Issue 5146 - Implement DownloadableSubscription parsing in C++

compiled/Base64.cpp

+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-present eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus 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 General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Base64.h"
+
+static const char base64_alphabet[] = {
+  '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', '+', '/'
+};
+
+// Note: this base64 encoding fill with 0 instead of using padding.
+// ie it is not conformant.
+OwnedString ToBase64(const uint8_t* buffer, size_t len)
+{
+  String::size_type length = (len / 3 * 4) + (1 + len % 3);
+  OwnedString output(length);
+  String::size_type outputIndex = 0;
+  uint8_t input[3];
+  for (size_t i = 0; i < len; i += 3)
+  {
+    size_t left = len - i;
+    if (left > 3)
+      left = 3;
+    for (size_t j = 0; j < left; j++)
+      input[j] = *buffer++;
+    switch (left) {
+    case 1:
+      input[1] = 0;
+    case 2:
+      input[2] = 0;
+    }
+
+    output[outputIndex++] = base64_alphabet[input[0] >> 2];
+    output[outputIndex++] = base64_alphabet[((input[0] & 0x03) << 4) + (input[1] >> 4)];
+    if (left > 1)
+      output[outputIndex++] = base64_alphabet[((input[1] & 0x0f) << 2) + (input[2] >> 6)];
+    if (left > 2)
+      output[outputIndex++] = base64_alphabet[input[2] & 0x3f];
+  }
+
+  return output;
+}