Bug 720771 - Implementing finalization for CData values. r=jorendorff

js/src/ctypes/CTypes.cpp

@@ -21,6 +21,7 @@
  *
  * Contributor(s):
  *  Dan Witte <dwitte@mozilla.com>
+ *  David Rajchenbach-Teller <dteller@mozilla.com>
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either the GNU General Public License Version 2 or later (the "GPL"), or
@@ -62,6 +63,9 @@
 #include <windows.h>
 #endif
 
+#include "mozilla/StandardInteger.h"
+#include "mozilla/Scoped.h"
+
 using namespace std;
 
 namespace js {
@@ -94,7 +98,7 @@ namespace CType {
   static JSBool HasInstance(JSContext* cx, JSObject* obj, const jsval* v, JSBool* bp);
 
 
-  /**
+  /*
    * Get the global "ctypes" object.
    *
    * |obj| must be a CType object.
@@ -185,7 +189,8 @@ namespace CData {
   static JSBool Address(JSContext* cx, unsigned argc, jsval* vp);
   static JSBool ReadString(JSContext* cx, unsigned argc, jsval* vp);
   static JSBool ToSource(JSContext* cx, unsigned argc, jsval* vp);
-
+  static JSString *GetSourceString(JSContext *cx, JSObject *typeObj,
+                                   void *data);
   static JSBool ErrnoGetter(JSContext* cx, JSObject *obj, jsid idval,
                             jsval* vp);
 
@@ -195,6 +200,116 @@ namespace CData {
 #endif // defined(XP_WIN)
 }
 
+namespace CDataFinalizer {
+  /*
+   * Attach a C function as a finalizer to a JS object.
+   *
+   * This function is available from JS as |ctypes.withFinalizer|.
+   *
+   * JavaScript signature:
+   * function(CData, CData):   CDataFinalizer
+   *          value  finalizer finalizable
+   *
+   * Where |finalizer| is a one-argument function taking a value
+   * with the same type as |value|.
+   */
+  static JSBool Construct(JSContext* cx, unsigned argc, jsval *vp);
+
+  /*
+   * Private data held by |CDataFinalizer|.
+   *
+   * See also |enum CDataFinalizerSlot| for the slots of
+   * |CDataFinalizer|.
+   *
+   * Note: the private data may be NULL, if |dispose|, |forget| or the
+   * finalizer has already been called.
+   */
+  struct Private {
+    /*
+     * The C data to pass to the code.
+     * Finalization/|dispose|/|forget| release this memory.
+     */
+    void *cargs;
+
+    /*
+     * The total size of the buffer pointed by |cargs|
+     */
+    size_t cargs_size;
+
+    /*
+     * Low-level signature information.
+     * Finalization/|dispose|/|forget| release this memory.
+     */
+    ffi_cif CIF;
+
+    /*
+     * The C function to invoke during finalization.
+     * Do not deallocate this.
+     */
+    uintptr_t code;
+
+    /*
+     * A buffer for holding the return value.
+     * Finalization/|dispose|/|forget| release this memory.
+     */
+    void *rvalue;
+  };
+
+  /*
+   * Methods of instances of |CDataFinalizer|
+   */
+  namespace Methods {
+    static JSBool Dispose(JSContext* cx, unsigned argc, jsval *vp);
+    static JSBool Forget(JSContext* cx, unsigned argc, jsval *vp);
+    static JSBool ToSource(JSContext* cx, unsigned argc, jsval *vp);
+    static JSBool ToString(JSContext* cx, unsigned argc, jsval *vp);
+  }
+
+  /*
+   * Utility functions
+   *
+   * @return true if |obj| is a CDataFinalizer, false otherwise.
+   */
+  static bool IsCDataFinalizer(JSObject *obj);
+
+  /*
+   * Clean up the finalization information of a CDataFinalizer.
+   *
+   * Used by |Finalize|, |Dispose| and |Forget|.
+   *
+   * @param p The private information of the CDataFinalizer. If NULL,
+   * this function does nothing.
+   * @param obj Either NULL, if the object should not be cleaned up (i.e.
+   * during finalization) or a CDataFinalizer JSObject. Always use NULL
+   * if you are calling from a finalizer.
+   */
+  static void Cleanup(Private *p, JSObject *obj);
+
+  /*
+   * Perform the actual call to the finalizer code.
+   */
+  static void CallFinalizer(Private *p, JSObject *ctypes);
+
+  /*
+   * Return the CType of a CDataFinalizer object, or NULL if the object
+   * has been cleaned-up already.
+   */
+  static JSObject *GetCType(JSContext *cx, JSObject *obj);
+
+  /*
+   * Perform finalization of a |CDataFinalizer|
+   */
+  static void Finalize(JSFreeOp *fop, JSObject *obj);
+
+  /*
+   * Return the jsval contained by this finalizer.
+   *
+   * Note that the jsval is actually not recorded, but converted back from C.
+   */
+  static bool GetValue(JSContext *cx, JSObject *obj, jsval *result);
+ }
+
+
 // Int64Base provides functions common to Int64 and UInt64.
 namespace Int64Base {
   JSObject* Construct(JSContext* cx, JSObject* proto, uint64_t data,
@@ -300,6 +415,30 @@ static JSClass sCClosureClass = {
   NULL, NULL, NULL, NULL, CClosure::Trace
 };
 
+/*
+ * Class representing the prototype of CDataFinalizer.
+ */
+static JSClass sCDataFinalizerProtoClass = {
+  "CDataFinalizer",
+  0,
+  JS_PropertyStub, JS_PropertyStub, JS_PropertyStub, JS_StrictPropertyStub,
+  JS_EnumerateStub, JS_ResolveStub, JS_ConvertStub
+};
+
+/*
+ * Class representing instances of CDataFinalizer.
+ *
+ * Instances of CDataFinalizer have both private data (with type
+ * |CDataFinalizer::Private|) and slots (see |CDataFinalizerSlots|).
+ */
+static JSClass sCDataFinalizerClass = {
+  "CDataFinalizer",
+  JSCLASS_HAS_PRIVATE | JSCLASS_HAS_RESERVED_SLOTS(CDATAFINALIZER_SLOTS),
+  JS_PropertyStub, JS_PropertyStub, JS_PropertyStub, JS_StrictPropertyStub,
+  JS_EnumerateStub, JS_ResolveStub, JS_ConvertStub, CDataFinalizer::Finalize,
+};
+
+
 #define CTYPESFN_FLAGS \
   (JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT)
 
@@ -312,6 +451,9 @@ static JSClass sCClosureClass = {
 #define CDATAFN_FLAGS \
   (JSPROP_READONLY | JSPROP_PERMANENT)
 
+#define CDATAFINALIZERFN_FLAGS \
+  (JSPROP_READONLY | JSPROP_PERMANENT)
+
 static JSPropertySpec sCTypeProps[] = {
   { "name", 0, CTYPESPROP_FLAGS, CType::NameGetter, NULL },
   { "size", 0, CTYPESPROP_FLAGS, CType::SizeGetter, NULL },
@@ -341,6 +483,18 @@ static JSFunctionSpec sCDataFunctions[] = {
   JS_FS_END
 };
 
+static JSPropertySpec sCDataFinalizerProps[] = {
+  { 0, 0, 0, NULL, NULL }
+};
+
+static JSFunctionSpec sCDataFinalizerFunctions[] = {
+  JS_FN("dispose",  CDataFinalizer::Methods::Dispose,  0, CDATAFINALIZERFN_FLAGS),
+  JS_FN("forget",   CDataFinalizer::Methods::Forget,   0, CDATAFINALIZERFN_FLAGS),
+  JS_FN("toString", CDataFinalizer::Methods::ToString, 0, CDATAFINALIZERFN_FLAGS),
+  JS_FN("toSource", CDataFinalizer::Methods::ToSource, 0, CDATAFINALIZERFN_FLAGS),
+  JS_FS_END
+};
+
 static JSFunctionSpec sPointerFunction =
   JS_FN("PointerType", PointerType::Create, 1, CTYPESCTOR_FLAGS);
 
@@ -484,6 +638,7 @@ static JSPropertySpec sModuleProps[] = {
 };
 
 static JSFunctionSpec sModuleFunctions[] = {
+  JS_FN("CDataFinalizer", CDataFinalizer::Construct, 2, CTYPESFN_FLAGS),
   JS_FN("open", Library::Open, 1, CTYPESFN_FLAGS),
   JS_FN("cast", CData::Cast, 2, CTYPESFN_FLAGS),
   JS_FN("getRuntime", CData::GetRuntime, 1, CTYPESFN_FLAGS),
@@ -505,9 +660,16 @@ NewUCString(JSContext* cx, const AutoString& from)
   return JS_NewUCStringCopyN(cx, from.begin(), from.length());
 }
 
+/*
+ * Return a size rounded up to a multiple of a power of two.
+ *
+ * Note: |align| must be a power of 2.
+ */
 JS_ALWAYS_INLINE size_t
 Align(size_t val, size_t align)
 {
+  // Ensure that align is a power of two.
+  MOZ_ASSERT(align != 0 && (align & (align - 1)) == 0);
   return ((val - 1) | (align - 1)) + 1;
 }
 
@@ -969,6 +1131,26 @@ GetCallbacks(JSObject* obj)
   return static_cast<JSCTypesCallbacks*>(JSVAL_TO_PRIVATE(result));
 }
 
+// Utility function to access a property of an object as an object
+// returns false and sets the error if the property does not exist
+// or is not an object
+bool GetObjectProperty(JSContext *cx, JSObject *obj,
+                       const char *property, JSObject **result)
+{
+  jsval val;
+  if (!JS_GetProperty(cx, obj, property, &val)) {
+    return false;
+  }
+
+  if (JSVAL_IS_PRIMITIVE(val)) {
+    JS_ReportError(cx, "missing or non-object field");
+    return false;
+  }
+
+  *result = JSVAL_TO_OBJECT(val);
+  return true;
+}
+
 JS_BEGIN_EXTERN_C
 
 JS_PUBLIC_API(JSBool)
@@ -992,6 +1174,30 @@ JS_InitCTypesClass(JSContext* cx, JSObject* global)
       !JS_DefineProperties(cx, ctypes, sModuleProps))
     return false;
 
+  // Set up ctypes.CDataFinalizer.prototype.
+  JSObject* ctor;
+  if (!GetObjectProperty(cx, ctypes, "CDataFinalizer", &ctor)) {
+    return NULL;
+  }
+
+  JSObject* prototype = JS_NewObject(cx, &sCDataFinalizerProtoClass,
+                                     NULL, ctypes);
+  if (!prototype)
+    return NULL;
+
+  if (!JS_DefineProperties(cx, prototype, sCDataFinalizerProps) ||
+      !JS_DefineFunctions(cx, prototype, sCDataFinalizerFunctions))
+    return NULL;
+
+  if (!JS_DefineProperty(cx, ctor, "prototype", OBJECT_TO_JSVAL(prototype),
+                         NULL, NULL, JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT))
+    return NULL;
+
+  if (!JS_DefineProperty(cx, prototype, "constructor", OBJECT_TO_JSVAL(ctor),
+                         NULL, NULL, JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT))
+    return NULL;
+
+
   // Seal the ctypes object, to prevent modification.
   return JS_FreezeObject(cx, ctypes);
 }
@@ -1273,7 +1479,15 @@ jsvalToInteger(JSContext* cx, jsval val, IntegerType* result)
       return ConvertExact(i, result);
     }
 
-    return false; 
+    if (CDataFinalizer::IsCDataFinalizer(obj)) {
+      jsval innerData;
+      if (!CDataFinalizer::GetValue(cx, obj, &innerData)) {
+        return false; // Nothing to convert
+      }
+      return jsvalToInteger(cx, innerData, result);
+    }
+
+    return false;
   }
   if (JSVAL_IS_BOOLEAN(val)) {
     // Implicitly promote boolean values to 0 or 1, like C.
@@ -1444,6 +1658,15 @@ jsvalToBigInteger(JSContext* cx,
       int64_t i = Int64Base::GetInt(obj);
       return ConvertExact(i, result);
     }
+
+    if (CDataFinalizer::IsCDataFinalizer(obj)) {
+      jsval innerData;
+      if (!CDataFinalizer::GetValue(cx, obj, &innerData)) {
+        return false; // Nothing to convert
+      }
+      return jsvalToBigInteger(cx, innerData, allowString, result);
+    }
+
   }
   return false;
 }
@@ -1784,20 +2007,40 @@ ImplicitConvert(JSContext* cx,
 {
   JS_ASSERT(CType::IsSizeDefined(targetType));
 
-  // First, check if val is a CData object of type targetType.
+  // First, check if val is either a CData object or a CDataFinalizer
+  // of type targetType.
   JSObject* sourceData = NULL;
   JSObject* sourceType = NULL;
-  if (!JSVAL_IS_PRIMITIVE(val) &&
-      CData::IsCData(JSVAL_TO_OBJECT(val))) {
-    sourceData = JSVAL_TO_OBJECT(val);
-    sourceType = CData::GetCType(sourceData);
+  if (!JSVAL_IS_PRIMITIVE(val)) {
+    if (CData::IsCData(JSVAL_TO_OBJECT(val))) {
+      sourceData = JSVAL_TO_OBJECT(val);
+      sourceType = CData::GetCType(sourceData);
 
-    // If the types are equal, copy the buffer contained within the CData.
-    // (Note that the buffers may overlap partially or completely.)
-    if (CType::TypesEqual(sourceType, targetType)) {
-      size_t size = CType::GetSize(sourceType);
-      memmove(buffer, CData::GetData(sourceData), size);
-      return true;
+      // If the types are equal, copy the buffer contained within the CData.
+      // (Note that the buffers may overlap partially or completely.)
+      if (CType::TypesEqual(sourceType, targetType)) {
+        size_t size = CType::GetSize(sourceType);
+        memmove(buffer, CData::GetData(sourceData), size);
+        return true;
+      }
+    } else if (CDataFinalizer::IsCDataFinalizer(JSVAL_TO_OBJECT(val))) {
+      sourceData = JSVAL_TO_OBJECT(val);
+      sourceType = CDataFinalizer::GetCType(cx, sourceData);
+
+      CDataFinalizer::Private *p = (CDataFinalizer::Private *)
+        JS_GetPrivate(sourceData);
+
+      if (!p) {
+        // We have called |dispose| or |forget| already.
+        JS_ReportError(cx, "Attempting to convert an empty CDataFinalizer");
+        return JS_FALSE;
+      }
+
+      // If the types are equal, copy the buffer contained within the CData.
+      if (CType::TypesEqual(sourceType, targetType)) {
+        memmove(buffer, p->cargs, p->cargs_size);
+        return true;
+      }
     }
   }
 
@@ -6026,6 +6269,26 @@ CData::ReadString(JSContext* cx, unsigned argc, jsval* vp)
   return JS_TRUE;
 }
 
+JSString *
+CData::GetSourceString(JSContext *cx, JSObject *typeObj, void *data)
+{
+  // Walk the types, building up the toSource() string.
+  // First, we build up the type expression:
+  // 't.ptr' for pointers;
+  // 't.array([n])' for arrays;
+  // 'n' for structs, where n = t.name, the struct's name. (We assume this is
+  // bound to a variable in the current scope.)
+  AutoString source;
+  BuildTypeSource(cx, typeObj, true, source);
+  AppendString(source, "(");
+  if (!BuildDataSource(cx, typeObj, data, false, source))
+    return NULL;
+
+  AppendString(source, ")");
+
+  return NewUCString(cx, source);
+}
+
 JSBool
 CData::ToSource(JSContext* cx, unsigned argc, jsval* vp)
 {
@@ -6046,24 +6309,11 @@ CData::ToSource(JSContext* cx, unsigned argc, jsval* vp)
     JSObject* typeObj = CData::GetCType(obj);
     void* data = CData::GetData(obj);
 
-    // Walk the types, building up the toSource() string.
-    // First, we build up the type expression:
-    // 't.ptr' for pointers;
-    // 't.array([n])' for arrays;
-    // 'n' for structs, where n = t.name, the struct's name. (We assume this is
-    // bound to a variable in the current scope.)
-    AutoString source;
-    BuildTypeSource(cx, typeObj, true, source);
-    AppendString(source, "(");
-    if (!BuildDataSource(cx, typeObj, data, false, source))
-      return JS_FALSE;
-
-    AppendString(source, ")");
-
-    result = NewUCString(cx, source);
-  }
-  else
+    result = CData::GetSourceString(cx, typeObj, data);
+  } else {
     result = JS_NewStringCopyZ(cx, "[CData proto object]");
+  }
+
   if (!result)
     return JS_FALSE;
 
@@ -6098,6 +6348,485 @@ CData::LastErrorGetter(JSContext* cx, JSObject* obj, jsid, jsval* vp)
 }
 #endif // defined(XP_WIN)
 
+JSBool
+CDataFinalizer::Methods::ToSource(JSContext *cx, unsigned argc, jsval *vp)
+{
+  JSObject* objThis = JS_THIS_OBJECT(cx, vp);
+  if (!objThis || !CDataFinalizer::IsCDataFinalizer(objThis)) {
+    JS_ReportError(cx, "not a CDataFinalizer");
+    return JS_FALSE;
+  }
+
+  CDataFinalizer::Private *p = (CDataFinalizer::Private *)
+    JS_GetPrivate(objThis);
+
+  JSString *strMessage;
+  if (!p) {
+    strMessage = JS_NewStringCopyZ(cx, "ctypes.CDataFinalizer()");
+  } else {
+    JSObject *objType = CDataFinalizer::GetCType(cx, objThis);
+    if (!objType) {
+      JS_ReportError(cx, "CDataFinalizer has no type");
+      return JS_FALSE;
+    }
+
+    AutoString source;
+    AppendString(source, "ctypes.CDataFinalizer(");
+    JSString *srcValue = CData::GetSourceString(cx, objType, p->cargs);
+    if (!srcValue) {
+      return JS_FALSE;
+    }
+    AppendString(source, srcValue);
+    AppendString(source, ", ");
+    jsval valCodePtrType = JS_GetReservedSlot(objThis,
+                                              SLOT_DATAFINALIZER_CODETYPE);
+    if (JSVAL_IS_PRIMITIVE(valCodePtrType)) {
+      return JS_FALSE;
+    }
+
+    JSString *srcDispose =
+      CData::GetSourceString(cx, JSVAL_TO_OBJECT(valCodePtrType),
+                             &(p->code));
+    if (!srcDispose) {
+      return JS_FALSE;
+    }
+
+    AppendString(source, srcDispose);
+    AppendString(source, ")");
+    strMessage = NewUCString(cx, source);
+  }
+
+  if (!strMessage) {
+    // This is a memory issue, no error message
+    return JS_FALSE;
+  }
+
+  JS_SET_RVAL(cx, vp, STRING_TO_JSVAL(strMessage));
+  return JS_TRUE;
+}
+
+JSBool
+CDataFinalizer::Methods::ToString(JSContext *cx, unsigned argc, jsval *vp)
+{
+  JSObject* objThis = JS_THIS_OBJECT(cx, vp);
+  if (!objThis || !CDataFinalizer::IsCDataFinalizer(objThis)) {
+    JS_ReportError(cx, "not a CDataFinalizer");
+    return JS_FALSE;
+  }
+
+  JSString *strMessage;
+  jsval value;
+  if (!JS_GetPrivate(objThis)) {
+    // Pre-check whether CDataFinalizer::GetValue can fail
+    // to avoid reporting an error when not appropriate.
+    strMessage = JS_NewStringCopyZ(cx, "[CDataFinalizer - empty]");
+    if (!strMessage) {
+      return JS_FALSE;
+    }
+  } else if (!CDataFinalizer::GetValue(cx, objThis, &value)) {
+    JS_NOT_REACHED("Could not convert an empty CDataFinalizer");
+  } else {
+    strMessage = JS_ValueToString(cx, value);
+    if (!strMessage) {
+      return JS_FALSE;
+    }
+  }
+  JS_SET_RVAL(cx, vp, STRING_TO_JSVAL(strMessage));
+  return JS_TRUE;
+}
+
+bool
+CDataFinalizer::IsCDataFinalizer(JSObject *obj)
+{
+  return JS_GetClass(obj) == &sCDataFinalizerClass;
+}
+
+
+JSObject *
+CDataFinalizer::GetCType(JSContext *cx, JSObject *obj)
+{
+  MOZ_ASSERT(IsCDataFinalizer(obj));
+
+  jsval valData = JS_GetReservedSlot(obj,
+                                     SLOT_DATAFINALIZER_VALTYPE);
+  if (JSVAL_IS_VOID(valData)) {
+    return NULL;
+  }
+
+  return JSVAL_TO_OBJECT(valData);
+}
+
+bool
+CDataFinalizer::GetValue(JSContext *cx, JSObject *obj, jsval *aResult)
+{
+  MOZ_ASSERT(IsCDataFinalizer(obj));
+
+  CDataFinalizer::Private *p = (CDataFinalizer::Private *)
+    JS_GetPrivate(obj);
+
+  if (!p) {
+    JS_ReportError(cx, "Attempting to get the value of an empty CDataFinalizer");
+    return false;  // We have called |dispose| or |forget| already.
+  }
+
+  return ConvertToJS(cx, GetCType(cx, obj),
+                     /*parent*/NULL, p -> cargs, false, true, aResult);
+}
+
+/*
+ * Attach a C function as a finalizer to a JS object.
+ *
+ * Pseudo-JS signature:
+ * function(CData<T>, CData<T -> U>): CDataFinalizer<T>
+ *          value,    finalizer
+ *
+ * This function attaches strong references to the following values:
+ * - the CType of |value|
+ *
+ * Note: This function takes advantage of the fact that non-variadic
+ * CData functions are initialized during creation.
+ */
+JSBool
+CDataFinalizer::Construct(JSContext* cx, unsigned argc, jsval *vp)
+{
+  JSObject* objSelf = JSVAL_TO_OBJECT(JS_CALLEE(cx, vp));
+  JSObject *objProto;
+  if (!GetObjectProperty(cx, objSelf, "prototype", &objProto)) {
+    JS_ReportError(cx, "CDataFinalizer.prototype does not exist");
+    return JS_FALSE;
+  }
+
+  // Get arguments
+  if (argc == 0) { // Special case: the empty (already finalized) object
+    JSObject *objResult = JS_NewObject(cx, &sCDataFinalizerClass, objProto, NULL);
+    JS_SET_RVAL(cx, vp, OBJECT_TO_JSVAL(objResult));
+    return JS_TRUE;
+  }
+
+  if (argc != 2) {
+    JS_ReportError(cx, "CDataFinalizer takes 2 arguments");
+    return JS_FALSE;
+  }
+
+  jsval* argv = JS_ARGV(cx, vp);
+  jsval valCodePtr = argv[1];
+  if (!JSVAL_IS_OBJECT(valCodePtr) || JSVAL_IS_NULL(valCodePtr)) {
+    return TypeError(cx, "_a CData object_ of a function pointer type",
+                     valCodePtr);
+  }
+  JSObject *objCodePtr = JSVAL_TO_OBJECT(valCodePtr);
+
+  //Note: Using a custom argument formatter here would be awkward (requires
+  //a destructor just to uninstall the formatter).
+
+  // 2. Extract argument type of |objCodePtr|
+  if (!CData::IsCData(objCodePtr)) {
+    return TypeError(cx, "a _CData_ object of a function pointer type",
+                     valCodePtr);
+  }
+  JSObject *objCodePtrType = CData::GetCType(objCodePtr);
+  MOZ_ASSERT(objCodePtrType);
+
+  TypeCode typCodePtr = CType::GetTypeCode(objCodePtrType);
+  if (typCodePtr != TYPE_pointer) {
+    return TypeError(cx, "a CData object of a function _pointer_ type",
+                     OBJECT_TO_JSVAL(objCodePtrType));
+  }
+
+  JSObject *objCodeType = PointerType::GetBaseType(objCodePtrType);
+  MOZ_ASSERT(objCodeType);
+
+  TypeCode typCode = CType::GetTypeCode(objCodeType);
+  if (typCode != TYPE_function) {
+    return TypeError(cx, "a CData object of a _function_ pointer type",
+                     OBJECT_TO_JSVAL(objCodePtrType));
+  }
+  uintptr_t code = *reinterpret_cast<uintptr_t*>(CData::GetData(objCodePtr));
+  if (!code) {
+    return TypeError(cx, "a CData object of a _non-NULL_ function pointer type",
+                     OBJECT_TO_JSVAL(objCodePtrType));
+  }
+
+  FunctionInfo* funInfoFinalizer =
+    FunctionType::GetFunctionInfo(objCodeType);
+  MOZ_ASSERT(funInfoFinalizer);
+
+  if ((funInfoFinalizer->mArgTypes.length() != 1)
+      || (funInfoFinalizer->mIsVariadic)) {
+    return TypeError(cx, "a function accepting exactly one argument",
+                     OBJECT_TO_JSVAL(objCodeType));
+  }
+  JSObject *objArgType = funInfoFinalizer->mArgTypes[0];
+
+  // Invariant: At this stage, we know that funInfoFinalizer->mIsVariadic
+  // is |false|. Therefore, funInfoFinalizer->mCIF has already been initialized.
+
+  bool freePointer = false;
+
+  // 3. Perform dynamic cast of |argv[0]| into |objType|, store it in |cargs|
+
+  size_t sizeArg;
+  jsval valData = argv[0];
+  if (!CType::GetSafeSize(objArgType, &sizeArg)) {
+    return TypeError(cx, "(an object with known size)", valData);
+  }
+
+  ScopedFreePtr<void> cargs(malloc(sizeArg));
+
+  if (!ImplicitConvert(cx, valData, objArgType, cargs.get(),
+                       false, &freePointer)) {
+    return TypeError(cx, "(an object that can be converted to the following type)",
+                     OBJECT_TO_JSVAL(objArgType));
+  }
+  if (freePointer) {
+    // Note: We could handle that case, if necessary.
+    JS_ReportError(cx, "Internal Error during CDataFinalizer. Object cannot be represented");
+    return JS_FALSE;
+  }
+
+  // 4. Prepare buffer for holding return value
+
+  JSObject *returnType = funInfoFinalizer->mReturnType;
+  ScopedFreePtr<void> rvalue;
+  if (CType::GetTypeCode(returnType) != TYPE_void_t) {
+    rvalue = malloc(Align(CType::GetSize(returnType),
+                          sizeof(ffi_arg)));
+  } //Otherwise, simply do not allocate
+
+  // 5. Create |objResult|
+
+  JSObject *objResult = JS_NewObject(cx, &sCDataFinalizerClass, objProto, NULL);
+  if (!objResult) {
+    return JS_FALSE;
+  }
+
+  // Used by GetCType
+  JS_SetReservedSlot(objResult,
+                     SLOT_DATAFINALIZER_VALTYPE,
+                     OBJECT_TO_JSVAL(objArgType));
+
+  // Used by ToSource
+  JS_SetReservedSlot(objResult,
+                     SLOT_DATAFINALIZER_CODETYPE,
+                     OBJECT_TO_JSVAL(objCodePtrType));
+
+  ffi_abi abi;
+  if (!GetABI(cx, OBJECT_TO_JSVAL(funInfoFinalizer->mABI), &abi)) {
+    JS_ReportError(cx, "Internal Error: "
+                   "Invalid ABI specification in CDataFinalizer");
+    return false;
+  }
+
+  ffi_type* rtype = CType::GetFFIType(cx, funInfoFinalizer->mReturnType);
+  if (!rtype) {
+    JS_ReportError(cx, "Internal Error: "
+                   "Could not access ffi type of CDataFinalizer");
+    return JS_FALSE;
+  }
+
+  // 7. Store C information as private
+  ScopedFreePtr<CDataFinalizer::Private>
+    p((CDataFinalizer::Private*)malloc(sizeof(CDataFinalizer::Private)));
+
+  memmove(&p->CIF, &funInfoFinalizer->mCIF, sizeof(ffi_cif));
+
+  p->cargs = cargs.forget();
+  p->rvalue = rvalue.forget();
+  p->cargs_size = sizeArg;
+  p->code = code;
+
+
+  JS_SetPrivate(objResult, p.forget());
+  JS_SET_RVAL(cx, vp, OBJECT_TO_JSVAL(objResult));
+  return JS_TRUE;
+}
+
+
+/*
+ * Actually call the finalizer. Does not perform any cleanup on the object.
+ *
+ * Preconditions: |this| must be a |CDataFinalizer|, |p| must be non-null.
+ * The function fails if |this| has gone through |Forget|/|Dispose|
+ * or |Finalize|.
+ *
+ * In contexts that should update errno/winLastError, callers should provide
+ * argument |ctypes|, which must point to global object ctypes. In other cases,
+ * this argument should be NULL.
+ */
+void
+CDataFinalizer::CallFinalizer(CDataFinalizer::Private *p, JSObject *ctypes)
+{
+  int savedErrno = errno;
+  errno = 0;
+#if defined(XP_WIN)
+  int32_t savedLastError = GetLastError();
+  SetLastError(0);
+#endif // defined(XP_WIN)
+
+  ffi_call(&p->CIF, FFI_FN(p->code), p->rvalue, &p->cargs);
+
+  int errnoStatus = errno;
+  errno = savedErrno;
+#if defined(XP_WIN)
+  int32_t lastErrorStatus = GetLastError();
+  SetLastError(savedLastError);
+#endif // defined(XP_WIN)
+
+  if (!ctypes) {
+    return;
+  }
+
+  JS_SetReservedSlot(ctypes, SLOT_ERRNO, INT_TO_JSVAL(errnoStatus));
+#if defined(XP_WIN)
+  JS_SetReservedSlot(ctypes, SLOT_LASTERROR, INT_TO_JSVAL(lastErrorStatus));
+#endif // defined(XP_WIN)
+}
+
+/*
+ * Forget the value.
+ *
+ * Preconditions: |this| must be a |CDataFinalizer|.
+ * The function fails if |this| has gone through |Forget|/|Dispose|
+ * or |Finalize|.
+ *
+ * Does not call the finalizer. Cleans up the Private memory and releases all
+ * strong references.
+ */
+JSBool
+CDataFinalizer::Methods::Forget(JSContext* cx, unsigned argc, jsval *vp)
+{
+  if (argc != 0) {
+    JS_ReportError(cx, "CDataFinalizer.prototype.forget takes no arguments");
+    return JS_FALSE;
+  }
+
+  JSObject *obj = JS_THIS_OBJECT(cx, vp);
+  if (!obj || !CDataFinalizer::IsCDataFinalizer(obj)) {
+    return TypeError(cx, "a CDataFinalizer", OBJECT_TO_JSVAL(obj));
+  }
+
+  CDataFinalizer::Private *p = (CDataFinalizer::Private *)
+    JS_GetPrivate(obj);
+
+  if (!p) {
+    JS_ReportError(cx, "forget called on an empty CDataFinalizer");
+    return JS_FALSE;
+  }
+
+  jsval valJSData;
+  if (!ConvertToJS(cx, GetCType(cx, obj), NULL, p->cargs, false, true, &valJSData)) {
+    JS_ReportError(cx, "CDataFinalizer value cannot be represented");
+    return JS_FALSE;
+  }
+
+  CDataFinalizer::Cleanup(p, obj);
+
+  JS_SET_RVAL(cx, vp, valJSData);
+  return JS_TRUE;
+}
+
+/*
+ * Clean up the value.
+ *
+ * Preconditions: |this| must be a |CDataFinalizer|.
+ * The function fails if |this| has gone through |Forget|/|Dispose|
+ * or |Finalize|.
+ *
+ * Calls the finalizer, cleans up the Private memory and releases all
+ * strong references.
+ */
+JSBool
+CDataFinalizer::Methods::Dispose(JSContext* cx, unsigned argc, jsval *vp)
+{
+  if (argc != 0) {
+    JS_ReportError(cx, "CDataFinalizer.prototype.dispose takes no arguments");
+    return JS_FALSE;
+  }
+
+  JSObject *obj = JS_THIS_OBJECT(cx, vp);
+  if (!obj || !CDataFinalizer::IsCDataFinalizer(obj)) {
+    return TypeError(cx, "a CDataFinalizer", OBJECT_TO_JSVAL(obj));
+  }
+
+  CDataFinalizer::Private *p = (CDataFinalizer::Private *)
+    JS_GetPrivate(obj);
+
+  if (!p) {
+    JS_ReportError(cx, "dispose called on an empty CDataFinalizer.");
+    return JS_FALSE;
+  }
+
+  jsval valType = JS_GetReservedSlot(obj, SLOT_DATAFINALIZER_VALTYPE);
+  JS_ASSERT(!JSVAL_IS_PRIMITIVE(valType));
+
+  JSObject *objCTypes = CType::GetGlobalCTypes(cx, JSVAL_TO_OBJECT(valType));
+
+  CDataFinalizer::CallFinalizer(p, objCTypes);
+  CDataFinalizer::Cleanup(p, obj);
+
+  JS_SET_RVAL(cx, vp, JSVAL_VOID);
+  return JS_TRUE;
+}
+
+/*
+ * Perform finalization.
+ *
+ * Preconditions: |this| must be the result of |CDataFinalizer|.
+ * It may have gone through |Forget|/|Dispose|.
+ *
+ * If |this| has not gone through |Forget|/|Dispose|, calls the
+ * finalizer, cleans up the Private memory and releases all
+ * strong references.
+ */
+void
+CDataFinalizer::Finalize(JSFreeOp* fop, JSObject* obj)
+{
+  CDataFinalizer::Private *p = (CDataFinalizer::Private *)
+    JS_GetPrivate(obj);
+
+  if (!p) {
+    return;
+  }
+
+  CDataFinalizer::CallFinalizer(p, NULL);
+  CDataFinalizer::Cleanup(p, NULL);
+}
+
+/*
+ * Perform cleanup of a CDataFinalizer
+ *
+ * Release strong references, cleanup |Private|.
+ *
+ * Argument |p| contains the private information of the CDataFinalizer. If NULL,
+ * this function does nothing.
+ * Argument |obj| should contain |NULL| during finalization (or in any context
+ * in which the object itself should not be cleaned up), or a CDataFinalizer
+ * object otherwise.
+ */
+void
+CDataFinalizer::Cleanup(CDataFinalizer::Private *p, JSObject *obj)
+{
+  if (!p) {
+    return;  // We have already cleaned up
+  }
+
+  free(p->cargs);
+  free(p->rvalue);
+  free(p);
+
+  if (!obj) {
+    return;  // No slots to clean up
+  }
+
+  JS_ASSERT(CDataFinalizer::IsCDataFinalizer(obj));
+
+  JS_SetPrivate(obj, NULL);
+  for (int i = 0; i < CDATAFINALIZER_SLOTS; ++i) {
+    JS_SetReservedSlot(obj, i, JSVAL_NULL);
+  }
+}
+
+
 /*******************************************************************************
 ** Int64 and UInt64 implementation
 *******************************************************************************/

js/src/ctypes/CTypes.h

@@ -430,6 +430,16 @@ enum CClosureSlot {
   CCLOSURE_SLOTS
 };
 
+enum CDataFinalizerSlot {
+  // The type of the value (a CType JSObject).
+  // We hold it to permit ImplicitConvert and ToSource.
+  SLOT_DATAFINALIZER_VALTYPE           = 0,
+  // The type of the function used at finalization (a CType JSObject).
+  // We hold it to permit |ToSource|.
+  SLOT_DATAFINALIZER_CODETYPE          = 1,
+  CDATAFINALIZER_SLOTS
+};
+
 enum TypeCtorSlot {
   SLOT_FN_CTORPROTO = 0 // ctypes.{Pointer,Array,Struct}Type.prototype
   // JSFunction objects always get exactly two slots.