WebCore/platform/text/Base64.cpp

/*
   Copyright (C) 2000-2001 Dawit Alemayehu <adawit@kde.org>
   Copyright (C) 2006 Alexey Proskuryakov <ap@webkit.org>
   Copyright (C) 2007, 2008 Apple Inc. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License (LGPL)
   version 2 as published by the Free Software Foundation.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

   This code is based on the java implementation in HTTPClient
   package by Ronald Tschalär Copyright (C) 1996-1999.
*/

#include "config.h"
#include "Base64.h"

#include <limits.h>

#include <wtf/Platform.h>
#include <wtf/StringExtras.h>

namespace WebCore {

static const char base64EncMap[64] = {
    0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
    0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50,
    0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
    0x59, 0x5A, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66,
    0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E,
    0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76,
    0x77, 0x78, 0x79, 0x7A, 0x30, 0x31, 0x32, 0x33,
    0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x2B, 0x2F
};

static const char base64DecMap[128] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x3E, 0x00, 0x00, 0x00, 0x3F,
    0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B,
    0x3C, 0x3D, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
    0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
    0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
    0x17, 0x18, 0x19, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20,
    0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
    0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30,
    0x31, 0x32, 0x33, 0x00, 0x00, 0x00, 0x00, 0x00
};

void base64Encode(const Vector<char>& in, Vector<char>& out, bool insertLFs)
{
    out.clear();
    if (in.isEmpty())
        return;

    // If the input string is pathologically large, just return nothing.
    // Note: Keep this in sync with the "out_len" computation below.
    // Rather than being perfectly precise, this is a bit conservative.
    const unsigned maxInputBufferSize = UINT_MAX / 77 * 76 / 4 * 3 - 2;
    if (in.size() > maxInputBufferSize)
        return;

    unsigned sidx = 0;
    unsigned didx = 0;
    const char* data = in.data();
    const unsigned len = in.size();

    unsigned out_len = ((len + 2) / 3) * 4;

    // Deal with the 76 character per line limit specified in RFC 2045.
    insertLFs = (insertLFs && out_len > 76);
    if (insertLFs)
        out_len += ((out_len - 1) / 76);

    int count = 0;
    out.grow(out_len);

    // 3-byte to 4-byte conversion + 0-63 to ascii printable conversion
    if (len > 1) {
        while (sidx < len - 2) {
            if (insertLFs) {
                if (count && (count % 76) == 0)
                    out[didx++] = '\n';
                count += 4;
            }
            out[didx++] = base64EncMap[(data[sidx] >> 2) & 077];
            out[didx++] = base64EncMap[(data[sidx + 1] >> 4) & 017 | (data[sidx] << 4) & 077];
            out[didx++] = base64EncMap[(data[sidx + 2] >> 6) & 003 | (data[sidx + 1] << 2) & 077];
            out[didx++] = base64EncMap[data[sidx + 2] & 077];
            sidx += 3;
        }
    }

    if (sidx < len) {
        if (insertLFs && (count > 0) && (count % 76) == 0)
           out[didx++] = '\n';

        out[didx++] = base64EncMap[(data[sidx] >> 2) & 077];
        if (sidx < len - 1) {
            out[didx++] = base64EncMap[(data[sidx + 1] >> 4) & 017 | (data[sidx] << 4) & 077];
            out[didx++] = base64EncMap[(data[sidx + 1] << 2) & 077];
        } else
            out[didx++] = base64EncMap[(data[sidx] << 4) & 077];
    }

    // Add padding
    while (didx < out.size()) {
        out[didx] = '=';
        didx++;
    }
}

bool base64Decode(const Vector<char>& in, Vector<char>& out)
{
    out.clear();

    // If the input string is pathologically large, just return nothing.
    if (in.size() > UINT_MAX)
        return false;

    return base64Decode(in.data(), in.size(), out);
}

bool base64Decode(const char* data, unsigned len, Vector<char>& out)
{
    out.clear();
    if (len == 0)
        return true;

    while (len && data[len-1] == '=')
        --len;

    out.grow(len);
    for (unsigned idx = 0; idx < len; idx++) {
        unsigned char ch = data[idx];
        if ((ch > 47 && ch < 58) || (ch > 64 && ch < 91) || (ch > 96 && ch < 123) || ch == '+' || ch == '/' || ch == '=')
            out[idx] = base64DecMap[ch];
        else
            return false;
    }

    // 4-byte to 3-byte conversion
    unsigned outLen = len - ((len + 3) / 4);
    if (!outLen || ((outLen + 2) / 3) * 4 < len)
        return false;

    unsigned sidx = 0;
    unsigned didx = 0;
    if (outLen > 1) {
        while (didx < outLen - 2) {
            out[didx] = (((out[sidx] << 2) & 255) | ((out[sidx + 1] >> 4) & 003));
            out[didx + 1] = (((out[sidx + 1] << 4) & 255) | ((out[sidx + 2] >> 2) & 017));
            out[didx + 2] = (((out[sidx + 2] << 6) & 255) | (out[sidx + 3] & 077));
            sidx += 4;
            didx += 3;
        }
    }

    if (didx < outLen)
        out[didx] = (((out[sidx] << 2) & 255) | ((out[sidx + 1] >> 4) & 003));

    if (++didx < outLen)
        out[didx] = (((out[sidx + 1] << 4) & 255) | ((out[sidx + 2] >> 2) & 017));

    if (outLen < out.size())
        out.shrink(outLen);

    return true;
}

}