Use JSStringCreateWithUTF8CString and skip NSString decoding when loading the bundle

Summary: public

Benchmarking our startup path has shown we spend a lot of time decoding strings (iPhone 4S / iPhone 5):

* reading a 2MB JS bundle: 35ms / 15ms
* decoding is to an `NSString`: 186ms / 78ms
* transforming that to a `JSString`: 29ms / 10ms

Instead of going through an `NSString` transformation, we generate a null-terminated bundle (0.1ms / 0.05ms to copy the data) and use `JSStringCreateWithUTF8CString` (121ms / 53ms) to generate the string. That makes decoding 70% faster.

Reviewed By: javache

Differential Revision: D2541140

fb-gh-sync-id: 09a016b8edfd46a9b62682c76705564d2024e75e

Examples/UIExplorer/UIExplorerUnitTests/RCTContextExecutorTests.m

@@ -40,7 +40,7 @@
 - (void)testNativeLoggingHookExceptionBehavior
 {
   dispatch_semaphore_t doneSem = dispatch_semaphore_create(0);
-  [_executor executeApplicationScript:@"var x = {toString: function() { throw 1; }}; nativeLoggingHook(x);"
+  [_executor executeApplicationScript:[@"var x = {toString: function() { throw 1; }}; nativeLoggingHook(x);" dataUsingEncoding:NSUTF8StringEncoding]
                            sourceURL:[NSURL URLWithString:@"file://"]
                           onComplete:^(__unused id error){
                             dispatch_semaphore_signal(doneSem);
@@ -128,7 +128,7 @@ static uint64_t _get_time_nanoseconds(void)
     } \
   ";
 
-  [_executor executeApplicationScript:script sourceURL:[NSURL URLWithString:@"http://localhost:8081/"] onComplete:^(__unused NSError *error) {
+  [_executor executeApplicationScript:[script dataUsingEncoding:NSUTF8StringEncoding] sourceURL:[NSURL URLWithString:@"http://localhost:8081/"] onComplete:^(__unused NSError *error) {
     NSMutableArray *params = [NSMutableArray new];
     id data = @1;
     for (int i = 0; i < 4; i++) {

Libraries/WebSocket/RCTWebSocketExecutor.m

@@ -148,7 +148,7 @@ RCT_EXPORT_MODULE()
   });
 }
 
-- (void)executeApplicationScript:(NSString *)script sourceURL:(NSURL *)URL onComplete:(RCTJavaScriptCompleteBlock)onComplete
+- (void)executeApplicationScript:(NSData *)script sourceURL:(NSURL *)URL onComplete:(RCTJavaScriptCompleteBlock)onComplete
 {
   NSDictionary *message = @{
     @"method": @"executeApplicationScript",

React/Base/RCTBatchedBridge.m

@@ -116,8 +116,8 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
   dispatch_group_t initModulesAndLoadSource = dispatch_group_create();
   dispatch_group_enter(initModulesAndLoadSource);
   __weak RCTBatchedBridge *weakSelf = self;
-  __block NSString *sourceCode;
-  [self loadSource:^(NSError *error, NSString *source) {
+  __block NSData *sourceCode;
+  [self loadSource:^(NSError *error, NSData *source) {
     if (error) {
       dispatch_async(dispatch_get_main_queue(), ^{
         [weakSelf stopLoadingWithError:error];
@@ -184,7 +184,7 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
   RCTPerformanceLoggerStart(RCTPLScriptDownload);
   int cookie = RCTProfileBeginAsyncEvent(0, @"JavaScript download", nil);
 
-  RCTSourceLoadBlock onSourceLoad = ^(NSError *error, NSString *source) {
+  RCTSourceLoadBlock onSourceLoad = ^(NSError *error, NSData *source) {
     RCTProfileEndAsyncEvent(0, @"init,download", cookie, @"JavaScript download", nil);
     RCTPerformanceLoggerEnd(RCTPLScriptDownload);
 
@@ -195,12 +195,13 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
 
     // Force JS __DEV__ value to match RCT_DEBUG
     if (shouldOverrideDev) {
-      NSRange range = [source rangeOfString:@"__DEV__="];
+      NSString *sourceString = [[NSString alloc] initWithData:source encoding:NSUTF8StringEncoding];
+      NSRange range = [sourceString rangeOfString:@"__DEV__="];
       RCTAssert(range.location != NSNotFound, @"It looks like the implementation"
                 "of __DEV__ has changed. Update -[RCTBatchedBridge loadSource:].");
       NSRange valueRange = {range.location + range.length, 2};
-      if ([[source substringWithRange:valueRange] isEqualToString:@"!1"]) {
-        source = [source stringByReplacingCharactersInRange:valueRange withString:@" 1"];
+      if ([[sourceString substringWithRange:valueRange] isEqualToString:@"!1"]) {
+        source = [[sourceString stringByReplacingCharactersInRange:valueRange withString:@" 1"] dataUsingEncoding:NSUTF8StringEncoding];
       }
     }
 
@@ -355,7 +356,7 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
                              callback:onComplete];
 }
 
-- (void)executeSourceCode:(NSString *)sourceCode
+- (void)executeSourceCode:(NSData *)sourceCode
 {
   if (!self.valid || !_javaScriptExecutor) {
     return;
@@ -363,7 +364,7 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
 
   RCTSourceCode *sourceCodeModule = self.modules[RCTBridgeModuleNameForClass([RCTSourceCode class])];
   sourceCodeModule.scriptURL = self.bundleURL;
-  sourceCodeModule.scriptText = sourceCode;
+  sourceCodeModule.scriptData = sourceCode;
 
   [self enqueueApplicationScript:sourceCode url:self.bundleURL onComplete:^(NSError *loadError) {
     if (!self.isValid) {
@@ -585,7 +586,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
   }
 }
 
-- (void)enqueueApplicationScript:(NSString *)script
+- (void)enqueueApplicationScript:(NSData *)script
                              url:(NSURL *)url
                       onComplete:(RCTJavaScriptCompleteBlock)onComplete
 {

React/Base/RCTBridgeDelegate.h

@@ -7,7 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  */
 
-typedef void (^RCTSourceLoadBlock)(NSError *error, NSString *source);
+typedef void (^RCTSourceLoadBlock)(NSError *error, NSData *source);
 
 @class RCTBridge;
 

React/Base/RCTJavaScriptExecutor.h

@@ -46,7 +46,7 @@ typedef void (^RCTJavaScriptCallback)(id json, NSError *error);
 /**
  * Runs an application script, and notifies of the script load being complete via `onComplete`.
  */
-- (void)executeApplicationScript:(NSString *)script
+- (void)executeApplicationScript:(NSData *)script
                        sourceURL:(NSURL *)sourceURL
                       onComplete:(RCTJavaScriptCompleteBlock)onComplete;
 

React/Base/RCTJavaScriptLoader.m

@@ -36,8 +36,10 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
     NSString *filePath = scriptURL.path;
     dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       NSError *error = nil;
-      NSString *rawText = [NSString stringWithContentsOfFile:filePath usedEncoding:NULL error:&error];
-      onComplete(error, rawText);
+      NSData *source = [NSData dataWithContentsOfFile:filePath
+                                              options:NSDataReadingMappedIfSafe
+                                                error:&error];
+      onComplete(error, source);
     });
     return;
   }
@@ -71,10 +73,10 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
         encoding = CFStringConvertEncodingToNSStringEncoding(cfEncoding);
       }
     }
-    NSString *rawText = [[NSString alloc] initWithData:data encoding:encoding];
 
     // Handle HTTP errors
     if ([response isKindOfClass:[NSHTTPURLResponse class]] && ((NSHTTPURLResponse *)response).statusCode != 200) {
+      NSString *rawText = [[NSString alloc] initWithData:data encoding:encoding];
       NSDictionary *userInfo;
       NSDictionary *errorDetails = RCTJSONParse(rawText, nil);
       if ([errorDetails isKindOfClass:[NSDictionary class]] &&
@@ -101,7 +103,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
       onComplete(error, nil);
       return;
     }
-    onComplete(nil, rawText);
+    onComplete(nil, data);
   }];
 
   [task resume];

React/Executors/RCTContextExecutor.m

@@ -494,7 +494,7 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
   }), 0, @"js_call", (@{@"module":name, @"method": method, @"args": arguments}))];
 }
 
-- (void)executeApplicationScript:(NSString *)script
+- (void)executeApplicationScript:(NSData *)script
                        sourceURL:(NSURL *)sourceURL
                       onComplete:(RCTJavaScriptCompleteBlock)onComplete
 {
@@ -508,9 +508,15 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
       return;
     }
 
+    // JSStringCreateWithUTF8CString expects a null terminated C string
+    NSMutableData *nullTerminatedScript = [NSMutableData dataWithCapacity:script.length + 1];
+
+    [nullTerminatedScript appendData:script];
+    [nullTerminatedScript appendBytes:"" length:1];
+
     RCTPerformanceLoggerStart(RCTPLScriptExecution);
     JSValueRef jsError = NULL;
-    JSStringRef execJSString = JSStringCreateWithCFString((__bridge CFStringRef)script);
+    JSStringRef execJSString = JSStringCreateWithUTF8CString(nullTerminatedScript.bytes);
     JSStringRef jsURL = JSStringCreateWithCFString((__bridge CFStringRef)sourceURL.absoluteString);
     JSValueRef result = JSEvaluateScript(strongSelf->_context.ctx, execJSString, NULL, jsURL, 0, &jsError);
     JSStringRelease(jsURL);

React/Executors/RCTWebViewExecutor.m

@@ -130,7 +130,7 @@ RCT_EXPORT_MODULE()
  * debugger. So we have to use this (essentially) async API - and register
  * ourselves as the webview delegate to be notified when load is complete.
  */
-- (void)executeApplicationScript:(NSString *)script
+- (void)executeApplicationScript:(NSData *)script
                        sourceURL:(NSURL *)url
                       onComplete:(RCTJavaScriptCompleteBlock)onComplete
 {
@@ -142,6 +142,7 @@ RCT_EXPORT_MODULE()
   }
 
   RCTAssert(onComplete != nil, @"");
+  NSString *scriptString = [[NSString alloc] initWithData:script encoding:NSUTF8StringEncoding];
   __weak RCTWebViewExecutor *weakSelf = self;
   _onApplicationScriptLoaded = ^(NSError *error){
     RCTWebViewExecutor *strongSelf = weakSelf;
@@ -163,23 +164,23 @@ RCT_EXPORT_MODULE()
     }];
     [_objectsToInject removeAllObjects];
     [scriptWithInjections appendString:@"/* END NATIVELY INJECTED OBJECTS */\n"];
-    [scriptWithInjections appendString:script];
-    script = scriptWithInjections;
+    [scriptWithInjections appendString:scriptString];
+    scriptString = scriptWithInjections;
   }
 
-  script = [_commentsRegex stringByReplacingMatchesInString:script
-                                                    options:0
-                                                      range:NSMakeRange(0, script.length)
-                                               withTemplate:@""];
-  script = [_scriptTagsRegex stringByReplacingMatchesInString:script
-                                                      options:0
-                                                        range:NSMakeRange(0, script.length)
-                                                 withTemplate:@"\\\\<$1\\\\>"];
+  scriptString = [_commentsRegex stringByReplacingMatchesInString:scriptString
+                                                          options:0
+                                                            range:NSMakeRange(0, script.length)
+                                                     withTemplate:@""];
+  scriptString = [_scriptTagsRegex stringByReplacingMatchesInString:scriptString
+                                                            options:0
+                                                              range:NSMakeRange(0, script.length)
+                                                       withTemplate:@"\\\\<$1\\\\>"];
 
   NSString *runScript =
     [NSString
       stringWithFormat:@"<html><head></head><body><script type='text/javascript'>%@</script></body></html>",
-      script
+      scriptString
     ];
   [_webView loadHTMLString:runScript baseURL:url];
 }

React/Modules/RCTSourceCode.h

@@ -13,7 +13,7 @@
 
 @interface RCTSourceCode : NSObject <RCTBridgeModule>
 
-@property (nonatomic, copy) NSString *scriptText;
+@property (nonatomic, copy) NSData *scriptData;
 @property (nonatomic, copy) NSURL *scriptURL;
 
 @end

React/Modules/RCTSourceCode.m

@@ -27,8 +27,10 @@ RCT_EXPORT_MODULE()
 RCT_EXPORT_METHOD(getScriptText:(RCTResponseSenderBlock)successCallback
                   failureCallback:(RCTResponseErrorBlock)failureCallback)
 {
-  if (RCT_DEV && self.scriptText && self.scriptURL) {
-    successCallback(@[@{@"text": self.scriptText, @"url": self.scriptURL.absoluteString}]);
+  if (RCT_DEV && self.scriptData && self.scriptURL) {
+    NSString *scriptText = [[NSString alloc] initWithData:self.scriptData encoding:NSUTF8StringEncoding];
+
+    successCallback(@[@{@"text": scriptText, @"url": self.scriptURL.absoluteString}]);
   } else {
     failureCallback(RCTErrorWithMessage(@"Source code is not available"));
   }