Add new HTTP/2 and HPACK decoder in net/http2/.

net/http2/decoder/decode_buffer.cc

Index: net/http2/decoder/decode_buffer.cc
diff --git a/net/http2/decoder/decode_buffer.cc b/net/http2/decoder/decode_buffer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..15235bae4b53db8bcc127f190aee6a5df70deba8
--- /dev/null
+++ b/net/http2/decoder/decode_buffer.cc
@@ -0,0 +1,90 @@
+// Copyright 2016 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 "net/http2/decoder/decode_buffer.h"
+
+namespace net {
+
+bool DecodeBuffer::SlowDecodeUnsignedInt(uint32_t field_size,
+                                         uint32_t field_offset,
+                                         uint32_t* decode_offset,
+                                         uint32_t* value) {
+  DCHECK_LT(0u, field_size);
+  DCHECK_LE(field_size, 4u);
+  DCHECK(decode_offset != nullptr);
+  DCHECK_LE(field_offset, *decode_offset);
+  const uint32_t next_field_offset = field_offset + field_size;
+  if (*decode_offset == field_offset) {
+    // Starting to decode field. It is possible we will reach this point
+    // twice, once when we've just exhausted the input, and once when
+    // resuming decoding with a new input buffer.
+    // Clear the field; we do NOT assume that the caller has done so
+    // previously.
+    *value = 0;
+  } else if (*decode_offset >= next_field_offset) {
+    // We already decoded this field.
+    return true;
+  }
+  do {
+    if (Empty()) {
+      return false;  // Not done decoding.
+    }
+    *value = *value << 8 | DecodeUInt8();
+    (*decode_offset)++;
+  } while (*decode_offset < next_field_offset);
+  return true;
+}
+
+bool DecodeBuffer::SlowDecodeUInt8(uint32_t field_offset,
+                                   uint32_t* decode_offset,
+                                   uint8_t* value) {
+  uint32_t tmp = *value;
+  const bool done = SlowDecodeUnsignedInt(1 /* field_size */, field_offset,
+                                          decode_offset, &tmp);
+  *value = tmp & 0xff;
+  DCHECK_EQ(tmp, *value);
+  return done;
+}
+
+bool DecodeBuffer::SlowDecodeUInt16(uint32_t field_offset,
+                                    uint32_t* decode_offset,
+                                    uint16_t* value) {
+  uint32_t tmp = *value;
+  const bool done = SlowDecodeUnsignedInt(2 /* field_size */, field_offset,
+                                          decode_offset, &tmp);
+  *value = tmp & 0xffff;
+  DCHECK_EQ(tmp, *value);
+  return done;
+}
+
+bool DecodeBuffer::SlowDecodeUInt24(uint32_t field_offset,
+                                    uint32_t* decode_offset,
+                                    uint32_t* value) {
+  uint32_t tmp = *value;
+  const bool done = SlowDecodeUnsignedInt(3 /* field_size */, field_offset,
+                                          decode_offset, &tmp);
+  *value = tmp & 0xffffff;
+  DCHECK_EQ(tmp, *value);
+  return done;
+}
+
+bool DecodeBuffer::SlowDecodeUInt31(uint32_t field_offset,
+                                    uint32_t* decode_offset,
+                                    uint32_t* value) {
+  uint32_t tmp = *value;
+  const bool done = SlowDecodeUnsignedInt(4 /* field_size */, field_offset,
+                                          decode_offset, &tmp);
+  *value = tmp & 0x7fffffff;
+  DCHECK_EQ(tmp & 0x7fffffff, *value);
+  return done;
+}
+
+bool DecodeBuffer::SlowDecodeUInt32(uint32_t field_offset,
+                                    uint32_t* decode_offset,
+                                    uint32_t* value) {
+  return SlowDecodeUnsignedInt(4 /* field_size */, field_offset, decode_offset,
+                               value);
+}
+
+}  // namespace net