Add string_piece_util

Following functions are implemented for further performance
optimization.

* JoinStringPiece
* SplitStringPiece
* EqualsCaseInsensitiveASCII
* ToLowerASCII

To improve performance of CLParser, I will introduce above functions
into include_normalize-win32.cc.

1 files changed, 78 insertions, 0 deletions

diff --git a/src/string_piece_util.cc b/src/string_piece_util.cc
new file mode 100644
index 0000000..8e1ecfd
--- /dev/null
+++ b/src/string_piece_util.cc
@@ -0,0 +1,78 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// 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 "string_piece_util.h"
+
+#include <algorithm>
+#include <string>
+#include <vector>
+using namespace std;
+
+vector<StringPiece> SplitStringPiece(StringPiece input, char sep) {
+  vector<StringPiece> elems;
+  elems.reserve(count(input.begin(), input.end(), sep) + 1);
+
+  StringPiece::const_iterator pos = input.begin();
+
+  for (;;) {
+    const char* next_pos = find(pos, input.end(), sep);
+    if (next_pos == input.end()) {
+      elems.push_back(StringPiece(pos, input.end() - pos));
+      break;
+    }
+    elems.push_back(StringPiece(pos, next_pos - pos));
+    pos = next_pos + 1;
+  }
+
+  return elems;
+}
+
+string JoinStringPiece(const vector<StringPiece>& list, char sep) {
+  if (list.size() == 0){
+    return "";
+  }
+
+  string ret;
+
+  {
+    size_t cap = list.size() - 1;
+    for (size_t i = 0; i < list.size(); ++i) {
+      cap += list[i].len_;
+    }
+    ret.reserve(cap);
+  }
+
+  for (size_t i = 0; i < list.size(); ++i) {
+    if (i != 0) {
+      ret += sep;
+    }
+    ret.append(list[i].str_, list[i].len_);
+  }
+
+  return ret;
+}
+
+bool EqualsCaseInsensitiveASCII(StringPiece a, StringPiece b) {
+  if (a.len_ != b.len_) {
+    return false;
+  }
+
+  for (size_t i = 0; i < a.len_; ++i) {
+    if (ToLowerASCII(a.str_[i]) != ToLowerASCII(b.str_[i])) {
+      return false;
+    }
+  }
+
+  return true;
+}