Refactor base64 and additional testcase for without padding

velox/common/encode/Base.cpp

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "velox/common/encode/Base.h"
+
+#include <stdint.h>
+
+namespace facebook::velox::encoding {
+
+bool Base::isPadded(const char* data, size_t len) {
+  return (len > 0 && data[len - 1] == kBasePad) ? true : false;
+}
+
+size_t Base::countPadding(const char* src, size_t len) {
+  size_t padding_count = 0;
+  while (len > 0 && src[len - 1] == kBasePad) {
+    padding_count++;
+    len--;
+  }
+
+  return padding_count;
+}
+
+uint8_t Base::baseReverseLookup(
+    const int base,
+    char p,
+    const Base::ReverseIndex& reverse_lookup) {
+  auto curr = reverse_lookup[(uint8_t)p];
+  // Value of encoded character shall be less than base.
+  if (curr >= base) {
+    throw BaseException(
+        "Base::decode() - invalid input string: invalid characters");
+  }
+
+  return curr;
+}
+
+} // namespace facebook::velox::encoding

velox/common/encode/Base.h

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <exception>
+#include <map>
+#include <string>
+
+#include <folly/Range.h>
+
+namespace facebook::velox::encoding {
+
+class BaseException : public std::exception {
+ public:
+  explicit BaseException(const char* msg) : msg_(msg) {}
+  const char* what() const noexcept override {
+    return msg_;
+  }
+
+ protected:
+  const char* msg_;
+};
+
+/// Base class for all binary encoding scheme for reversibly translating between
+/// byte sequences and printable ASCII strings specified by RFC 4648.
+class Base {
+ public:
+  using Charset = std::array<char, 64>;
+  using ReverseIndex = std::array<uint8_t, 256>;
+
+  // Checks is there padding in encoded data
+  static bool isPadded(const char* src, size_t len);
+
+  // Counts the number of padding characters in encoded data.
+  static size_t countPadding(const char* src, size_t len);
+
+  // Gets value corresponding to an encoded character
+  static uint8_t
+  baseReverseLookup(const int base, char p, const ReverseIndex& table);
+
+  // Padding character used in encoding
+  constexpr static char kBasePad = '=';
+};
+
+//  Validate the character in charset with ReverseIndex table
+constexpr bool checkForwardIndex(
+    uint8_t idx,
+    const Base::Charset& charset,
+    const Base::ReverseIndex& table) {
+  return (table[static_cast<uint8_t>(charset[idx])] == idx) &&
+      (idx > 0 ? checkForwardIndex(idx - 1, charset, table) : true);
+}
+
+/// Similar to strchr(), but for null-terminated const strings.
+/// Another difference is that we do not consider "\0" to be present in the
+/// string.
+/// Returns true if "str" contains the character c.
+constexpr bool constCharsetContains(
+    const Base::Charset& charset,
+    int base,
+    uint8_t idx,
+    const char c) {
+  return idx < base &&
+      ((charset[idx] == c) || constCharsetContains(charset, base, idx + 1, c));
+}
+
+//  Validate the value in ReverseIndex table with charset.
+constexpr bool checkReverseIndex(
+    uint8_t idx,
+    const Base::Charset& charset,
+    int base,
+    const Base::ReverseIndex& table) {
+  return (table[idx] == 255
+              ? !constCharsetContains(charset, base, 0, static_cast<char>(idx))
+              : (charset[table[idx]] == idx)) &&
+      (idx > 0 ? checkReverseIndex(idx - 1, charset, base, table) : true);
+}
+
+} // namespace facebook::velox::encoding