Implement basic classes for HPACK (HTTP/2 compression)

net/spdy/hpack_header_table.cc

+#include "net/spdy/hpack_header_table.h"
+
+#include "base/logging.h"
+#include "net/spdy/hpack_string_util.h"
+
+namespace net {
+
+HpackHeaderTable::HpackHeaderTable() : size_(0), max_size_(4096) {}
+
+HpackHeaderTable::~HpackHeaderTable() {}
+
+uint32 HpackHeaderTable::GetEntryCount() const {
+  size_t size = entries_.size();
+  DCHECK_LE(size, kuint32max);
+  return static_cast<uint32>(size);
+}
+
+const HpackEntry& HpackHeaderTable::GetEntry(uint32 index) const {
+  CHECK_LT(index, GetEntryCount());
+  return entries_[index];
+}
+
+HpackEntry* HpackHeaderTable::GetMutableEntry(uint32 index) {
+  CHECK_LT(index, GetEntryCount());
+  return &entries_[index];
+}
+
+void HpackHeaderTable::SetMaxSize(uint32 max_size) {
+  max_size_ = max_size;
+  while (size_ > max_size_) {
+    CHECK(!entries_.empty());
+    size_ -= entries_.back().Size();
+    entries_.pop_back();
+  }
+}
+
+void HpackHeaderTable::TryAddEntry(
+    const HpackEntry& entry,
+    int32* index,
+    std::vector<uint32>* removed_referenced_indices) {
+  *index = -1;
+  removed_referenced_indices->clear();
+
+  // The algorithm used here is described in 3.3.3. We're assuming
+  // that the given entry is caching the name/value.
+  size_t target_size = 0;
+  size_t size_t_max_size = static_cast<size_t>(max_size_);
+  if (entry.Size() <= size_t_max_size) {
+    // The conditional implies the difference can fit in 32 bits.
+    target_size = size_t_max_size - entry.Size();
+  }
+  while ((static_cast<size_t>(size_) > target_size) && !entries_.empty()) {
+    if (entries_.back().IsReferenced()) {
+      removed_referenced_indices->push_back(entries_.size() - 1);
+    }
+    size_ -= entries_.back().Size();
+    entries_.pop_back();
+  }
+
+  if (entry.Size() <= size_t_max_size) {
+    // Implied by the exit condition of the while loop above and the
+    // condition of the if.
+    DCHECK_LE(static_cast<size_t>(size_) + entry.Size(), size_t_max_size);
+    size_ += entry.Size();
+    *index = 0;
+    entries_.push_front(entry);
+  }
+}
+
+}  // namespace net