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https://issues.apache.org/jira/browse/MYNEWT-555?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Christopher Collins resolved MYNEWT-555.
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Resolution: Fixed
> BLE Host - Avoid mbuf copy on chr read
> --------------------------------------
>
> Key: MYNEWT-555
> URL: https://issues.apache.org/jira/browse/MYNEWT-555
> Project: Mynewt
> Issue Type: Bug
> Components: Nimble
> Reporter: Christopher Collins
> Assignee: Christopher Collins
> Fix For: v1_0_0_rel
>
>
> When the host receives any form of characteristic read request, an extraneous
> mbuf gets allocated. The sequence is:
> * Allocate new mbuf.
> * Pass new mbuf to application code so app can fill in characteristic value.
> * Copy characteristic value out of new mbuf into response mbuf
> * Free new mbuf
> The reason for the extra allocation is to simplify reads that specify
> non-zero offsets. In the case of a GATT read, the peer may read from
> different offsets of the characteristic. In an effort to simplify the API, I
> decided the requested offset should be hidden from the application. Instead,
> the application always provides the full characteristic value, and the host
> copies the requested portion out of the user-filled mbuf and into the ACL
> data packet.
> The fix is to try to reuse the response to hold the characteristic data.
> This can be done if the read request specifies an offset of 0. For non-zero
> offsets, the old behavior remains: allocate an extra mbuf and copy the data.
> Additional context:
> https://lists.apache.org/thread.html/78358745716cac9512b3c659dfe9b9b7bbb1354ee4c38d6da137bcc0@%3Cdev.mynewt.apache.org%3E
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