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[idl_parser] Improve symbols lookup thru parent namespaces (#6407)

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Added the new method LookupTableByName for searching symbols in parent namespaces.
This method speedup (x50 or greater) symbol resolution (enum or struct) in parent namespaces.
The speedup was measured without `table.empty()` guard condition.

This method should suppress fuzzer timeout issue without artificial limits for nested namespaces (https://oss-fuzz.com/testcase-detail/6244168439169024).

Additionally, this commit speedup (x5) the GetFullyQualifiedName method by removing unnecessary temporary std::string object.
This commit is contained in:
Vladimir Glavnyy
2021-01-20 03:49:24 +07:00
committed by GitHub
parent 91b0958c43
commit 75c859e98f
2 changed files with 37 additions and 16 deletions
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1
include/flatbuffers/idl.h
View File

@@ -856,6 +856,7 @@ class Parser : public ParserState {
flexbuffers::Builder *builder);
StructDef *LookupStruct(const std::string &id) const;
StructDef *LookupStructThruParentNamespaces(const std::string &id) const;
std::string UnqualifiedName(const std::string &fullQualifiedName);

52
src/idl_parser.cpp
View File

@@ -227,9 +227,10 @@ std::string Namespace::GetFullyQualifiedName(const std::string &name,
if (components.empty() || !max_components) { return name; }
std::string stream_str;
for (size_t i = 0; i < std::min(components.size(), max_components); i++) {
if (i) { stream_str += '.'; }
stream_str += std::string(components[i]);
stream_str += components[i];
stream_str += '.';
}
if (!stream_str.empty()) stream_str.pop_back();
if (name.length()) {
stream_str += '.';
stream_str += name;
@@ -237,6 +238,29 @@ std::string Namespace::GetFullyQualifiedName(const std::string &name,
return stream_str;
}
template<typename T>
T *LookupTableByName(const SymbolTable<T> &table, const std::string &name,
const Namespace &current_namespace, size_t skip_top) {
const auto &components = current_namespace.components;
if (table.dict.empty()) return nullptr;
if (components.size() < skip_top) return nullptr;
const auto N = components.size() - skip_top;
std::string full_name;
for (size_t i = 0; i < N; i++) {
full_name += components[i];
full_name += '.';
}
for (size_t i = N; i > 0; i--) {
full_name += name;
auto obj = table.Lookup(full_name);
if (obj) return obj;
auto len = full_name.size() - components[i - 1].size() - 1 - name.size();
full_name.resize(len);
}
FLATBUFFERS_ASSERT(full_name.empty());
return table.Lookup(name); // lookup in global namespace
}
// Declare tokens we'll use. Single character tokens are represented by their
// ascii character code (e.g. '{'), others above 256.
// clang-format off
@@ -576,13 +600,7 @@ CheckedError Parser::ParseNamespacing(std::string *id, std::string *last) {
EnumDef *Parser::LookupEnum(const std::string &id) {
// Search thru parent namespaces.
for (int components = static_cast<int>(current_namespace_->components.size());
components >= 0; components--) {
auto ed = enums_.Lookup(
current_namespace_->GetFullyQualifiedName(id, components));
if (ed) return ed;
}
return nullptr;
return LookupTableByName(enums_, id, *current_namespace_, 0);
}
StructDef *Parser::LookupStruct(const std::string &id) const {
@@ -591,6 +609,13 @@ StructDef *Parser::LookupStruct(const std::string &id) const {
return sd;
}
StructDef *Parser::LookupStructThruParentNamespaces(
const std::string &id) const {
auto sd = LookupTableByName(structs_, id, *current_namespace_, 1);
if (sd) sd->refcount++;
return sd;
}
CheckedError Parser::ParseTypeIdent(Type &type) {
std::string id = attribute_;
EXPECT(kTokenIdentifier);
@@ -1980,13 +2005,8 @@ StructDef *Parser::LookupCreateStruct(const std::string &name,
}
return struct_def;
}
if (!definition) {
// Search thru parent namespaces.
for (size_t components = current_namespace_->components.size();
components && !struct_def; components--) {
struct_def = LookupStruct(
current_namespace_->GetFullyQualifiedName(name, components - 1));
}
if (!definition && !struct_def) {
struct_def = LookupStructThruParentNamespaces(name);
}
if (!struct_def && create_if_new) {
struct_def = new StructDef();