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) {
-  if (input.empty() || input[0] > '9' || input[0] < '0')
-    return false;
+namespace {
 
-  int result;
-  if (!base::StringToInt(input, &result))
-    return false;
+// 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.
 
-  *output = result;
-  return true;
+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>
+ParseIntegerResult ParseIntegerHelper(const base::StringPiece& input,
+                                      ParseIntegerSignPolicy sign_policy,
+                                      T* output) {
+  if (input.empty())
+    return ParseIntegerResult::FAILED_PARSE;
+
+  bool starts_with_negative = input[0] == '-';
+  bool starts_with_digit = input[0] >= '0' && input[0] <= '9';
+
+  // Numbers must start with either a digit or a negative sign
+  //
+  // Reject everythin else to prevent the permissive behavior of
+  // StringToIntXXX() when it comes to accepting a leading '+'.
+  switch (sign_policy) {
+    case ParseIntegerSignPolicy::NON_NEGATIVE:
+      if (!starts_with_digit)
+        return ParseIntegerResult::FAILED_PARSE;
+      break;
+
+    case ParseIntegerSignPolicy::ANY:
+      if (!starts_with_digit && !starts_with_negative)
+        return ParseIntegerResult::FAILED_PARSE;
+      break;
+  }
+
+  // Dispatch to the appropriate flavor of base::StringToXXX() by calling one of
+  // the type-specific overloads.
+  T result;
+  if (StringToNumber(input, &result)) {
+    *output = result;
+    return ParseIntegerResult::OK;
+  }
+
+  // Set an error that distinguishes between parsing/underflow/overflow errors.
+  //
+  // Note that base::StringToXXX() functions have a magical API that modify the
+  // output on failure to indicate whether underflow/overflow happened.
+  //
+  // You would think these can be used here, but unfortunately they return those
+  // magic values in multiple cases making it impossible to distinguish
+  // underflow/overflow from failed parsing due to leading/trailing whitespace.
+  //
+  // So instead look at the number to see if it was valid.
+
+  // Strip any leading negative sign off the number.
+  base::StringPiece numeric_portion =
+      starts_with_negative ? input.substr(1) : input;
+
+  // Test if |numeric_portion| is a valid non-negative integer.
+  if (!numeric_portion.empty() &&
+      numeric_portion.find_first_not_of("0123456789") == std::string::npos) {
+    // If it was, the failure must have been due to underflow/overflow.
+    return starts_with_negative ? ParseIntegerResult::FAILED_UNDERFLOW
+                                : ParseIntegerResult::FAILED_OVERFLOW;
+  }
+
+  // Otherwise it was a mundane parsing error.
+  return ParseIntegerResult::FAILED_PARSE;
+}
+
+template <typename T>
+bool ParseNonNegativeIntegerHelper(const base::StringPiece& input, T* output) {
+  auto result =
+      ParseIntegerHelper(input, ParseIntegerSignPolicy::NON_NEGATIVE, output);
+  return result == ParseIntegerResult::OK;
+}
+
+}  // namespace
+
+ParseIntegerResult ParseInteger(const base::StringPiece& input,
+                                ParseIntegerSignPolicy sign_policy,
+                                int32_t* output) {
+  return ParseIntegerHelper(input, sign_policy, output);
+}
+
+ParseIntegerResult ParseInteger(const base::StringPiece& input,
+                                ParseIntegerSignPolicy sign_policy,
+                                uint32_t* output) {
+  return ParseIntegerHelper(input, sign_policy, output);
+}
+
+ParseIntegerResult ParseInteger(const base::StringPiece& input,
+                                ParseIntegerSignPolicy sign_policy,
+                                int64_t* output) {
+  return ParseIntegerHelper(input, sign_policy, output);
+}
+
+ParseIntegerResult ParseInteger(const base::StringPiece& input,
+                                ParseIntegerSignPolicy sign_policy,
+                                uint64_t* output) {
+  return ParseIntegerHelper(input, sign_policy, output);
+}
+
+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);
 }
 
 }  // namespace net