gecko/js/src/jstypedarray.cpp

/* -*- Mode: c++; c-basic-offset: 4; tab-width: 40; indent-tabs-mode: nil -*- */
/* vim: set ts=40 sw=4 et tw=78: */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla WebGL impl
 *
 * The Initial Developer of the Original Code is
 *   Mozilla Corp
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Vladimir Vukicevic <vladimir@pobox.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include <string.h>

#include "jstypes.h"
#include "jsstdint.h"
#include "jsutil.h"
#include "jshash.h"
#include "jsprf.h"
#include "jsapi.h"
#include "jsarray.h"
#include "jsatom.h"
#include "jsbool.h"
#include "jsbuiltins.h"
#include "jscntxt.h"
#include "jsversion.h"
#include "jsgc.h"
#include "jsinterp.h"
#include "jslock.h"
#include "jsnum.h"
#include "jsobj.h"
#include "jsstaticcheck.h"
#include "jsbit.h"
#include "jsvector.h"
#include "jstypedarray.h"

using namespace js;

/*
 * ArrayBuffer
 *
 * This class holds the underlying raw buffer that the TypedArray classes
 * access.  It can be created explicitly and passed to a TypedArray, or
 * can be created implicitly by constructing a TypedArray with a size.
 */
ArrayBuffer *
ArrayBuffer::fromJSObject(JSObject *obj)
{
    JS_ASSERT(obj->getClass() == &ArrayBuffer::jsclass);
    return reinterpret_cast<ArrayBuffer*>(obj->getPrivate());
}

JSBool
ArrayBuffer::prop_getByteLength(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
{
    ArrayBuffer *abuf = ArrayBuffer::fromJSObject(obj);
    if (abuf)
        *vp = INT_TO_JSVAL(jsint(abuf->byteLength));
    return true;
}

void
ArrayBuffer::class_finalize(JSContext *cx, JSObject *obj)
{
    ArrayBuffer *abuf = ArrayBuffer::fromJSObject(obj);
    if (abuf)
        abuf->freeStorage(cx);
    delete abuf;
}

/*
 * new ArrayBuffer(byteLength)
 */
JSBool
ArrayBuffer::class_constructor(JSContext *cx, JSObject *obj,
                               uintN argc, jsval *argv, jsval *rval)
{
    if (!JS_IsConstructing(cx)) {
        obj = js_NewObject(cx, &ArrayBuffer::jsclass, NULL, NULL);
        if (!obj)
            return false;
        *rval = OBJECT_TO_JSVAL(obj);
    }

    if (argc == 0) {
        JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                             JSMSG_TYPED_ARRAY_BAD_ARGS);
        return false;
    }

    int32 nbytes = js_ValueToECMAInt32(cx, &argv[0]);
    if (JSVAL_IS_NULL(argv[0]))
        return false;

    if (nbytes < 0 || !INT_FITS_IN_JSVAL(nbytes)) {
        /*
         * We're just not going to support arrays that are bigger than what will fit
         * as an integer jsval; if someone actually ever complains (validly), then we
         * can fix.
         */
        JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                             JSMSG_BAD_ARRAY_LENGTH);
        return false;
    }

    ArrayBuffer *abuf = new ArrayBuffer();
    if (!abuf) {
        JS_ReportOutOfMemory(cx);
        return false;
    }

    if (!abuf->allocateStorage(cx, nbytes)) {
        delete abuf;
        return false;
    }

    obj->setPrivate(abuf);
    return true;
}

bool
ArrayBuffer::allocateStorage(JSContext *cx, uint32 nbytes)
{
    JS_ASSERT(data == 0);

    if (nbytes) {
        data = cx->calloc(nbytes);
        if (!data) {
            JS_ReportOutOfMemory(cx);
            return false;
        }
    }

    byteLength = nbytes;
    return true;
}

void
ArrayBuffer::freeStorage(JSContext *cx)
{
    if (data) {
        cx->free(data);
#ifdef DEBUG
        // the destructor asserts that data is 0 in debug builds
        data = NULL;
#endif
    }
}

ArrayBuffer::~ArrayBuffer()
{
    JS_ASSERT(data == NULL);
}

/*
 * TypedArray
 *
 * The non-templated base class for the specific typed implementations.
 * This class holds all the member variables that are used by
 * the subclasses.
 */

TypedArray *
TypedArray::fromJSObject(JSObject *obj)
{
    return reinterpret_cast<TypedArray*>(obj->getPrivate());
}

inline bool
TypedArray::isArrayIndex(JSContext *cx, jsid id, jsuint *ip)
{
    jsuint index;
    if (js_IdIsIndex(id, &index) && index < length) {
        if (ip)
            *ip = index;
        return true;
    }

    return false;
}

JSBool
TypedArray::prop_getBuffer(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
{
    TypedArray *tarray = fromJSObject(obj);
    if (tarray)
        *vp = OBJECT_TO_JSVAL(tarray->bufferJS);
    return true;
}

JSBool
TypedArray::prop_getByteOffset(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
{
    TypedArray *tarray = fromJSObject(obj);
    if (tarray)
        *vp = INT_TO_JSVAL(tarray->byteOffset);
    return true;
}

JSBool
TypedArray::prop_getByteLength(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
{
    TypedArray *tarray = fromJSObject(obj);
    if (tarray)
        *vp = INT_TO_JSVAL(tarray->byteLength);
    return true;
}

JSBool
TypedArray::prop_getLength(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
{
    TypedArray *tarray = fromJSObject(obj);
    if (tarray)
        *vp = INT_TO_JSVAL(tarray->length);
    return true;
}

JSBool
TypedArray::obj_lookupProperty(JSContext *cx, JSObject *obj, jsid id,
                               JSObject **objp, JSProperty **propp)
{
    TypedArray *tarray = fromJSObject(obj);
    JS_ASSERT(tarray);

    if (tarray->isArrayIndex(cx, id)) {
        *propp = (JSProperty *) id;
        *objp = obj;
        return true;
    }

    JSObject *proto = STOBJ_GET_PROTO(obj);
    if (!proto) {
        *objp = NULL;
        *propp = NULL;
        return true;
    }

    return proto->lookupProperty(cx, id, objp, propp);
}

void
TypedArray::obj_dropProperty(JSContext *cx, JSObject *obj, JSProperty *prop)
{
#ifdef DEBUG
    TypedArray *tarray = fromJSObject(obj);
    JS_ASSERT_IF(tarray, tarray->isArrayIndex(cx, (jsid) prop));
#endif
}

void
TypedArray::obj_trace(JSTracer *trc, JSObject *obj)
{
    TypedArray *tarray = fromJSObject(obj);
    JS_ASSERT(tarray);

    obj->traceProtoAndParent(trc);

    JS_CALL_OBJECT_TRACER(trc, tarray->bufferJS, "typedarray.buffer");
}

JSBool
TypedArray::obj_getAttributes(JSContext *cx, JSObject *obj, jsid id, JSProperty *prop,
                              uintN *attrsp)
{
    *attrsp = (id == ATOM_TO_JSID(cx->runtime->atomState.lengthAtom))
              ? JSPROP_PERMANENT | JSPROP_READONLY
              : JSPROP_PERMANENT | JSPROP_ENUMERATE;
    return true;
}

JSBool
TypedArray::obj_setAttributes(JSContext *cx, JSObject *obj, jsid id, JSProperty *prop,
                              uintN *attrsp)
{
    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                         JSMSG_CANT_SET_ARRAY_ATTRS);
    return false;
}

/* Helper clamped uint8 type */

int32 JS_FASTCALL
js_TypedArray_uint8_clamp_double(const double x)
{
    // Not < so that NaN coerces to 0
    if (!(x >= 0))
        return 0;

    if (x > 255)
        return 255;

    jsdouble toTruncate = x + 0.5;
    JSUint8 y = JSUint8(toTruncate);

    /*
     * now val is rounded to nearest, ties rounded up.  We want
     * rounded to nearest ties to even, so check whether we had a
     * tie.
     */
    if (y == toTruncate) {
        /*
         * It was a tie (since adding 0.5 gave us the exact integer
         * we want).  Since we rounded up, we either already have an
         * even number or we have an odd number but the number we
         * want is one less.  So just unconditionally masking out the
         * ones bit should do the trick to get us the value we
         * want.
         */
        return (y & ~1);
    }

    return y;
}

JS_DEFINE_CALLINFO_1(extern, INT32, js_TypedArray_uint8_clamp_double, DOUBLE, 1, 1)


struct uint8_clamped {
    uint8 val;

    uint8_clamped() { }
    uint8_clamped(const uint8_clamped& other) : val(other.val) { }

    // invoke our assignment helpers for constructor conversion
    uint8_clamped(uint8 x)    { *this = x; }
    uint8_clamped(uint16 x)   { *this = x; }
    uint8_clamped(uint32 x)   { *this = x; }
    uint8_clamped(int8 x)     { *this = x; }
    uint8_clamped(int16 x)    { *this = x; }
    uint8_clamped(int32 x)    { *this = x; }
    uint8_clamped(jsdouble x) { *this = x; }

    inline uint8_clamped& operator= (const uint8_clamped& x) {
        val = x.val;
        return *this;
    }

    inline uint8_clamped& operator= (uint8 x) {
        val = x;
        return *this;
    }

    inline uint8_clamped& operator= (uint16 x) {
        val = (x > 255) ? 255 : 0;
        return *this;
    }

    inline uint8_clamped& operator= (uint32 x) {
        val = (x > 255) ? 255 : 0;
        return *this;
    }

    inline uint8_clamped& operator= (int8 x) {
        val = (x >= 0) ? uint8(x) : 0;
        return *this;
    }

    inline uint8_clamped& operator= (int16 x) {
        val = (x >= 0)
              ? ((x < 255)
                 ? uint8(x)
                 : 255)
              : 0;
        return *this;
    }

    inline uint8_clamped& operator= (int32 x) { 
        val = (x >= 0)
              ? ((x < 255)
                 ? uint8(x)
                 : 255)
              : 0;
        return *this;
    }

    inline uint8_clamped& operator= (const jsdouble x) { 
        val = js_TypedArray_uint8_clamp_double(x);
        return *this;
    }

    inline operator uint8() const {
        return val;
    }
};

/* Make sure the compiler isn't doing some funky stuff */
JS_STATIC_ASSERT(sizeof(uint8_clamped) == 1);

template<typename NativeType> static inline const int TypeIDOfType();
template<> inline const int TypeIDOfType<int8>() { return TypedArray::TYPE_INT8; }
template<> inline const int TypeIDOfType<uint8>() { return TypedArray::TYPE_UINT8; }
template<> inline const int TypeIDOfType<int16>() { return TypedArray::TYPE_INT16; }
template<> inline const int TypeIDOfType<uint16>() { return TypedArray::TYPE_UINT16; }
template<> inline const int TypeIDOfType<int32>() { return TypedArray::TYPE_INT32; }
template<> inline const int TypeIDOfType<uint32>() { return TypedArray::TYPE_UINT32; }
template<> inline const int TypeIDOfType<float>() { return TypedArray::TYPE_FLOAT32; }
template<> inline const int TypeIDOfType<double>() { return TypedArray::TYPE_FLOAT64; }
template<> inline const int TypeIDOfType<uint8_clamped>() { return TypedArray::TYPE_UINT8_CLAMPED; }

template<typename NativeType> class TypedArrayTemplate;

typedef TypedArrayTemplate<int8> Int8Array;
typedef TypedArrayTemplate<uint8> Uint8Array;
typedef TypedArrayTemplate<int16> Int16Array;
typedef TypedArrayTemplate<uint16> Uint16Array;
typedef TypedArrayTemplate<int32> Int32Array;
typedef TypedArrayTemplate<uint32> Uint32Array;
typedef TypedArrayTemplate<float> Float32Array;
typedef TypedArrayTemplate<double> Float64Array;
typedef TypedArrayTemplate<uint8_clamped> Uint8ClampedArray;

template<typename NativeType>
class TypedArrayTemplate
  : public TypedArray
{
  public:
    typedef TypedArrayTemplate<NativeType> ThisTypeArray;

    static JSObjectOps fastObjectOps;
    static JSObjectMap fastObjectMap;

    static JSFunctionSpec jsfuncs[];

    static inline JSClass *slowClass()
    {
        return &TypedArray::slowClasses[TypeIDOfType<NativeType>()];
    }

    static inline JSClass *fastClass()
    {
        return &TypedArray::fastClasses[TypeIDOfType<NativeType>()];
    }

    static JSObjectOps *getObjectOps(JSContext *cx, JSClass *clasp)
    {
        return &fastObjectOps;
    }

    static JSBool
    obj_getProperty(JSContext *cx, JSObject *obj, jsid id, jsval *vp)
    {
        ThisTypeArray *tarray = ThisTypeArray::fromJSObject(obj);
        JS_ASSERT(tarray);

        if (id == ATOM_TO_JSID(cx->runtime->atomState.lengthAtom)) {
            *vp = INT_TO_JSVAL(tarray->length);
            return true;
        }

        jsuint index;
        if (tarray->isArrayIndex(cx, id, &index)) {
            // this inline function is specialized for each type
            tarray->copyIndexToValue(cx, index, vp);
        } else {
            JSObject *obj2;
            JSProperty *prop;
            JSScopeProperty *sprop;

            JSObject *proto = STOBJ_GET_PROTO(obj);
            if (!proto) {
                *vp = JSVAL_VOID;
                return true;
            }

            *vp = JSVAL_VOID;
            if (js_LookupPropertyWithFlags(cx, proto, id, cx->resolveFlags, &obj2, &prop) < 0)
                return false;

            if (prop) {
                if (OBJ_IS_NATIVE(obj2)) {
                    sprop = (JSScopeProperty *) prop;
                    if (!js_NativeGet(cx, obj, obj2, sprop, JSGET_METHOD_BARRIER, vp))
                        return false;
                }
                obj2->dropProperty(cx, prop);
            }
        }

        return true;
    }

    static JSBool
    obj_setProperty(JSContext *cx, JSObject *obj, jsid id, jsval *vp)
    {
        ThisTypeArray *tarray = ThisTypeArray::fromJSObject(obj);
        JS_ASSERT(tarray);

        if (id == ATOM_TO_JSID(cx->runtime->atomState.lengthAtom)) {
            *vp = INT_TO_JSVAL(tarray->length);
            return true;
        }

        jsuint index;
        // We can't just chain to js_SetProperty, because we're not a normal object.
        if (!tarray->isArrayIndex(cx, id, &index)) {
#if 0
            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                 JSMSG_TYPED_ARRAY_BAD_INDEX);
            return false;
#endif
            // Silent ignore is better than an exception here, because
            // at some point we may want to support other properties on
            // these objects.  This is especially true when these arrays
            // are used to implement HTML Canvas 2D's PixelArray objects,
            // which used to be plain old arrays.
            *vp = JSVAL_VOID;
            return true;
        }

        if (JSVAL_IS_INT(*vp)) {
            tarray->setIndex(index, NativeType(JSVAL_TO_INT(*vp)));
        } else if (JSVAL_IS_DOUBLE(*vp)) {
            tarray->setIndex(index, NativeType(*JSVAL_TO_DOUBLE(*vp)));
        } else {
            jsdouble d;
            if (JS_ValueToNumber(cx, *vp, &d))
                tarray->setIndex(index, NativeType(d));
        }

        return true;
    }

    static JSBool
    obj_defineProperty(JSContext *cx, JSObject *obj, jsid id, jsval value,
                       JSPropertyOp getter, JSPropertyOp setter, uintN attrs)
    {
        if (id == ATOM_TO_JSID(cx->runtime->atomState.lengthAtom))
            return true;

        return obj_setProperty(cx, obj, id, &value);
    }

    static JSBool
    obj_deleteProperty(JSContext *cx, JSObject *obj, jsval id, jsval *rval)
    {
        if (id == ATOM_TO_JSID(cx->runtime->atomState.lengthAtom)) {
            *rval = JSVAL_FALSE;
            return true;
        }

        TypedArray *tarray = TypedArray::fromJSObject(obj);
        JS_ASSERT(tarray);

        if (tarray->isArrayIndex(cx, id)) {
            *rval = JSVAL_FALSE;
            return true;
        }

        *rval = JSVAL_TRUE;
        return true;
    }

    static JSBool
    obj_enumerate(JSContext *cx, JSObject *obj, JSIterateOp enum_op,
                  jsval *statep, jsid *idp)
    {
        ThisTypeArray *tarray = ThisTypeArray::fromJSObject(obj);
        JS_ASSERT(tarray);

        jsint curVal;
        switch (enum_op) {
          case JSENUMERATE_INIT:
            *statep = JSVAL_ZERO;
            if (idp)
                *idp = INT_TO_JSID(tarray->length);
            break;

          case JSENUMERATE_NEXT:
            curVal = JSVAL_TO_INT(*statep);
            *idp = INT_TO_JSID(curVal);
            *statep = (curVal == int32(tarray->length))
                      ? JSVAL_NULL
                      : INT_TO_JSVAL(curVal+1);
            break;

          case JSENUMERATE_DESTROY:
            *statep = JSVAL_NULL;
            break;
        }

        return true;
    }

    static JSType
    obj_typeOf(JSContext *cx, JSObject *obj)
    {
        return JSTYPE_OBJECT;
    }

    /*
     * new [Type]Array(length)
     * new [Type]Array(otherTypedArray)
     * new [Type]Array(JSArray)
     * new [Type]Array(ArrayBuffer, [optional] byteOffset, [optional] length)
     */
    static JSBool
    class_constructor(JSContext *cx, JSObject *obj,
                      uintN argc, jsval *argv, jsval *rval)
    {
        //
        // Note: this is a constructor for slowClass, not fastClass!
        //

        if (!JS_IsConstructing(cx)) {
            obj = js_NewObject(cx, slowClass(), NULL, NULL);
            if (!obj)
                return false;
            *rval = OBJECT_TO_JSVAL(obj);
        }

        ThisTypeArray *tarray = 0;

        // must have at least one arg
        if (argc == 0) {
            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                 JSMSG_TYPED_ARRAY_BAD_ARGS);
            return false;
        }

        // figure out the type of the first argument
        if (JSVAL_IS_INT(argv[0])) {
            int32 len = JSVAL_TO_INT(argv[0]);
            if (len < 0) {
                JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                     JSMSG_BAD_ARRAY_LENGTH);

                return false;
            }

            tarray = new ThisTypeArray();
            if (!tarray) {
                JS_ReportOutOfMemory(cx);
                return false;
            }

            if (!tarray->init(cx, len)) {
                delete tarray;
                return false;
            }
        } else if (JSVAL_IS_OBJECT(argv[0])) {
            int32 byteOffset = -1;
            int32 length = -1;

            if (argc > 1) {
                byteOffset = js_ValueToInt32(cx, &argv[1]);
                if (JSVAL_IS_NULL(argv[1]))
                    return false;

                if (byteOffset < 0) {
                    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                         JSMSG_TYPED_ARRAY_NEGATIVE_ARG, "1");
                    return false;
                }
            }

            if (argc > 2) {
                length = js_ValueToInt32(cx, &argv[2]);
                if (JSVAL_IS_NULL(argv[2]))
                    return false;

                if (length < 0) {
                    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                         JSMSG_TYPED_ARRAY_NEGATIVE_ARG, "2");
                    return false;
                }
            }

            tarray = new ThisTypeArray();
            if (!tarray) {
                JS_ReportOutOfMemory(cx);
                return false;
            }

            if (!tarray->init(cx, JSVAL_TO_OBJECT(argv[0]), byteOffset, length)) {
                delete tarray;
                return false;
            }
        } else {
            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                 JSMSG_TYPED_ARRAY_BAD_ARGS);
            return false;
        }

        makeFastWithPrivate(cx, obj, tarray);
        return true;
    }

    static void
    class_finalize(JSContext *cx, JSObject *obj)
    {
        ThisTypeArray *tarray = ThisTypeArray::fromJSObject(obj);
        delete tarray;
    }

    /* slice(start[, end]) */
    static JSBool
    fun_slice(JSContext *cx, uintN argc, jsval *vp)
    {
        jsval *argv;
        JSObject *obj;

        argv = JS_ARGV(cx, vp);
        obj = JS_THIS_OBJECT(cx, vp);

        ThisTypeArray *tarray = ThisTypeArray::fromJSObject(obj);
        if (!tarray)
            return true;

        // these are the default values
        int32 begin = 0, end = tarray->length;
        int32 length = int32(tarray->length);

        if (argc > 0) {
            begin = js_ValueToInt32(cx, &argv[0]);
            if (JSVAL_IS_NULL(argv[0]))
                return false;
            if (begin < 0) {
                begin += length;
                if (begin < 0)
                    begin = 0;
            } else if (begin > length) {
                begin = length;
            }

            if (argc > 1) {
                end = js_ValueToInt32(cx, &argv[1]);
                if (JSVAL_IS_NULL(argv[1]))
                    return false;
                if (end < 0) {
                    end += length;
                    if (end < 0)
                        end = 0;
                } else if (end > length) {
                    end = length;
                }
            }
        }

        if (begin > end)
            begin = end;

        ThisTypeArray *ntarray = tarray->slice(begin, end);
        if (!ntarray) {
            // this should rarely ever happen
            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                 JSMSG_TYPED_ARRAY_BAD_ARGS);
            return false;
        }

        // note the usage of JS_NewObject here -- we don't want the
        // constructor to be called!
        JSObject *nobj = JS_NewObject(cx, slowClass(), NULL, NULL);
        if (!nobj)
            return false;

        makeFastWithPrivate(cx, nobj, ntarray);

        *vp = OBJECT_TO_JSVAL(nobj);
        return true;
    }

    static ThisTypeArray *
    fromJSObject(JSObject *obj)
    {
        JS_ASSERT(obj->getClass() == fastClass());
        return reinterpret_cast<ThisTypeArray*>(obj->getPrivate());
    }

    // helper used by both the constructor and Slice()
    static void
    makeFastWithPrivate(JSContext *cx, JSObject *obj, ThisTypeArray *tarray)
    {
        JS_ASSERT(obj->getClass() == slowClass());

        obj->setPrivate(tarray);

        // now munge the classword and make this into a fast typed
        // array class, since it's an instance
        obj->classword ^= jsuword(slowClass());
        obj->classword |= jsuword(fastClass());

        obj->map = &fastObjectMap;
    }

  public:
    TypedArrayTemplate() { }

    bool
    init(JSContext *cx, uint32 len)
    {
        type = TypeIDOfType<NativeType>();
        return createBufferWithSizeAndCount(cx, sizeof(NativeType), len);
    }

    bool
    init(JSContext *cx, JSObject *other, int32 byteOffsetInt = -1, int32 lengthInt = -1)
    {
        type = TypeIDOfType<NativeType>();

        //printf ("Constructing with type %d other %p offset %d length %d\n", type, other, byteOffset, length);

        if (JS_IsArrayObject(cx, other)) {
            jsuint len;
            if (!JS_GetArrayLength(cx, other, &len))
                return false;
            if (!createBufferWithSizeAndCount(cx, sizeof(NativeType), len))
                return false;
            if (!copyFrom(cx, other, len))
                return false;
        } else if (js_IsTypedArray(other)) {
            TypedArray *tarray = TypedArray::fromJSObject(other);

            //printf ("SizeAndCount: %d %d\n", sizeof(NativeType), tarray->length);

            if (!createBufferWithSizeAndCount(cx, sizeof(NativeType), tarray->length))
                return false;
            if (!copyFrom(tarray))
                return false;
        } else if (other->getClass() == &ArrayBuffer::jsclass) {
            ArrayBuffer *abuf = ArrayBuffer::fromJSObject(other);

            //printf ("buffer: %d %d %d\n", abuf->byteLength, abuf->byteLength / sizeof(NativeType), len * sizeof(NativeType) == abuf->byteLength);
            uint32 boffset = (byteOffsetInt < 0) ? 0 : uint32(byteOffsetInt);

            if (boffset > abuf->byteLength || boffset % sizeof(NativeType) != 0) {
                JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                     JSMSG_TYPED_ARRAY_BAD_ARGS);
                return false; // invalid byteOffset
            }

            uint32 len;
            if (lengthInt < 0) {
                len = (abuf->byteLength - boffset) / sizeof(NativeType);
                if (len * sizeof(NativeType) != (abuf->byteLength - boffset)) {
                    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                         JSMSG_TYPED_ARRAY_BAD_ARGS);
                    return false; // given byte array doesn't map exactly to sizeof(NativeType)*N
                }
            } else {
                len = (uint32) lengthInt;
            }

            if (boffset + len*sizeof(NativeType) > abuf->byteLength) {
                JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                     JSMSG_TYPED_ARRAY_BAD_ARGS);
                return false; // boffset+len is too big for the arraybuffer
            }

            buffer = abuf;
            bufferJS = other;
            byteOffset = boffset;
            byteLength = len * sizeof(NativeType);
            length = len;
            data = abuf->offsetData(boffset);
        } else {
            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                 JSMSG_TYPED_ARRAY_BAD_ARGS);
            return false;
        }

        return true;
    }

    const NativeType
    getIndex(uint32 index) const
    {
        return *(static_cast<const NativeType*>(data) + index);
    }

    void
    setIndex(uint32 index, NativeType val)
    {
        *(static_cast<NativeType*>(data) + index) = val;
    }

    inline void copyIndexToValue(JSContext *cx, uint32 index, jsval *vp);

    ThisTypeArray *
    slice(uint32 begin, uint32 end)
    {
        if (begin > length || end > length)
            return NULL;

        ThisTypeArray *tarray = new ThisTypeArray();
        if (!tarray)
            return NULL;

        tarray->buffer = buffer;
        tarray->bufferJS = bufferJS;
        tarray->byteOffset = byteOffset + begin * sizeof(NativeType);
        tarray->byteLength = (end - begin) * sizeof(NativeType);
        tarray->length = end - begin;
        tarray->type = type;
        tarray->data = buffer->offsetData(tarray->byteOffset);

        return tarray;
    }

  protected:
    bool
    copyFrom(JSContext *cx, JSObject *ar, jsuint len)
    {
        NativeType *dest = static_cast<NativeType*>(data);

        if (ar->isDenseArray()) {
            JS_ASSERT(ar->fslots[JSSLOT_ARRAY_LENGTH] == (jsval)len);

            jsval *src = ar->dslots;

            for (uintN i = 0; i < len; ++i) {
                jsval v = *src++;
                if (JSVAL_IS_INT(v)) {
                    *dest++ = NativeType(JSVAL_TO_INT(v));
                } else if (JSVAL_IS_DOUBLE(v)) {
                    *dest++ = NativeType(*JSVAL_TO_DOUBLE(v));
                } else {
                    jsdouble dval;
                    if (!JS_ValueToNumber(cx, v, &dval))
                        return false;
                    *dest++ = NativeType(dval);
                }
            }
        } else {
            // slow path
            jsval v;

            for (uintN i = 0; i < len; ++i) {
                if (!JS_GetElement(cx, ar, i, &v))
                    return false;

                if (JSVAL_IS_INT(v)) {
                    *dest++ = NativeType(JSVAL_TO_INT(v));
                } else if (JSVAL_IS_DOUBLE(v)) {
                    *dest++ = NativeType(*JSVAL_TO_DOUBLE(v));
                } else {
                    jsdouble dval;
                    if (!JS_ValueToNumber(cx, v, &dval))
                        return false;
                    *dest++ = NativeType(dval);
                }
            }
        }

        return true;
    }

    bool
    copyFrom(TypedArray *tarray)
    {
        NativeType *dest = static_cast<NativeType*>(data);

        if (tarray->type == type) {
            memcpy(dest, tarray->data, tarray->byteLength);
            return true;
        }

        switch (tarray->type) {
          case TypedArray::TYPE_INT8: {
            int8 *src = static_cast<int8*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          case TypedArray::TYPE_UINT8:
          case TypedArray::TYPE_UINT8_CLAMPED: {
            uint8 *src = static_cast<uint8*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          case TypedArray::TYPE_INT16: {
            int16 *src = static_cast<int16*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          case TypedArray::TYPE_UINT16: {
            uint16 *src = static_cast<uint16*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          case TypedArray::TYPE_INT32: {
            int32 *src = static_cast<int32*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          case TypedArray::TYPE_UINT32: {
            uint32 *src = static_cast<uint32*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          case TypedArray::TYPE_FLOAT32: {
            float *src = static_cast<float*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          case TypedArray::TYPE_FLOAT64: {
            double *src = static_cast<double*>(tarray->data);
            for (uintN i = 0; i < length; ++i)
                *dest++ = NativeType(*src++);
            break;
          }
          default:
            JS_NOT_REACHED("copyFrom with a TypedArray of unknown type");
            break;
        }

        return true;
    }

    bool
    createBufferWithSizeAndCount(JSContext *cx, uint32 size, uint32 count)
    {
        int32 bytelen = size * count;
        if (bytelen / size != count) {
            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                 JSMSG_NEED_DIET, "size and count");
            return false;
        }

        if (!createBufferWithByteLength(cx, bytelen))
            return false;

        length = count;
        return true;
    }

    bool
    createBufferWithByteLength(JSContext *cx, int32 bytes)
    {
        if (!INT_FITS_IN_JSVAL(bytes)) {
            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                 JSMSG_NEED_DIET, "byte length");
            return false;
        }

        jsval argv = INT_TO_JSVAL(bytes);
        JSObject *obj = JS_ConstructObjectWithArguments(cx, &ArrayBuffer::jsclass, NULL, NULL,
                                                        1, &argv);
        if (!obj)
            return false;

        bufferJS = obj;
        buffer = ArrayBuffer::fromJSObject(obj);

        byteOffset = 0;
        byteLength = bytes;
        data = buffer->data;

        return true;
    }
};

// this default implementation is only valid for integer types
// less than 32-bits in size.
template<typename NativeType>
void
TypedArrayTemplate<NativeType>::copyIndexToValue(JSContext *cx, uint32 index, jsval *vp)
{
    JS_STATIC_ASSERT(sizeof(NativeType) < 4);

    *vp = INT_TO_JSVAL(getIndex(index));
}

// and we need to specialize for 32-bit integers and floats
template<>
void
TypedArrayTemplate<int32>::copyIndexToValue(JSContext *cx, uint32 index, jsval *vp)
{
    int32 val = getIndex(index);
    if (INT_FITS_IN_JSVAL(val)) {
        *vp = INT_TO_JSVAL(val);
    } else {
        jsdouble *dp = js_NewWeaklyRootedDouble(cx, jsdouble(val));
        *vp = dp ? DOUBLE_TO_JSVAL(dp) : JSVAL_VOID;
    }
}

template<>
void
TypedArrayTemplate<uint32>::copyIndexToValue(JSContext *cx, uint32 index, jsval *vp)
{
    uint32 val = getIndex(index);
    if (val < uint32(JSVAL_INT_MAX)) {
        *vp = INT_TO_JSVAL(int32(val));
    } else {
        jsdouble *dp = js_NewWeaklyRootedDouble(cx, jsdouble(val));
        *vp = dp ? DOUBLE_TO_JSVAL(dp) : JSVAL_VOID;
    }
}

template<>
void
TypedArrayTemplate<float>::copyIndexToValue(JSContext *cx, uint32 index, jsval *vp)
{
    float val = getIndex(index);
    if (!js_NewWeaklyRootedNumber(cx, jsdouble(val), vp))
        *vp = JSVAL_VOID;
}

template<>
void
TypedArrayTemplate<double>::copyIndexToValue(JSContext *cx, uint32 index, jsval *vp)
{
    double val = getIndex(index);
    if (!js_NewWeaklyRootedNumber(cx, jsdouble(val), vp))
        *vp = JSVAL_VOID;
}

/***
 *** JS impl
 ***/

/*
 * ArrayBuffer (base)
 */

JSClass ArrayBuffer::jsclass = {
    "ArrayBuffer",
    JSCLASS_HAS_PRIVATE | JSCLASS_HAS_CACHED_PROTO(JSProto_ArrayBuffer),
    JS_PropertyStub, JS_PropertyStub, JS_PropertyStub, JS_PropertyStub,
    JS_EnumerateStub, JS_ResolveStub, JS_ConvertStub, ArrayBuffer::class_finalize,
    JSCLASS_NO_OPTIONAL_MEMBERS
};

JSPropertySpec ArrayBuffer::jsprops[] = {
    { "byteLength",
      -1, JSPROP_SHARED | JSPROP_PERMANENT | JSPROP_READONLY,
      ArrayBuffer::prop_getByteLength, ArrayBuffer::prop_getByteLength },
    {0,0,0,0,0}
};

/*
 * shared TypedArray
 */

JSPropertySpec TypedArray::jsprops[] = {
    { js_length_str,
      -1, JSPROP_SHARED | JSPROP_PERMANENT | JSPROP_READONLY,
      TypedArray::prop_getLength, TypedArray::prop_getLength },
    { "byteLength",
      -1, JSPROP_SHARED | JSPROP_PERMANENT | JSPROP_READONLY,
      TypedArray::prop_getByteLength, TypedArray::prop_getByteLength },
    { "byteOffset",
      -1, JSPROP_SHARED | JSPROP_PERMANENT | JSPROP_READONLY,
      TypedArray::prop_getByteOffset, TypedArray::prop_getByteOffset },
    { "buffer",
      -1, JSPROP_SHARED | JSPROP_PERMANENT | JSPROP_READONLY,
      TypedArray::prop_getBuffer, TypedArray::prop_getBuffer },
    {0,0,0,0,0}
};


/*
 * TypedArray boilerplate
 */

#define IMPL_TYPED_ARRAY_STATICS(_typedArray)                                  \
template<> JSObjectMap _typedArray::fastObjectMap(&_typedArray::fastObjectOps, \
                                                  JSObjectMap::SHAPELESS);     \
template<> JSObjectOps _typedArray::fastObjectOps = {                          \
    &_typedArray::fastObjectMap,                                               \
    _typedArray::obj_lookupProperty,                                           \
    _typedArray::obj_defineProperty,                                           \
    _typedArray::obj_getProperty,                                              \
    _typedArray::obj_setProperty,                                              \
    _typedArray::obj_getAttributes,                                            \
    _typedArray::obj_setAttributes,                                            \
    _typedArray::obj_deleteProperty,                                           \
    js_DefaultValue,                                                           \
    _typedArray::obj_enumerate,                                                \
    js_CheckAccess,                                                            \
    _typedArray::obj_typeOf,                                                   \
    _typedArray::obj_trace,                                                    \
    NULL,                                                                      \
    _typedArray::obj_dropProperty,                                             \
    NULL, NULL, NULL,                                                          \
    NULL                                                                       \
};                                                                             \
template<> JSFunctionSpec _typedArray::jsfuncs[] = {                           \
    JS_FN("slice", _typedArray::fun_slice, 2, 0),                              \
    JS_FS_END                                                                  \
}

#define IMPL_TYPED_ARRAY_SLOW_CLASS(_typedArray)                               \
{                                                                              \
    #_typedArray,                                                              \
    JSCLASS_HAS_PRIVATE | JSCLASS_HAS_CACHED_PROTO(JSProto_##_typedArray),     \
    JS_PropertyStub, JS_PropertyStub, JS_PropertyStub, JS_PropertyStub,        \
    JS_EnumerateStub, JS_ResolveStub, JS_ConvertStub, JS_FinalizeStub,         \
    JSCLASS_NO_OPTIONAL_MEMBERS                                                \
}

#define IMPL_TYPED_ARRAY_FAST_CLASS(_typedArray)                               \
{                                                                              \
    #_typedArray,                                                              \
    JSCLASS_HAS_PRIVATE,                                                       \
    JS_PropertyStub, JS_PropertyStub, JS_PropertyStub, JS_PropertyStub,        \
    JS_EnumerateStub, JS_ResolveStub, JS_ConvertStub,                          \
    _typedArray::class_finalize,                                               \
    _typedArray::getObjectOps, NULL, NULL, NULL,                               \
    NULL, NULL, NULL, NULL                                                     \
}

#define INIT_TYPED_ARRAY_CLASS(_typedArray,_type)                              \
do {                                                                           \
    proto = js_InitClass(cx, obj, NULL,                                        \
                         &TypedArray::slowClasses[TypedArray::_type],          \
                         _typedArray::class_constructor, 3,                    \
                         _typedArray::jsprops,                                 \
                         _typedArray::jsfuncs,                                 \
                         NULL, NULL);                                          \
    if (!proto)                                                                \
        return NULL;                                                           \
    proto->setPrivate(0);                                                      \
} while (0)

IMPL_TYPED_ARRAY_STATICS(Int8Array);
IMPL_TYPED_ARRAY_STATICS(Uint8Array);
IMPL_TYPED_ARRAY_STATICS(Int16Array);
IMPL_TYPED_ARRAY_STATICS(Uint16Array);
IMPL_TYPED_ARRAY_STATICS(Int32Array);
IMPL_TYPED_ARRAY_STATICS(Uint32Array);
IMPL_TYPED_ARRAY_STATICS(Float32Array);
IMPL_TYPED_ARRAY_STATICS(Float64Array);
IMPL_TYPED_ARRAY_STATICS(Uint8ClampedArray);

JSClass TypedArray::fastClasses[TYPE_MAX] = {
    IMPL_TYPED_ARRAY_FAST_CLASS(Int8Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Uint8Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Int16Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Uint16Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Int32Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Uint32Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Float32Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Float64Array),
    IMPL_TYPED_ARRAY_FAST_CLASS(Uint8ClampedArray)
};

JSClass TypedArray::slowClasses[TYPE_MAX] = {
    IMPL_TYPED_ARRAY_SLOW_CLASS(Int8Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Uint8Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Int16Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Uint16Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Int32Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Uint32Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Float32Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Float64Array),
    IMPL_TYPED_ARRAY_SLOW_CLASS(Uint8ClampedArray)
};

JS_FRIEND_API(JSObject *)
js_InitTypedArrayClasses(JSContext *cx, JSObject *obj)
{
    /* Idempotency required: we initialize several things, possibly lazily. */
    JSObject *stop;
    if (!js_GetClassObject(cx, obj, JSProto_ArrayBuffer, &stop))
        return NULL;
    if (stop)
        return stop;

    JSObject *proto;

    INIT_TYPED_ARRAY_CLASS(Int8Array,TYPE_INT8);
    INIT_TYPED_ARRAY_CLASS(Uint8Array,TYPE_UINT8);
    INIT_TYPED_ARRAY_CLASS(Int16Array,TYPE_INT16);
    INIT_TYPED_ARRAY_CLASS(Uint16Array,TYPE_UINT16);
    INIT_TYPED_ARRAY_CLASS(Int32Array,TYPE_INT32);
    INIT_TYPED_ARRAY_CLASS(Uint32Array,TYPE_UINT32);
    INIT_TYPED_ARRAY_CLASS(Float32Array,TYPE_FLOAT32);
    INIT_TYPED_ARRAY_CLASS(Float64Array,TYPE_FLOAT64);
    INIT_TYPED_ARRAY_CLASS(Uint8ClampedArray,TYPE_UINT8_CLAMPED);

    proto = js_InitClass(cx, obj, NULL, &ArrayBuffer::jsclass,
                         ArrayBuffer::class_constructor, 1,
                         ArrayBuffer::jsprops, NULL, NULL, NULL);
    if (!proto)
        return NULL;

    proto->setPrivate(NULL);
    return proto;
}

JS_FRIEND_API(JSBool)
js_IsArrayBuffer(JSObject *obj)
{
    return obj && obj->getClass() == &ArrayBuffer::jsclass;
}

JS_FRIEND_API(JSBool)
js_IsTypedArray(JSObject *obj)
{
    return obj &&
           obj->getClass() >= &TypedArray::fastClasses[0] &&
           obj->getClass() <  &TypedArray::fastClasses[TypedArray::TYPE_MAX];
}

JS_FRIEND_API(JSObject *)
js_CreateArrayBuffer(JSContext *cx, jsuint nbytes)
{
    JSAutoTempValueRooter tvr(cx);
    js_NewNumberInRootedValue(cx, jsdouble(nbytes), tvr.addr());

    JSAutoTempValueRooter rval(cx);
    if (!ArrayBuffer::class_constructor(cx, cx->globalObject,
                                        1, tvr.addr(), 
                                        rval.addr()))
        return NULL;

    return JSVAL_TO_OBJECT(rval.value());
}

static inline bool
TypedArrayConstruct(JSContext *cx, jsint atype, uintN argc, jsval *argv, jsval *rv)
{
    switch (atype) {
      case TypedArray::TYPE_INT8:
        return Int8Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_UINT8:
        return Uint8Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_INT16:
        return Int16Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_UINT16:
        return Uint16Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_INT32:
        return Int32Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_UINT32:
        return Uint32Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_FLOAT32:
        return Float32Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_FLOAT64:
        return Float64Array::class_constructor(cx, cx->globalObject, argc, argv, rv);

      case TypedArray::TYPE_UINT8_CLAMPED:
        return Uint8ClampedArray::class_constructor(cx, cx->globalObject, argc, argv, rv);

      default:
        JS_NOT_REACHED("shouldn't have gotten here");
        return false;
    }
}

JS_FRIEND_API(JSObject *)
js_CreateTypedArray(JSContext *cx, jsint atype, jsuint nelements)
{
    JS_ASSERT(atype >= 0 && atype < TypedArray::TYPE_MAX);

    jsval vals[2];
    JSAutoTempValueRooter tvr(cx, 2, vals);

    if (!js_NewNumberInRootedValue(cx, jsdouble(nelements), &vals[0]))
        return NULL;

    if (!TypedArrayConstruct(cx, atype, 1, &vals[0], &vals[1]))
        return NULL;

    return JSVAL_TO_OBJECT(vals[1]);
}

JS_FRIEND_API(JSObject *)
js_CreateTypedArrayWithArray(JSContext *cx, jsint atype, JSObject *arrayArg)
{
    JS_ASSERT(atype >= 0 && atype < TypedArray::TYPE_MAX);

    jsval vals[2];
    JSAutoTempValueRooter tvr(cx, 2, vals);

    vals[0] = OBJECT_TO_JSVAL(arrayArg);

    if (!TypedArrayConstruct(cx, atype, 1, &vals[0], &vals[1]))
        return NULL;

    return JSVAL_TO_OBJECT(vals[1]);
}

JS_FRIEND_API(JSObject *)
js_CreateTypedArrayWithBuffer(JSContext *cx, jsint atype, JSObject *bufArg,
                              jsint byteoffset, jsint length)
{
    JS_ASSERT(atype >= 0 && atype < TypedArray::TYPE_MAX);
    JS_ASSERT(bufArg && ArrayBuffer::fromJSObject(bufArg));
    /* if byteoffset is -1, length must be -1 */
    JS_ASSERT(length < 0 || byteoffset >= 0);

    jsval vals[4];
    JSAutoTempValueRooter tvr(cx, 4, vals);

    int argc = 1;
    vals[0] = OBJECT_TO_JSVAL(bufArg);

    if (byteoffset >= 0) {
        js_NewNumberInRootedValue(cx, jsdouble(byteoffset), &vals[1]);
        argc++;
    }

    if (length >= 0) {
        js_NewNumberInRootedValue(cx, jsdouble(length), &vals[1]);
        argc++;
    }

    js_NewNumberInRootedValue(cx, jsdouble(byteoffset), &vals[0]);

    if (!TypedArrayConstruct(cx, atype, argc, &vals[0], &vals[3]))
        return NULL;

    return JSVAL_TO_OBJECT(vals[3]);
}