device/bluetooth: Implemented UriBeacon decoder.

device/bluetooth/uribeacon/uri_encoder.cc

Index: device/bluetooth/uribeacon/uri_encoder.cc
diff --git a/device/bluetooth/uribeacon/uri_encoder.cc b/device/bluetooth/uribeacon/uri_encoder.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2604b4fc0612cd3a37f29e21dce3ce52ff373576
--- /dev/null
+++ b/device/bluetooth/uribeacon/uri_encoder.cc
@@ -0,0 +1,106 @@
+// Copyright 2015 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 "uri_encoder.h"
+
+using base::StringPiece;
+
+namespace {
+
+struct expansion {
+  char code;
+  const char* value;
+};
+
+// The two following data structures are the expansions code tables for URI
+// encoding described in the following specification:
+// https://github.com/google/uribeacon/blob/master/specification/AdvertisingMode.md
+
+// For the prefix of the URI.
+struct expansion prefix_expansions_list[] = {
+    {0, "http://www."},
+    {1, "https://www."},
+    {2, "http://"},
+    {3, "https://"},
+    {4, "urn:uuid:"},
+};
+
+// For the remaining part of the URI.
+struct expansion expansions_list[] = {
+    {0, ".com/"},
+    {1, ".org/"},
+    {2, ".edu/"},
+    {3, ".net/"},
+    {4, ".info/"},
+    {5, ".biz/"},
+    {6, ".gov/"},
+    {7, ".com"},
+    {8, ".org"},
+    {9, ".edu"},
+    {10, ".net"},
+    {11, ".info"},
+    {12, ".biz"},
+    {13, ".gov"},
+};
+
+}  // namespace
+
+void device::EncodeUriBeaconUri(const StringPiece& input, std::string* output) {

[armansito, 2015/02/26 00:39:15]

It's generally difficult to understand what the code below is doing. It would be
nice to break this down into separate helpers for encoding the prefix and the
suffix, finding the prefix and suffix of a URI, and so on.

[dvh, 2015/03/03 20:26:03]

Done.

+  unsigned int i = 0;
+  const char* bytes = input.data();
+  while (i < input.size()) {
+    int found = -1;
+    int foundLength = -1;

[armansito, 2015/02/26 00:39:15]

Variable names need to be all lowercase and using underscores instead of
camel-case. Here and everywhere else. (See style guide:
http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Variable_Names)

[dvh, 2015/03/03 20:26:03]

Done.

+    struct expansion* table = NULL;
+    unsigned int tableLength = 0;
+    if (i == 0) {
+      // Prefix of the URI.
+      table = prefix_expansions_list;
+      tableLength =
+          sizeof(prefix_expansions_list) / sizeof(prefix_expansions_list[0]);

[armansito, 2015/02/26 00:39:15]

Use arraysize(x) from base/ (i.e. arraysize(prefix_expansions_list)).

[dvh, 2015/03/03 20:26:03]

Done.

+    } else {
+      table = expansions_list;
+      tableLength = sizeof(expansions_list) / sizeof(expansions_list[0]);
+    }
+    // Search for the longest match.
+    for (unsigned int k = 0; k < tableLength; k++) {
+      const char* value = table[k].value;
+      int len = strlen(table[k].value);
+      if (strncmp(bytes + i, value, len) == 0 && len > foundLength) {
+        found = k;
+        foundLength = len;
+      }
+    }
+    if (found != -1) {
+      char b = (char)found;
+      output->append(&b, 1);
+      i += strlen(table[found].value);
+    } else {
+      output->append(bytes + i, 1);
+      i++;
+    }
+  }
+}

[armansito, 2015/02/26 00:39:15]

You should generally make sure that the native C++ encoding for characters on
all platforms matches the encoding that you're targeting for URI beacon.

[dvh, 2015/03/03 20:26:03]

Done.

+
+void device::DecodeUriBeaconUri(const StringPiece& input, std::string* output) {
+  const char* bytes = input.data();
+  unsigned int length = input.size();
+  for (unsigned int i = 0; i < length; i++) {
+    const char* expansion_value = NULL;
+    if (i == 0 &&
+        (unsigned char)bytes[i] < sizeof(prefix_expansions_list) /
+                                      sizeof(prefix_expansions_list[0])) {
+      // Prefix of the URI.
+      expansion_value = prefix_expansions_list[(unsigned char)bytes[i]].value;
+    } else if ((unsigned char)bytes[i] <
+               sizeof(expansions_list) / sizeof(expansions_list[0])) {
+      expansion_value = expansions_list[(unsigned char)bytes[i]].value;
+    }
+    if (expansion_value == NULL) {
+      output->append(&bytes[i], 1);
+    } else {
+      output->append(expansion_value, strlen(expansion_value));
+    }
+  }
+}