Add real support for uint128.

net/base/int128.h

+// Copyright (c) 2012 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_INT128_H_
+#define NET_BASE_INT128_H_
+
+#include <iosfwd>
+#include "base/basictypes.h"
+#include "net/base/net_export.h"
+
+struct uint128_pod;
+
+// An unsigned 128-bit integer type. Thread-compatible.
+class uint128 {
+public:
+  uint128();  // Sets to 0, but don't trust on this behavior.
+  uint128(uint64 top, uint64 bottom);
+  uint128(int bottom);
+  uint128(uint32 bottom);   // Top 96 bits = 0
+  uint128(uint64 bottom);   // hi_ = 0
+  uint128(const uint128 &val);
+  uint128(const uint128_pod &val);
+
+  void Initialize(uint64 top, uint64 bottom);
+
+  uint128& operator=(const uint128& b);
+
+  // Arithmetic operators.
+  // TODO: division, etc.
+  uint128& operator+=(const uint128& b);
+  uint128& operator-=(const uint128& b);
+  uint128& operator*=(const uint128& b);
+  uint128 operator++(int);
+  uint128 operator--(int);
+  uint128& operator<<=(int);
+  uint128& operator>>=(int);
+  uint128& operator&=(const uint128& b);
+  uint128& operator|=(const uint128& b);
+  uint128& operator^=(const uint128& b);
+  uint128& operator++();
+  uint128& operator--();
+
+  friend uint64 Uint128Low64(const uint128& v);
+  friend uint64 Uint128High64(const uint128& v);
+
+  // We add "std::" to avoid including all of port.h.
+  friend NET_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& o,
+                                                     const uint128& b);
+
+private:
+  // Little-endian memory order optimizations can benefit from
+  // having lo_ first, hi_ last.
+  // See util/endian/endian.h and Load128/Store128 for storing a uint128.
+  uint64        lo_;
+  uint64        hi_;
+
+  // Not implemented, just declared for catching automatic type conversions.
+  uint128(uint8);
+  uint128(uint16);
+  uint128(float v);
+  uint128(double v);
+};
+
+// This is a POD form of uint128 which can be used for static variables which
+// need to be operated on as uint128.
+struct uint128_pod {
+  // Note: The ordering of fields is different than 'class uint128' but the
+  // same as its 2-arg constructor.  This enables more obvious initialization
+  // of static instances, which is the primary reason for this struct in the
+  // first place.  This does not seem to defeat any optimizations wrt
+  // operations involving this struct.
+  uint64 hi;
+  uint64 lo;
+};
+
+NET_EXPORT_PRIVATE extern const uint128_pod kuint128max;
+
+// allow uint128 to be logged
+NET_EXPORT_PRIVATE extern std::ostream& operator<<(std::ostream& o,
+                                                   const uint128& b);
+
+// Methods to access low and high pieces of 128-bit value.
+// Defined externally from uint128 to facilitate conversion
+// to native 128-bit types when compilers support them.
+inline uint64 Uint128Low64(const uint128& v) { return v.lo_; }
+inline uint64 Uint128High64(const uint128& v) { return v.hi_; }
+
+// TODO: perhaps it would be nice to have int128, a signed 128-bit type?
+
+// --------------------------------------------------------------------------
+//                      Implementation details follow
+// --------------------------------------------------------------------------
+inline bool operator==(const uint128& lhs, const uint128& rhs) {
+  return (Uint128Low64(lhs) == Uint128Low64(rhs) &&
+          Uint128High64(lhs) == Uint128High64(rhs));
+}
+inline bool operator!=(const uint128& lhs, const uint128& rhs) {
+  return !(lhs == rhs);
+}
+inline uint128& uint128::operator=(const uint128& b) {
+  lo_ = b.lo_;
+  hi_ = b.hi_;
+  return *this;
+}
+
+inline uint128::uint128(): lo_(0), hi_(0) { }
+inline uint128::uint128(uint64 top, uint64 bottom) : lo_(bottom), hi_(top) { }
+inline uint128::uint128(const uint128 &v) : lo_(v.lo_), hi_(v.hi_) { }
+inline uint128::uint128(const uint128_pod &v) : lo_(v.lo), hi_(v.hi) { }
+inline uint128::uint128(uint64 bottom) : lo_(bottom), hi_(0) { }
+inline uint128::uint128(uint32 bottom) : lo_(bottom), hi_(0) { }
+inline uint128::uint128(int bottom) : lo_(bottom), hi_(0) {
+  if (bottom < 0) {
+    --hi_;
+  }
+}
+inline void uint128::Initialize(uint64 top, uint64 bottom) {
+  hi_ = top;
+  lo_ = bottom;
+}
+
+// Comparison operators.
+
+#define CMP128(op)                                                \
+inline bool operator op(const uint128& lhs, const uint128& rhs) { \
+  return (Uint128High64(lhs) == Uint128High64(rhs)) ?             \
+      (Uint128Low64(lhs) op Uint128Low64(rhs)) :                  \
+      (Uint128High64(lhs) op Uint128High64(rhs));                 \
+}
+
+CMP128(<)
+CMP128(>)
+CMP128(>=)
+CMP128(<=)
+
+#undef CMP128
+
+// Unary operators
+
+inline uint128 operator-(const uint128& val) {
+  const uint64 hi_flip = ~Uint128High64(val);
+  const uint64 lo_flip = ~Uint128Low64(val);
+  const uint64 lo_add = lo_flip + 1;
+  if (lo_add < lo_flip) {
+    return uint128(hi_flip + 1, lo_add);
+  }
+  return uint128(hi_flip, lo_add);
+}
+
+inline bool operator!(const uint128& val) {
+  return !Uint128High64(val) && !Uint128Low64(val);
+}
+
+// Logical operators.
+
+inline uint128 operator~(const uint128& val) {
+  return uint128(~Uint128High64(val), ~Uint128Low64(val));
+}
+
+#define LOGIC128(op)                                                 \
+inline uint128 operator op(const uint128& lhs, const uint128& rhs) { \
+  return uint128(Uint128High64(lhs) op Uint128High64(rhs),           \
+                 Uint128Low64(lhs) op Uint128Low64(rhs));            \
+}
+
+LOGIC128(|)
+LOGIC128(&)
+LOGIC128(^)
+
+#undef LOGIC128
+
+#define LOGICASSIGN128(op)                                   \
+inline uint128& uint128::operator op(const uint128& other) { \
+  hi_ op other.hi_;                                          \
+  lo_ op other.lo_;                                          \
+  return *this;                                              \
+}
+
+LOGICASSIGN128(|=)
+LOGICASSIGN128(&=)
+LOGICASSIGN128(^=)
+
+#undef LOGICASSIGN128
+
+// Shift operators.
+
+inline uint128 operator<<(const uint128& val, int amount) {
+  // uint64 shifts of >= 64 are undefined, so we will need some special-casing.
+  if (amount < 64) {
+    if (amount == 0) {
+      return val;
+    }
+    uint64 new_hi = (Uint128High64(val) << amount) |
+                    (Uint128Low64(val) >> (64 - amount));
+    uint64 new_lo = Uint128Low64(val) << amount;
+    return uint128(new_hi, new_lo);
+  } else if (amount < 128) {
+    return uint128(Uint128Low64(val) << (amount - 64), 0);
+  } else {
+    return uint128(0, 0);
+  }
+}
+
+inline uint128 operator>>(const uint128& val, int amount) {
+  // uint64 shifts of >= 64 are undefined, so we will need some special-casing.
+  if (amount < 64) {
+    if (amount == 0) {
+      return val;
+    }
+    uint64 new_hi = Uint128High64(val) >> amount;
+    uint64 new_lo = (Uint128Low64(val) >> amount) |
+                    (Uint128High64(val) << (64 - amount));
+    return uint128(new_hi, new_lo);
+  } else if (amount < 128) {
+    return uint128(0, Uint128High64(val) >> (amount - 64));
+  } else {
+    return uint128(0, 0);
+  }
+}
+
+inline uint128& uint128::operator<<=(int amount) {
+  // uint64 shifts of >= 64 are undefined, so we will need some special-casing.
+  if (amount < 64) {
+    if (amount != 0) {
+      hi_ = (hi_ << amount) | (lo_ >> (64 - amount));
+      lo_ = lo_ << amount;
+    }
+  } else if (amount < 128) {
+    hi_ = lo_ << (amount - 64);
+    lo_ = 0;
+  } else {
+    hi_ = 0;
+    lo_ = 0;
+  }
+  return *this;
+}
+
+inline uint128& uint128::operator>>=(int amount) {
+  // uint64 shifts of >= 64 are undefined, so we will need some special-casing.
+  if (amount < 64) {
+    if (amount != 0) {
+      lo_ = (lo_ >> amount) | (hi_ << (64 - amount));
+      hi_ = hi_ >> amount;
+    }
+  } else if (amount < 128) {
+    hi_ = 0;
+    lo_ = hi_ >> (amount - 64);
+  } else {
+    hi_ = 0;
+    lo_ = 0;
+  }
+  return *this;
+}
+
+inline uint128 operator+(const uint128& lhs, const uint128& rhs) {
+  return uint128(lhs) += rhs;
+}
+
+inline uint128 operator-(const uint128& lhs, const uint128& rhs) {
+  return uint128(lhs) -= rhs;
+}
+
+inline uint128 operator*(const uint128& lhs, const uint128& rhs) {
+  return uint128(lhs) *= rhs;
+}
+
+inline uint128& uint128::operator+=(const uint128& b) {
+  hi_ += b.hi_;
+  uint64 lolo = lo_ + b.lo_;
+  if (lolo < lo_)
+    ++hi_;
+  lo_ = lolo;
+  return *this;
+}
+
+inline uint128& uint128::operator-=(const uint128& b) {
+  hi_ -= b.hi_;
+  if (b.lo_ > lo_)
+    --hi_;
+  lo_ -= b.lo_;
+  return *this;
+}
+
+inline uint128& uint128::operator*=(const uint128& b) {
+  uint64 a96 = hi_ >> 32;
+  uint64 a64 = hi_ & 0xffffffffu;
+  uint64 a32 = lo_ >> 32;
+  uint64 a00 = lo_ & 0xffffffffu;
+  uint64 b96 = b.hi_ >> 32;
+  uint64 b64 = b.hi_ & 0xffffffffu;
+  uint64 b32 = b.lo_ >> 32;
+  uint64 b00 = b.lo_ & 0xffffffffu;
+  // multiply [a96 .. a00] x [b96 .. b00]
+  // terms higher than c96 disappear off the high side
+  // terms c96 and c64 are safe to ignore carry bit
+  uint64 c96 = a96 * b00 + a64 * b32 + a32 * b64 + a00 * b96;
+  uint64 c64 = a64 * b00 + a32 * b32 + a00 * b64;
+  this->hi_ = (c96 << 32) + c64;
+  this->lo_ = 0;
+  // add terms after this one at a time to capture carry
+  *this += uint128(a32 * b00) << 32;
+  *this += uint128(a00 * b32) << 32;
+  *this += a00 * b00;
+  return *this;
+}
+
+inline uint128 uint128::operator++(int) {
+  uint128 tmp(*this);
+  *this += 1;
+  return tmp;
+}
+
+inline uint128 uint128::operator--(int) {
+  uint128 tmp(*this);
+  *this -= 1;
+  return tmp;
+}
+
+inline uint128& uint128::operator++() {
+  *this += 1;
+  return *this;
+}
+
+inline uint128& uint128::operator--() {
+  *this -= 1;
+  return *this;
+}
+
+#endif  // NET_BASE_INT128_H_