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..639ae593f89c2a66f80ce128faed4587821f9151
--- /dev/null
+++ b/webrtc/base/string_to_number.cc
@@ -0,0 +1,80 @@
+/*
+ *  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 {
+
+template <typename T>
+typename std::enable_if<std::is_integral<T>::value && std::is_signed<T>::value,
+                        rtc::Optional<T>>::type
+StringToNumber(const char* str, int base) {
+  static_assert(
+      sizeof(long long int) >= sizeof(T),

[kwiberg-webrtc, 2017/02/18 12:28:53]

Compare std::numeric_limits<>::min() and ::max() instead? Since the types have
the same signedness, the comparison should work just fine.

+      "StringToNumber only supports signed integers as large as long long int");
+  RTC_DCHECK(str);
+  char* end = nullptr;
+  errno = 0;
+  const long long int value = std::strtoll(str, &end, base);
+  if (end && *end == 0 && end != str && errno == 0 &&

[kwiberg-webrtc, 2017/02/18 12:28:53]

Style nit: *end == '\0'

+      value >= std::numeric_limits<T>::min() &&
+      value <= std::numeric_limits<T>::max()) {
+    return rtc::Optional<T>(static_cast<T>(value));
+  }
+  return rtc::Optional<T>();
+}
+
+template <typename T>
+typename std::enable_if<std::is_integral<T>::value &&
+                            std::is_unsigned<T>::value,
+                        rtc::Optional<T>>::type
+StringToNumber(const char* str, int base) {
+  static_assert(
+      sizeof(long long int) >= sizeof(T),
+      "StringToNumber only supports unsigned integers as large as unsigned "
+      "long long int");
+  RTC_DCHECK(str);
+  // 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.
+  bool is_negative = false;
+  for (const char *ptr = str; isspace(*ptr) || *ptr == '-'; ++ptr) {
+    if (*ptr == '-') {
+      is_negative = true;
+    }
+  }
+  char* end = nullptr;
+  errno = 0;
+  const unsigned long long int value = std::strtoull(str, &end, base);
+  if (end && *end == 0 && end != str && errno == 0 &&
+      value >= std::numeric_limits<T>::min() &&

[kwiberg-webrtc, 2017/02/18 12:28:53]

value and T are both unsigned, so this is trivially true.

+      value <= std::numeric_limits<T>::max() && (value == 0 || !is_negative)) {
+    return rtc::Optional<T>(static_cast<T>(value));

[kwiberg-webrtc, 2017/02/18 12:28:53]

Hmm. Do you have a unit test for e.g. parsing "-256" to a uint8_t?

+  }
+  return rtc::Optional<T>();
+}
+
+#define RTC_STN_INSTANCE(T) \
+  template rtc::Optional<T> StringToNumber<T>(const char*, int)
+
+RTC_STN_INSTANCE(signed char);
+RTC_STN_INSTANCE(unsigned char);
+RTC_STN_INSTANCE(short);
+RTC_STN_INSTANCE(unsigned short);
+RTC_STN_INSTANCE(int);
+RTC_STN_INSTANCE(unsigned int);
+RTC_STN_INSTANCE(long);
+RTC_STN_INSTANCE(unsigned long);
+RTC_STN_INSTANCE(long long);
+RTC_STN_INSTANCE(unsigned long long);
+
+#undef RTC_STN_INSTANCE
+
+}  // namespace rtc