src/cx/hash_key.h

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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/**
 * \file hash_key.h
 * \brief Interface for map implementations.
 * \author Mike Becker
 * \author Olaf Wintermann
 * \version 3.0
 * \copyright 2-Clause BSD License
 */


#ifndef UCX_HASH_KEY_H
#define UCX_HASH_KEY_H

#include "stddef.h"

#ifdef __cplusplus
extern "C" {
#endif

/** Internal structure for a key within a hash map. */
struct cx_hash_key_s {
    /** The key data. */
    union {
        unsigned char *bytes;
        unsigned char const *cbytes;
        char *str;
        char const *cstr;
        void *obj;
        void const *cobj;
    } data;
    /**
     * The key data length.
     */
    size_t len;
    /** The hash value of the key data. */
    unsigned hash;
};

/**
 * Type for a hash key.
 */
typedef struct cx_hash_key_s CxHashKey;

/**
 * Computes a murmur2 32 bit hash.
 *
 * You need to initialize \c data and \c len in the key struct.
 * The hash is then directly written to that struct.
 *
 * \note If \c data is \c NULL, the hash is defined as 1574210520.
 *
 * @param key the key, the hash shall be computed for
 */
void cx_hash_murmur(CxHashKey *key);

/**
 * Computes a hash key from a string.
 *
 * The string needs to be zero-terminated.
 *
 * @param str the string
 * @return the hash key
 */
__attribute__((__warn_unused_result__))
CxHashKey cx_hash_key_str(char const *str);

/**
 * Computes a hash key from a byte array.
 *
 * @param bytes the array
 * @param len the length
 * @return the hash key
 */
__attribute__((__warn_unused_result__))
CxHashKey cx_hash_key_bytes(
        unsigned char const *bytes,
        size_t len
);

/**
 * Computes a hash key for an arbitrary object.
 *
 * The computation uses the in-memory representation that might not be
 * the same on different platforms. Therefore, this hash should not be
 * used for data exchange with different machines.
 *
 * @param obj a pointer to an arbitrary object
 * @param len the length of object in memory
 * @return the hash key
 */
__attribute__((__warn_unused_result__))
CxHashKey cx_hash_key(
        void const *obj,
        size_t len
);

#ifdef __cplusplus
} // extern "C"
#endif

#endif // UCX_HASH_KEY_H