4coder/4ed_hash_functions.cpp

/*
 * Mr. 4th Dimention - Allen Webster
 *
 * 26.08.2018
 *
 * Generic hash functions
 *
 */

// TOP

internal u64
table_hash_u8(u8 *v, i32 size){
    u64 hash = 0;
    for (u8 *p = v, *e = v + size; p < e; p += 1){
        u8 k = *p;
        k *= 81;
        k = ((u8)(k << 4)) | ((u8)(k >> 4));
        hash ^= k;
        hash *= 11;
        hash += 237;
    }
    return(hash);
}
internal u64
table_hash_u16(u16 *v, i32 size){
    u64 hash = 0;
    for (u16 *p = v, *e = v + size; p < e; p += 1){
        u16 k = *p;
        k *= 11601;
        k = ((u16)(k << 8)) | ((u16)(k >> 8));
        hash ^= k;
        hash *= 11;
        hash += 12525;
    }
    return(hash);
}
internal u64
table_hash_u32(u32 *v, i32 size){
    u64 hash = 0;
    for (u32 *p = v, *e = v + size; p < e; p += 1){
        u32 k = *p;
        k *= 3432918353U;
        k = ((u32)(k << 16)) | ((u32)(k >> 16));
        hash ^= k;
        hash *= 11;
        hash += 2041000173U;
    }
    return(hash);
}
internal u64
table_hash_u64(u64 *v, i32 size){
    u64 hash = 0;
    for (u64 *p = v, *e = v + size; p < e; p += 1){
        u64 k = *p;
        k *= 14744272059406101841ULL;
        k = ((u64)(k << 32)) | ((u64)(k >> 32));
        hash ^= k;
        hash *= 11;
        hash += 8766028991911375085ULL;
    }
    return(hash);
}
internal u64
table_hash(void *v, i32 it_size, i32 size){
    u64 hash = 0;
    switch (it_size){
        case 1:
        {
            hash = table_hash_u8((u8*)v, size);
        }break;
        case 2:
        {
            hash = table_hash_u16((u16*)v, size);
        }break;
        case 4:
        {
            hash = table_hash_u32((u32*)v, size);
        }break;
        case 8:
        {
            hash = table_hash_u64((u64*)v, size);
        }break;
        default:
        {
            hash = table_hash_u8((u8*)v, it_size*size);
        }break;
    }
    return(hash);
}

// BOTTOM