Pickle::Write* micro-optimizations

base/pickle.cc

 // 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.
 
 #include "base/pickle.h"
 
 #include <stdlib.h>
 
 #include <algorithm>  // for max()
 
@@ skipping 135 matching lines @@
     return false;
   *data = read_from;
   return true;
 }
 
 // Payload is uint32 aligned.
 
 Pickle::Pickle()
     : header_(NULL),
       header_size_(sizeof(Header)),
-      capacity_(0) {
+      capacity_(0),
+      write_offset_(0) {
   Resize(kPayloadUnit);
   header_->payload_size = 0;
 }
 
 Pickle::Pickle(int header_size)
     : header_(NULL),
       header_size_(AlignInt(header_size, sizeof(uint32))),
-      capacity_(0) {
+      capacity_(0),
+      write_offset_(0) {
   DCHECK_GE(static_cast<size_t>(header_size), sizeof(Header));
   DCHECK_LE(header_size, kPayloadUnit);
   Resize(kPayloadUnit);
   header_->payload_size = 0;
 }
 
 Pickle::Pickle(const char* data, int data_len)
     : header_(reinterpret_cast<Header*>(const_cast<char*>(data))),
       header_size_(0),
-      capacity_(kCapacityReadOnly) {
+      capacity_(kCapacityReadOnly),
+      write_offset_(0) {
   if (data_len >= static_cast<int>(sizeof(Header)))
     header_size_ = data_len - header_->payload_size;
 
   if (header_size_ > static_cast<unsigned int>(data_len))
     header_size_ = 0;
 
   if (header_size_ != AlignInt(header_size_, sizeof(uint32)))
     header_size_ = 0;
 
   // If there is anything wrong with the data, we're not going to use it.
   if (!header_size_)
     header_ = NULL;
 }
 
 Pickle::Pickle(const Pickle& other)
     : header_(NULL),
       header_size_(other.header_size_),
-      capacity_(0) {
-  size_t payload_size = header_size_ + other.header_->payload_size;
-  Resize(payload_size);
-  memcpy(header_, other.header_, payload_size);
+      capacity_(0),
+      write_offset_(other.write_offset_) {
+  Resize(other.header_->payload_size);
+  memcpy(header_, other.header_, header_size_ + other.header_->payload_size);
 }
 
 Pickle::~Pickle() {
   if (capacity_ != kCapacityReadOnly)
     free(header_);
 }
 
 Pickle& Pickle::operator=(const Pickle& other) {
   if (this == &other) {
     NOTREACHED();
     return *this;
   }
   if (capacity_ == kCapacityReadOnly) {
     header_ = NULL;
     capacity_ = 0;
   }
   if (header_size_ != other.header_size_) {
     free(header_);
     header_ = NULL;
     header_size_ = other.header_size_;
   }
-  Resize(other.header_size_ + other.header_->payload_size);
+  Resize(other.header_->payload_size);
   memcpy(header_, other.header_,
          other.header_size_ + other.header_->payload_size);
+  write_offset_ = other.write_offset_;
   return *this;
 }
 
 bool Pickle::WriteString(const std::string& value) {
   if (!WriteInt(static_cast<int>(value.size())))
     return false;
 
   return WriteBytes(value.data(), static_cast<int>(value.size()));
 }
 
@@ skipping 10 matching lines @@
     return false;
 
   return WriteBytes(value.data(),
                     static_cast<int>(value.size()) * sizeof(char16));
 }
 
 bool Pickle::WriteData(const char* data, int length) {
   return length >= 0 && WriteInt(length) && WriteBytes(data, length);
 }
 
-bool Pickle::WriteBytes(const void* data, int data_len) {
+inline void Pickle::WriteBytesCommon(const void* data, size_t length) {
   DCHECK_NE(kCapacityReadOnly, capacity_) << "oops: pickle is readonly";
+  size_t data_len = AlignInt(length, sizeof(uint32));
+  DCHECK_GE(data_len, length);
+#ifdef ARCH_CPU_64_BITS
+  DCHECK_LE(data_len, kuint32max);
+#endif
+  DCHECK_LE(write_offset_, kuint32max - data_len);
+  size_t new_size = write_offset_ + data_len;
+  if (new_size > capacity_) {
+    Resize(std::max(capacity_ * 2, new_size));
+  }
 
-  char* dest = BeginWrite(data_len);
-  if (!dest)
-    return false;
+  char* write = mutable_payload() + write_offset_;
+  memcpy(write, data, length);
+  memset(write + length, 0, data_len - length);
+  header_->payload_size = write_offset_ + length;
+  write_offset_ = new_size;
+}
 
-  memcpy(dest, data, data_len);
-
-  EndWrite(dest, data_len);
+bool Pickle::WriteBytes(const void* data, int length) {
+  WriteBytesCommon(data, length);
   return true;
 }
 
-void Pickle::Reserve(size_t length) {
-  // write at a uint32-aligned offset from the beginning of the header
-  size_t offset = AlignInt(header_->payload_size, sizeof(uint32));
-
-  size_t new_size = offset + length;
-  size_t needed_size = header_size_ + new_size;
-  if (needed_size > capacity_)
-    Resize(capacity_ * 2 + needed_size);
+template <size_t length> void Pickle::WriteBytesStatic(const void* data) {
+  WriteBytesCommon(data, length);
 }
 
-char* Pickle::BeginWrite(size_t length) {
-  // write at a uint32-aligned offset from the beginning of the header
-  size_t offset = AlignInt(header_->payload_size, sizeof(uint32));
+template void Pickle::WriteBytesStatic<2>(const void* data);
+template void Pickle::WriteBytesStatic<4>(const void* data);
+template void Pickle::WriteBytesStatic<8>(const void* data);
 
-  size_t new_size = offset + length;
-  size_t needed_size = header_size_ + new_size;
-  if (needed_size > capacity_)
-    Resize(std::max(capacity_ * 2, needed_size));
-
+void Pickle::Reserve(size_t length) {
+  size_t data_len = AlignInt(length, sizeof(uint32));
+  DCHECK_GE(data_len, length);
 #ifdef ARCH_CPU_64_BITS
-  DCHECK_LE(length, kuint32max);
+  DCHECK_LE(data_len, kuint32max);
 #endif
-
-  header_->payload_size = static_cast<uint32>(new_size);
-  return mutable_payload() + offset;
-}
-
-void Pickle::EndWrite(char* dest, int length) {
-  // Zero-pad to keep tools like valgrind from complaining about uninitialized
-  // memory.
-  if (length % sizeof(uint32))
-    memset(dest + length, 0, sizeof(uint32) - (length % sizeof(uint32)));
+  DCHECK_LE(write_offset_, kuint32max - data_len);
+  size_t new_size = write_offset_ + data_len;
+  if (new_size > capacity_)
+    Resize(capacity_ * 2 + new_size);
 }
 
 void Pickle::Resize(size_t new_capacity) {
   CHECK_NE(capacity_, kCapacityReadOnly);
 
   new_capacity = AlignInt(new_capacity, kPayloadUnit);
-  void* p = realloc(header_, new_capacity);
+  void* p = realloc(header_, header_size_ + new_capacity);
   header_ = reinterpret_cast<Header*>(p);
   capacity_ = new_capacity;
 }
 
 // static
 const char* Pickle::FindNext(size_t header_size,
                              const char* start,
                              const char* end) {
   DCHECK_EQ(header_size, AlignInt(header_size, sizeof(uint32)));
   DCHECK_LE(header_size, static_cast<size_t>(kPayloadUnit));
 
   if (static_cast<size_t>(end - start) < sizeof(Header))
     return NULL;
 
   const Header* hdr = reinterpret_cast<const Header*>(start);
   const char* payload_base = start + header_size;
   const char* payload_end = payload_base + hdr->payload_size;
   if (payload_end < payload_base)
     return NULL;
 
   return (payload_end > end) ? NULL : payload_end;
 }