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

net/base/parse_number.h

 // 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.
 
 #ifndef NET_BASE_PARSE_NUMBER_H_
 #define NET_BASE_PARSE_NUMBER_H_
 
 #include "base/compiler_specific.h"
 #include "base/strings/string_piece.h"
 #include "net/base/net_export.h"
 
 // This file contains utility functions for parsing numbers, in the context of
 // network protocols.
 //
 // Q: Doesn't //base already provide these in string_number_conversions.h, with
 //    functions like base::StringToInt()?
 //
 // A: Yes, and those functions are used under the hood by these
 //    implementations.
 //
 //    However using the number parsing functions from //base directly in network
 //    code can lead to subtle bugs, as the //base versions  are more permissive.
 //    For instance "+99" is successfully parsed by base::StringToInt().
 //
 //    However in the majority of places in //net, a leading plus on a number
 //    should be considered invalid. For instance when parsing a host:port pair
 //    you wouldn't want to recognize "foo:+99" as having a port of 99. The same
 //    issue applies when parsing a content-length header.
 //
+//    Another difficulty with using base::StringToInt() is distinguishing
+//    overflow/underflow from parsing failures.
+//
 //    To reduce the risk of such problems, use of these functions over the
 //    //base versions.
 
 class GURL;
 
 namespace net {
 
-//  Parses a string representing a decimal number to an |int|. Returns true on
-//  success, and fills |*output| with the result. Note that  |*output| is not
-//  modified on failure.
+// Policy for parsing of integers that determines which form of numbers will be
+// accepted.
+enum class ParseInteger {
+  // Accept inputs of the form:
+  //
+  //    1*DIGIT
+  //
+  // This is consistent with the description in RFC 2616 for representing
+  // numbers, as well as many other HTTP related standards.
+  DISALLOW_NEGATIVE,
+
+  // Accept inputs of the form:
+  //
+  //    ["-"] 1*DIGIT
+  //
+  // In other words, the number can optional start with a negative sign. Note
+  // that -0 is also counted as a valid input.
+  ALLOW_NEGATIVE
+};
+
+// The specific reason why a ParseInteger*() function failed.
+enum class ParseIntegerError {
+  // The parsed number couldn't fit into the provided output type because it was
+  // too large.
+  FAILED_OVERFLOW,
+
+  // The parsed number couldn't fit into the provided output type because it was
+  // too small (negative).
+  FAILED_UNDERFLOW,
+
+  // The number failed to be parsed because it wasn't a valid decimal number (as
+  // determined by the policy).
+  FAILED_PARSE,
+};
+
+// ParseIntegerBase10() parses a string representing a decimal number to a
+// SIGNED integer result.
 //
-//  Recognized inputs take the form:
-//    1*DIGIT
+// Returns true on success, and fills |*output| with the result. If
+// |optional_error| was non-null, then it is filled with the reason for the
+// failure.
 //
-//  Where DIGIT is an ASCII number in the range '0' - '9'
+// On failure it is guaranteed that |*output| was not modified.
 //
-//  Note that:
-//   * Parsing is locale independent
-//   * Leading zeros are allowed (numbers needn't be in minimal encoding)
-//   * Inputs that would overflow the output are rejected.
-//   * Only accepts integers
-//
-//  Examples of recognized inputs are:
-//    "13"
-//    "0"
-//    "00013"
-//
-//  Examples of rejected inputs are:
-//    "  13"
-//    "-13"
-//    "+13"
-//    "0x15"
-//    "13.3"
-NET_EXPORT bool ParseNonNegativeDecimalInt(const base::StringPiece& input,
-                                           int* output) WARN_UNUSED_RESULT;
+// See the ParseInteger enum for a description of what types of input are
+// accepted. Note that although the output type is signed, the parsing of
+// negative values can be disallowed by selecting the
+// ParseInteger::DISALLOW_NEGATIVE.
+NET_EXPORT bool ParseIntegerBase10(const base::StringPiece& input,
+                                   ParseInteger policy,
+                                   int32_t* output,
+                                   ParseIntegerError* optional_error = nullptr)
+    WARN_UNUSED_RESULT;
+
+NET_EXPORT bool ParseIntegerBase10(const base::StringPiece& input,
+                                   ParseInteger policy,
+                                   int64_t* output,
+                                   ParseIntegerError* optional_error = nullptr)
+    WARN_UNUSED_RESULT;
+
+// ParseUnsignedIntegerBase10() is the same as calling ParseIntegerBase10()
+// except:
+//  * The output type is unsigned
+//  * The policy is implied to be ParseInteger::DISALLOW_NEGATIVE
+NET_EXPORT bool ParseUnsignedIntegerBase10(
+    const base::StringPiece& input,
+    uint32_t* output,
+    ParseIntegerError* optional_error = nullptr) WARN_UNUSED_RESULT;
+
+NET_EXPORT bool ParseUnsignedIntegerBase10(
+    const base::StringPiece& input,
+    uint64_t* output,
+    ParseIntegerError* optional_error = nullptr) WARN_UNUSED_RESULT;
 
 }  // namespace net
 
 #endif  // NET_BASE_PARSE_NUMBER_H_