Nearly eliminate heap allocations required to resolve a NPIdentifier from a V8 string.

I'd like to / hope to put together some automated tests to focus on NPRuntime scripting.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@410 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 40 insertions, 18 deletions

diff --git a/webkit/port/bindings/v8/npruntime.cpp b/webkit/port/bindings/v8/npruntime.cpp
index 074fa46..f47790a 100644
--- a/webkit/port/bindings/v8/npruntime.cpp
+++ b/webkit/port/bindings/v8/npruntime.cpp
@@ -31,6 +31,7 @@
 #include <string>
 #include <v8.h>
 #include "base/stats_counters.h"
+#include "base/string_piece.h"
 #include "bindings/npruntime.h"
 #include "np_v8object.h"
 #include "npruntime_priv.h"
@@ -49,7 +50,7 @@ using namespace v8;
 // Need a platform abstraction which we can use.
 // static Lock StringIdentifierMapLock;
 
-typedef std::map<std::string, PrivateIdentifier*> StringIdentifierMap;
+typedef std::map<StringPiece, PrivateIdentifier*> StringIdentifierMap;
 
 static StringIdentifierMap* getStringIdentifierMap() {
     static StringIdentifierMap* stringIdentifierMap = 0;
@@ -78,18 +79,26 @@ NPIdentifier NPN_GetStringIdentifier(const NPUTF8* name) {
     if (name) {
         // AutoLock safeLock(StringIdentifierMapLock);
 
-        StringIdentifierMap::iterator iter =
-            getStringIdentifierMap()->find(std::string(name));
-        if (iter != getStringIdentifierMap()->end())
+        StringIdentifierMap* identMap = getStringIdentifierMap();
+
+        // We use StringPiece here as the key-type to avoid a string copy to
+        // construct the map key.
+        StringPiece nameStr(name);
+        StringIdentifierMap::iterator iter = identMap->find(nameStr);
+        if (iter != identMap->end())
             return static_cast<NPIdentifier>(iter->second);
 
-        PrivateIdentifier* identifier = reinterpret_cast<PrivateIdentifier*>(
-            malloc(sizeof(PrivateIdentifier)));
-        // We never release identifier names, so this dictionary will grow,
-        // as will the memory for the identifier name strings.
+        size_t nameLen = nameStr.length();
+
+        // We never release identifier names, so this dictionary will grow, as
+        // will the memory for the identifier name strings.
+        PrivateIdentifier* identifier = static_cast<PrivateIdentifier*>(
+            malloc(sizeof(PrivateIdentifier) + nameLen + 1));
+        memcpy(identifier + 1, name, nameLen + 1);
         identifier->isString = true;
-        identifier->value.string = strdup(name);
-        (*getStringIdentifierMap())[std::string(name)] = identifier;
+        identifier->value.string = reinterpret_cast<NPUTF8*>(identifier + 1);
+        (*identMap)[StringPiece(identifier->value.string, nameLen)] =
+            identifier;
         return (NPIdentifier)identifier;
     }
 
@@ -109,8 +118,10 @@ void NPN_GetStringIdentifiers(const NPUTF8** names, int32_t nameCount,
 NPIdentifier NPN_GetIntIdentifier(int32_t intid) {
     // AutoLock safeLock(IntIdentifierMapLock);
 
-    IntIdentifierMap::iterator iter = getIntIdentifierMap()->find(intid);
-    if (iter != getIntIdentifierMap()->end())
+    IntIdentifierMap* identMap = getIntIdentifierMap();
+
+    IntIdentifierMap::iterator iter = identMap->find(intid);
+    if (iter != identMap->end())
         return static_cast<NPIdentifier>(iter->second);
 
     PrivateIdentifier* identifier = reinterpret_cast<PrivateIdentifier*>(
@@ -118,7 +129,7 @@ NPIdentifier NPN_GetIntIdentifier(int32_t intid) {
     // We never release identifier names, so this dictionary will grow.
     identifier->isString = false;
     identifier->value.number = intid;
-    (*getIntIdentifierMap())[intid] = identifier;
+    (*identMap)[intid] = identifier;
     return (NPIdentifier)identifier;
 }
 
diff --git a/webkit/port/bindings/v8/v8_np_utils.cpp b/webkit/port/bindings/v8/v8_np_utils.cpp
index 06e02b8..3887460 100644
--- a/webkit/port/bindings/v8/v8_np_utils.cpp
+++ b/webkit/port/bindings/v8/v8_np_utils.cpp
@@ -31,6 +31,7 @@
 
 #include "v8_np_utils.h"
 
+#include "base/scoped_ptr.h"
 #include "base/string_util.h"
 #include "DOMWindow.h"
 #include "Frame.h"
@@ -118,9 +119,19 @@ v8::Handle<v8::Value> ConvertNPVariantToV8Object(const NPVariant* variant,
 
 // Helper function to create an NPN String Identifier from a v8 string.
 NPIdentifier GetStringIdentifier(v8::Handle<v8::String> str) {
-  char *buf = new char[str->Length() + 1];
-  str->WriteAscii(buf);
-  NPIdentifier ident = NPN_GetStringIdentifier(buf);
-  delete[] buf;
-  return ident;
+  const int kStackBufSize = 100;
+
+  int buf_len = str->Length() + 1;
+  if (buf_len <= kStackBufSize) {
+    // Use local stack buffer to avoid heap allocations for small strings.
+    // Here we should only use the stack space for stack_buf when it's used,
+    // not when we use the heap.
+    char stack_buf[kStackBufSize];
+    str->WriteAscii(stack_buf);
+    return NPN_GetStringIdentifier(stack_buf);
+  }
+
+  scoped_array<char> heap_buf(new char[buf_len]);
+  str->WriteAscii(heap_buf.get());
+  return NPN_GetStringIdentifier(heap_buf.get());
 }