/*

 * Copyright 2001-2004 Unicode, Inc.

 *

 * Disclaimer

 *

 * This source code is provided as is by Unicode, Inc. No claims are

 * made as to fitness for any particular purpose. No warranties of any

 * kind are expressed or implied. The recipient agrees to determine

 * applicability of information provided. If this file has been

 * purchased on magnetic or optical media from Unicode, Inc., the

 * sole remedy for any claim will be exchange of defective media

 * within 90 days of receipt.

 *

 * Limitations on Rights to Redistribute This Code

 *

 * Unicode, Inc. hereby grants the right to freely use the information

 * supplied in this file in the creation of products supporting the

 * Unicode Standard, and to make copies of this file in any form

 * for internal or external distribution as long as this notice

 * remains attached.

 */

/* ---------------------------------------------------------------------

    Conversions between UTF32, UTF-16, and UTF-8. Source code file.

    Author: Mark E. Davis, 1994.

    Rev History: Rick McGowan, fixes & updates May 2001.

    Sept 2001: fixed const & error conditions per

    mods suggested by S. Parent & A. Lillich.

    June 2002: Tim Dodd added detection and handling of incomplete

    source sequences, enhanced error detection, added casts

    to eliminate compiler warnings.

    July 2003: slight mods to back out aggressive FFFE detection.

    Jan 2004: updated switches in from-UTF8 conversions.

    Oct 2004: updated to use UNI_MAX_LEGAL_UTF32 in UTF-32 conversions.

    See the header file "ConvertUTF.h" for complete documentation.

------------------------------------------------------------------------ */

#include "convertutf.h"

#ifdef CVTUTF_DEBUG

#include <stdio.h>

#endif

static const int halfShift  = 10; /* used for shifting by 10 bits */

static const UTF32 halfBase = 0x0010000UL;

static const UTF32 halfMask = 0x3FFUL;

#define UNI_SUR_HIGH_START  (UTF32)0xD800

#define UNI_SUR_HIGH_END    (UTF32)0xDBFF

#define UNI_SUR_LOW_START   (UTF32)0xDC00

#define UNI_SUR_LOW_END     (UTF32)0xDFFF

#define false      0

#define true        1

/* --------------------------------------------------------------------- */

ConversionResult ConvertUTF32toUTF16(

    const UTF32** sourceStart, const UTF32* sourceEnd,

    UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags)

{

    ConversionResult result = conversionOK;

    const UTF32* source = *sourceStart;

    UTF16* target = *targetStart;

    while (source < sourceEnd)

    {

        UTF32 ch;

        if (target >= targetEnd)

        {

            result = targetExhausted;

            break;

        }

        ch = *source++;

        if (ch <= UNI_MAX_BMP)   /* Target is a character <= 0xFFFF */

        {

            /* UTF-16 surrogate values are illegal in UTF-32; 0xffff or 0xfffe are both reserved values */

            if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)

            {

                if (flags == strictConversion)

                {

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

                    result = sourceIllegal;

                    break;

                }

                else

                {

                    *target++ = UNI_REPLACEMENT_CHAR;

                }

            }

            else

            {

                *target++ = (UTF16)ch; /* normal case */

            }

        }

        else if (ch > UNI_MAX_LEGAL_UTF32)

        {

            if (flags == strictConversion)

            {

                result = sourceIllegal;

            }

            else

            {

                *target++ = UNI_REPLACEMENT_CHAR;

            }

        }

        else

        {

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

            if (target + 1 >= targetEnd)

            {

                --source; /* Back up source pointer! */

                result = targetExhausted;

                break;

            }

            ch -= halfBase;

            *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START);

            *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START);

        }

    }

    *sourceStart = source;

    *targetStart = target;

    return result;

}

/* --------------------------------------------------------------------- */

ConversionResult ConvertUTF16toUTF32(

    const UTF16** sourceStart, const UTF16* sourceEnd,

    UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags)

{

    ConversionResult result = conversionOK;

    const UTF16* source = *sourceStart;

    UTF32* target = *targetStart;

    UTF32 ch, ch2;

    while (source < sourceEnd)

    {

        const UTF16* oldSource = source; /*  In case we have to back up because of target overflow. */

        ch = *source++;

        /* If we have a surrogate pair, convert to UTF32 first. */

        if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END)

        {

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

            if (source < sourceEnd)

            {

                ch2 = *source;

                /* If it's a low surrogate, convert to UTF32. */

                if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END)

                {

                    ch = ((ch - UNI_SUR_HIGH_START) << halfShift)

                         + (ch2 - UNI_SUR_LOW_START) + halfBase;

                    ++source;

                }

                else if (flags == strictConversion)   /* 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 (flags == strictConversion)

        {

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

            if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)

            {

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

                result = sourceIllegal;

                break;

            }

        }

        if (target >= targetEnd)

        {

            source = oldSource; /* Back up source pointer! */

            result = targetExhausted;

            break;

        }

        *target++ = ch;

    }

    *sourceStart = source;

    *targetStart = target;

#ifdef CVTUTF_DEBUG

    if (result == sourceIllegal)

    {

        fprintf(stderr, "ConvertUTF16toUTF32 illegal seq 0x%04x,%04x\n", ch, ch2);

        fflush(stderr);

    }

#endif

    return result;

}

/* --------------------------------------------------------------------- */

/*

 * Index into the table below with the first byte of a UTF-8 sequence to

 * get the number of trailing bytes that are supposed to follow it.

 * Note that *legal* UTF-8 values can't have 4 or 5-bytes. The table is

 * left as-is for anyone who may want to do such conversion, which was

 * allowed in earlier algorithms.

 */

static const char trailingBytesForUTF8[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, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5

};

/*

 * 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 UTF32 offsetsFromUTF8[6] = { 0x00000000UL, 0x00003080UL, 0x000E2080UL,

                                        0x03C82080UL, 0xFA082080UL, 0x82082080UL

                                        };

/*

 * 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 UTF8 firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };

/* --------------------------------------------------------------------- */

/* The interface converts a whole buffer to avoid function-call overhead.

 * Constants have been gathered. Loops & conditionals have been removed as

 * much as possible for efficiency, in favor of drop-through switches.

 * (See "Note A" at the bottom of the file for equivalent code.)

 * If your compiler supports it, the "isLegalUTF8" call can be turned

 * into an inline function.

 */

/* --------------------------------------------------------------------- */

ConversionResult ConvertUTF16toUTF8(

    const UTF16** sourceStart, const UTF16* sourceEnd,

    UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags)

{

    ConversionResult result = conversionOK;

    const UTF16* source = *sourceStart;

    UTF8* target = *targetStart;

    while (source < sourceEnd)

    {

        UTF32 ch;

        unsigned short bytesToWrite = 0;

        const UTF32 byteMask = 0xBF;

        const UTF32 byteMark = 0x80;

        const UTF16* oldSource = source; /* In case we have to back up because of target overflow. */

        ch = *source++;

        /* If we have a surrogate pair, convert to UTF32 first. */

        if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END)

        {

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

            if (source < sourceEnd)

            {

                UTF32 ch2 = *source;

                /* If it's a low surrogate, convert to UTF32. */

                if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END)

                {

                    ch = ((ch - UNI_SUR_HIGH_START) << halfShift)

                         + (ch2 - UNI_SUR_LOW_START) + halfBase;

                    ++source;

                }

                else if (flags == strictConversion)   /* 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 (flags == strictConversion)

        {

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

            if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)

            {

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

                result = sourceIllegal;

                break;

            }

        }

        /* Figure out how many bytes the result will require */

        if (ch < (UTF32)0x80)

        {

            bytesToWrite = 1;

        }

        else if (ch < (UTF32)0x800)

        {

            bytesToWrite = 2;

        }

        else if (ch < (UTF32)0x10000)

        {

            bytesToWrite = 3;

        }

        else if (ch < (UTF32)0x110000)

        {

            bytesToWrite = 4;

        }

        else

        {

            bytesToWrite = 3;

            ch = UNI_REPLACEMENT_CHAR;

        }

        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 = (UTF8)((ch | byteMark) & byteMask);

            ch >>= 6;

        case 3:

            *--target = (UTF8)((ch | byteMark) & byteMask);

            ch >>= 6;

        case 2:

            *--target = (UTF8)((ch | byteMark) & byteMask);

            ch >>= 6;

        case 1:

            *--target = (UTF8)(ch | firstByteMark[bytesToWrite]);

        }

        target += bytesToWrite;

    }

    *sourceStart = source;

    *targetStart = target;

    return result;

}

/* --------------------------------------------------------------------- */

/*

 * Utility routine to tell whether a sequence of bytes is legal UTF-8.

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

 * If not calling this from ConvertUTF8to*, then the length can be set by:

 *  length = trailingBytesForUTF8[*source]+1;

 * and the sequence is illegal right away if there aren't that many bytes

 * available.

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

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

 */

static Boolean isLegalUTF8(const UTF8 *source, int length)

{

    UTF8 a;

    const UTF8 *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;

}

/* --------------------------------------------------------------------- */

/*

 * Exported function to return whether a UTF-8 sequence is legal or not.

 * This is not used here; it's just exported.

 */

Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd)

{

    int length = trailingBytesForUTF8[*source]+1;

    if (source+length > sourceEnd)

    {

        return false;

    }

    return isLegalUTF8(source, length);

}

/* --------------------------------------------------------------------- */

ConversionResult ConvertUTF8toUTF16(

    const UTF8** sourceStart, const UTF8* sourceEnd,

    UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags)

{

    ConversionResult result = conversionOK;

    const UTF8* source = *sourceStart;

    UTF16* target = *targetStart;

    while (source < sourceEnd)

    {

        UTF32 ch = 0;

        unsigned short extraBytesToRead = trailingBytesForUTF8[*source];

        if (source + extraBytesToRead >= sourceEnd)

        {

            result = sourceExhausted;

            break;

        }

        /* Do this check whether lenient or strict */

        if (! isLegalUTF8(source, extraBytesToRead+1))

        {

            result = sourceIllegal;

            break;

        }

        /*

         * The cases all fall through. See "Note A" below.

         */

        switch (extraBytesToRead)

        {

        case 5:

            ch += *source++;

            ch <<= 6; /* remember, illegal UTF-8 */

        case 4:

            ch += *source++;

            ch <<= 6; /* remember, illegal UTF-8 */

        case 3:

            ch += *source++;

            ch <<= 6;

        case 2:

            ch += *source++;

            ch <<= 6;

        case 1:

            ch += *source++;

            ch <<= 6;

        case 0:

            ch += *source++;

        }

        ch -= offsetsFromUTF8[extraBytesToRead];

        if (target >= targetEnd)

        {

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

            result = targetExhausted;

            break;

        }

        if (ch <= UNI_MAX_BMP)   /* Target is a character <= 0xFFFF */

        {

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

            if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)

            {

                if (flags == strictConversion)

                {

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

                    result = sourceIllegal;

                    break;

                }

                else

                {

                    *target++ = UNI_REPLACEMENT_CHAR;

                }

            }

            else

            {

                *target++ = (UTF16)ch; /* normal case */

            }

        }

        else if (ch > UNI_MAX_UTF16)

        {

            if (flags == strictConversion)

            {

                result = sourceIllegal;

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

                break; /* Bail out; shouldn't continue */

            }

            else

            {

                *target++ = UNI_REPLACEMENT_CHAR;

            }

        }

        else

        {

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

            if (target + 1 >= targetEnd)

            {

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

                result = targetExhausted;

                break;

            }

            ch -= halfBase;

            *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START);

            *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START);

        }

    }