Add an encoder/decoder for quoted-printable.

chrome/browser/net/quoted_printable.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/net/quoted_printable.h"
+
+#include "base/logging.h"
+#include "base/string_util.h"
+
+namespace {
+
+const int kMaxCharPerLine = 76;
+const char* const kEOL = "\r\n";
+
+const char kHexTable[] = "0123456789ABCDEF";
+
+}  // namespace
+
+namespace chrome {
+namespace browser {
+namespace net {
+
+void QuotedPrintableEncode(const std::string& input, std::string* output) {
+  // The number of characters in the current line.
+  int char_count = 0;
+  for (std::string::const_iterator iter = input.begin();
+       iter != input.end(); ++iter) {
+    bool last_char = (iter + 1 == input.end());
+    char c = *iter;
+    // Whether this character can be inserted without encoding.
+    bool as_is = false;
+    // All printable ASCII characters can be included as is (but for =).
+    if (c >= '!' && c <= '~' && c != '=') {
+      as_is = true;
+    }
+
+    // Space and tab characters can be included as is if they don't appear at
+    // the end of a line or at then end of the input.
+    if (!as_is && (c == '\t' || c == ' ') && !last_char &&
+        !IsEOL(iter + 1, input)) {
+      as_is = true;
+    }
+
+    // End of line should be converted to CR-LF sequences.
+    if (!last_char) {
+      int eol_len = IsEOL(iter, input);
+      if (eol_len > 0) {
+        output->append(kEOL);
+        char_count = 0;
+        iter += (eol_len - 1);  // -1 because we'll ++ in the for() above.
+        continue;
+      }
+    }
+
+    // Insert a soft line break if necessary.
+    int min_chars_needed = as_is ? kMaxCharPerLine - 2 : kMaxCharPerLine - 4;
+    if (!last_char && char_count > min_chars_needed) {
+      output->append("=");
+      output->append(kEOL);
+      char_count = 0;
+    }
+
+    // Finally, insert the actual character(s).
+    if (as_is) {
+      output->append(1, c);
+      char_count++;
+    } else {
+      output->append("=");
+      output->append(1, kHexTable[static_cast<int>((c >> 4) & 0xF)]);
+      output->append(1, kHexTable[static_cast<int>(c & 0x0F)]);
+      char_count += 3;
+    }
+  }
+}
+
+bool QuotedPrintableDecode(const std::string& input, std::string* output) {
+  bool success = true;
+  for (std::string::const_iterator iter = input.begin();
+       iter!= input.end(); ++iter) {
+    char c = *iter;
+    if (c != '=') {
+      output->append(1, c);
+      continue;
+    }
+    if (input.end() - iter < 3) {
+      LOG(ERROR) << "unfinished = sequence in input string.";
+      success = false;
+      output->append(1, c);
+      continue;
+    }
+    char c2 = *(++iter);
+    char c3 = *(++iter);
+    if (c2 == '\r' && c3 == '\n') {
+      // Soft line break, ignored.
+      continue;
+    }
+
+    if (!IsHexDigit(c2) || !IsHexDigit(c3)) {
+      LOG(ERROR) << "invalid = sequence, = followed by non hexa digit " <<
+          "chars: " << c2 << " " << c3;
+      success = false;
+      // Just insert the chars as is.
+      output->append("=");
+      output->append(1, c2);
+      output->append(1, c3);
+      continue;
+    }
+
+    int i1 = HexDigitToInt(c2);
+    int i2 = HexDigitToInt(c3);
+    char r = static_cast<char>(((i1 << 4) & 0xF0) | (i2 & 0x0F));
+    output->append(1, r);
+  }
+  return success;
+}
+
+int IsEOL(const std::string::const_iterator& iter, const std::string& input) {
+  if (*iter == '\n')
+    return 1;  // Single LF.
+
+  if (*iter == '\r') {
+    if ((iter + 1) == input.end() || *(iter + 1) != '\n')
+      return 1;  // Single CR (Commodore and Old Macs).
+    return 2;  // CR-LF.
+  }
+
+  return 0;
+}
+
+}  // namespace net
+}  // namespace browser
+}  // namespace chrome