Extend net/base/parse_number.h for parsing of negative numbers, and determining if there was overflo

net/base/parse_number.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/base/parse_number.h"
 
+#include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 
 namespace net {
 
-bool ParseNonNegativeDecimalInt(const base::StringPiece& input, int* output) {
+namespace {
+
+// The string to number conversion functions in //base include the type in the
+// name (like StringToInt64()). The following wrapper methods create a
+// consistent interface to StringToXXX() that calls the appropriate //base
+// version. This simplifies writing generic code with a template.
+
+bool StringToNumber(const base::StringPiece& input, int32_t* output) {
+  // This assumes ints are 32-bits.
+  return base::StringToInt(input, output);
+}
+
+bool StringToNumber(const base::StringPiece& input, uint32_t* output) {
+  // This assumes ints are 32-bits
+  return base::StringToUint(input, output);
+}
+
+bool StringToNumber(const base::StringPiece& input, int64_t* output) {
+  return base::StringToInt64(input, output);
+}
+
+bool StringToNumber(const base::StringPiece& input, uint64_t* output) {
+  return base::StringToUint64(input, output);
+}
+
+template <typename T>
+bool ParseNonNegativeIntegerHelper(const base::StringPiece& input, T* output) {
+  // The input MUST start with a decimal digit, since it is not allowed to start
+  // with '-' (by virtue of being non-negative), and nor is it allowed to start
+  // with '+'.
   if (input.empty() || input[0] > '9' || input[0] < '0')
     return false;
 
-  int result;
-  if (!base::StringToInt(input, &result))
+  // Dispatch to the appropriate flavor of base::StringToXXX() by calling one of
+  // the overloads defined above.
+  T result;
+  if (!StringToNumber(input, &result))
+    return false;
+
+  // The result cannot be negative since inputs starting with a '-' were already
+  // rejected.
+  DCHECK_GE(result, T());
+
+  *output = result;
+  return true;
+}
+
+template <typename T>
+bool ParseSignedIntegerHelper(const base::StringPiece& input, T* output) {
+  // The input MUST start with a decimal digit or a '-'. Numbers starting with
+  // '+' are rejected here (since StringToNumber() might otherwise accept it).
+  if (input.empty() ||
+      !(input[0] == '-' || (input[0] >= '0' && input[0] <= '9'))) {
+    return false;
+  }
+
+  // Dispatch to the appropriate flavor of base::StringToXXX() by calling one of
+  // the overloads defined above.
+  T result;
+  if (!StringToNumber(input, &result))
     return false;
 
   *output = result;
   return true;
 }
 
+}  // namespace
+
+bool ParseNonNegativeInteger(const base::StringPiece& input, int32_t* output) {
+  return ParseNonNegativeIntegerHelper(input, output);
+}
+
+bool ParseNonNegativeInteger(const base::StringPiece& input, uint32_t* output) {
+  return ParseNonNegativeIntegerHelper(input, output);
+}
+
+bool ParseNonNegativeInteger(const base::StringPiece& input, int64_t* output) {
+  return ParseNonNegativeIntegerHelper(input, output);
+}
+
+bool ParseNonNegativeInteger(const base::StringPiece& input, uint64_t* output) {
+  return ParseNonNegativeIntegerHelper(input, output);
+}
+
+bool ParseSignedInteger(const base::StringPiece& input, int64_t* output) {
+  return ParseSignedIntegerHelper(input, output);
+}
+
+bool ParseSignedInteger(const base::StringPiece& input, int32_t* output) {
+  return ParseSignedIntegerHelper(input, output);
+}
+
 }  // namespace net