#ifndef GUF_HASH_H
#define GUF_HASH_H
#include "guf_common.h"

/*
    FNV-1a (32-bit and 64-bit) hash functions. 
    Generally, you should always call csr_hash with GUF_HASH_INIT as the hash argument, unless you want to create "chains" of hashes. 
    cf. http://www.isthe.com/chongo/tech/comp/fnv/ (last retrieved: 2023-11-30)
*/ 

#ifdef GUF_IMPL_STATIC
    #define GUF_FN_KEYWORDS static
#else
    #define GUF_FN_KEYWORDS
#endif

#define GUF_HASH32_INIT UINT32_C(2166136261)
#define GUF_HASH64_INIT UINT64_C(14695981039346656037)

GUF_FN_KEYWORDS uint32_t guf_hash32(const void *data, ptrdiff_t num_bytes, uint32_t hash); // FNV-1a (32 bit)
GUF_FN_KEYWORDS uint64_t guf_hash64(const void *data, ptrdiff_t num_bytes, uint64_t hash); // FNV-1a (64 bit)

#ifdef GUF_HASH_32_BIT
    typedef uint32_t guf_hash_size_t;
    #define GUF_HASH_INIT GUF_HASH32_INIT
    #define GUF_HASH_MAX UINT32_MAX
    static inline guf_hash_size_t guf_hash(const void *data, ptrdiff_t num_bytes, uint32_t hash) {
        return guf_hash32(data, num_bytes, hash);
    }
#else
    typedef uint64_t guf_hash_size_t;
    #define GUF_HASH_INIT GUF_HASH64_INIT
    #define GUF_HASH_MAX UINT64_MAX
    static inline guf_hash_size_t guf_hash(const void *data, ptrdiff_t num_bytes, uint64_t hash) {
        return guf_hash64(data, num_bytes, hash);
    }
#endif

#endif

#if defined(GUF_IMPL) || defined(GUF_IMPL_STATIC) 
#include "guf_assert.h"

GUF_FN_KEYWORDS uint32_t guf_hash32(const void *data, ptrdiff_t num_bytes, uint32_t hash)
{
    GUF_ASSERT_RELEASE(data);
    GUF_ASSERT_RELEASE(num_bytes > 0);
    const unsigned char *data_bytes = (const unsigned char*)data; // This does not break strict-aliasing rules I think...
    const uint32_t FNV_32_PRIME = 16777619ul;
    for (ptrdiff_t i = 0; i < num_bytes; ++i) {
        hash ^= data_bytes[i];
        hash *= FNV_32_PRIME;
    }
    return hash;
}

GUF_FN_KEYWORDS uint64_t guf_hash64(const void *data, ptrdiff_t num_bytes, uint64_t hash)
{
    GUF_ASSERT_RELEASE(data);
    GUF_ASSERT_RELEASE(num_bytes > 0);
    const unsigned char *data_bytes = (const unsigned char*)data; // This does not break strict-aliasing rules I think...
    const uint64_t FNV_64_PRIME = 1099511628211ull;
    for (ptrdiff_t i = 0; i < num_bytes; ++i) {
        hash ^= data_bytes[i];
        hash *= FNV_64_PRIME;
    }
    return hash;
}

#undef GUF_IMPL
#undef GUF_IMPL_STATIC
#endif /* endif GUF_IMPL/GUF_IMPL_STATIC */

#undef GUF_FN_KEYWORDS