Generate the Chrome policy schema at compile time.

components/policy/core/common/schema.cc

 // Copyright 2013 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 "components/policy/core/common/schema.h"
 
 #include <algorithm>
+#include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
+#include "base/memory/scoped_vector.h"
 #include "components/json_schema/json_schema_constants.h"
 #include "components/json_schema/json_schema_validator.h"
 #include "components/policy/core/common/schema_internal.h"
 
 namespace policy {
 
+using internal::PropertiesNode;
+using internal::PropertyNode;
+using internal::SchemaData;
+using internal::SchemaNode;
+
 namespace {
 
+const int kInvalid = -1;
+
 bool SchemaTypeToValueType(const std::string& type_string,
                            base::Value::Type* type) {
   // Note: "any" is not an accepted type.
   static const struct {
     const char* schema_type;
     base::Value::Type value_type;
   } kSchemaToValueTypeMap[] = {
     { json_schema_constants::kArray,        base::Value::TYPE_LIST       },
     { json_schema_constants::kBoolean,      base::Value::TYPE_BOOLEAN    },
     { json_schema_constants::kInteger,      base::Value::TYPE_INTEGER    },
     { json_schema_constants::kNull,         base::Value::TYPE_NULL       },
     { json_schema_constants::kNumber,       base::Value::TYPE_DOUBLE     },
     { json_schema_constants::kObject,       base::Value::TYPE_DICTIONARY },
     { json_schema_constants::kString,       base::Value::TYPE_STRING     },
   };
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(kSchemaToValueTypeMap); ++i) {
     if (kSchemaToValueTypeMap[i].schema_type == type_string) {
       *type = kSchemaToValueTypeMap[i].value_type;
       return true;
     }
   }
   return false;
 }
 
 }  // namespace
 
-Schema::Iterator::Iterator(const internal::PropertiesNode* properties)
-    : it_(properties->begin),
-      end_(properties->end) {}
+// A SchemaOwner can either Wrap() a SchemaData owned elsewhere (currently used
+// to wrap the Chrome schema, which is generated at compile time), or it can
+// own its own SchemaData. In that case, the Internal class holds the data
+// referenced by the SchemaData substructures.
+class SchemaOwner::Internal {
+ public:
+  Internal() {}
+  ~Internal() {}
+
+  SchemaData schema_data;
+  // TODO: compute the sizes of these arrays before filling them up to avoid
+  // having to resize them.
+  ScopedVector<std::string> strings;
+  std::vector<SchemaNode> schema_nodes;
+  std::vector<PropertyNode> property_nodes;
+  std::vector<PropertiesNode> properties_nodes;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Internal);
+};
+
+Schema::Iterator::Iterator(const SchemaData* data, const PropertiesNode* node)
+    : data_(data),
+      it_(data->property_nodes + node->begin),
+      end_(data->property_nodes + node->end) {}
 
 Schema::Iterator::Iterator(const Iterator& iterator)
-    : it_(iterator.it_),
+    : data_(iterator.data_),
+      it_(iterator.it_),
       end_(iterator.end_) {}
 
 Schema::Iterator::~Iterator() {}
 
 Schema::Iterator& Schema::Iterator::operator=(const Iterator& iterator) {
+  data_ = iterator.data_;
   it_ = iterator.it_;
   end_ = iterator.end_;
   return *this;
 }
 
 bool Schema::Iterator::IsAtEnd() const {
   return it_ == end_;
 }
 
 void Schema::Iterator::Advance() {
   ++it_;
 }
 
 const char* Schema::Iterator::key() const {
   return it_->key;
 }
 
 Schema Schema::Iterator::schema() const {
-  return Schema(it_->schema);
+  return Schema(data_, data_->schema_nodes + it_->schema);
 }
 
-Schema::Schema() : schema_(NULL) {}
+Schema::Schema() : data_(NULL), node_(NULL) {}
 
-Schema::Schema(const internal::SchemaNode* schema) : schema_(schema) {}
+Schema::Schema(const SchemaData* data, const SchemaNode* node)
+    : data_(data), node_(node) {}
 
-Schema::Schema(const Schema& schema) : schema_(schema.schema_) {}
+Schema::Schema(const Schema& schema)
+    : data_(schema.data_), node_(schema.node_) {}
 
 Schema& Schema::operator=(const Schema& schema) {
-  schema_ = schema.schema_;
+  data_ = schema.data_;
+  node_ = schema.node_;
   return *this;
 }
 
 base::Value::Type Schema::type() const {
   CHECK(valid());
-  return schema_->type;
+  return node_->type;
 }
 
 Schema::Iterator Schema::GetPropertiesIterator() const {
   CHECK(valid());
   CHECK_EQ(base::Value::TYPE_DICTIONARY, type());
-  return Iterator(
-      static_cast<const internal::PropertiesNode*>(schema_->extra));
+  return Iterator(data_, data_->properties_nodes + node_->extra);
 }
 
 namespace {
 
-bool CompareKeys(const internal::PropertyNode& node, const std::string& key) {
+bool CompareKeys(const PropertyNode& node, const std::string& key) {
   return node.key < key;
 }
 
 }  // namespace
 
 Schema Schema::GetKnownProperty(const std::string& key) const {
   CHECK(valid());
   CHECK_EQ(base::Value::TYPE_DICTIONARY, type());
-  const internal::PropertiesNode* properties_node =
-      static_cast<const internal::PropertiesNode*>(schema_->extra);
-  const internal::PropertyNode* it = std::lower_bound(
-      properties_node->begin, properties_node->end, key, CompareKeys);
-  if (it != properties_node->end && it->key == key)
-    return Schema(it->schema);
+  const PropertiesNode* node = data_->properties_nodes + node_->extra;
+  const PropertyNode* begin = data_->property_nodes + node->begin;
+  const PropertyNode* end = data_->property_nodes + node->end;
+  const PropertyNode* it = std::lower_bound(begin, end, key, CompareKeys);
+  if (it != end && it->key == key)
+    return Schema(data_, data_->schema_nodes + it->schema);
   return Schema();
 }
 
 Schema Schema::GetAdditionalProperties() const {
   CHECK(valid());
   CHECK_EQ(base::Value::TYPE_DICTIONARY, type());
-  return Schema(
-      static_cast<const internal::PropertiesNode*>(schema_->extra)->additional);
+  const PropertiesNode* node = data_->properties_nodes + node_->extra;
+  if (node->additional == kInvalid)
+    return Schema();
+  return Schema(data_, data_->schema_nodes + node->additional);
 }
 
 Schema Schema::GetProperty(const std::string& key) const {
   Schema schema = GetKnownProperty(key);
   return schema.valid() ? schema : GetAdditionalProperties();
 }
 
 Schema Schema::GetItems() const {
   CHECK(valid());
   CHECK_EQ(base::Value::TYPE_LIST, type());
-  return Schema(static_cast<const internal::SchemaNode*>(schema_->extra));
+  if (node_->extra == kInvalid)
+    return Schema();
+  return Schema(data_, data_->schema_nodes + node_->extra);
 }
 
-SchemaOwner::SchemaOwner(const internal::SchemaNode* root) : root_(root) {}
+SchemaOwner::SchemaOwner(const SchemaData* data, scoped_ptr<Internal> internal)
+    : internal_(internal.Pass()), data_(data) {}
 
-SchemaOwner::~SchemaOwner() {
-  for (size_t i = 0; i < property_nodes_.size(); ++i)
-    delete[] property_nodes_[i];
+SchemaOwner::~SchemaOwner() {}
+
+Schema SchemaOwner::schema() const {
+  // data_->schema_nodes[0] is the root node.
+  return Schema(data_, data_->schema_nodes + 0);

[pastarmovj, 2013/10/22 09:30:46]

I don't think this "+ 0" really adds much value here.

[Joao da Silva, 2013/10/22 12:53:27]

Done.

 }
 
 // static
-scoped_ptr<SchemaOwner> SchemaOwner::Wrap(const internal::SchemaNode* schema) {
-  return scoped_ptr<SchemaOwner>(new SchemaOwner(schema));
+scoped_ptr<SchemaOwner> SchemaOwner::Wrap(const SchemaData* data) {
+  return make_scoped_ptr(new SchemaOwner(data, scoped_ptr<Internal>()));
 }
 
 // static
 scoped_ptr<SchemaOwner> SchemaOwner::Parse(const std::string& content,
                                            std::string* error) {
   // Validate as a generic JSON schema.
   scoped_ptr<base::DictionaryValue> dict =
       JSONSchemaValidator::IsValidSchema(content, error);
   if (!dict)
     return scoped_ptr<SchemaOwner>();
 
   // Validate the main type.
   std::string string_value;
   if (!dict->GetString(json_schema_constants::kType, &string_value) ||
       string_value != json_schema_constants::kObject) {
     *error =
         "The main schema must have a type attribute with \"object\" value.";
     return scoped_ptr<SchemaOwner>();
   }
 
   // Checks for invalid attributes at the top-level.
   if (dict->HasKey(json_schema_constants::kAdditionalProperties) ||
       dict->HasKey(json_schema_constants::kPatternProperties)) {
     *error = "\"additionalProperties\" and \"patternProperties\" are not "
              "supported at the main schema.";
     return scoped_ptr<SchemaOwner>();
   }
 
-  scoped_ptr<SchemaOwner> impl(new SchemaOwner(NULL));
-  impl->root_ = impl->Parse(*dict, error);
-  if (!impl->root_)
-    impl.reset();
-  return impl.PassAs<SchemaOwner>();
+  scoped_ptr<Internal> internal(new Internal);
+  if (Parse(*dict, error, internal.get()) == kInvalid)
+    return scoped_ptr<SchemaOwner>();
+  SchemaData* data = &internal->schema_data;
+  data->schema_nodes = vector_as_array(&internal->schema_nodes);
+  data->property_nodes = vector_as_array(&internal->property_nodes);
+  data->properties_nodes = vector_as_array(&internal->properties_nodes);
+  return make_scoped_ptr(new SchemaOwner(data, internal.Pass()));
 }
 
-const internal::SchemaNode* SchemaOwner::Parse(
+// static
+int SchemaOwner::Parse(
     const base::DictionaryValue& schema,
-    std::string* error) {
+    std::string* error,
+    Internal* internal) {
   std::string type_string;
   if (!schema.GetString(json_schema_constants::kType, &type_string)) {
     *error = "The schema type must be declared.";
-    return NULL;
+    return kInvalid;
   }
 
   base::Value::Type type = base::Value::TYPE_NULL;
   if (!SchemaTypeToValueType(type_string, &type)) {
     *error = "Type not supported: " + type_string;
-    return NULL;
+    return kInvalid;
   }
 
   if (type == base::Value::TYPE_DICTIONARY)
-    return ParseDictionary(schema, error);
+    return ParseDictionary(schema, error, internal);
   if (type == base::Value::TYPE_LIST)
-    return ParseList(schema, error);
+    return ParseList(schema, error, internal);
 
-  internal::SchemaNode* node = new internal::SchemaNode;
-  node->type = type;
-  node->extra = NULL;
-  schema_nodes_.push_back(node);
-  return node;
+  int index = static_cast<int>(internal->schema_nodes.size());
+  internal->schema_nodes.push_back(SchemaNode());
+  SchemaNode& node = internal->schema_nodes.back();
+  node.type = type;
+  node.extra = kInvalid;
+  return index;
 }
 
-const internal::SchemaNode* SchemaOwner::ParseDictionary(
+// static
+int SchemaOwner::ParseDictionary(
     const base::DictionaryValue& schema,
-    std::string* error) {
-  internal::PropertiesNode* properties_node = new internal::PropertiesNode;
-  properties_node->begin = NULL;
-  properties_node->end = NULL;
-  properties_node->additional = NULL;
-  properties_nodes_.push_back(properties_node);
+    std::string* error,
+    Internal* internal) {
+  // Note: recursive calls to Parse() invalidate iterators and references into
+  // the vectors.
+
+  // Reserve an index for this dictionary at the front, so that the root node
+  // is at index 0.
+  int index = static_cast<int>(internal->schema_nodes.size());
+  internal->schema_nodes.push_back(SchemaNode());
+
+  int extra = static_cast<int>(internal->properties_nodes.size());
+  internal->properties_nodes.push_back(PropertiesNode());
+  internal->properties_nodes[extra].begin = kInvalid;
+  internal->properties_nodes[extra].end = kInvalid;
+  internal->properties_nodes[extra].additional = kInvalid;
 
   const base::DictionaryValue* dict = NULL;

[dconnelly, 2013/10/22 11:55:52]

Can these be moved closer to their first use?

[Joao da Silva, 2013/10/22 12:53:27]

Done.

   const base::DictionaryValue* properties = NULL;
+
+  if (schema.GetDictionary(json_schema_constants::kAdditionalProperties,
+                           &dict)) {
+    int additional = Parse(*dict, error, internal);
+    if (additional == kInvalid)
+      return kInvalid;
+    internal->properties_nodes[extra].additional = additional;
+  }
+
   if (schema.GetDictionary(json_schema_constants::kProperties, &properties)) {
-    internal::PropertyNode* property_nodes =
-        new internal::PropertyNode[properties->size()];
-    property_nodes_.push_back(property_nodes);
+    int base_index = static_cast<int>(internal->property_nodes.size());
+    // This reserves nodes for all of the |properties|, and makes sure they
+    // are contiguous. Recursive calls to Parse() will append after these
+    // elements.
+    internal->property_nodes.resize(base_index + properties->size());
 
-    size_t index = 0;
+    int index = base_index;

[pastarmovj, 2013/10/22 09:30:46]

Just a warning that this redefines the variable index declared at line 268. It
seems safe but I'd rather avoid it to make the code easier to understand and
debug.

[Joao da Silva, 2013/10/22 12:53:27]

Renamed the outer "index" to "schema_index".

     for (base::DictionaryValue::Iterator it(*properties);
          !it.IsAtEnd(); it.Advance(), ++index) {
       // This should have been verified by the JSONSchemaValidator.
       CHECK(it.value().GetAsDictionary(&dict));
-      const internal::SchemaNode* sub_schema = Parse(*dict, error);
-      if (!sub_schema)
-        return NULL;
-      std::string* key = new std::string(it.key());
-      keys_.push_back(key);
-      property_nodes[index].key = key->c_str();
-      property_nodes[index].schema = sub_schema;
+      int extra = Parse(*dict, error, internal);
+      if (extra == kInvalid)
+        return kInvalid;
+      internal->strings.push_back(new std::string(it.key()));
+      internal->property_nodes[index].key = internal->strings.back()->c_str();
+      internal->property_nodes[index].schema = extra;
     }
-    CHECK_EQ(properties->size(), index);
-    properties_node->begin = property_nodes;
-    properties_node->end = property_nodes + index;
+    CHECK_EQ(static_cast<int>(properties->size()), index - base_index);
+    internal->properties_nodes[extra].begin = base_index;
+    internal->properties_nodes[extra].end = index;
   }
 
-  if (schema.GetDictionary(json_schema_constants::kAdditionalProperties,
-                           &dict)) {
-    const internal::SchemaNode* sub_schema = Parse(*dict, error);
-    if (!sub_schema)
-      return NULL;
-    properties_node->additional = sub_schema;
-  }
-
-  internal::SchemaNode* schema_node = new internal::SchemaNode;
-  schema_node->type = base::Value::TYPE_DICTIONARY;
-  schema_node->extra = properties_node;
-  schema_nodes_.push_back(schema_node);
-  return schema_node;
+  internal->schema_nodes[index].type = base::Value::TYPE_DICTIONARY;
+  internal->schema_nodes[index].extra = extra;
+  return index;
 }
 
-const internal::SchemaNode* SchemaOwner::ParseList(
+// static
+int SchemaOwner::ParseList(
     const base::DictionaryValue& schema,
-    std::string* error) {
+    std::string* error,
+    Internal* internal) {
   const base::DictionaryValue* dict = NULL;
   if (!schema.GetDictionary(json_schema_constants::kItems, &dict)) {
     *error = "Arrays must declare a single schema for their items.";
-    return NULL;
+    return kInvalid;
   }
-  const internal::SchemaNode* items_schema_node = Parse(*dict, error);
-  if (!items_schema_node)
-    return NULL;
-
-  internal::SchemaNode* schema_node = new internal::SchemaNode;
-  schema_node->type = base::Value::TYPE_LIST;
-  schema_node->extra = items_schema_node;
-  schema_nodes_.push_back(schema_node);
-  return schema_node;
+  int extra = Parse(*dict, error, internal);
+  if (extra == kInvalid)
+    return kInvalid;
+  int index = static_cast<int>(internal->schema_nodes.size());
+  internal->schema_nodes.push_back(SchemaNode());
+  internal->schema_nodes[index].type = base::Value::TYPE_LIST;
+  internal->schema_nodes[index].extra = extra;
+  return index;
 }
 
 }  // namespace policy