Implementing Binary glTF reader for the VR controller model

chrome/browser/android/vr_shell/gltf_parser.cc

 // Copyright 2017 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 "chrome/browser/android/vr_shell/gltf_parser.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback_helpers.h"
 #include "base/files/file_util.h"
 #include "base/json/json_file_value_serializer.h"
+#include "base/json/json_string_value_serializer.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/strings/string_util.h"
+#include "base/sys_byteorder.h"
 #include "net/base/data_url.h"
 #include "net/base/filename_util.h"
 #include "url/gurl.h"
 
 namespace vr_shell {
 
+namespace {
+constexpr const char kFailedtoReadBinaryGltfMsg[] =

[mthiesse, 2017/04/28 15:51:34]

Wrap this in #if defined(DCHECK_IS_ON)

[mthiesse, 2017/04/28 16:11:45]

I know this makes the code cleaner, but to avoid extra strings, I think you
should just hard-code it where it's used in the debug logs and delete the
constexpr here.

+    "Failed to read binary glTF: ";
+constexpr const char kGltfMagic[] = "glTF";
+constexpr const char kBinaryGltfBufferName[] = "binary_glTF";
+constexpr uint32_t kJsonGltfFormat = 0;
+
+enum {

[mthiesse, 2017/04/28 15:51:34]

Why is this an enum? Looks like just making constants would be a better fit?

[acondor_, 2017/04/28 16:07:01]

Done.

+  kVersionStart = 4,
+  kLengthStart = 8,
+  kContentLengthStart = 12,
+  kContentFormatStart = 16,
+  kContentStart = 20
+};
+
+uint32_t GetLE32(const char* data) {
+  const uint32_t* int_data = reinterpret_cast<const uint32_t*>(data);
+  return base::ByteSwapToLE32(*int_data);
+}
+
+}  // namespace
+
 GltfParser::GltfParser() {}
 
 GltfParser::~GltfParser() = default;
 
 std::unique_ptr<gltf::Asset> GltfParser::Parse(
     const base::DictionaryValue& dict,
     std::vector<std::unique_ptr<gltf::Buffer>>* buffers,
     const base::FilePath& path) {
+  DCHECK(buffers && buffers->size() <= 1);
   path_ = path;
   asset_ = base::MakeUnique<gltf::Asset>();
 
   base::ScopedClosureRunner runner(
       base::Bind(&GltfParser::Clear, base::Unretained(this)));
 
   if (!ParseInternal(dict, buffers))
     return nullptr;
 
   return std::move(asset_);
 }
 
 std::unique_ptr<gltf::Asset> GltfParser::Parse(
     const base::FilePath& gltf_path,
     std::vector<std::unique_ptr<gltf::Buffer>>* buffers) {
+  DCHECK(buffers && buffers->size() <= 1);
   JSONFileValueDeserializer json_deserializer(gltf_path);
   int error_code;
   std::string error_msg;
   auto asset_value = json_deserializer.Deserialize(&error_code, &error_msg);
   if (!asset_value)
     return nullptr;
   base::DictionaryValue* asset;
   if (!asset_value->GetAsDictionary(&asset))
     return nullptr;
   return Parse(*asset, buffers, gltf_path);
@@ skipping 29 matching lines @@
       return false;
     asset_->SetMainScene(asset_->GetScene(scene_it->second));
   }
 
   return true;
 }
 
 bool GltfParser::SetBuffers(
     const base::DictionaryValue& dict,
     std::vector<std::unique_ptr<gltf::Buffer>>* buffers) {
-  buffers->clear();
+  size_t buffer_cnt = 0;

[mthiesse, 2017/04/28 15:51:34]

nit: avoid using abbreviations in variable names like 'cnt'

[acondor_, 2017/04/28 16:07:01]

Done.

   for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
     const base::DictionaryValue* buffer_dict;
     if (!it.value().GetAsDictionary(&buffer_dict))
       return false;
 
+    if (it.key() == kBinaryGltfBufferName) {
+      if (buffers->size() == buffer_cnt)
+        return false;
+      buffer_ids_[it.key()] = 0;
+      continue;
+    }
+
     std::string uri_str;
     if (!buffer_dict->GetString("uri", &uri_str))
       return false;
     auto buffer = ProcessUri(uri_str);
     if (!buffer)
       return false;
 
     int byte_length;
     if (buffer_dict->GetInteger("byteLength", &byte_length) &&
         static_cast<int>(buffer->length()) != byte_length)
       return false;
 
     buffer_ids_[it.key()] = buffers->size();
     buffers->push_back(std::move(buffer));
+    ++buffer_cnt;
   }
   return true;
 }
 
 std::unique_ptr<gltf::Buffer> GltfParser::ProcessUri(
     const std::string& uri_str) {
   auto uri = path_.empty() ? GURL(uri_str)
                            : net::FilePathToFileURL(path_).Resolve(uri_str);
   if (!uri.is_valid())
     return nullptr;
@@ skipping 204 matching lines @@
   asset_.reset();
   path_.clear();
   buffer_ids_.clear();
   buffer_view_ids_.clear();
   accessor_ids_.clear();
   node_ids_.clear();
   mesh_ids_.clear();
   scene_ids_.clear();
 }
 
+std::unique_ptr<gltf::Asset> BinaryGltfParser::Parse(
+    const base::StringPiece& glb_content,
+    std::vector<std::unique_ptr<gltf::Buffer>>* buffers,
+    const base::FilePath& path) {
+  DCHECK(buffers && buffers->empty());
+  if (glb_content.length() < kContentStart) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Incomplete data";

[mthiesse, 2017/04/28 15:51:34]

Make these DLOGs? Best to avoid adding strings to release builds.

+    return nullptr;
+  }
+  if (!glb_content.starts_with(kGltfMagic)) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Unknown magic number";
+    return nullptr;
+  }
+  if (GetLE32(glb_content.data() + kVersionStart) != 1) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Unknown version";

[mthiesse, 2017/04/28 15:51:34]

nit: s/Unknown/Unsupported

+    return nullptr;
+  }
+  if (GetLE32(glb_content.data() + kLengthStart) != glb_content.length()) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Incorrect file size";
+    return nullptr;
+  }
+  uint32_t content_length = GetLE32(glb_content.data() + kContentLengthStart);
+  if (kContentStart + content_length > glb_content.length()) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Invalid content length";
+    return nullptr;
+  }
+  if (GetLE32(glb_content.data() + kContentFormatStart) != kJsonGltfFormat) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Unknown glTF format";

[mthiesse, 2017/04/28 15:51:34]

nit: s/Unknown/Unsupported

+    return nullptr;
+  }
+
+  base::StringPiece gltf_content(glb_content.data() + kContentStart,
+                                 content_length);
+  int error_code;
+  std::string error_msg;
+  JSONStringValueDeserializer json_deserializer(gltf_content);
+  auto gltf_value = json_deserializer.Deserialize(&error_code, &error_msg);
+  if (!gltf_value) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Content not a valid JSON";
+    return nullptr;
+  }
+  base::DictionaryValue* gltf_dict;
+  if (!gltf_value->GetAsDictionary(&gltf_dict)) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Content is not a valid glTF";
+    return nullptr;
+  }
+
+  auto glb_buffer = base::MakeUnique<gltf::Buffer>(
+      glb_content.substr(kContentStart + content_length));
+  buffers->push_back(std::move(glb_buffer));
+  GltfParser gltf_parser;
+  auto gltf_asset = gltf_parser.Parse(*gltf_dict, buffers);
+  if (!gltf_asset) {
+    LOG(ERROR) << kFailedtoReadBinaryGltfMsg << "Content is not a valid glTF";
+    buffers->clear();
+    return nullptr;
+  }
+  return gltf_asset;
+}
+
 }  // namespace vr_shell