// There are 2 reasons why not use existing unicodeconv.cpp:

// 1) "unicode->foreign" in existing unicodeconv.cpp is quite slow, especially

//    for huge code pages (e.g, Asia code pages). See INC127598.

//

// 2) GB18030 has 32-bit code that existing unicodeconv.cpp cannot handle.

//

// The algorithm of this special version unicodeconv.cpp is straightforward:

// 1) foreign->unicode:

//    1.1) 1 byte/2 byte->unicode bmp: use existing mechanism; mapping table in

//              "cp54936_2byte_tounicode.cpp", which is generated with command

//              "perl -w ..\group\FatConversionTable.pl cp54936_2byte.txt".

//

//    1.2) 4 byte->unicode bmp: convert the 4-byte code to a 16-bit index, then

//              search into the mapping table in "cp54936_4byte_tounicode.cpp",

//              which is generated with command

//              "perl -w ..\group\cp54936_4byte_tounicode.pl cp54936_4byte.txt".

//

//    1.3) 4 byte->unicode non-bmp: calculate with formula in this file.

//

// 2) unicode->foreign:

//    2.1) unicode bmp->1/2/4 byte: the huge table in "cp54936_allbmp_fromunicode.cpp"

//              can map directly, which is generated with command

//              "perl -w ..\group\cp54936_allbmp_fromunicode.pl cp54936_2byte.txt cp54936_4byte.txt".

//

//    2.2) unicode non-bmp->4 byte: calculate with formula in this file.

//

// The function cp54936_2byte_tounicode.cpp::TConvDataStruct::

// ConvertSingleUnicode() is not used anymore. It's reserved just because not

// changing the tool FatConversionTable.pl.

//

// About the mapping table "cp54936_2byte.txt" and "cp54936_4byte.txt":

// 1) All Private Used Area (PUA) code points are reserved.

// 2) All GB18030 code points that mapping to undefined Unicode are reserved.

//

//

// About the formula for non-bmp calculation:

// 1) All code points from 0x10000 to 0x10FFFF are supported.

// 2) Code points in 0x10000-0x1FFFF and 0x30000-0x10FFFF are summarized from

//    the GB18030 standard, since the standard does not define the mapping for

//    code points out of 0x20000-0x2FFFF.

#include <e32std.h>

#include <e32def.h>

#include <e32des8.h> 

#include "unicodeconv.h"

#include "cp54936.h"

enum TFccPanic

	{

	EBadForeignCode = 0,

	E4ByteIndexOutOfRange,

	EPanicBadIndices1,

	EInavlidUnicodeValue

	};

void Panic(TFccPanic aPanic)

	{

	User::Panic(_L("FatCharsetConv"),aPanic);

	}

//replacement character to be used when unicode cannot be converted

const TUint8 KForeignReplacement = 0x5F;

const TUint8 KU10000Byte1 = 0x90;

const TUint8 KU10000Byte2 = 0x30;

const TUint8 KU10000Byte3 = 0x81;

const TUint8 KU10000Byte4 = 0x30;

inline TBool IsSupplementary(TUint aChar)

/**

@param aChar The 32-bit code point value of a Unicode character.

@return True, if aChar is supplementary character; false, otherwise.

*/

	{

	return (aChar > 0xFFFF);

	}

inline TBool IsSurrogate(TText16 aInt16)

/**

@return True, if aText16 is high surrogate or low surrogate; false, otherwise.

*/

	{

	return (aInt16 & 0xF800) == 0xD800;

	}

inline TBool IsHighSurrogate(TText16 aInt16)

/**

@return True, if aText16 is high surrogate; false, otherwise.

*/

	{

	return (aInt16 & 0xFC00) == 0xD800;

	}

inline TBool IsLowSurrogate(TText16 aInt16)

/**

@return True, if aText16 is low surrogate; false, otherwise.

*/

	{

	return (aInt16 & 0xFC00) == 0xDC00;

	}

inline TUint JoinSurrogate(TText16 aHighSurrogate, TText16 aLowSurrogate)

/**

Combine a high surrogate and a low surrogate into a supplementary character.

@return The 32-bit code point value of the generated Unicode supplementary

        character.

*/

	{

	return ((aHighSurrogate - 0xD7F7) << 10) + aLowSurrogate;

	}

inline TText16 GetHighSurrogate(TUint aChar)

/**

Retrieve the high surrogate of a supplementary character.

@param aChar The 32-bit code point value of a Unicode character.

@return High surrogate of aChar, if aChar is a supplementary character; 

        aChar itself, if aChar is not a supplementary character.

*/

	{

	return STATIC_CAST(TText16, 0xD7C0 + (aChar >> 10));

	}

inline TText16 GetLowSurrogate(TUint aChar)

/**

Retrieve the low surrogate of a supplementary character.

@param aChar The 32-bit code point value of a Unicode character.

@return Low surrogate of aChar, if aChar is a supplementary character; 

        zero, if aChar is not a supplementary character.

*/

	{

	return STATIC_CAST(TText16, 0xDC00 | (aChar & 0x3FF));

	}

//This function converts from Unicoded characters, to foreign characters and adds them into a descriptor

EXPORT_C void UnicodeConv::ConvertFromUnicodeL(TDes8& aForeign, const TDesC16& aUnicode)

	{

    UnicodeConv::ConvertFromUnicodeL(aForeign, aUnicode, ETrue);

    }

//This function converts from Unicoded characters, to foreign characters and adds them into a descriptor

EXPORT_C TInt UnicodeConv::ConvertFromUnicodeL(TDes8& aForeign, const TDesC16& aUnicode, TBool leaveWhenOverflow)

	{

	const TInt length = aUnicode.Length();

	const TUint16* unicode = aUnicode.Ptr();

	const TUint16* guard = unicode + length;

	TUint8* foreign = const_cast<TUint8*>(aForeign.Ptr());

	TUint8* foreignguard = foreign + aForeign.MaxLength();

	//loop going through the character of the unicode descriptor

	while (unicode < guard)

		{

		TUint32 unicodeChar = *unicode++;

		if (IsHighSurrogate(unicodeChar))

			{

			if (unicode >= guard || !IsLowSurrogate(*unicode))

				{

				if (foreign >= foreignguard)

					{

                    aForeign.SetLength(foreign-aForeign.Ptr());

					if (leaveWhenOverflow)

						User::Leave(KErrOverflow);

                    else

                    	return KErrOverflow;

					}

				*foreign++ = KForeignReplacement;

				continue;

				}

			unicodeChar = JoinSurrogate(unicodeChar, *unicode++);

			}

		if (IsLowSurrogate(unicodeChar))

			{

			if (foreign >= foreignguard)

				{

				aForeign.SetLength(foreign-aForeign.Ptr());

				if (leaveWhenOverflow)

					User::Leave(KErrOverflow);

				else

					return KErrOverflow;

				}

			*foreign++ = KForeignReplacement;

			continue;

			}

		TUint8 b1, b2, b3, b4;		// byte 1,2,3,4 of result GB18030 code.

		TInt count;					// byte count of result GB18030 code; can be 1, 2 or 4.

		// unicode to cp54936

		if (IsSupplementary(unicodeChar))

			{

			unicodeChar -= 0x10000;

			b4 = unicodeChar % 10 + KU10000Byte4;

			unicodeChar /= 10;

			b3 = unicodeChar % 126 + KU10000Byte3;

			unicodeChar /= 126;

			b2 = unicodeChar % 10 + KU10000Byte2;

			b1 = unicodeChar / 10 + KU10000Byte1;

			count = 4;

			}

		else

			{

			TUint32 foreignChar;

			foreignChar = KMappingTableUnicodeBmp2CP54936[unicodeChar];

			b1 = ((foreignChar >> 24) & 0xFF);

			b2 = ((foreignChar >> 16) & 0xFF);

			b3 = ((foreignChar >> 8) & 0xFF);

			b4 = (foreignChar & 0xFF);

			count = 1;

			if (b1)

				{

				count = 4;

				}

			else

				{

				__ASSERT_DEBUG(b2==0, Panic(EBadForeignCode));

				if (b3)

					{

					count = 2;

					}

				}

			}

		if (foreign + count > foreignguard)

			{

			aForeign.SetLength(foreign-aForeign.Ptr());

            if (leaveWhenOverflow)

            	User::Leave(KErrOverflow);

            else

            	return KErrOverflow;

			}

		if (count == 4)

			{

			*foreign++ = b1;

			*foreign++ = b2;

			}

		if (count >= 2)

			*foreign++ = b3;

		*foreign++ = b4;

		}

	aForeign.SetLength(foreign-aForeign.Ptr());

	return KErrNone;

	}

//This function converts from foreign characters into unicode and adds them into a descriptor

EXPORT_C void UnicodeConv::ConvertToUnicodeL(TDes16& aUnicode, const TDesC8& aForeign)

	{

    UnicodeConv::ConvertToUnicodeL(aUnicode, aForeign, ETrue);

    }

//This function converts from foreign characters into unicode and adds them into a descriptor

EXPORT_C TInt UnicodeConv::ConvertToUnicodeL(TDes16& aUnicode, const TDesC8& aForeign, TBool leaveWhenOverflow)

	{

	const TInt foreignLength = aForeign.Length();

	const TUint8* foreign = aForeign.Ptr();

	const TUint8* guard = foreign + foreignLength;

	TUint16* unicode = const_cast<TUint16*>(aUnicode.Ptr());

	TUint16* unicodeguard = unicode + aUnicode.MaxLength();

	TUint8 b1, b2, b3, b4;

	enum TCodeType

	{

	E1Byte = 0,

	E2Byte,

	E4ByteBmp,

	E4ByteSupplementary,

	EError,

	};

	TCodeType codetype;

	TUint32 unicodeChar;

	//loop going through the characters of the foreign descriptor

	while (foreign < guard)

		{

		// roughly, detect which area the foreign code belongs to

		b1 = *foreign++;

		if (b1 <= 0x7F)

			codetype = E1Byte;

		else if (b1 == 0x80 || b1 > 0xFE)

			codetype = EError;

		else if (foreign >= guard)

			codetype = EError;

		else

			{

			b2 = *foreign++;

			if (b2 >= 0x40 && b2 <= 0xFE && b2 != 0x7F)

				codetype = E2Byte;

			else if (b2 < 0x30 || b2 > 0x39)

				codetype = EError;

			else if (foreign+1 >= guard)

				codetype = EError;

			else

				{

				b3 = *foreign++;

				if (b3 < 0x81 || b3 > 0xFE)

					codetype = EError;

				else

					{

					b4 = *foreign++;

					if (b4 < 0x30 || b4 > 0x39)

						codetype = EError;

					else if (b1 >= 0x81 && b1 <= 0x84)		// 0x81308130-0x8439FE39

						codetype = E4ByteBmp;

					else if (b1 >= 0x90 && b1 <= 0xE3)		// 0x90308130-0xE339FE39

						codetype = E4ByteSupplementary;

					else

						codetype = EError;					// others are reserved

					}

				}

			}

		// cp54936 to unicode

		if (codetype == E1Byte)

			{

			unicodeChar = b1;

			}

		else if (codetype == E2Byte)

			{

			// conventional algorithm used in FatCharsetConv

			const TLeadOrSingle* structPtr = TConvDataStruct::KFirstByteConversions + (b1-0x80);

			if (structPtr->iUnicodeIfSingle)

				unicodeChar = structPtr->iUnicodeIfSingle;

			else if (TConvDataStruct::KMinTrailByte <= b2 && b2 <= TConvDataStruct::KMaxTrailByte)

				unicodeChar = TConvDataStruct::KDoubleByteConversions[structPtr->iDoubleByteIndex + (b2 - TConvDataStruct::KMinTrailByte)];

			else

				unicodeChar = 0xFFFD;

			}

		else if (codetype == E4ByteBmp)

			{

			TUint index = (b1-0x81)*12600 + (b2-0x30)*1260 + (b3-0x81)*10 + (b4-0x30);

			__ASSERT_DEBUG(index<39420, Panic(E4ByteIndexOutOfRange));

			unicodeChar = KMappingTable4ByteBmp2Unicode[index];

			}

		else if (codetype == E4ByteSupplementary)

			{

			unicodeChar = 0x10000 + (b1 - KU10000Byte1) * 12600 +

									(b2 - KU10000Byte2) * 1260 +

									(b3 - KU10000Byte3) * 10 +

									(b4 - KU10000Byte4);

			__ASSERT_DEBUG(unicodeChar >= 0x10000 && unicodeChar <= 0x10FFFF, Panic(EInavlidUnicodeValue));

			}

		else

			{

			unicodeChar = 0xFFFD;

			}

		// append to output buffer

		if (IsSupplementary(unicodeChar))

			{

			if (unicode + 1 >= unicodeguard)

				{

				aUnicode.SetLength(unicode-aUnicode.Ptr());

				if (leaveWhenOverflow)

					User::Leave(KErrOverflow);

				else

					return KErrOverflow;

				}

			*unicode++ = GetHighSurrogate(unicodeChar);

			*unicode++ = GetLowSurrogate(unicodeChar);

			}

		else

			{

			if (unicode >= unicodeguard)

				{

				aUnicode.SetLength(unicode-aUnicode.Ptr());

                if (leaveWhenOverflow)

                	User::Leave(KErrOverflow);

                else

                	return KErrOverflow;

				}

			*unicode++ = unicodeChar;

			}

		}

	aUnicode.SetLength(unicode-aUnicode.Ptr());

	return KErrNone;

	}

EXPORT_C TBool UnicodeConv::IsLegalShortNameCharacter (TUint aCharacter)

	{

	//1. aCharacter >= 0x0080 

	if (aCharacter>=0x0080)

		{

		// Since all Unicode characters can be mapped to GB18030, so no need to

		// test the converting.

		if (aCharacter <= 0x10FFFF && !IsSurrogate(aCharacter))

			return ETrue;

		else

			return EFalse;

		}

    // For most common cases: 

    // Note: lower case characters are considered legal DOS char here. 

	if ((aCharacter>='a' && aCharacter<='z') || 

	    (aCharacter>='A' && aCharacter<='Z') || 

	    (aCharacter>='0' && aCharacter<='9'))

			{

			return ETrue;

			}

    // Checking for illegal chars: 

    // 2. aCharacter <= 0x20 

    // Note: leading 0x05 byte should be guarded by callers of this function 

    //  as the information of the position of the character is required. 

	if (aCharacter < 0x20)

		return EFalse;

	// Space (' ') is not considered as a legal DOS char here.

	if (aCharacter == 0x20)

		return EFalse;

	// 3. 0x20 < aCharacter < 0x80 

    // According to FAT Spec, "following characters are not legal in any bytes of DIR_Name": 

    switch (aCharacter) 

            { 

            case 0x22:        // '"' 

            case 0x2A:        // '*' 

            case 0x2B:        // '+' 

            case 0x2C:        // ',' 

            //case 0x2E:        // '.'   // Although '.' is not allowed in any bytes of DIR_Name, it 

                                         // is a valid character in short file names. 

            case 0x2F:        // '/' 

            case 0x3A:        // ':' 

            case 0x3B:        // ';' 

            case 0x3C:        // '<' 

            case 0x3D:        // '=' 

            case 0x3E:        // '>' 

            case 0x3F:        // '?' 

            case 0x5B:        // '[' 

            case 0x5C:        // '\' 

            case 0x5D:        // ']' 

            case 0x7C:        // '|' 

            	return EFalse; 

            default: 

            	return ETrue; 

            } 

	}