sjis.c

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>

#include "sjis.h"

static unsigned int *LookupTable;
static unsigned int NumLookupTableEntries;

int SetSJISToUnicodeLookupTable(void *table, unsigned int TableLength)
{
    LookupTable           = table;
    NumLookupTableEntries = TableLength / sizeof(unsigned int) / 2;
    return 0;
}

wchar_t ConvertSJISToUnicodeChar(unsigned short int SourceChar)
{
    unsigned int index;
    wchar_t UnicodeChar;

    if (SourceChar < 0x80) {
        UnicodeChar = SourceChar;
    } else {
        UnicodeChar = UNICODE_REPLACEMENT_CHAR;
        for (index = 0; index < NumLookupTableEntries; index++) {
            if (LookupTable[index * 2 + 0] == SourceChar) {
                UnicodeChar = LookupTable[index * 2 + 1];
                break;
            }
        }
    }

    return UnicodeChar;
}

int SJISToUnicode(const unsigned char *SJISStringIn, int length, wchar_t *UnicodeStringOut, unsigned int NumUChars)
{
    unsigned int i, NumChars;
    const char *SourceString;
    unsigned short int SJISCharacter;
    int result;

    for (result = 0, i = 0, SourceString = SJISStringIn, NumChars = 0; NumChars < NumUChars; i += GetSJISCharLength(SJISCharacter), NumChars++) {
        if (length > 0 && i >= length)
            break;

        if ((SJISCharacter = GetNextSJISChar(&SourceString)) == '\0') {
            UnicodeStringOut[NumChars++] = '\0';
            break;
        }

        UnicodeStringOut[NumChars] = ConvertSJISToUnicodeChar(SJISCharacter);
    }

    return (result == 0 ? NumChars : result);
}

int GetSJISCharLengthFromString(const char *SJISCharacter)
{
    return ((SJISCharacter[0] & 0x80) ? 2 : 1);
}

int GetSJISCharLength(unsigned short int SJISCharacter)
{
    return ((SJISCharacter & 0x8000) ? 2 : 1);
}

unsigned short int GetNextSJISChar(const char **string)
{
    int CharLength;
    unsigned short int NextSJISChar;

    CharLength = GetSJISCharLengthFromString(*string);
    if (CharLength == 1) {
        NextSJISChar = (*string)[0];
        (*string)++;
    } else {
        ((unsigned char *)&NextSJISChar)[1] = (*string)[0];
        ((unsigned char *)&NextSJISChar)[0] = (*string)[1];
        (*string) += 2;
    }

    return NextSJISChar;
}