Source/WTF/wtf/SixCharacterHash.cpp

/*
 * Copyright (C) 2013 Apple Inc. 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 APPLE INC. ``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 APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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 */

#include "config.h"
#include <wtf/SixCharacterHash.h>

#include <wtf/ASCIICType.h>

namespace WTF {

unsigned sixCharacterHashStringToInteger(std::span<const char, 6> string)
{
    unsigned hash = 0;

    for (auto c : string) {
        hash *= 62;
        RELEASE_ASSERT(c); // FIXME: Why does this need to be a RELEASE_ASSERT?
        if (isASCIIUpper(c)) {
            hash += c - 'A';
            continue;
        }
        if (isASCIILower(c)) {
            hash += c - 'a' + 26;
            continue;
        }
        ASSERT(isASCIIDigit(c));
        hash += c - '0' + 26 * 2;
    }

    return hash;
}

std::array<char, 6> integerToSixCharacterHashString(unsigned hash)
{
    static constexpr std::array<char, 62> table {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
    };
    std::array<char, 6> buffer;
    unsigned accumulator = hash;
    for (unsigned i = 6; i--;) {
        buffer[i] = table[accumulator % 62];
        accumulator /= 62;
    }
    return buffer;
}

} // namespace WTF