Replace the existing SpdyHeaderBlock typedef with a class.

net/spdy/spdy_header_block.cc

Index: net/spdy/spdy_header_block.cc
diff --git a/net/spdy/spdy_header_block.cc b/net/spdy/spdy_header_block.cc
index 6e72451112d96c7d982070976b2fbbd6003f6df0..d12ab70cb9000c78e4d3bd0da1224cdc1bb31485 100644
--- a/net/spdy/spdy_header_block.cc
+++ b/net/spdy/spdy_header_block.cc
@@ -4,10 +4,207 @@
 
 #include "net/spdy/spdy_header_block.h"
 
+#include <algorithm>
+#include <ios>
+#include <utility>
+#include <vector>
+
+#include "base/logging.h"
 #include "base/values.h"
 #include "net/http/http_log_util.h"
 
+using base::StringPiece;
+using std::dec;
+using std::hex;
+using std::max;
+using std::min;
+
 namespace net {
+namespace {
+
+// SpdyHeaderBlock::Storage uses a small initial block in case we only have a
+// minimal set of headers.
+const size_t kInitialStorageBlockSize = 512;
+
+// SpdyHeaderBlock::Storage allocates blocks of this size by default.
+const size_t kDefaultStorageBlockSize = 2048;
+
+// When copying a SpdyHeaderBlock, the new block will allocate at most this
+// much memory for the initial contiguous block.
+const size_t kMaxContiguousAllocation = 16 * 1024;
+
+}  // namespace
+
+// This class provides a backing store for StringPieces. It uses a sequence of
+// large, contiguous blocks. It has the property that StringPieces that refer
+// to data in Storage are never invalidated until the Storage is deleted.
+//
+// Write operations always append to the last block. If there is not enough
+// space to perform the write, a new block is allocated, and any unused space
+// is wasted.
+class SpdyHeaderBlock::Storage {
+ public:
+  Storage() : bytes_used_(0) {}
+  ~Storage() { Clear(); }
+
+  void Reserve(size_t additional_space) {
+    if (blocks_.empty()) {
+      AllocBlock(max(additional_space, kInitialStorageBlockSize));
+    } else {
+      const Block& last = blocks_.back();
+      if (last.size - last.used < additional_space) {
+        AllocBlock(max(additional_space, kDefaultStorageBlockSize));
+      }
+    }
+  }
+
+  StringPiece Write(const StringPiece s) {
+    Reserve(s.size());
+    Block* last = &blocks_.back();
+    memcpy(last->data + last->used, s.data(), s.size());
+    StringPiece out(last->data + last->used, s.size());
+    VLOG(3) << "Write result: " << hex
+            << reinterpret_cast<const void*>(out.data()) << ", " << dec
+            << out.size();
+    last->used += s.size();
+    bytes_used_ += s.size();
+    return out;
+  }
+
+  void Clear() {
+    while (!blocks_.empty()) {
+      delete[] blocks_.back().data;
+      blocks_.pop_back();
+    }
+    bytes_used_ = 0;
+  }
+
+  size_t BytesUsed() const { return bytes_used_; }
+
+ private:
+  // TODO(bnc): As soon as move semantics are allowed, change from naked pointer
+  // to scoped_ptr<>, or better yet, unique_ptr<>.
+  struct Block {
+    char* data;
+    size_t size = 0;
+    size_t used = 0;
+
+    Block(char* data, size_t s) : data(data), size(s), used(0) {}
+  };
+
+  void AllocBlock(size_t size) {
+    blocks_.push_back(Block(new char[size], size));
+  }
+
+  std::vector<Block> blocks_;
+  size_t bytes_used_;
+
+  DISALLOW_COPY_AND_ASSIGN(Storage);
+};
+
+SpdyHeaderBlock::StringPieceProxy::StringPieceProxy(
+    SpdyHeaderBlock::MapType* block,
+    SpdyHeaderBlock::Storage* storage,
+    SpdyHeaderBlock::MapType::iterator lookup_result,
+    const StringPiece key)
+    : block_(block),
+      storage_(storage),
+      lookup_result_(lookup_result),
+      key_(key) {}
+
+SpdyHeaderBlock::StringPieceProxy::~StringPieceProxy() {}
+
+SpdyHeaderBlock::StringPieceProxy& SpdyHeaderBlock::StringPieceProxy::operator=(
+    const StringPiece value) {
+  if (lookup_result_ == block_->end()) {
+    VLOG(1) << "Inserting: (" << key_ << ", " << value << ")";
+    lookup_result_ =
+        block_->insert(std::make_pair(key_, storage_->Write(value))).first;
+  } else {
+    VLOG(1) << "Updating key: " << key_ << " with value: " << value;
+    lookup_result_->second = storage_->Write(value);
+  }
+  return *this;
+}
+
+SpdyHeaderBlock::StringPieceProxy::operator StringPiece() const {
+  return (lookup_result_ == block_->end()) ? StringPiece()
+                                           : lookup_result_->second;
+}
+
+void SpdyHeaderBlock::StringPieceProxy::reserve(size_t size) {
+  storage_->Reserve(size);
+}
+
+SpdyHeaderBlock::SpdyHeaderBlock() : storage_(new Storage) {}
+
+SpdyHeaderBlock::~SpdyHeaderBlock() {}
+
+SpdyHeaderBlock::SpdyHeaderBlock(const SpdyHeaderBlock& other)
+    : storage_(new Storage) {
+  storage_->Reserve(min(other.storage_->BytesUsed(), kMaxContiguousAllocation));
+  for (auto iter : other) {
+    AppendHeader(iter.first, iter.second);
+  }
+}
+
+SpdyHeaderBlock& SpdyHeaderBlock::operator=(const SpdyHeaderBlock& other) {
+  clear();
+  storage_->Reserve(min(other.storage_->BytesUsed(), kMaxContiguousAllocation));
+  for (auto iter : other) {
+    AppendHeader(iter.first, iter.second);
+  }
+  return *this;
+}
+
+void SpdyHeaderBlock::clear() {
+  block_.clear();
+  storage_->Clear();
+}
+
+void SpdyHeaderBlock::insert(
+    const SpdyHeaderBlock::MapType::value_type& value) {
+  ReplaceOrAppendHeader(value.first, value.second);
+}
+
+SpdyHeaderBlock::StringPieceProxy SpdyHeaderBlock::operator[](
+    const StringPiece key) {
+  VLOG(2) << "Operator[] saw key: " << key;
+  StringPiece out_key;
+  auto iter = block_.find(key);
+  if (iter == block_.end()) {
+    // We write the key first, to assure that the StringPieceProxy has a
+    // reference to a valid StringPiece in its operator=.
+    out_key = storage_->Write(key);
+    VLOG(2) << "Key written as: " << hex << static_cast<const void*>(key.data())
+            << ", " << dec << key.size();
+  } else {
+    out_key = iter->first;
+  }
+  return StringPieceProxy(&block_, storage_.get(), iter, out_key);
+}
+
+bool SpdyHeaderBlock::operator==(const SpdyHeaderBlock& other) const {
+  return size() == other.size() && std::equal(begin(), end(), other.begin());
+}
+
+void SpdyHeaderBlock::ReplaceOrAppendHeader(const StringPiece key,
+                                            const StringPiece value) {
+  // TODO(birenroy): Write new value in place of old value, if it fits.
+  auto iter = block_.find(key);
+  if (iter == block_.end()) {
+    VLOG(1) << "Inserting: (" << key << ", " << value << ")";
+    AppendHeader(key, value);
+  } else {
+    VLOG(1) << "Updating key: " << iter->first << " with value: " << value;
+    iter->second = storage_->Write(value);
+  }
+}
+
+void SpdyHeaderBlock::AppendHeader(const StringPiece key,
+                                   const StringPiece value) {
+  block_.insert(make_pair(storage_->Write(key), storage_->Write(value)));
+}
 
 scoped_ptr<base::Value> SpdyHeaderBlockNetLogCallback(
     const SpdyHeaderBlock* headers,
@@ -17,8 +214,9 @@ scoped_ptr<base::Value> SpdyHeaderBlockNetLogCallback(
   for (SpdyHeaderBlock::const_iterator it = headers->begin();
        it != headers->end(); ++it) {
     headers_dict->SetWithoutPathExpansion(
-        it->first, new base::StringValue(ElideHeaderValueForNetLog(
-                       capture_mode, it->first, it->second)));
+        it->first.as_string(),
+        new base::StringValue(ElideHeaderValueForNetLog(
+            capture_mode, it->first.as_string(), it->second.as_string())));
   }
   dict->Set("headers", headers_dict);
   return dict.Pass();
@@ -40,10 +238,12 @@ bool SpdyHeaderBlockFromNetLogParam(
 
   for (base::DictionaryValue::Iterator it(*header_dict); !it.IsAtEnd();
        it.Advance()) {
-    if (!it.value().GetAsString(&(*headers)[it.key()])) {
+    std::string value;
+    if (!it.value().GetAsString(&value)) {
       headers->clear();
       return false;
     }
+    (*headers)[it.key()] = value;
   }
   return true;
 }