Avoid heap allocations in IPAddress

net/base/ip_address.cc

Index: net/base/ip_address.cc
diff --git a/net/base/ip_address.cc b/net/base/ip_address.cc
index cf18650fd7c51480455dabc0e8aa3b1f0e51b735..431b6a841f15d2c2bf356936d1bc4a216efc5daa 100644
--- a/net/base/ip_address.cc
+++ b/net/base/ip_address.cc
@@ -22,7 +22,7 @@ const uint8_t kIPv4MappedPrefix[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF};
 // Note that this function assumes:
 // * |ip_address| is at least |prefix_length_in_bits| (bits) long;
 // * |ip_prefix| is at least |prefix_length_in_bits| (bits) long.
-bool IPAddressPrefixCheck(const std::vector<uint8_t>& ip_address,
+bool IPAddressPrefixCheck(const net::IPAddress::IPAddressBytes& ip_address,
                           const uint8_t* ip_prefix,
                           size_t prefix_length_in_bits) {
   // Compare all the bytes that fall entirely within the prefix.
@@ -51,7 +51,7 @@ bool IPAddressPrefixCheck(const std::vector<uint8_t>& ip_address,
 // www.iana.org/assignments/ipv4-address-space/ipv4-address-space.xhtml
 // www.iana.org/assignments/iana-ipv4-special-registry/
 // iana-ipv4-special-registry.xhtml
-bool IsReservedIPv4(const std::vector<uint8_t>& ip_address) {
+bool IsReservedIPv4(const net::IPAddress::IPAddressBytes& ip_address) {
   // Different IP versions have different range reservations.
   DCHECK_EQ(net::IPAddress::kIPv4AddressSize, ip_address.size());
   struct {
@@ -79,7 +79,7 @@ bool IsReservedIPv4(const std::vector<uint8_t>& ip_address) {
 // addresses outside these ranges are reserved.
 // Sources for info:
 // www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml
-bool IsReservedIPv6(const std::vector<uint8_t>& ip_address) {
+bool IsReservedIPv6(const net::IPAddress::IPAddressBytes& ip_address) {
   // Different IP versions have different range reservations.
   DCHECK_EQ(net::IPAddress::kIPv6AddressSize, ip_address.size());
   struct {
@@ -103,7 +103,7 @@ bool IsReservedIPv6(const std::vector<uint8_t>& ip_address) {
 }
 
 bool ParseIPLiteralToBytes(const base::StringPiece& ip_literal,
-                           std::vector<uint8_t>* bytes) {
+                           net::IPAddress::IPAddressBytes* bytes) {
   // |ip_literal| could be either an IPv4 or an IPv6 literal. If it contains
   // a colon however, it must be an IPv6 address.
   if (ip_literal.find(':') != base::StringPiece::npos) {
@@ -132,18 +132,71 @@ bool ParseIPLiteralToBytes(const base::StringPiece& ip_literal,
 
 namespace net {
 
+IPAddress::IPAddressBytes::IPAddressBytes() : size_(0) {}
+
+IPAddress::IPAddressBytes::IPAddressBytes(const uint8_t* data, size_t data_len)
+    : size_(data_len) {
+  CHECK_GE(16u, data_len);
+  memcpy(bytes_.data(), data, data_len);

[eroman, 2017/05/15 22:15:23]

If you want to avoid relying on undefined behavior, unfortunately you need to
special case the data_len == 0 case, because the C definition of memcpy() is
stupid, and nullptr parameters lead to undefined behavior (even if length is
zero). Go figure.

[Ryan Hamilton, 2017/05/17 18:26:41]

Done.

+}
+
+net::IPAddress::IPAddressBytes::~IPAddressBytes() {}
+net::IPAddress::IPAddressBytes::IPAddressBytes(
+    net::IPAddress::IPAddressBytes const& other) = default;
+
+bool operator<(const IPAddress::IPAddressBytes& lhs,
+               const IPAddress::IPAddressBytes& rhs) {
+  if (lhs.size_ < rhs.size_)
+    return true;
+  if (lhs.size_ > rhs.size_)
+    return false;
+  for (size_t i = 0; i < lhs.size_; ++i) {
+    if (lhs.bytes_[i] < rhs.bytes_[i])
+      return true;
+  }
+  return false;
+}
+
+bool operator>(const IPAddress::IPAddressBytes& lhs,
+               const IPAddress::IPAddressBytes& rhs) {
+  if (lhs.size_ > rhs.size_)
+    return true;
+  if (lhs.size_ < rhs.size_)
+    return false;
+  for (size_t i = 0; i < lhs.size_; ++i) {
+    if (lhs.bytes_[i] > rhs.bytes_[i])
+      return true;
+  }
+  return false;
+}
+
+bool operator==(const IPAddress::IPAddressBytes& lhs,
+                const IPAddress::IPAddressBytes& rhs) {
+  if (lhs.size_ != rhs.size_)
+    return false;
+  for (size_t i = 0; i < lhs.size_; ++i) {
+    if (lhs.bytes_[i] != rhs.bytes_[i])
+      return false;
+  }
+  return true;
+}
+
+bool operator!=(const IPAddress::IPAddressBytes& lhs,
+                const IPAddress::IPAddressBytes& rhs) {
+  return !(lhs == rhs);
+}
+
 IPAddress::IPAddress() {}
 
 IPAddress::IPAddress(const std::vector<uint8_t>& address)
-    : ip_address_(address) {}
+    : ip_address_(address.data(), address.size()) {}
 
 IPAddress::IPAddress(const IPAddress& other) = default;
 
 IPAddress::IPAddress(const uint8_t* address, size_t address_len)
-    : ip_address_(address, address + address_len) {}
+    : ip_address_(address, address_len) {}
 
 IPAddress::IPAddress(uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3) {
-  ip_address_.reserve(4);
   ip_address_.push_back(b0);
   ip_address_.push_back(b1);
   ip_address_.push_back(b2);
@@ -166,9 +219,22 @@ IPAddress::IPAddress(uint8_t b0,
                      uint8_t b13,
                      uint8_t b14,
                      uint8_t b15) {
-  const uint8_t address[] = {b0, b1, b2,  b3,  b4,  b5,  b6,  b7,
-                             b8, b9, b10, b11, b12, b13, b14, b15};
-  ip_address_ = std::vector<uint8_t>(std::begin(address), std::end(address));
+  ip_address_.push_back(b0);
+  ip_address_.push_back(b1);
+  ip_address_.push_back(b2);
+  ip_address_.push_back(b3);
+  ip_address_.push_back(b4);
+  ip_address_.push_back(b5);
+  ip_address_.push_back(b6);
+  ip_address_.push_back(b7);
+  ip_address_.push_back(b8);
+  ip_address_.push_back(b9);
+  ip_address_.push_back(b10);
+  ip_address_.push_back(b11);
+  ip_address_.push_back(b12);
+  ip_address_.push_back(b13);
+  ip_address_.push_back(b14);
+  ip_address_.push_back(b15);
 }
 
 IPAddress::~IPAddress() {}
@@ -208,15 +274,21 @@ bool IPAddress::IsIPv4MappedIPv6() const {
 }
 
 bool IPAddress::AssignFromIPLiteral(const base::StringPiece& ip_literal) {
-  std::vector<uint8_t> number;
+  IPAddressBytes number;
 
+  // TODO(rch): change the contract so ip_address_ is cleared on failure,
+  // to avoid needing this temporary at all.
   if (!ParseIPLiteralToBytes(ip_literal, &number))
     return false;
 
-  std::swap(number, ip_address_);
+  ip_address_ = number;
   return true;
 }
 
+std::vector<uint8_t> IPAddress::BytesAsVector() const {
+  return std::vector<uint8_t>(ip_address_.begin(), ip_address_.end());
+}
+
 // static
 IPAddress IPAddress::IPv4Localhost() {
   static const uint8_t kLocalhostIPv4[] = {127, 0, 0, 1};