<div class="gmail_quote">On Fri, Jan 16, 2009 at 12:06 PM, Matthew Flatt <<a href="mailto:mflatt@cs.utah.edu">mflatt@cs.utah.edu</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div><div></div><div class="Wj3C7c"> > (define-struct byte-port (bytes port) #:property prop:input-port 1) > > Are there any issues (cost, synchronization, etc) with using port structs > this way that I need to think about? </div></div>No --- that should work well. There is an overhead in using the wrapped port, but it's small compared to most any operation on the port. </blockquote><div> Thanks for verifying, Matthew.  I did a quick test and found that the overhead is minimal.  I also compared against `substring` as reference, and found that regular string port still has a bit of overhead above substring.  Is the overhead due to synchronization primitives? Thanks, yc (define s "this is a string that we are going to read and peek from") (define-struct wport (inner port) #:property prop:input-port 1) (define (open-input-wport s)   (make-wport s ((cond ((string? s) open-input-string)                        ((bytes? s) open-input-bytes)                        (else (error 'open-input-wport "Unknown type: ~a" s))) s))) (define (test-port in count)   (for ((i (in-range 0 count)))        (read-bytes 50 in)        (file-position in 0))) (define (test-string s count)   (for ((i (in-range 0 count)))        (substring s 0 50))) (define (test count)   (let ((in1 (open-input-string s))         (in2 (open-input-wport s)))     (time (test-port in1 count))     (time (test-port in2 count))     (time (test-string s count))     )) (test 500) ;; cpu time: 0 real time: 0 gc time: 0 ;; string port ;; cpu time: 1 real time: 1 gc time: 0 ;; wrapped port ;; cpu time: 0 real time: 0 gc time: 0 ;; substring (test 5000) ;; cpu time: 3 real time: 4 gc time: 0 ;; cpu time: 36 real time: 35 gc time: 31 ;; cpu time: 2 real time: 2 gc time: 0 (test 50000) ;; cpu time: 30 real time: 30 gc time: 0 ;; cpu time: 43 real time: 43 gc time: 1 ;; cpu time: 14 real time: 14 gc time: 0 (test 500000) ;; cpu time: 195 real time: 195 gc time: 4 ;; cpu time: 291 real time: 291 gc time: 4 ;; cpu time: 134 real time: 134 gc time: 7 (test 5000000) ;; cpu time: 1982 real time: 1982 gc time: 64 ;; cpu time: 3081 real time: 3080 gc time: 69 ;; cpu time: 1464 real time: 1465 gc time: 205 </div> </div>