slice.js - mozsearch

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// |jit-test| skip-if: !this.SharedArrayBuffer

// SharedArrayBuffer.prototype.slice

load(libdir + "asserts.js");

let buf = new SharedArrayBuffer(1024);

let bufAsI8 = new Int8Array(buf);

for ( let i=0 ; i < buf.length ; i++ )

    bufAsI8[i] = i;

let base = 10;

let len = 10;

let buf2 = buf.slice(base, base+len);

// Smells right?

assertEq(buf2 instanceof SharedArrayBuffer, true);

assertEq(buf2.byteLength, len);

// Data got copied correctly?

let buf2AsI8 = new Int8Array(buf2);

for ( let i=0 ; i < buf2AsI8.length ; i++ )

    assertEq(buf2AsI8[i], bufAsI8[base+i]);

// Storage not shared?

let correct = bufAsI8[base];

bufAsI8[base]++;

assertEq(buf2AsI8[0], correct);

// Start beyond end

let notail = buf.slice(buf.byteLength+1);

assertEq(notail.byteLength, 0);

// Negative start

let tail = buf.slice(-5, buf.byteLength);

assertEq(tail.byteLength, 5);

let tailAsI8 = new Int8Array(tail);

for ( let i=0 ; i < tailAsI8.length ; i++ )

    assertEq(tailAsI8[i], bufAsI8[buf.byteLength-5+i]);

// Negative end

let head = buf.slice(0, -5);

assertEq(head.byteLength, buf.byteLength-5);

let headAsI8 = new Int8Array(head);

for ( let i=0 ; i < headAsI8.length ; i++ )

    assertEq(headAsI8[i], bufAsI8[i]);

// Subtyping

class MySharedArrayBuffer1 extends SharedArrayBuffer {

    constructor(n) { super(n) }

let myBuf = new MySharedArrayBuffer1(1024);

let myBufAsI8 = new Int8Array(myBuf);

for ( let i=0 ; i < myBuf.length ; i++ )

    myBufAsI8[i] = i;

let myBufSlice = myBuf.slice(0, 20);

assertEq(myBufSlice instanceof MySharedArrayBuffer1, true);

assertEq(myBufSlice.byteLength, 20);

let myBufSliceAsI8 = new Int8Array(myBufSlice);

for ( let i=0 ; i < myBufSlice.length ; i++ )

    assertEq(myBufAsI8[i], myBufSliceAsI8[i]);

// Error mode: the method requires an object

assertThrowsInstanceOf(() => buf.slice.call(false, 0, 1), TypeError);

// Error mode: the method is not generic.

assertThrowsInstanceOf(() => buf.slice.call([1,2,3], 0, 1), TypeError);

// Error mode (step 15): the buffer constructed on behalf of slice

// is too short.

class MySharedArrayBuffer2 extends SharedArrayBuffer {

    constructor(n) { super(n-1) }

let myBuf2 = new MySharedArrayBuffer2(10);

assertThrowsInstanceOf(() => myBuf2.slice(0, 5), TypeError);

// Error mode (step 13): the buffer constructed on behalf of slice

// is not a SharedArrayBuffer.

let subvert = false;

class MySharedArrayBuffer3 extends SharedArrayBuffer {

    constructor(n) {

	super(n);

	if (subvert)

	    return new Array(n);

let myBuf3 = new MySharedArrayBuffer3(10);

subvert = true;

assertThrowsInstanceOf(() => myBuf3.slice(0, 5), TypeError);

// Error mode (step 14): the buffer constructed on behalf of slice

// is the same as the input buffer.

let sneaky = null;

class MySharedArrayBuffer4 extends SharedArrayBuffer {

    constructor(n) {

	super(n);

	if (sneaky)

	    return sneaky;

let myBuf4 = new MySharedArrayBuffer4(10);

sneaky = myBuf4;

assertThrowsInstanceOf(() => myBuf4.slice(0, 5), TypeError);