1 files changed, 101 insertions, 0 deletions
diff --git a/Firestore/core/src/firebase/firestore/util/string_printf.cc b/Firestore/core/src/firebase/firestore/util/string_printf.cc
new file mode 100644
index 0000000..60cc564
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/util/string_printf.cc
@@ -0,0 +1,101 @@
+/*
+ * 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_printf.h"
+
+#include <stdio.h>
+
+namespace firebase {
+namespace firestore {
+namespace util {
+
+void StringAppendV(std::string* dst, const char* format, va_list ap) {
+  // First try with a small fixed size buffer
+  static const int kSpaceLength = 1024;
+  char space[kSpaceLength];
+
+  // It's possible for methods that use a va_list to invalidate
+  // the data in it upon use.  The fix is to make a copy
+  // of the structure before using it and use that copy instead.
+  va_list backup_ap;
+  va_copy(backup_ap, ap);
+  int result = vsnprintf(space, kSpaceLength, format, backup_ap);
+  va_end(backup_ap);
+
+  if (result < kSpaceLength) {
+    if (result >= 0) {
+      // Normal case -- everything fit.
+      dst->append(space, result);
+      return;
+    }
+
+#ifdef _MSC_VER
+    // Error or MSVC running out of space.  MSVC 8.0 and higher
+    // can be asked about space needed with the special idiom below:
+    va_copy(backup_ap, ap);
+    result = vsnprintf(nullptr, 0, format, backup_ap);
+    va_end(backup_ap);
+#endif
+
+    if (result < 0) {
+      // Just an error.
+      return;
+    }
+  }
+
+  // Increase the buffer size to the size requested by vsnprintf,
+  // plus one for the closing \0.
+  size_t initial_size = dst->size();
+  size_t target_size = initial_size + result;
+
+  dst->resize(target_size + 1);
+  char* buf = &(*dst)[initial_size];
+  int buf_remain = result + 1;
+
+  // Restore the va_list before we use it again
+  va_copy(backup_ap, ap);
+  result = vsnprintf(buf, buf_remain, format, backup_ap);
+  va_end(backup_ap);
+
+  if (result >= 0 && result < buf_remain) {
+    // It fit and vsnprintf copied in directly. Resize down one to
+    // remove the trailing \0.
+    dst->resize(target_size);
+  } else {
+    // Didn't fit. Leave the original string unchanged.
+    dst->resize(initial_size);
+  }
+}
+
+std::string StringPrintf(const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  std::string result;
+  StringAppendV(&result, format, ap);
+  va_end(ap);
+  return result;
+}
+
+void StringAppendF(std::string* dst, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  StringAppendV(dst, format, ap);
+  va_end(ap);
+}
+
+}  // namespace util
+}  // namespace firestore
+}  // namespace firebase