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EnsureCapacity can throw if called against sparse mode array #746

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Jun 8, 2020
Merged

EnsureCapacity can throw if called against sparse mode array #746

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12 changes: 12 additions & 0 deletions Jint.Tests/Runtime/ArrayTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,5 +52,17 @@ public void EmptyStringKey()

Assert.Equal(8, result);
}

[Fact]
public void LargeArraySize()
{
const string code = @"
let arr = [];
for (let i = 0; i < 10000; i++) arr.push(i);
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Showing off with these let keywords now ;)

for (let i=0;i<10000;i++) arr.splice(0, 1);
";
var engine = new Engine();
engine.Execute(code);
}
}
}
12 changes: 7 additions & 5 deletions Jint/Native/Array/ArrayInstance.cs
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Expand Up @@ -648,13 +648,15 @@ private void ConvertToSparse()

internal void EnsureCapacity(uint capacity)
{
if (capacity <= MaxDenseArrayLength && capacity > (uint) _dense.Length)
if (capacity > MaxDenseArrayLength || _dense is null || capacity <= (uint) _dense.Length)
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I understand that the capacity doubles?

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Capacity is decided by the caller, we can grow as asked if it hasn't flipped to be dictionary (sparse) already. Usually logic asks for double the size but for example splice knows what to expect and thus was signaling specific size when algorithm is at specific point. Same like using constructor parameter, can signal known size.

{
// need to grow
var newArray = new PropertyDescriptor[capacity];
System.Array.Copy(_dense, newArray, _dense.Length);
_dense = newArray;
return;
}

// need to grow
var newArray = new PropertyDescriptor[capacity];
System.Array.Copy(_dense, newArray, _dense.Length);
_dense = newArray;
}

public IEnumerator<JsValue> GetEnumerator()
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