Introduce prepareJavaScript jsi API

Summary:
This adds a new jsi API prepareJavaScript. This accepts the same
parameters as evaluateJavaScript() but does not evaluate anything; instead
it returns a new object PreparedJavaScript which can itself be evaluated,
via the new API evaluatePreparedJavaScript().

There is a new empty class PreparedJavaScript which may be subclassed by
each Runtime variant to store its particular prepared form.

Reviewed By: mhorowitz

Differential Revision: D10491585

fbshipit-source-id: 702b9e23f2ff03d71a8ab17efb7e154b16dd8e87

React/React.xcodeproj/project.pbxproj

@@ -794,6 +794,9 @@
 		3DFE0D1B1DF8575800459392 /* YGMacros.h in Copy Headers */ = {isa = PBXBuildFile; fileRef = 130A77041DF767AF001F9587 /* YGMacros.h */; };
 		3DFE0D1C1DF8575800459392 /* Yoga.h in Copy Headers */ = {isa = PBXBuildFile; fileRef = 130A77081DF767AF001F9587 /* Yoga.h */; };
 		3EDCA8A51D3591E700450C31 /* RCTErrorInfo.m in Sources */ = {isa = PBXBuildFile; fileRef = 3EDCA8A41D3591E700450C31 /* RCTErrorInfo.m */; };
+		4F56C93822167A4800DB9F3F /* jsilib.h in Headers */ = {isa = PBXBuildFile; fileRef = 4F56C93722167A4800DB9F3F /* jsilib.h */; };
+		4F56C93922167A4D00DB9F3F /* jsilib.h in Copy Headers */ = {isa = PBXBuildFile; fileRef = 4F56C93722167A4800DB9F3F /* jsilib.h */; };
+		4F56C93A2216A3B700DB9F3F /* jsilib.h in Copy Headers */ = {isa = PBXBuildFile; fileRef = 4F56C93722167A4800DB9F3F /* jsilib.h */; };
 		50E98FEA21460B0D00CD9289 /* RCTWKWebViewManager.m in Sources */ = {isa = PBXBuildFile; fileRef = 50E98FE621460B0D00CD9289 /* RCTWKWebViewManager.m */; };
 		50E98FEB21460B0D00CD9289 /* RCTWKWebView.h in Headers */ = {isa = PBXBuildFile; fileRef = 50E98FE721460B0D00CD9289 /* RCTWKWebView.h */; };
 		50E98FEC21460B0D00CD9289 /* RCTWKWebView.m in Sources */ = {isa = PBXBuildFile; fileRef = 50E98FE821460B0D00CD9289 /* RCTWKWebView.m */; };
@@ -1753,6 +1756,7 @@
 				ED296FC7214C9B4B00B7C4FE /* instrumentation.h in Copy Headers */,
 				ED296FC6214C9B4400B7C4FE /* JSIDynamic.h in Copy Headers */,
 				ED296FC5214C9B3E00B7C4FE /* jsi-inl.h in Copy Headers */,
+				4F56C93A2216A3B700DB9F3F /* jsilib.h in Copy Headers */,
 			);
 			name = "Copy Headers";
 			runOnlyForDeploymentPostprocessing = 0;
@@ -1780,6 +1784,7 @@
 				EDEBC71D214B40F900DD5AC8 /* JSIDynamic.h in Copy Headers */,
 				EDEBC71E214B40F900DD5AC8 /* JSCRuntime.h in Copy Headers */,
 				EDEBC71F214B40F900DD5AC8 /* jsi.h in Copy Headers */,
+				4F56C93922167A4D00DB9F3F /* jsilib.h in Copy Headers */,
 			);
 			name = "Copy Headers";
 			runOnlyForDeploymentPostprocessing = 0;
@@ -2058,6 +2063,7 @@
 		3EDCA8A21D3591E700450C31 /* RCTErrorCustomizer.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RCTErrorCustomizer.h; sourceTree = "<group>"; };
 		3EDCA8A31D3591E700450C31 /* RCTErrorInfo.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RCTErrorInfo.h; sourceTree = "<group>"; };
 		3EDCA8A41D3591E700450C31 /* RCTErrorInfo.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RCTErrorInfo.m; sourceTree = "<group>"; };
+		4F56C93722167A4800DB9F3F /* jsilib.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = jsilib.h; sourceTree = "<group>"; };
 		50E98FE621460B0D00CD9289 /* RCTWKWebViewManager.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RCTWKWebViewManager.m; sourceTree = "<group>"; };
 		50E98FE721460B0D00CD9289 /* RCTWKWebView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RCTWKWebView.h; sourceTree = "<group>"; };
 		50E98FE821460B0D00CD9289 /* RCTWKWebView.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RCTWKWebView.m; sourceTree = "<group>"; };
@@ -3040,6 +3046,7 @@
 				EDEBC6DF214B3F6800DD5AC8 /* BUCK */,
 				EDEBC6E0214B3F6800DD5AC8 /* instrumentation.h */,
 				EDEBC6E1214B3F6800DD5AC8 /* jsi.h */,
+				4F56C93722167A4800DB9F3F /* jsilib.h */,
 			);
 			path = jsi;
 			sourceTree = "<group>";
@@ -3590,6 +3597,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				EDEBC6E9214B3F6800DD5AC8 /* jsi.h in Headers */,
+				4F56C93822167A4800DB9F3F /* jsilib.h in Headers */,
 				EDEBC6E7214B3F6800DD5AC8 /* JSCRuntime.h in Headers */,
 				EDEBC6E5214B3F6800DD5AC8 /* JSIDynamic.h in Headers */,
 				EDEBC6E2214B3F6800DD5AC8 /* jsi-inl.h in Headers */,

ReactCommon/jsi/BUCK

@@ -12,6 +12,7 @@ rn_xplat_cxx_library(
         "instrumentation.h",
         "jsi.h",
         "jsi-inl.h",
+        "jsilib.h",
     ],
     compiler_flags = [
         "-O3",

ReactCommon/jsi/JSCRuntime.cpp

@@ -9,6 +9,7 @@
 #include <atomic>
 #include <condition_variable>
 #include <cstdlib>
+#include <jsi/jsilib.h>
 #include <mutex>
 #include <queue>
 #include <sstream>
@@ -36,6 +37,13 @@ class JSCRuntime : public jsi::Runtime {
   JSCRuntime(JSGlobalContextRef ctx);
   ~JSCRuntime();
 
+  std::shared_ptr<const jsi::PreparedJavaScript> prepareJavaScript(
+      const std::shared_ptr<const jsi::Buffer> &buffer,
+      std::string sourceURL) override;
+
+  void evaluatePreparedJavaScript(
+    const std::shared_ptr<const jsi::PreparedJavaScript>& js) override;
+
   void evaluateJavaScript(
       const std::shared_ptr<const jsi::Buffer> &buffer,
       const std::string& sourceURL) override;
@@ -318,6 +326,23 @@ JSCRuntime::~JSCRuntime() {
 #endif
 }
 
+std::shared_ptr<const jsi::PreparedJavaScript> JSCRuntime::prepareJavaScript(
+    const std::shared_ptr<const jsi::Buffer> &buffer,
+    std::string sourceURL) {
+  return std::make_shared<jsi::SourceJavaScriptPreparation>(
+      buffer, std::move(sourceURL));
+}
+
+void JSCRuntime::evaluatePreparedJavaScript(
+  const std::shared_ptr<const jsi::PreparedJavaScript>& js) {
+  assert(
+      dynamic_cast<const jsi::SourceJavaScriptPreparation*>(js.get()) &&
+      "preparedJavaScript must be a SourceJavaScriptPreparation");
+  auto sourceJs =
+      std::static_pointer_cast<const jsi::SourceJavaScriptPreparation>(js);
+  evaluateJavaScript(sourceJs, sourceJs->sourceURL());
+}
+
 void JSCRuntime::evaluateJavaScript(
     const std::shared_ptr<const jsi::Buffer> &buffer,
     const std::string& sourceURL) {

ReactCommon/jsi/jsi.cpp

@@ -24,6 +24,8 @@ void throwJSError(Runtime& rt, const char* msg) {
 
 Buffer::~Buffer() {}
 
+PreparedJavaScript::~PreparedJavaScript() = default;
+
 Value HostObject::get(Runtime&, const PropNameID&) {
   return Value();
 }

ReactCommon/jsi/jsi.h

@@ -52,6 +52,18 @@ class StringBuffer : public Buffer {
   std::string s_;
 };
 
+/// PreparedJavaScript is a base class repesenting JavaScript which is in a form
+/// optimized for execution, in a runtime-specific way. Construct one via
+/// jsi::Runtime::prepareJavaScript().
+/// ** This is an experimental API that is subject to change. **
+class PreparedJavaScript {
+ protected:
+  PreparedJavaScript() = default;
+
+ public:
+  virtual ~PreparedJavaScript() = 0;
+};
+
 class Runtime;
 class Pointer;
 class PropNameID;
@@ -145,6 +157,25 @@ class Runtime {
   virtual void evaluateJavaScript(
       const std::shared_ptr<const Buffer>& buffer,
       const std::string& sourceURL) = 0;
+
+  /// Prepares to evaluate the given JavaScript \c buffer by processing it into
+  /// a form optimized for execution. This may include pre-parsing, compiling,
+  /// etc. If the input is invalid (for example, cannot be parsed), a
+  /// JSIException will be thrown. The resulting object is tied to the
+  /// particular concrete type of Runtime from which it was created. It may be
+  /// used (via evaluatePreparedJavaScript) in any Runtime of the same concrete
+  /// type.
+  /// The PreparedJavaScript object may be passed to multiple VM instances, so
+  /// they can all share and benefit from the prepared script.
+  virtual std::shared_ptr<const PreparedJavaScript> prepareJavaScript(
+      const std::shared_ptr<const Buffer>& buffer,
+      std::string sourceURL) = 0;
+
+  /// Evaluates a PreparedJavaScript. If evaluation causes an error, a
+  /// JSIException will be thrown.
+  virtual void evaluatePreparedJavaScript(
+      const std::shared_ptr<const PreparedJavaScript>& js) = 0;
+
   /// \return the global object
   virtual Object global() = 0;
 
@@ -304,8 +335,8 @@ class PropNameID : public Pointer {
  public:
   using Pointer::Pointer;
 
-  PropNameID(Runtime &runtime, const PropNameID &other)
-      : Pointer(runtime.clonePropNameID(other.ptr_)) {}
+  PropNameID(Runtime& runtime, const PropNameID& other)
+      : PropNameID(runtime.clonePropNameID(other.ptr_)) {}
 
   PropNameID(PropNameID&& other) = default;
   PropNameID& operator=(PropNameID&& other) = default;
@@ -1031,13 +1062,7 @@ class Value {
   ValueKind kind_;
   Data data_;
 
-  // In the future: Value becomes NaN-boxed.  In the Hermes impl, if
-  // the object contains a PinnedHermesValue, we need to be able to
-  // get a pointer to it; this can be casted from 'this'.  In the JSC
-  // impl, we need to be able to convert the boxed value into a JSC
-  // ref.  This can be done by casting this, deferencing it to get a
-  // number, doing some bit masks, and then casting again into the
-  // desired JSC ref type.
+  // In the future: Value becomes NaN-boxed. See T40538354.
 };
 
 /// Not movable and not copyable RAII marker advising the underlying

ReactCommon/jsi/jsilib.h

@@ -0,0 +1,57 @@
+//  Copyright (c) Facebook, Inc. and its affiliates.
+//
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+
+#pragma once
+
+#include <jsi/jsi.h>
+
+namespace facebook {
+namespace jsi {
+
+class FileBuffer : public Buffer {
+ public:
+  FileBuffer(const std::string& path);
+  ~FileBuffer();
+
+  size_t size() const override {
+    return size_;
+  }
+
+  const uint8_t* data() const override {
+    return data_;
+  }
+
+ private:
+  size_t size_;
+  uint8_t* data_;
+};
+
+// A trivial implementation of PreparedJavaScript that simply stores the source
+// buffer and URL.
+class SourceJavaScriptPreparation final : public jsi::PreparedJavaScript,
+                                          public jsi::Buffer {
+  std::shared_ptr<const jsi::Buffer> buf_;
+  std::string sourceURL_;
+
+ public:
+  SourceJavaScriptPreparation(
+      std::shared_ptr<const jsi::Buffer> buf,
+      std::string sourceURL)
+      : buf_(std::move(buf)), sourceURL_(std::move(sourceURL)) {}
+
+  const std::string& sourceURL() const {
+    return sourceURL_;
+  }
+
+  size_t size() const override {
+    return buf_->size();
+  }
+  const uint8_t* data() const override {
+    return buf_->data();
+  }
+};
+
+} // namespace jsi
+} // namespace facebook