commit d91d6d6a80748f277fd938a412211e5af28913b1
author Ian Rogers <irogers@google.com> Wed Sep 25 20:26:14 2013 -0700
committer Ian Rogers <irogers@google.com> Thu Sep 26 21:08:25 2013 -0700
tree 5c45f4ae53aab3f530284a97dc328b4e38ce7c94
parent 9c11b56296b8cffc94b0b854ce6cff7e014b8d57

Introduce Signature type to avoid string comparisons.

Method resolution currently creates strings to then compare with strings formed
from methods in other dex files. The temporary strings are purely created for
the sake of comparisons. This change creates a new Signature type that
represents a method signature but not as a string. This type supports
comparisons and so can be used when searching for methods in resolution.

With this change malloc is no longer the hottest method during dex2oat (now its
memset) and allocations during verification have been reduced. The verifier is
commonly what is populating the dex cache for methods and fields not declared
in the dex file itself.

Change-Id: I5ef0542823fbcae868aaa4a2457e8da7df0e9dae

runtime/dex_file.cc

diff --git a/runtime/dex_file.cc b/runtime/dex_file.cc
index 098ab67..275dcc5 100644
--- a/runtime/dex_file.cc
+++ b/runtime/dex_file.cc
@@ -503,8 +503,8 @@
 }
 
 // Given a signature place the type ids into the given vector
-bool DexFile::CreateTypeList(uint16_t* return_type_idx, std::vector<uint16_t>* param_type_idxs,
-                             const std::string& signature) const {
+bool DexFile::CreateTypeList(const StringPiece& signature, uint16_t* return_type_idx,
+                             std::vector<uint16_t>* param_type_idxs) const {
   if (signature[0] != '(') {
     return false;
   }
@@ -518,6 +518,7 @@
       process_return = true;
       continue;
     }
+    // TODO: avoid building a string.
     std::string descriptor;
     descriptor += c;
     while (c == '[') {  // process array prefix
@@ -557,35 +558,18 @@
   return false;  // failed to correctly parse return type
 }
 
-// Materializes the method descriptor for a method prototype.  Method
-// descriptors are not stored directly in the dex file.  Instead, one
-// must assemble the descriptor from references in the prototype.
-std::string DexFile::CreateMethodSignature(uint32_t proto_idx, int32_t* unicode_length) const {
-  const ProtoId& proto_id = GetProtoId(proto_idx);
-  std::string descriptor;
-  descriptor.push_back('(');
-  const TypeList* type_list = GetProtoParameters(proto_id);
-  size_t parameter_length = 0;
-  if (type_list != NULL) {
-    // A non-zero number of arguments.  Append the type names.
-    for (size_t i = 0; i < type_list->Size(); ++i) {
-      const TypeItem& type_item = type_list->GetTypeItem(i);
-      uint32_t type_idx = type_item.type_idx_;
-      uint32_t type_length;
-      const char* name = StringByTypeIdx(type_idx, &type_length);
-      parameter_length += type_length;
-      descriptor.append(name);
-    }
+const Signature DexFile::CreateSignature(const StringPiece& signature) const {
+  uint16_t return_type_idx;
+  std::vector<uint16_t> param_type_indices;
+  bool success = CreateTypeList(signature, &return_type_idx, &param_type_indices);
+  if (!success) {
+    return Signature::NoSignature();
   }
-  descriptor.push_back(')');
-  uint32_t return_type_idx = proto_id.return_type_idx_;
-  uint32_t return_type_length;
-  const char* name = StringByTypeIdx(return_type_idx, &return_type_length);
-  descriptor.append(name);
-  if (unicode_length != NULL) {
-    *unicode_length = parameter_length + return_type_length + 2;  // 2 for ( and )
+  const ProtoId* proto_id = FindProtoId(return_type_idx, param_type_indices);
+  if (proto_id == NULL) {
+    return Signature::NoSignature();
   }
-  return descriptor;
+  return Signature(this, *proto_id);
 }
 
 int32_t DexFile::GetLineNumFromPC(const mirror::ArtMethod* method, uint32_t rel_pc) const {
@@ -831,6 +815,30 @@
   }
 }
 
+std::string Signature::ToString() const {
+  if (dex_file_ == nullptr) {
+    CHECK(proto_id_ == nullptr);
+    return "<no signature>";
+  }
+  const DexFile::TypeList* params = dex_file_->GetProtoParameters(*proto_id_);
+  std::string result;
+  if (params == nullptr) {
+    result += "()";
+  } else {
+    result += "(";
+    for (uint32_t i = 0; i < params->Size(); ++i) {
+      result += dex_file_->StringByTypeIdx(params->GetTypeItem(i).type_idx_);
+    }
+    result += ")";
+  }
+  result += dex_file_->StringByTypeIdx(proto_id_->return_type_idx_);
+  return result;
+}
+
+std::ostream& operator<<(std::ostream& os, const Signature& sig) {
+  return os << sig.ToString();
+}
+
 // Decodes the header section from the class data bytes.
 void ClassDataItemIterator::ReadClassDataHeader() {
   CHECK(ptr_pos_ != NULL);