1 files changed, 117 insertions, 0 deletions
diff --git a/encoding.cc b/encoding.cc
new file mode 100644
index 0000000..702b2c4
--- /dev/null
+++ b/encoding.cc
@@ -0,0 +1,117 @@
+// Copyright 2016, 2018 Benjamin Barenblat
+//
+// 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 "encoding.h"
+
+#include <array>
+#include <cstdlib>
+#include <functional>
+#include <ios>
+#include <sstream>
+#include <string>
+
+#include <glog/logging.h>
+
+namespace scoville {
+
+namespace {
+
+void WriteAsciiAsHex(const char c, std::ostringstream* const out) {
+  if (1 < sizeof(c) && 0x100 <= c) {
+    // Not ASCII!
+    throw EncodingFailure("could not encode non-ASCII character '" +
+                          std::string(1, c) + "'");
+  }
+  *out << std::hex << static_cast<int>(c);
+}
+
+char ReadHexAsAscii(std::istringstream* const in) {
+  std::array<char, 3> hex_str;
+  in->get(hex_str.data(), hex_str.size());
+  char* decoded_end;
+  const char result =
+      static_cast<char>(std::strtol(hex_str.data(), &decoded_end, 16));
+  if (decoded_end == hex_str.data()) {
+    throw DecodingFailure("could not decode invalid hex");
+  }
+  return result;
+}
+
+bool IsVfatBadCharacter(const char c) noexcept {
+  return (0 <= c && c < 0x20) || c == '*' || c == '?' || c == '<' || c == '>' ||
+         c == '|' || c == '"' || c == ':' || c == '\\';
+}
+
+bool IsVfatBadLastCharacter(const char c) noexcept {
+  return IsVfatBadCharacter(c) || c == '.' || c == ' ';
+}
+
+void EncodeStream(std::istringstream* const in, std::ostringstream* const out) {
+  char c;
+  while (!in->get(c).eof()) {
+    in->peek();
+    const bool processing_last_character = in->eof();
+
+    if (IsVfatBadCharacter(c) ||
+        (processing_last_character && IsVfatBadLastCharacter(c))) {
+      *out << '%';
+      WriteAsciiAsHex(c, out);
+    } else if (c == '%') {
+      *out << "%%";
+    } else {
+      *out << c;
+    }
+  }
+}
+
+void DecodeStream(std::istringstream* const in, std::ostringstream* const out) {
+  char c;
+  while (!in->get(c).eof()) {
+    if (c == '%') {
+      if (in->peek() == '%') {
+        in->ignore();
+        *out << "%";
+      } else {
+        *out << ReadHexAsAscii(in);
+      }
+    } else {
+      *out << c;
+    }
+  }
+}
+
+std::string TransformString(
+    std::function<void(std::istringstream*, std::ostringstream*)> f,
+    const std::string& in) {
+  std::istringstream in_stream(in);
+  std::ostringstream out_stream;
+  f(&in_stream, &out_stream);
+  return out_stream.str();
+}
+
+}  // namespace
+
+std::string Encode(const std::string& in) {
+  const std::string result = TransformString(EncodeStream, in);
+  VLOG(1) << "Encode: \"" << in << "\" -> \"" << result << "\"";
+  return result;
+}
+
+std::string Decode(const std::string& in) {
+  const std::string result = TransformString(DecodeStream, in);
+  VLOG(1) << "Decode: \"" << in << "\" -> \"" << result << "\"";
+  return result;
+}
+
+}  // scoville