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Fix Typedarray.slice fastpath when the content type is matching #4898

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Fix Typedarray.slice fastpath when the content type is matching #4898

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22 changes: 19 additions & 3 deletions jerry-core/ecma/builtin-objects/typedarray/ecma-builtin-typedarray-prototype.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1628,14 +1628,30 @@ ecma_builtin_typedarray_prototype_slice (ecma_value_t this_arg, /**< this argume
return ECMA_VALUE_ERROR;
}

JERRY_ASSERT (new_typedarray_info.offset == 0);

src_buffer_p += relative_start << info_p->shift;

if (info_p->id == new_typedarray_info.id)
{
// 22.2.3.23. Step 22. h-i.
memcpy (dst_buffer_p, src_buffer_p, count << info_p->shift);

if (JERRY_LIKELY (new_typedarray_info.offset == 0))
{
memcpy (dst_buffer_p, src_buffer_p, count << info_p->shift);
}
else if (count >= new_typedarray_info.offset)
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What if count is less than the target offset? I don't think this condition is correct.

var buf = new ArrayBuffer(10);
var a1 = new Int8Array(buf, 0, 5);
a1.fill(1);
a1.constructor = {
    [Symbol.species]: function (len) {
        return new Int8Array(buf, 5, 5);
    }
};
var a2 = a1.slice(2,4);
res = new Int8Array(buf, 0, 10);

Also, I don't think checking the offset is the right way, we need to check whether the two typedarrays use the same arraybuffer instead, and only then fall back to copying element-by-element.

{
uint32_t byte_shift = (uint32_t) (1 << info_p->shift);

while (count)
{
memmove (dst_buffer_p, src_buffer_p, byte_shift);

dst_buffer_p += byte_shift;
src_buffer_p += byte_shift;

count--;
}
}
}
else
{
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31 changes: 31 additions & 0 deletions tests/jerry/es.next/regression-test-issue-4888.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
// Copyright JS Foundation and other contributors, http://js.foundation
//
// Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

var ab = new Int8Array(20).map((v, i) => i + 1).buffer;
var ta = new Int8Array(ab, 0, 10);
ta.constructor = {
[Symbol.species]: function (len) {
return new Int8Array(ab, 1, len);
}
};

var tb = ta.slice();

for (let e of ta) {
assert(e === 1);
}

for (let e of tb) {
assert(e === 1);
}