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Add write-data-frame-region for zero-copy DATA frame sending #7

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Add write-data-frame-region for zero-copy DATA frame sending #7

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30 changes: 30 additions & 0 deletions core/frames/data.lisp
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Original file line number Diff line number Diff line change
Expand Up @@ -498,6 +498,36 @@ As always, use untrace to stop tracing."
(incf start (length datum))))
data)))

(defun write-data-frame-region (stream source source-offset payload-length
&key padded end-stream)
"Write a DATA frame from SOURCE[SOURCE-OFFSET..SOURCE-OFFSET+PAYLOAD-LENGTH).
Like WRITE-DATA-FRAME but copies only the specified region into the frame
buffer, avoiding an intermediate SUBSEQ allocation when sending a portion of
a larger buffer as a single DATA frame."
(declare (type (simple-array (unsigned-byte 8) (*)) source)
(type fixnum source-offset payload-length)
(optimize (speed 3)))
(let* ((padded-length (padded-length payload-length padded))
(buffer (make-octet-buffer (+ 9 padded-length)))
(keys (list :end-stream end-stream)))
(declare (dynamic-extent keys))
(write-frame-header-to-vector buffer 0 padded-length +data-frame+
(flags-to-code keys)
(get-stream-id stream) nil)
(let ((frame-start (cond (padded (setf (aref buffer 9) (length padded)) 10)
(t 9))))
(replace buffer source :start1 frame-start
:start2 source-offset
:end2 (the fixnum (+ source-offset payload-length)))
(when padded
(replace buffer padded :start1 (- (length buffer) (length padded)))))
(account-write-window-contribution (get-connection stream)
stream payload-length)
(queue-frame (get-connection stream) buffer)
(when end-stream
(change-state-on-write-end stream))
buffer))

(define-frame-writer 8 write-window-update-frame stream-or-connection nil 4
((window-size-increment 31)) ((reserved t)) "```
+-+-------------------------------------------------------------+
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