Added integer parsing functions in base/string_to_number.h

webrtc/base/string_to_number.cc

Index: webrtc/base/string_to_number.cc
diff --git a/webrtc/base/string_to_number.cc b/webrtc/base/string_to_number.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f8809268a28029d54149487f1cba66050355bc82
--- /dev/null
+++ b/webrtc/base/string_to_number.cc
@@ -0,0 +1,49 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <cstdlib>
+
+#include "webrtc/base/string_to_number.h"
+
+namespace rtc {
+namespace string_to_number_internal {
+
+rtc::Optional<signed_type> ParseSigned(const char* str, int base) {
+  RTC_DCHECK(str);
+  if (isdigit(str[0]) || str[0] == '-') {
+    char* end = nullptr;
+    errno = 0;
+    const signed_type value = std::strtoll(str, &end, base);
+    if (end && *end == '\0' && errno == 0) {
+      return rtc::Optional<signed_type>(value);
+    }
+  }
+  return rtc::Optional<signed_type>();
+}
+
+rtc::Optional<unsigned_type> ParseUnsigned(const char* str, int base) {
+  RTC_DCHECK(str);
+  if (isdigit(str[0]) || str[0] == '-') {
+    // Explicitly discard negative values. std::strtoull parsing causes unsigned
+    // wraparound. We cannot just reject values that start with -, though, since
+    // -0 is perfectly fine, as is -0000000000000000000000000000000.
+    const bool is_negative = str[0] == '-';
+    char* end = nullptr;
+    errno = 0;
+    const unsigned_type value = std::strtoull(str, &end, base);
+    if (end && *end == '\0' && errno == 0 && (value == 0 || !is_negative)) {
+      return rtc::Optional<unsigned_type>(value);
+    }
+  }
+  return rtc::Optional<unsigned_type>();
+}
+
+}  // namespace string_to_number_internal
+}  // namespace rtc