[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/core/common/autofill_util.cc

+// 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 "components/autofill/core/common/autofill_util.h"
+
+#include <vector>
+
+#include "base/command_line.h"
+#include "base/i18n/case_conversion.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "components/autofill/core/common/autofill_switches.h"
+
+namespace autofill {
+
+bool IsFeatureSubstringMatchEnabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSuggestionsWithSubstringMatch);
+}
+
+bool IsContentsPrefixOfSuggestionToken(const base::string16& field_suggestion,
+                                       const base::string16& field_contents,
+                                       bool case_sensitive) {
+  if (!IsFeatureSubstringMatchEnabled()) {
+    return false;
+  }
+
+  bool result = false;
+  std::vector<base::string16> suggestion_tokens;
+  Tokenize(field_suggestion, base::ASCIIToUTF16(" .,-_@"), &suggestion_tokens);
+
+  // Check whether the |field_contents| prefixes any of the |field_suggestion|'s
+  // token.
+  for (auto token : suggestion_tokens) {
+    result = StartsWith(token, field_contents, case_sensitive);
+    if (result)
+      break;
+  }
+
+  return result;
+}
+
+base::string16::size_type ComputeRange(const base::string16& field_suggestion,
+                                       const base::string16& field_contents,
+                                       size_t* start,
+                                       size_t* end) {
+  base::string16::size_type offset = 0;
+  base::string16::size_type next_offset = 0;
+  do {
+    // Loop through until we find either the |field_contents| begins with the
+    // |suggestion| or character right before |offset| is one of the splitting
+    // characters.
+    base::string16 suggestion(field_suggestion.substr(next_offset));
+    offset = StartsAt(suggestion, field_contents, false);

[danakj, 2015/04/02 18:31:43]

Why not just std::search() here? Is this a common operation? I see no other
callers of it in this CL.

[Pritam Nikam, 2015/04/06 06:13:10]

Earlier, plan was to use StartsAt at all places where ComputeRange currently
added. But calculating selection range may need to consider delimiter characters
as well. Just like StartsWith/EndsWith utility APIs, I thought of keeping basic
string utility that shall return the beginning of search string i.e. StartAt
(with case-sensitivity) next to these APIs in string_util.h/cc, and add a
wrapper utility API very specific to this feature under autofill_util.cc. That
is why you could find only single caller of StartsAt, and through out this CL
you could find ComputeRange being called. I'm kind of confuse what to keep and
what to shred.

Please revert with your inputs.

+    if (base::string16::npos != offset) {
+      next_offset = offset + next_offset + 1;
+      if ((offset == 0) || ContainsOnlyChars(suggestion.substr(offset - 1, 1),
+                                             base::ASCIIToUTF16(" .,-_@"))) {
+        offset = next_offset - 1;
+        *start = offset + field_contents.size();
+        *end = field_suggestion.size();
+        break;
+      }
+    }
+  } while (base::string16::npos != offset);
+
+  return offset;
+}
+
+}  // namespace autofill