT_FFFD() macros

 * and their obsolete sibling UTF8_NEXT_CHAR_SAFE().

 *

 * U8_NEXT() supports NUL-terminated strings indicated via length<0.

 *

 * The "strict" parameter controls the error behavior:

 * <0  "Safe" behavior of U8_NEXT():

 *     -1: All illegal byte sequences yield U_SENTINEL=-1.

 *     -2: Same as -1, except 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.

 *     -3: All illegal byte sequences yield U+FFFD.

 *  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.

 *

 * 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=U8_COUNT_TRAIL_BYTES(c);

    U_ASSERT(count <= 5); /* U8_COUNT_TRAIL_BYTES returns value 0...5 */

    if(i+count<=length || length<0) {

        uint8_t trail;

        U8_MASK_LEAD_BYTE(c, count);

        /* support NUL-terminated strings: do not read beyond the first non-trail byte */

        switch(count) {

        /* each branch falls through to the next one */

        case 0:

            /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */

        case 5:

        case 4:

            /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */

            break;

        case 3:

            trail=s[i++]-0x80;

            c=(c<<6)|trail;

            /* c>=0x110 would result in code point>0x10ffff, outside Unicode */

            if(c>=0x110 || trail>0x3f) { break; }

            U_FALLTHROUGH;

        case 2:

            trail=s[i++]-0x80;

            c=(c<<6)|trail;

            /*

             * test for a surrogate d800..dfff unless we are lenient:

             * before the last (c<<6), a surrogate is c=360..37f

             */

            if(((c&0xffe0)==0x360 && strict!=-2) || trail>0x3f) { break; }

            U_FALLTHROUGH;

        case 1:

            trail=s[i++]-0x80;

            c=(c<<6)|trail;

            if(trail>0x3f) { break; }

            /* correct sequence - all trail bytes have (b7..b6)==(10) */

            if(c>=utf8_minLegal[count] &&

                    /* strict: forbid non-characters like U+fffe */

                    (strict<=0 || !U_IS_UNICODE_NONCHAR(c))) {

                *pi=i;

                return c;

            }

        /* no default branch to optimize switch()  - all values are covered */

        }

    } else {

        /* too few bytes left */

        count=length-i;

    }

    /* error handling */

    i=*pi;

    while(count>0 && U8_IS_TRAIL(s[i])) {

        ++i;

        --count;

    }

    c=errorValue(i-*pi, strict);

    *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;

    if(!U8_IS_TRAIL(c)) { return errorValue(0, strict); }

    /* extract value bits from the last trail byte */

    c&=0x3f;

    for(;;) {

        if(i<=start) {

            /* no lead byte at all */

            return errorValue(0, strict);

        }

        /* 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=U8_COUNT_TRAIL_BYTES(b);

                if(count==shouldCount) {

                    /* set the new position */

                    *pi=i;

                    U8_MASK_LEAD_BYTE(b, count);

                    c|=(UChar32)b<<shift;

                    if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (U_IS_SURROGATE(c) && strict!=-2) || (strict>0 && U_IS_UNICODE_NONCHAR(c))) {

                        /* illegal sequence or (strict and non-character) */

                        if(count>=4) {

                            count=3;

                        }

                        c=errorValue(count, strict);

                    } 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;

                        c=errorValue(count, strict);

                    } else {

                        c=errorValue(0, strict);

                    }

                }

                break;

            } else if(count<5) {

                /* trail byte */

                c|=(UChar32)(b&0x3f)<<shift;

                ++count;

                shift+=6;

            } else {

                /* more than 5 trail bytes is illegal */

                c=errorValue(0, strict);

                break;

            }

        } else {

            /* single-byte character precedes trailing bytes */

            c=errorValue(0, strict);

            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(U8_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;

}