1 files changed, 94 insertions, 0 deletions
diff --git a/Firestore/core/src/firebase/firestore/util/string_format.cc b/Firestore/core/src/firebase/firestore/util/string_format.cc
new file mode 100644
index 0000000..bafdac2
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/util/string_format.cc
@@ -0,0 +1,94 @@
+/*
+ * Copyright 2018 Google
+ *
+ * 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 "Firestore/core/src/firebase/firestore/util/string_format.h"
+
+namespace firebase {
+namespace firestore {
+namespace util {
+namespace internal {
+
+static const char* kMissing = "<missing>";
+static const char* kInvalid = "<invalid>";
+
+std::string StringFormatPieces(
+    const char* format, std::initializer_list<absl::string_view> pieces) {
+  std::string result;
+
+  const char* format_iter = format;
+  const char* format_end = format + strlen(format);
+
+  auto pieces_iter = pieces.begin();
+  auto pieces_end = pieces.end();
+  auto append_next_piece = [&](std::string* dest) {
+    if (pieces_iter == pieces_end) {
+      dest->append(kMissing);
+    } else {
+      // Pass a piece through
+      dest->append(pieces_iter->data(), pieces_iter->size());
+      ++pieces_iter;
+    }
+  };
+
+  auto append_specifier = [&](char spec) {
+    switch (spec) {
+      case '%':
+        // Pass through literal %.
+        result.push_back('%');
+        break;
+
+      case 's': {
+        append_next_piece(&result);
+        break;
+      }
+
+      default:
+        result.append(kInvalid);
+        break;
+    }
+  };
+
+  // Iterate through the format string, advancing `format_iter` as we go.
+  while (true) {
+    const char* percent_ptr = std::find(format_iter, format_end, '%');
+
+    // percent either points to the next format specifier or the end of the
+    // format string. Either is safe to append here:
+    result.append(format_iter, percent_ptr);
+    if (percent_ptr == format_end) {
+      // No further pieces to format
+      break;
+    }
+
+    // Examine the specifier:
+    const char* spec_ptr = percent_ptr + 1;
+    if (spec_ptr == format_end) {
+      // Incomplete specifier, treat as a literal "%" and be done.
+      append_specifier('%');
+      break;
+    }
+    append_specifier(*spec_ptr);
+
+    format_iter = spec_ptr + 1;
+  }
+
+  return result;
+}
+
+}  // namespace internal
+}  // namespace util
+}  // namespace firestore
+}  // namespace firebase