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https://issues.apache.org/jira/browse/CASSANDRA-15410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16974246#comment-16974246
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Aleksey Yeschenko commented on CASSANDRA-15410:
-----------------------------------------------

I welcome this change in principle, but it makes me feel a little uneasy. 
Specifically, it relies implicitly on how the method is used two levels of 
abstraction up, and feels slightly brittle to me.

I wonder if you'd be open instead to a slightly less efficient but, 
importantly, still resize-avoiding alternative: modify {{CBUtil#writeString()}} 
(and {{CBUtil#writeLongString()}} while at it, just for consistency sake) to 
explicitly calculate the precise size of encoded string using 
{{TypeSizes#encodedUTF8Length()}} method, and then pass that value to 
{{ByteBufUtil#reserveAndWriteUtf8()}}. This way, yes, you would effectively 
calculate the size of the string twice, but the abstraction won't leak 
assumptions, and will still avoid unnecessary resizing.

> Avoid over-allocation of bytes for UTF8 string serialization 
> -------------------------------------------------------------
>
>                 Key: CASSANDRA-15410
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15410
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Messaging/Client
>            Reporter: Yifan Cai
>            Assignee: Yifan Cai
>            Priority: Normal
>             Fix For: 4.0
>
>
> In the current message encoding implementation, it first calculates the 
> `encodeSize` and allocates the bytebuffer with that size. 
> However, during encoding, it assumes the worst case of writing UTF8 string to 
> allocate bytes, i.e. assuming each letter takes 3 bytes. 
> The over-estimation further leads to resizing the underlying array and data 
> copy. 



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