cpl_base64.cpp

/******************************************************************************
 *
 * Project:  Common Portability Library
 * Purpose:  Encoding/Decoding Base64 strings
 * Author:   Paul Ramsey <pramsey@cleverelephant.ca>
 *           Dave Blasby <dblasby@gmail.com>
 *           René Nyffenegger
 *
 ******************************************************************************
 * Copyright (c) 2008 Paul Ramsey
 * Copyright (c) 2002 Refractions Research
 * Copyright (C) 2004-2008 René Nyffenegger
 * Copyright (c) 2010-2013, Even Rouault <even dot rouault at spatialys.com>
 *
 * (see also part way down the file for license terms for René's code)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies of this Software or works derived from this Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include "cpl_port.h"
#include "cpl_string.h"

#include <string>

#include "cpl_conv.h"

// Derived from MapServer's mappostgis.c.

/*
** Decode a base64 character.
*/
constexpr unsigned char CPLBase64DecodeChar[256] = {
    // Not Base64 characters.
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64,
    // +
    62,
    // Not Base64 characters.
    64, 64, 64,
    //  /
    63,
    // 0-9
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
    // Not Base64 characters.
    64, 64, 64, 64, 64, 64, 64,
    // A-Z
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
    21, 22, 23, 24, 25,
    // Not Base64 characters.
    64, 64, 64, 64, 64, 64,
    // a-z
    26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,
    45, 46, 47, 48, 49, 50, 51,
    // Not Base64 characters.
    64, 64, 64, 64, 64,
    // Not Base64 characters (upper 128 characters).
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64};

/************************************************************************/
/*                       CPLBase64DecodeInPlace()                       */
/************************************************************************/

/** Decode base64 string "pszBase64" (null terminated) in place.
 *
 * Returns length of decoded array or 0 on failure.
 */
int CPLBase64DecodeInPlace(GByte *pszBase64)
{
    if (pszBase64 && *pszBase64)
    {
        unsigned char *p = pszBase64;
        int offset_1 = 0;
        int offset_2 = 0;

        // Drop illegal chars first.
        for (; pszBase64[offset_1]; ++offset_1)
        {
            unsigned char c = pszBase64[offset_1];
            if ((CPLBase64DecodeChar[c] != 64) || (c == '='))
            {
                pszBase64[offset_2++] = c;
            }
        }

        for (int idx = 0; idx < offset_2; idx += 4)
        {
            unsigned char b1 = CPLBase64DecodeChar[pszBase64[idx]];
            unsigned char b2 = 0;
            unsigned char c3 = 'A';
            unsigned char c4 = 'A';

            if (idx + 3 < offset_2)
            {
                b2 = CPLBase64DecodeChar[pszBase64[idx + 1]];
                c3 = pszBase64[idx + 2];
                c4 = pszBase64[idx + 3];
            }
            else if (idx + 2 < offset_2)
            {
                b2 = CPLBase64DecodeChar[pszBase64[idx + 1]];
                c3 = pszBase64[idx + 2];
            }
            else if (idx + 1 < offset_2)
            {
                b2 = CPLBase64DecodeChar[pszBase64[idx + 1]];
                // c3 = 'A';
            }  // Else: Use the default values.

            const unsigned char b3 = CPLBase64DecodeChar[c3];
            const unsigned char b4 = CPLBase64DecodeChar[c4];

            *p++ = ((b1 << 2) | (b2 >> 4));
            if (p - pszBase64 == offset_1)
                break;
            if (c3 != '=')
            {
                *p++ = (((b2 & 0xf) << 4) | (b3 >> 2));
                if (p - pszBase64 == offset_1)
                    break;
            }
            if (c4 != '=')
            {
                *p++ = (((b3 & 0x3) << 6) | b4);
                if (p - pszBase64 == offset_1)
                    break;
            }
        }
        return static_cast<int>(p - pszBase64);
    }
    return 0;
}

/*
 * This function was extracted from the base64 cpp utility published by
 * René Nyffenegger. The code was modified into a form suitable for use in
 * CPL.  The original code can be found at:
 *
 * http://www.adp-gmbh.ch/cpp/common/base64.html.
 *
 * The following is the original notice of this function.
 *
 * base64.cpp and base64.h
 *
 *  Copyright (C) 2004-2008 René Nyffenegger
 *
 *  This source code is provided 'as-is', without any express or implied
 *  warranty. In no event will the author be held liable for any damages
 *  arising from the use of this software.
 *
 *  Permission is granted to anyone to use this software for any purpose,
 *  including commercial applications, and to alter it and redistribute it
 *  freely, subject to the following restrictions:
 *
 *  1. The origin of this source code must not be misrepresented; you must not
 *     claim that you wrote the original source code. If you use this source
 *     code in a product, an acknowledgment in the product documentation would
 *     be appreciated but is not required.
 *
 *  2. Altered source versions must be plainly marked as such, and must not be
 *     misrepresented as being the original source code.
 *
 *  3. This notice may not be removed or altered from any source distribution.
 *
 *  René Nyffenegger rene.nyffenegger@adp-gmbh.ch
 */

/************************************************************************/
/*                          CPLBase64Encode()                           */
/************************************************************************/

/** Base64 encode a buffer. */

char *CPLBase64Encode(int nDataLen, const GByte *pabyBytesToEncode)
{
    constexpr char base64Chars[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    const int kCharArray3Size = 3;
    const int kCharArray4Size = 4;
    unsigned char charArray3[kCharArray3Size] = {};

    std::string result("");
    int array3_idx = 0;
    while (nDataLen--)
    {
        charArray3[array3_idx++] = *(pabyBytesToEncode++);

        if (array3_idx == kCharArray3Size)
        {
            const unsigned char charArray4[kCharArray4Size] = {
                static_cast<unsigned char>((charArray3[0] & 0xfc) >> 2),
                static_cast<unsigned char>(((charArray3[0] & 0x03) << 4) +
                                           ((charArray3[1] & 0xf0) >> 4)),
                static_cast<unsigned char>(((charArray3[1] & 0x0f) << 2) +
                                           ((charArray3[2] & 0xc0) >> 6)),
                static_cast<unsigned char>(charArray3[2] & 0x3f)};

            for (int idx = 0; idx < kCharArray4Size; ++idx)
            {
                result += base64Chars[charArray4[idx]];
            }

            array3_idx = 0;
        }
    }

    if (array3_idx)
    {
        for (int idx = array3_idx; idx < kCharArray3Size; ++idx)
        {
            charArray3[idx] = '\0';
        }

        const unsigned char charArray4[kCharArray4Size] = {
            static_cast<unsigned char>((charArray3[0] & 0xfc) >> 2),
            static_cast<unsigned char>(((charArray3[0] & 0x03) << 4) +
                                       ((charArray3[1] & 0xf0) >> 4)),
            static_cast<unsigned char>(((charArray3[1] & 0x0f) << 2) +
                                       ((charArray3[2] & 0xc0) >> 6)),
            static_cast<unsigned char>(charArray3[2] & 0x3f)};

        for (int idx = 0; idx < (array3_idx + 1); ++idx)
        {
            result += base64Chars[charArray4[idx]];
        }

        while (array3_idx++ < kCharArray3Size)
            result += '=';
    }

    return CPLStrdup(result.c_str());
}