I've been troubled with a weird problem in read-response-body for a long
time.
I think read-response-body never return the received data when any break
happens. No matter the break caused by connection problem or user
interruption.
The only possible read-response-body returns data is connection never down
and all the data have been received even if I want to download a 2G file.
Or there's no
chance to write any data to the disk. When break occurs, all the received
data will evaporate.
Considering my terrible network, I decide not to pray for good luck when I
establish connection with our web module.
So here's a patch to fix it.
The new read-response-body will add the received data to the exceptional
information which used by "throw", if read-response-body can't continue to
work anymore, the received data will return with throw.
And there's a useful helper function to write this data to the disk ==>
(output-received-response-body e port)
However, add received data to the exceptions will cause troubles when
tracing or REPL throw exceptional information, because received data(as a
bytevector) is usually huge. So there's another helper function to get rid
of the received data after you handle the received data in your way. It
will re-throw the original information in case other program need to catch
it. ==> (throw-from-response-body-break e)
It's easy to use them, but you must catch anything when your code contains
read-response-body:
----------------------------cut-------------------------
(catch #t
(lambda ()
.....do some work with read-response-body...)
(lambda e
(output-received-response-body e port) ;; write
received-data to the disk or you may decide to store it to other place.
...
...
(throw-from-response-body-break e))) ;; re-throw the
original information in the last step.
---------------------------end---------------------------
Anyway, one may use it in his/her own way if he/she checkout their
implementation. The helper functions are not always necessary.
But I do think read-response-body should return the received data when it
breaks.
Any comments?
Regards.
From 6b6aef2192769ce12a2962b02d103a019f4bc9c6 Mon Sep 17 00:00:00 2001
From: NalaGinrut <nalagin...@gmail.com>
Date: Sun, 11 Mar 2012 23:02:07 +0800
Subject: [PATCH] read-response-body should return received data in any break
---
module/web/response.scm | 52 +++++++++++++++++++++++++++++++++++++++-------
1 files changed, 44 insertions(+), 8 deletions(-)
diff --git a/module/web/response.scm b/module/web/response.scm
index 07e1245..e3ea0a6 100644
--- a/module/web/response.scm
+++ b/module/web/response.scm
@@ -21,6 +21,7 @@
(define-module (web response)
#:use-module (rnrs bytevectors)
+ #:autoload (rnrs) (call-with-port)
#:use-module (ice-9 binary-ports)
#:use-module (ice-9 rdelim)
#:use-module (srfi srfi-9)
@@ -38,6 +39,8 @@
response-must-not-include-body?
read-response-body
+ output-received-response-body
+ throw-from-response-body-break
write-response-body
;; General headers
@@ -224,16 +227,49 @@ This is true for some response types, like those with code 304."
(= (response-code r) 204)
(= (response-code r) 304)))
-(define (read-response-body r)
+(define* (read-response-body r #:key (block 4096))
"Reads the response body from @var{r}, as a bytevector. Returns
@code{#f} if there was no response body."
- (let ((nbytes (response-content-length r)))
- (and nbytes
- (let ((bv (get-bytevector-n (response-port r) nbytes)))
- (if (= (bytevector-length bv) nbytes)
- bv
- (bad-response "EOF while reading response body: ~a bytes of ~a"
- (bytevector-length bv) nbytes))))))
+ (let* ((nbytes (response-content-length r))
+ (bv (and nbytes (make-bytevector nbytes)))
+ (start 0))
+ (catch #t
+ (lambda ()
+ (let lp((buf (get-bytevector-n (response-port r) block)))
+ (if (eof-object? buf)
+ bv
+ (let ((len (bytevector-length buf)))
+ (cond
+ ((<= len block)
+ (bytevector-copy! buf 0 bv start len)
+ (set! start (+ start len))
+ (lp (get-bytevector-n (response-port r) block)))
+ (else
+ (bad-response "EOF while reading response body: ~a bytes of ~a"
+ start nbytes)))))))
+ (lambda (k . e)
+ (let ((received (call-with-port
+ (open-bytevector-input-port bv)
+ (lambda (port)
+ (get-bytevector-n port start)))))
+ (throw k `(,@e (body ,@received))) ;; return the received data
+ )))))
+
+;; output the received data if there is, or do nothing
+(define (output-received-response-body e port)
+ (let ((received (assoc-ref (cadr e) 'body)))
+ (if received
+ (begin
+ (put-bytevector port received)
+ (force-output port)))))
+
+;; Exceptional information contains the received bytevector added from the
+;; read-response-body if any exception had been caught.
+;; If received data ware huge(it always does), it'd be a trouble during the tracing.
+;; This helper function could get rid of the received data from exceptional info,
+;; and re-throw it.
+(define (throw-from-response-body-break e)
+ (throw (car e) (list-head (cdr e) (1- (length (cdr e))))))
(define (write-response-body r bv)
"Write @var{bv}, a bytevector, to the port corresponding to the HTTP
--
1.7.0.4
