/*

 * Copyright (C) 2007 Apple Inc.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY

 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 

 */

#include "config.h"

#include "UTF8.h"

namespace WTF {

namespace Unicode {

inline int inlineUTF8SequenceLengthNonASCII(char b0)

{

    if ((b0 & 0xC0) != 0xC0)

        return 0;

    if ((b0 & 0xE0) == 0xC0)

        return 2;

    if ((b0 & 0xF0) == 0xE0)

        return 3;

    if ((b0 & 0xF8) == 0xF0)

        return 4;

    return 0;

}

inline int inlineUTF8SequenceLength(char b0)

{

    return (b0 & 0x80) == 0 ? 1 : inlineUTF8SequenceLengthNonASCII(b0);

}

int UTF8SequenceLength(char b0)

{

    return (b0 & 0x80) == 0 ? 1 : inlineUTF8SequenceLengthNonASCII(b0);

}

int decodeUTF8Sequence(const char* sequence)

{

    // Handle 0-byte sequences (never valid).

    const unsigned char b0 = sequence[0];

    const int length = inlineUTF8SequenceLength(b0);

    if (length == 0)

        return -1;

    // Handle 1-byte sequences (plain ASCII).

    const unsigned char b1 = sequence[1];

    if (length == 1) {

        if (b1)

            return -1;

        return b0;

    }

    // Handle 2-byte sequences.

    if ((b1 & 0xC0) != 0x80)

        return -1;

    const unsigned char b2 = sequence[2];

    if (length == 2) {

        if (b2)

            return -1;

        const int c = ((b0 & 0x1F) << 6) | (b1 & 0x3F);

        if (c < 0x80)

            return -1;

        return c;

    }

    // Handle 3-byte sequences.

    if ((b2 & 0xC0) != 0x80)

        return -1;

    const unsigned char b3 = sequence[3];

    if (length == 3) {

        if (b3)

            return -1;

        const int c = ((b0 & 0xF) << 12) | ((b1 & 0x3F) << 6) | (b2 & 0x3F);

        if (c < 0x800)

            return -1;

        // UTF-16 surrogates should never appear in UTF-8 data.

        if (c >= 0xD800 && c <= 0xDFFF)

            return -1;

        return c;

    }

    // Handle 4-byte sequences.

    if ((b3 & 0xC0) != 0x80)

        return -1;

    const unsigned char b4 = sequence[4];

    if (length == 4) {

        if (b4)

            return -1;

        const int c = ((b0 & 0x7) << 18) | ((b1 & 0x3F) << 12) | ((b2 & 0x3F) << 6) | (b3 & 0x3F);

        if (c < 0x10000 || c > 0x10FFFF)

            return -1;

        return c;

    }

    return -1;

}

// Once the bits are split out into bytes of UTF-8, this is a mask OR-ed

// into the first byte, depending on how many bytes follow.  There are

// as many entries in this table as there are UTF-8 sequence types.

// (I.e., one byte sequence, two byte... etc.). Remember that sequencs

// for *legal* UTF-8 will be 4 or fewer bytes total.

static const unsigned char firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };

ConversionResult convertUTF16ToUTF8(

    const UChar** sourceStart, const UChar* sourceEnd, 

    char** targetStart, char* targetEnd, bool strict)

{

    ConversionResult result = conversionOK;

    const UChar* source = *sourceStart;

    char* target = *targetStart;

    while (source < sourceEnd) {

        UChar32 ch;

        unsigned short bytesToWrite = 0;

        const UChar32 byteMask = 0xBF;

        const UChar32 byteMark = 0x80; 

        const UChar* oldSource = source; // In case we have to back up because of target overflow.

        ch = static_cast<unsigned short>(*source++);

        // If we have a surrogate pair, convert to UChar32 first.

        if (ch >= 0xD800 && ch <= 0xDBFF) {

            // If the 16 bits following the high surrogate are in the source buffer...

            if (source < sourceEnd) {

                UChar32 ch2 = static_cast<unsigned short>(*source);

                // If it's a low surrogate, convert to UChar32.

                if (ch2 >= 0xDC00 && ch2 <= 0xDFFF) {

                    ch = ((ch - 0xD800) << 10) + (ch2 - 0xDC00) + 0x0010000;

                    ++source;

                } else if (strict) { // it's an unpaired high surrogate

                    --source; // return to the illegal value itself

                    result = sourceIllegal;

                    break;

                }

            } else { // We don't have the 16 bits following the high surrogate.

                --source; // return to the high surrogate

                result = sourceExhausted;

                break;

            }

        } else if (strict) {

            // UTF-16 surrogate values are illegal in UTF-32

            if (ch >= 0xDC00 && ch <= 0xDFFF) {

                --source; // return to the illegal value itself

                result = sourceIllegal;

                break;

            }

        }

        // Figure out how many bytes the result will require

        if (ch < (UChar32)0x80) {

            bytesToWrite = 1;

        } else if (ch < (UChar32)0x800) {

            bytesToWrite = 2;

        } else if (ch < (UChar32)0x10000) {

            bytesToWrite = 3;

        } else if (ch < (UChar32)0x110000) {

            bytesToWrite = 4;

        } else {

            bytesToWrite = 3;

            ch = 0xFFFD;

        }

        target += bytesToWrite;

        if (target > targetEnd) {

            source = oldSource; // Back up source pointer!

            target -= bytesToWrite;

            result = targetExhausted;

            break;

        }

        switch (bytesToWrite) { // note: everything falls through.

            case 4: *--target = (char)((ch | byteMark) & byteMask); ch >>= 6;

            case 3: *--target = (char)((ch | byteMark) & byteMask); ch >>= 6;

            case 2: *--target = (char)((ch | byteMark) & byteMask); ch >>= 6;

            case 1: *--target =  (char)(ch | firstByteMark[bytesToWrite]);

        }

        target += bytesToWrite;

    }

    *sourceStart = source;

    *targetStart = target;

    return result;

}

// This must be called with the length pre-determined by the first byte.

// If presented with a length > 4, this returns false.  The Unicode

// definition of UTF-8 goes up to 4-byte sequences.

static bool isLegalUTF8(const unsigned char* source, int length)

{

    unsigned char a;

    const unsigned char* srcptr = source + length;

    switch (length) {

        default: return false;

        // Everything else falls through when "true"...

        case 4: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;

        case 3: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;

        case 2: if ((a = (*--srcptr)) > 0xBF) return false;

        switch (*source) {

            // no fall-through in this inner switch

            case 0xE0: if (a < 0xA0) return false; break;

            case 0xED: if (a > 0x9F) return false; break;

            case 0xF0: if (a < 0x90) return false; break;

            case 0xF4: if (a > 0x8F) return false; break;

            default:   if (a < 0x80) return false;

        }

        case 1: if (*source >= 0x80 && *source < 0xC2) return false;

    }

    if (*source > 0xF4)

        return false;

    return true;

}

// Magic values subtracted from a buffer value during UTF8 conversion.

// This table contains as many values as there might be trailing bytes

// in a UTF-8 sequence.

static const UChar32 offsetsFromUTF8[6] = { 0x00000000UL, 0x00003080UL, 0x000E2080UL, 

            0x03C82080UL, 0xFA082080UL, 0x82082080UL };

ConversionResult convertUTF8ToUTF16(

    const char** sourceStart, const char* sourceEnd, 

    UChar** targetStart, UChar* targetEnd, bool strict)

{

    ConversionResult result = conversionOK;

    const char* source = *sourceStart;

    UChar* target = *targetStart;

    while (source < sourceEnd) {

        UChar32 ch = 0;

        int extraBytesToRead = UTF8SequenceLength(*source) - 1;

        if (source + extraBytesToRead >= sourceEnd) {

            result = sourceExhausted;

            break;

        }

        // Do this check whether lenient or strict

        if (!isLegalUTF8(reinterpret_cast<const unsigned char*>(source), extraBytesToRead + 1)) {

            result = sourceIllegal;

            break;

        }

        // The cases all fall through.

        switch (extraBytesToRead) {

            case 5: ch += static_cast<unsigned char>(*source++); ch <<= 6; // remember, illegal UTF-8

            case 4: ch += static_cast<unsigned char>(*source++); ch <<= 6; // remember, illegal UTF-8

            case 3: ch += static_cast<unsigned char>(*source++); ch <<= 6;

            case 2: ch += static_cast<unsigned char>(*source++); ch <<= 6;

            case 1: ch += static_cast<unsigned char>(*source++); ch <<= 6;

            case 0: ch += static_cast<unsigned char>(*source++);

        }

        ch -= offsetsFromUTF8[extraBytesToRead];

        if (target >= targetEnd) {

            source -= (extraBytesToRead + 1); // Back up source pointer!

            result = targetExhausted; break;

        }

        if (ch <= 0xFFFF) {

            // UTF-16 surrogate values are illegal in UTF-32

            if (ch >= 0xD800 && ch <= 0xDFFF) {

                if (strict) {

                    source -= (extraBytesToRead + 1); // return to the illegal value itself

                    result = sourceIllegal;

                    break;

                } else

                    *target++ = 0xFFFD;

            } else

                *target++ = (UChar)ch; // normal case

        } else if (ch > 0x10FFFF) {

            if (strict) {

                result = sourceIllegal;

                source -= (extraBytesToRead + 1); // return to the start

                break; // Bail out; shouldn't continue

            } else

                *target++ = 0xFFFD;

        } else {

            // target is a character in range 0xFFFF - 0x10FFFF

            if (target + 1 >= targetEnd) {

                source -= (extraBytesToRead + 1); // Back up source pointer!

                result = targetExhausted;

                break;

            }

            ch -= 0x0010000UL;

            *target++ = (UChar)((ch >> 10) + 0xD800);

            *target++ = (UChar)((ch & 0x03FF) + 0xDC00);

        }

    }

    *sourceStart = source;

    *targetStart = target;

    return result;

}

}

}