FreeRDP/scripts/LOMHash.c

#include<stdio.h>
typedef unsigned short UINT16;
typedef unsigned char BYTE;
static UINT16 HuffCodeLOM[] = {
        0x0001, 0x0000, 0x0002, 0x0009, 0x0006, 0x0005, 0x000d, 0x000b, 0x0003, 0x001b, 0x0007, 0x0017, 0x0037, 
0x000f, 0x004f, 0x006f, 0x002f, 0x00ef, 0x001f, 0x005f, 0x015f, 0x009f, 0x00df, 0x01df, 0x003f, 0x013f, 0x00bf, 
0x01bf, 0x007f, 0x017f, 0x00ff, 0x01ff };

UINT16 HashTable[32] = { [0 ... 31] = 0xffff };

BYTE tab[4] = { 0, 4, 10, 19 };

UINT16 hash(UINT16 key)
{
        return ((key & 0x1f) ^ (key  >> 5) ^ (key >> 9));
}

BYTE minihash(UINT16 key)
{
        BYTE h;
        h = (key >> 4) & 0xf;
        return ((h ^ (h >> 2) ^ (h >> 3)) & 0x3);
}

void buildhashtable(void)
{
        int i,j;
        UINT16 h;
        for(i=0;i<32;i++)
        {
                h=hash(HuffCodeLOM[i]);
                if(HashTable[h]!=0xffff)
                {
                        HashTable[h] ^= (HuffCodeLOM[i] & 0xfe0) ^ 0xfe0;
                        HashTable[tab[minihash(HuffCodeLOM[i])]] = i;
                }
                else
                {
                        HashTable[h] = i;
                        HashTable[h] ^= 0xfe0;
                }
                printf("at %d %d=0x%hhx\n",i,h,HashTable[h]);
        }
}

BYTE getvalue(UINT16 huff)
{
        UINT16 h = HashTable[hash(huff)];
        if((h ^ huff) >> 5)
        {
                return h & 0x1f;
        }
        else
                return HashTable[tab[minihash(huff)]];
}

main()
{
        int i;
        buildhashtable();
        printf("static UINT16 HuffIndexLOM[32] = {\n");
        for(i=0;i<32;i++)
        {
                if(i == 31)
                        printf("0x%hx };\n",HashTable[i]);
                else
                        printf("0x%hx, ",HashTable[i]);
        }
        for(i=0;i<32;i++)
                        if(i != getvalue(HuffCodeLOM[i]))
                    printf("Fail :( at %d : 0x%04x got %d\n",i,HuffCodeLOM[i],getvalue(HuffCodeLOM[i]));
        return 0;
}