Fix parseTypeFromHeader for Hermes bytecode

Summary: Changelog: [Internal] Fix bug where Hermes bytecode bundles were not always recognized

Reviewed By: motiz88

Differential Revision: D34718511

fbshipit-source-id: 5bbebe49962d098988d99153b0938fbb5d449ae6

React/Base/RCTJavaScriptLoader.h

@@ -11,10 +11,7 @@
 
 extern NSString *const RCTJavaScriptLoaderErrorDomain;
 
-extern const UInt32 RCT_BYTECODE_ALIGNMENT;
-
-UInt32 RCTReadUInt32LE(NSData *script, UInt32 offset);
-bool RCTIsBytecodeBundle(NSData *script);
+extern const uint32_t RCT_BYTECODE_ALIGNMENT;
 
 NS_ENUM(NSInteger){
     RCTJavaScriptLoaderErrorNoScriptURL = 1,

React/Base/RCTJavaScriptLoader.mm

@@ -19,19 +19,7 @@
 
 NSString *const RCTJavaScriptLoaderErrorDomain = @"RCTJavaScriptLoaderErrorDomain";
 
-const UInt32 RCT_BYTECODE_ALIGNMENT = 4;
-UInt32 RCTReadUInt32LE(NSData *script, UInt32 offset)
-{
-  return [script length] < offset + 4 ? 0 : CFSwapInt32LittleToHost(*(((uint32_t *)[script bytes]) + offset / 4));
-}
-
-bool RCTIsBytecodeBundle(NSData *script)
-{
-  static const UInt32 BYTECODE_BUNDLE_MAGIC_NUMBER = 0xffe7c3c3;
-  return (
-      [script length] > 8 && RCTReadUInt32LE(script, 0) == BYTECODE_BUNDLE_MAGIC_NUMBER &&
-      RCTReadUInt32LE(script, 4) > 0);
-}
+const uint32_t RCT_BYTECODE_ALIGNMENT = 4;
 
 @interface RCTSource () {
  @public
@@ -47,12 +35,18 @@ bool RCTIsBytecodeBundle(NSData *script)
 
 static RCTSource *RCTSourceCreate(NSURL *url, NSData *data, int64_t length) NS_RETURNS_RETAINED
 {
+  using facebook::react::ScriptTag;
+  facebook::react::BundleHeader header;
+  [data getBytes:&header length:sizeof(header)];
+
   RCTSource *source = [RCTSource new];
   source->_url = url;
   // Multipart responses may give us an unaligned view into the buffer. This ensures memory is aligned.
-  source->_data = (RCTIsBytecodeBundle(data) && ((long)[data bytes] % RCT_BYTECODE_ALIGNMENT))
-      ? [[NSData alloc] initWithData:data]
-      : data;
+  if (parseTypeFromHeader(header) == ScriptTag::MetroHBCBundle && ((long)[data bytes] % RCT_BYTECODE_ALIGNMENT)) {
+    source->_data = [[NSData alloc] initWithData:data];
+  } else {
+    source->_data = data;
+  }
   source->_length = length;
   source->_filesChangedCount = RCTSourceFilesChangedCountNotBuiltByBundler;
   return source;
@@ -177,7 +171,7 @@ RCT_NOT_IMPLEMENTED(-(instancetype)init)
 
   facebook::react::ScriptTag tag = facebook::react::parseTypeFromHeader(header);
   switch (tag) {
-    case facebook::react::ScriptTag::HBCBundle:
+    case facebook::react::ScriptTag::MetroHBCBundle:
     case facebook::react::ScriptTag::RAMBundle:
       break;
 

React/CxxBridge/RCTCxxBridge.mm

@@ -113,13 +113,6 @@ class GetDescAdapter : public JSExecutorFactory {
 
 }
 
-static bool isRAMBundle(NSData *script)
-{
-  BundleHeader header;
-  [script getBytes:&header length:sizeof(header)];
-  return parseTypeFromHeader(header) == ScriptTag::RAMBundle;
-}
-
 static void notifyAboutModuleSetup(RCTPerformanceLogger *performanceLogger, const char *tag)
 {
   NSString *moduleName = [[NSString alloc] initWithUTF8String:tag];
@@ -1498,6 +1491,11 @@ RCT_NOT_IMPLEMENTED(-(instancetype)initWithBundleURL
   [self executeApplicationScript:script url:url async:NO];
 }
 
+static uint32_t RCTReadUInt32LE(NSData *script, uint32_t offset)
+{
+  return [script length] < offset + 4 ? 0 : CFSwapInt32LittleToHost(*(((uint32_t *)[script bytes]) + offset / 4));
+}
+
 - (void)executeApplicationScript:(NSData *)script url:(NSURL *)url async:(BOOL)async
 {
   [self _tryAndHandleError:^{
@@ -1506,18 +1504,22 @@ RCT_NOT_IMPLEMENTED(-(instancetype)initWithBundleURL
                                                         object:self->_parentBridge
                                                       userInfo:@{@"bridge" : self}];
 
+    BundleHeader header;
+    [script getBytes:&header length:sizeof(header)];
+    ScriptTag scriptType = parseTypeFromHeader(header);
+
     // hold a local reference to reactInstance in case a parallel thread
     // resets it between null check and usage
     auto reactInstance = self->_reactInstance;
-    if (reactInstance && RCTIsBytecodeBundle(script)) {
-      UInt32 offset = 8;
+    if (reactInstance && scriptType == ScriptTag::MetroHBCBundle) {
+      uint32_t offset = 8;
       while (offset < script.length) {
-        UInt32 fileLength = RCTReadUInt32LE(script, offset);
+        uint32_t fileLength = RCTReadUInt32LE(script, offset);
         NSData *unit = [script subdataWithRange:NSMakeRange(offset + 4, fileLength)];
         reactInstance->loadScriptFromString(std::make_unique<NSDataBigString>(unit), sourceUrlStr.UTF8String, false);
         offset += ((fileLength + RCT_BYTECODE_ALIGNMENT - 1) & ~(RCT_BYTECODE_ALIGNMENT - 1)) + 4;
       }
-    } else if (isRAMBundle(script)) {
+    } else if (scriptType == ScriptTag::RAMBundle) {
       [self->_performanceLogger markStartForTag:RCTPLRAMBundleLoad];
       auto ramBundle = std::make_unique<JSIndexedRAMBundle>(sourceUrlStr.UTF8String);
       std::unique_ptr<const JSBigString> scriptStr = ramBundle->getStartupCode();

ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.cpp

@@ -276,7 +276,7 @@ void CatalystInstanceImpl::jniLoadScriptFromFile(
     const std::string &sourceURL,
     bool loadSynchronously) {
   auto reactInstance = instance_;
-  if (reactInstance && Instance::isHBCBundle(fileName.c_str())) {
+  if (reactInstance && Instance::isMetroHBCBundle(fileName.c_str())) {
     std::unique_ptr<const JSBigFileString> script;
     RecoverableError::runRethrowingAsRecoverable<std::system_error>(
         [&fileName, &script]() {

ReactAndroid/src/main/jni/react/jni/JSLoader.cpp

@@ -77,7 +77,7 @@ loadScriptFromAssets(AAssetManager *manager, const std::string &assetName) {
         // script to ensure we have a terminator.
         const BundleHeader *header =
             reinterpret_cast<const BundleHeader *>(script->c_str());
-        if (parseTypeFromHeader(*header) == ScriptTag::HBCBundle) {
+        if (isHermesBytecodeBundle(*header)) {
           return script;
         }
       }

ReactCommon/cxxreact/Instance.cpp

@@ -109,7 +109,7 @@ void Instance::loadScriptFromString(
   }
 }
 
-bool Instance::isHBCBundle(const char *sourcePath) {
+bool Instance::isMetroHBCBundle(const char *sourcePath) {
   std::ifstream bundle_stream(sourcePath, std::ios_base::in);
   BundleHeader header;
 
@@ -118,7 +118,7 @@ bool Instance::isHBCBundle(const char *sourcePath) {
     return false;
   }
 
-  return parseTypeFromHeader(header) == ScriptTag::HBCBundle;
+  return parseTypeFromHeader(header) == ScriptTag::MetroHBCBundle;
 }
 
 bool Instance::isIndexedRAMBundle(const char *sourcePath) {

ReactCommon/cxxreact/Instance.h

@@ -56,7 +56,7 @@ class RN_EXPORT Instance {
       std::unique_ptr<const JSBigString> string,
       std::string sourceURL,
       bool loadSynchronously);
-  static bool isHBCBundle(const char *sourcePath);
+  static bool isMetroHBCBundle(const char *sourcePath);
   static bool isIndexedRAMBundle(const char *sourcePath);
   static bool isIndexedRAMBundle(std::unique_ptr<const JSBigString> *string);
   void loadRAMBundleFromString(

ReactCommon/cxxreact/JSBundleType.cpp

@@ -7,20 +7,21 @@
 
 #include "JSBundleType.h"
 
-#include <folly/Bits.h>
-
 namespace facebook {
 namespace react {
 
 static uint32_t constexpr RAMBundleMagicNumber = 0xFB0BD1E5;
-static uint32_t constexpr HBCBundleMagicNumber = 0xffe7c3c3;
+static uint32_t constexpr MetroHBCBundleMagicNumber = 0xFFE7C3C3;
+
+// "Hermes" in ancient Greek encoded in UTF-16BE and truncated to 8 bytes.
+static uint64_t constexpr HermesBCBundleMagicNumber = 0x1F1903C103BC1FC6;
 
 ScriptTag parseTypeFromHeader(const BundleHeader &header) {
-  switch (folly::Endian::little(header.magic)) {
+  switch (header.magic32.value) {
     case RAMBundleMagicNumber:
       return ScriptTag::RAMBundle;
-    case HBCBundleMagicNumber:
-      return ScriptTag::HBCBundle;
+    case MetroHBCBundleMagicNumber:
+      return ScriptTag::MetroHBCBundle;
     default:
       return ScriptTag::String;
   }
@@ -32,11 +33,15 @@ const char *stringForScriptTag(const ScriptTag &tag) {
       return "String";
     case ScriptTag::RAMBundle:
       return "RAM Bundle";
-    case ScriptTag::HBCBundle:
-      return "HBC Bundle";
+    case ScriptTag::MetroHBCBundle:
+      return "Metro Hermes Bytecode Bundle";
   }
   return "";
 }
 
+bool isHermesBytecodeBundle(const BundleHeader &header) {
+  return header.magic64 == HermesBCBundleMagicNumber;
+}
+
 } // namespace react
 } // namespace facebook

ReactCommon/cxxreact/JSBundleType.h

@@ -19,20 +19,18 @@ namespace facebook {
 namespace react {
 
 /*
- * ScriptTag
- *
  * Scripts given to the JS Executors to run could be in any of the following
  * formats. They are tagged so the executor knows how to run them.
+ * Hermes bytecode bundles (as encoded by hermesc, not metro) are not treated
+ * in a special way, they will be identified as ScriptTag::String.
  */
 enum struct ScriptTag {
   String = 0,
   RAMBundle,
-  HBCBundle,
+  MetroHBCBundle,
 };
 
 /**
- * BundleHeader
- *
  * RAM bundles and BC bundles begin with headers. For RAM bundles this is
  * 4 bytes, for BC bundles this is 12 bytes. This structure holds the first 12
  * bytes from a bundle in a way that gives access to that information.
@@ -43,27 +41,33 @@ struct FOLLY_PACK_ATTR BundleHeader {
     std::memset(this, 0, sizeof(BundleHeader));
   }
 
-  uint32_t magic;
-  uint32_t reserved_;
+  union {
+    struct {
+      uint32_t value;
+      uint32_t reserved_;
+    } magic32;
+    uint64_t magic64;
+  };
   uint32_t version;
 };
 FOLLY_PACK_POP
 
 /**
- * parseTypeFromHeader
- *
  * Takes the first 8 bytes of a bundle, and returns a tag describing the
  * bundle's format.
  */
 RN_EXPORT ScriptTag parseTypeFromHeader(const BundleHeader &header);
 
 /**
- * stringForScriptTag
- *
  * Convert an `ScriptTag` enum into a string, useful for emitting in errors
  * and diagnostic messages.
  */
 RN_EXPORT const char *stringForScriptTag(const ScriptTag &tag);
 
+/**
+ * Check whether a given bundle is hermesc-generated bytecode
+ */
+RN_EXPORT bool isHermesBytecodeBundle(const BundleHeader &header);
+
 } // namespace react
 } // namespace facebook