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..8cc08077f5726492cd00e0a9df4081d21089ce1a
--- /dev/null
+++ b/webrtc/base/string_to_number.cc
@@ -0,0 +1,48 @@
+/*
+ *  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 "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);

[kwiberg-webrtc, 2017/04/05 09:01:15]

#include <cstdlib>?

[ossu, 2017/04/05 10:15:36]

Ach, yes. Not sure why I didn't get IWYU warnings for that.

+    if (end && *end == '\0' && end != str && errno == 0) {

[kwiberg-webrtc, 2017/04/05 09:01:15]

That end != str is necessarily true if the first two conditions hold. DCHECK
instead?

[ossu, 2017/04/05 10:15:36]

I'm guessing maybe if it would highlight an error by letting end be str and str
was the empty string. The docs I'm reading say end points to "the character past
the last character interpreted". Eh, I don't know. Should probably be NULL if
conversion fails. I'll try without and see if the tests are still happy.

[kwiberg-webrtc, 2017/04/05 10:55:38]

It'll still work: since *end == '\0' and (isdigit(str[0]) || str[0] == '-'), you
know that end != str. So you can either move it to a DCHECK, or just remove it.

+      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);

[kwiberg-webrtc, 2017/04/05 09:01:15]

Wouldn't it be safer to discard the minus sign before giving the string to
strtoull?

[ossu, 2017/04/05 10:15:36]

Nah, it should be able to deal with that itself, according to the docs.

[kwiberg-webrtc, 2017/04/05 10:55:38]

Acknowledged.

+    if (end && *end == '\0' && end != str && errno == 0 &&
+        (value == 0 || !is_negative)) {
+      return rtc::Optional<unsigned_type>(value);
+    }
+  }
+  return rtc::Optional<unsigned_type>();
+}
+
+}  // namespace string_to_number_internal
+}  // namespace rtc