Avoid O(N) string[] allocations for N header values in GetCommaSeparatedValues #54808
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stephentoub
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davidfowl
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amcasey
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Are you interested in having a look before I merge, @BrennanConroy? |
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I can look after you merge. As you can imagine, I have a lot to catch up on. |
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Reduce allocation in HeaderDictionaryExtensions.GetCommaSeparatedValues
Description
The method parses the header value, adding each segment as a string into a StringValues. It does so one at a time, such that each addition requires allocating a new array one element larger than the previous, for O(N) allocations and O(N^2) work. The only consumer of that also doesn't actually use StringValues: it immediately ToArray's it. So this just builds up the array directly, starting with stack memory for the first four elements and growing into array pool buffers if more is needed, then producing a single array of the right size at the end.