Added integer parsing functions in base/string_to_number.h

They provide parsing of numbers from char* and std::string into any of
the fundamental integer types. Values are returned
in an rtc::Optional, which is left empty if parsing was unsuccessful.

BUG=webrtc:5806

Review-Url: https://codereview.webrtc.org/2696003004
Cr-Commit-Position: refs/heads/master@{#17557}

webrtc/base/BUILD.gn

@@ -156,6 +156,8 @@ rtc_static_library("rtc_base_approved") {
     "safe_conversions_impl.h",
     "sanitizer.h",
     "scoped_ref_ptr.h",
+    "string_to_number.cc",
+    "string_to_number.h",
     "stringencode.cc",
     "stringencode.h",
     "stringutils.cc",
@@ -780,6 +782,7 @@ if (rtc_include_tests) {
       "ratetracker_unittest.cc",
       "refcountedobject_unittest.cc",
       "safe_compare_unittest.cc",
+      "string_to_number_unittest.cc",
       "stringencode_unittest.cc",
       "stringutils_unittest.cc",
       "swap_queue_unittest.cc",

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

webrtc/base/string_to_number.h

@@ -0,0 +1,101 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_BASE_STRING_TO_NUMBER_H_
+#define WEBRTC_BASE_STRING_TO_NUMBER_H_
+
+#include <string>
+#include <limits>
+
+#include "webrtc/base/optional.h"
+
+namespace rtc {
+
+// This file declares a family of functions to parse integers from strings.
+// The standard C library functions either fail to indicate errors (atoi, etc.)
+// or are a hassle to work with (strtol, sscanf, etc.). The standard C++ library
+// functions (std::stoi, etc.) indicate errors by throwing exceptions, which
+// are disabled in WebRTC.
+//
+// Integers are parsed using one of the following functions:
+//   rtc::Optional<int-type> StringToNumber(const char* str, int base = 10);
+//   rtc::Optional<int-type> StringToNumber(const std::string& str,
+//                                          int base = 10);
+//
+// These functions parse a value from the beginning of a string into one of the
+// fundamental integer types, or returns an empty Optional if parsing
+// failed. Values outside of the range supported by the type will be
+// rejected. The strings must begin with a digit or a minus sign. No leading
+// space nor trailing contents are allowed.
+// By setting base to 0, one of octal, decimal or hexadecimal will be
+// detected from the string's prefix (0, nothing or 0x, respectively).
+// If non-zero, base can be set to a value between 2 and 36 inclusively.
+//
+// If desired, this interface could be extended with support for floating-point
+// types.
+
+namespace string_to_number_internal {
+// These must be (unsigned) long long, to match the signature of strto(u)ll.
+using unsigned_type = unsigned long long;  // NOLINT(runtime/int)
+using signed_type = long long;  // NOLINT(runtime/int)
+
+rtc::Optional<signed_type> ParseSigned(const char* str, int base);
+rtc::Optional<unsigned_type> ParseUnsigned(const char* str, int base);
+}  // namespace string_to_number_internal
+
+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 = 10) {
+  using string_to_number_internal::signed_type;
+  static_assert(
+      std::numeric_limits<T>::max() <=
+              std::numeric_limits<signed_type>::max() &&
+          std::numeric_limits<T>::lowest() >=
+              std::numeric_limits<signed_type>::lowest(),
+      "StringToNumber only supports signed integers as large as long long int");
+  rtc::Optional<signed_type> value =
+      string_to_number_internal::ParseSigned(str, base);
+  if (value && *value >= std::numeric_limits<T>::lowest() &&
+      *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 = 10) {
+  using string_to_number_internal::unsigned_type;
+  static_assert(std::numeric_limits<T>::max() <=
+                    std::numeric_limits<unsigned_type>::max(),
+                "StringToNumber only supports unsigned integers as large as "
+                "unsigned long long int");
+  rtc::Optional<unsigned_type> value =
+      string_to_number_internal::ParseUnsigned(str, base);
+  if (value && *value <= std::numeric_limits<T>::max()) {
+    return rtc::Optional<T>(static_cast<T>(*value));
+  }
+  return rtc::Optional<T>();
+}
+
+// The std::string overloads only exists if there is a matching const char*
+// version.
+template <typename T>
+auto StringToNumber(const std::string& str, int base = 10)
+    -> decltype(StringToNumber<T>(str.c_str(), base)) {
+  return StringToNumber<T>(str.c_str(), base);
+}
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_STRING_TO_NUMBER_H_

webrtc/base/string_to_number_unittest.cc

@@ -0,0 +1,115 @@
+/*
+ *  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"
+
+#include <string>
+#include <type_traits>
+#include <limits>
+
+#include "webrtc/base/gunit.h"
+
+namespace rtc {
+
+namespace {
+// clang-format off
+using IntegerTypes =
+    ::testing::Types<char,
+                     signed char, unsigned char,       // NOLINT(runtime/int)
+                     short,       unsigned short,      // NOLINT(runtime/int)
+                     int,         unsigned int,        // NOLINT(runtime/int)
+                     long,        unsigned long,       // NOLINT(runtime/int)
+                     long long,   unsigned long long,  // NOLINT(runtime/int)
+                     int8_t,      uint8_t,
+                     int16_t,     uint16_t,
+                     int32_t,     uint32_t,
+                     int64_t,     uint64_t>;
+// clang-format on
+
+template <typename T>
+class BasicNumberTest : public ::testing::Test {};
+
+TYPED_TEST_CASE_P(BasicNumberTest);
+
+TYPED_TEST_P(BasicNumberTest, TestValidNumbers) {
+  using T = TypeParam;
+  constexpr T min_value = std::numeric_limits<T>::lowest();
+  constexpr T max_value = std::numeric_limits<T>::max();
+  const std::string min_string = std::to_string(min_value);
+  const std::string max_string = std::to_string(max_value);
+  EXPECT_EQ(min_value, StringToNumber<T>(min_string));
+  EXPECT_EQ(min_value, StringToNumber<T>(min_string.c_str()));
+  EXPECT_EQ(max_value, StringToNumber<T>(max_string));
+  EXPECT_EQ(max_value, StringToNumber<T>(max_string.c_str()));
+  EXPECT_EQ(0, StringToNumber<T>("0"));
+  EXPECT_EQ(0, StringToNumber<T>("-0"));
+  EXPECT_EQ(0, StringToNumber<T>(std::string("-0000000000000")));
+}
+
+TYPED_TEST_P(BasicNumberTest, TestInvalidNumbers) {
+  using T = TypeParam;
+  // Value ranges aren't strictly enforced in this test, since that would either
+  // require doctoring specific strings for each data type, which is a hassle
+  // across platforms, or to be able to do addition of values larger than the
+  // largest type, which is another hassle.
+  constexpr T min_value = std::numeric_limits<T>::lowest();
+  constexpr T max_value = std::numeric_limits<T>::max();
+  // If the type supports negative values, make the large negative value
+  // approximately ten times larger. If the type is unsigned, just use -2.
+  const std::string too_low_string =
+      (min_value == 0) ? "-2" : (std::to_string(min_value) + "1");
+  // Make the large value approximately ten times larger than the maximum.
+  const std::string too_large_string = std::to_string(max_value) + "1";
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(too_low_string));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(too_low_string.c_str()));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(too_large_string));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(too_large_string.c_str()));
+}
+
+TYPED_TEST_P(BasicNumberTest, TestInvalidInputs) {
+  using T = TypeParam;
+  const char kInvalidCharArray[] = "Invalid string containing 47";
+  const char kPlusMinusCharArray[] = "+-100";
+  const char kNumberFollowedByCruft[] = "640x480";
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(kInvalidCharArray));
+  EXPECT_EQ(rtc::Optional<T>(),
+            StringToNumber<T>(std::string(kInvalidCharArray)));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(kPlusMinusCharArray));
+  EXPECT_EQ(rtc::Optional<T>(),
+            StringToNumber<T>(std::string(kPlusMinusCharArray)));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(kNumberFollowedByCruft));
+  EXPECT_EQ(rtc::Optional<T>(),
+            StringToNumber<T>(std::string(kNumberFollowedByCruft)));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(" 5"));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(" - 5"));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>("- 5"));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>(" -5"));
+  EXPECT_EQ(rtc::Optional<T>(), StringToNumber<T>("5 "));
+}
+
+REGISTER_TYPED_TEST_CASE_P(BasicNumberTest,
+                           TestValidNumbers,
+                           TestInvalidNumbers,
+                           TestInvalidInputs);
+
+}  // namespace
+
+INSTANTIATE_TYPED_TEST_CASE_P(StringToNumberTest_Integers,
+                              BasicNumberTest,
+                              IntegerTypes);
+
+TEST(StringToNumberTest, TestSpecificValues) {
+  EXPECT_EQ(rtc::Optional<uint8_t>(), StringToNumber<uint8_t>("256"));
+  EXPECT_EQ(rtc::Optional<uint8_t>(), StringToNumber<uint8_t>("-256"));
+  EXPECT_EQ(rtc::Optional<int8_t>(), StringToNumber<int8_t>("256"));
+  EXPECT_EQ(rtc::Optional<int8_t>(), StringToNumber<int8_t>("-256"));
+}
+
+}  // namespace rtc