Add new FileSourceProvider

Summary: Add a new interface to JSC that allows loading a file lazily from disk, i.e. using mmap, instead of loading the whole file upfront and copying into the VM.

Reviewed By: michalgr

Differential Revision: D3534042

fbshipit-source-id: 98b193cc7b7e33248073e2556ea94ce3391507c7

ReactCommon/cxxreact/Executor.h

@@ -7,6 +7,8 @@
 #include <string>
 #include <vector>
 
+#include <sys/mman.h>
+
 #include <folly/dynamic.h>
 
 #include "JSModulesUnbundle.h"
@@ -134,6 +136,68 @@ private:
   size_t m_size;
 };
 
+class JSBigMmapString : public JSBigString  {
+public:
+  enum class Encoding {
+    Unknown,
+    Ascii,
+    Utf8,
+    Utf16,
+  };
+
+
+  JSBigMmapString(int fd, size_t size, const uint8_t sha1[20], Encoding encoding) :
+    m_fd(fd),
+    m_size(size),
+    m_encoding(encoding),
+    m_str(nullptr)
+  {
+    memcpy(m_hash, sha1, 20);
+  }
+
+  ~JSBigMmapString() {
+    if (m_str) {
+      CHECK(munmap((void *)m_str, m_size) != -1);
+    }
+    close(m_fd);
+  }
+
+  bool isAscii() const override {
+    return m_encoding == Encoding::Ascii;
+  }
+
+  const char* c_str() const override {
+    if (!m_str) {
+      m_str = (const char *)mmap(0, m_size, PROT_READ, MAP_SHARED, m_fd, 0);
+      CHECK(m_str != MAP_FAILED);
+    }
+    return m_str;
+  }
+
+  size_t size() const override {
+    return m_size;
+  }
+
+  int fd() const {
+    return m_fd;
+  }
+
+  const uint8_t* hash() const {
+    return m_hash;
+  }
+
+  Encoding encoding() const {
+    return m_encoding;
+  }
+
+private:
+  int m_fd;
+  size_t m_size;
+  uint8_t m_hash[20];
+  Encoding m_encoding;
+  mutable const char *m_str;
+};
+
 class JSExecutor {
 public:
   /**

ReactCommon/cxxreact/JSCExecutor.cpp

@@ -253,10 +253,33 @@ void JSCExecutor::terminateOnJSVMThread() {
   m_context = nullptr;
 }
 
+#ifdef WITH_FBJSCEXTENSIONS
+static void loadApplicationSource(
+    const JSGlobalContextRef context,
+    const JSBigMmapString* script,
+    const std::string& sourceURL) {
+  String jsSourceURL(sourceURL.c_str());
+  bool is8bit = script->encoding() == JSBigMmapString::Encoding::Ascii || script->encoding() == JSBigMmapString::Encoding::Utf8;
+  JSSourceCodeRef sourceCode = JSCreateSourceCode(script->fd(), script->size(), jsSourceURL, script->hash(), is8bit);
+  evaluateSourceCode(context, sourceCode, jsSourceURL);
+  JSReleaseSourceCode(sourceCode);
+}
+#endif
+
 void JSCExecutor::loadApplicationScript(std::unique_ptr<const JSBigString> script, std::string sourceURL) throw(JSException) {
   SystraceSection s("JSCExecutor::loadApplicationScript",
                     "sourceURL", sourceURL);
 
+  #ifdef WITH_FBJSCEXTENSIONS
+  if (auto source = dynamic_cast<const JSBigMmapString *>(script.get())) {
+    loadApplicationSource(m_context, source, sourceURL);
+    bindBridge();
+    flush();
+    ReactMarker::logMarker("CREATE_REACT_CONTEXT_END");
+    return;
+  }
+  #endif
+
   #ifdef WITH_FBSYSTRACE
   fbsystrace_begin_section(
     TRACE_TAG_REACT_CXX_BRIDGE,

ReactCommon/cxxreact/JSCHelpers.cpp

@@ -44,47 +44,63 @@ JSValueRef evaluateScript(JSContextRef context, JSStringRef script, JSStringRef
   JSValueRef exn, result;
   result = JSEvaluateScript(context, script, NULL, source, 0, &exn);
   if (result == nullptr) {
-    Value exception = Value(context, exn);
-
-    std::string exceptionText = exception.toString().str();
-
-    // The null/empty-ness of source tells us if the JS came from a
-    // file/resource, or was a constructed statement.  The location
-    // info will include that source, if any.
-    std::string locationInfo = source != nullptr ? String::ref(source).str() : "";
-    Object exObject = exception.asObject();
-    auto line = exObject.getProperty("line");
-    if (line != nullptr && line.isNumber()) {
-      if (locationInfo.empty() && line.asInteger() != 1) {
-        // If there is a non-trivial line number, but there was no
-        // location info, we include a placeholder, and the line
-        // number.
-        locationInfo = folly::to<std::string>("<unknown file>:", line.asInteger());
-      } else if (!locationInfo.empty()) {
-        // If there is location info, we always include the line
-        // number, regardless of its value.
-        locationInfo += folly::to<std::string>(":", line.asInteger());
-      }
-    }
-
-    if (!locationInfo.empty()) {
-      exceptionText += " (" + locationInfo + ")";
-    }
-
-    LOG(ERROR) << "Got JS Exception: " << exceptionText;
-
-    Value jsStack = exObject.getProperty("stack");
-    if (jsStack.isNull() || !jsStack.isString()) {
-      throwJSExecutionException("%s", exceptionText.c_str());
-    } else {
-      LOG(ERROR) << "Got JS Stack: " << jsStack.toString().str();
-      throwJSExecutionExceptionWithStack(
-        exceptionText.c_str(), jsStack.toString().str().c_str());
-    }
+    formatAndThrowJSException(context, exn, source);
   }
   return result;
 }
 
+#if WITH_FBJSCEXTENSIONS
+JSValueRef evaluateSourceCode(JSContextRef context, JSSourceCodeRef source, JSStringRef sourceURL) {
+  JSValueRef exn, result;
+  result = JSEvaluateSourceCode(context, source, NULL, &exn);
+  if (result == nullptr) {
+    formatAndThrowJSException(context, exn, sourceURL);
+  }
+  return result;
+}
+#endif
+
+void formatAndThrowJSException(JSContextRef context, JSValueRef exn, JSStringRef source) {
+  Value exception = Value(context, exn);
+
+  std::string exceptionText = exception.toString().str();
+
+  // The null/empty-ness of source tells us if the JS came from a
+  // file/resource, or was a constructed statement.  The location
+  // info will include that source, if any.
+  std::string locationInfo = source != nullptr ? String::ref(source).str() : "";
+  Object exObject = exception.asObject();
+  auto line = exObject.getProperty("line");
+  if (line != nullptr && line.isNumber()) {
+    if (locationInfo.empty() && line.asInteger() != 1) {
+      // If there is a non-trivial line number, but there was no
+      // location info, we include a placeholder, and the line
+      // number.
+      locationInfo = folly::to<std::string>("<unknown file>:", line.asInteger());
+    } else if (!locationInfo.empty()) {
+      // If there is location info, we always include the line
+      // number, regardless of its value.
+      locationInfo += folly::to<std::string>(":", line.asInteger());
+    }
+  }
+
+  if (!locationInfo.empty()) {
+    exceptionText += " (" + locationInfo + ")";
+  }
+
+  LOG(ERROR) << "Got JS Exception: " << exceptionText;
+
+  Value jsStack = exObject.getProperty("stack");
+  if (jsStack.isNull() || !jsStack.isString()) {
+    throwJSExecutionException("%s", exceptionText.c_str());
+  } else {
+    LOG(ERROR) << "Got JS Stack: " << jsStack.toString().str();
+    throwJSExecutionExceptionWithStack(
+        exceptionText.c_str(), jsStack.toString().str().c_str());
+  }
+}
+
+
 JSValueRef makeJSError(JSContextRef ctx, const char *error) {
   JSValueRef nestedException = nullptr;
   JSValueRef args[] = { Value(ctx, String(error)) };

ReactCommon/cxxreact/JSCHelpers.h

@@ -49,6 +49,18 @@ JSValueRef evaluateScript(
     JSStringRef script,
     JSStringRef sourceURL);
 
+#if WITH_FBJSCEXTENSIONS
+JSValueRef evaluateSourceCode(
+    JSContextRef ctx,
+    JSSourceCodeRef source,
+    JSStringRef sourceURL);
+#endif
+
+void formatAndThrowJSException(
+    JSContextRef ctx,
+    JSValueRef exn,
+    JSStringRef sourceURL);
+
 JSValueRef makeJSError(JSContextRef ctx, const char *error);
 
 JSValueRef translatePendingCppExceptionToJSError(JSContextRef ctx, const char *exceptionLocation);