http-client: Update backport of chunked encoding support to Guile 2.0.5.

* guix/http-client.scm (read-chunk, read-chunk-body)
  [when-guile<=2.0.5]: Remove.
  (make-chunked-input-port) [when-guile<=2.0.5]: Update to Guile commit
  00d3ecf2.

guix/http-client.scm

@@ -1,7 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
-;;; Copyright © 2012 Free Software Foundation, Inc.
+;;; Copyright © 2012, 2015 Free Software Foundation, Inc.
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -65,8 +65,8 @@
        #'(begin body ...)))))
 
 (when-guile<=2.0.5
- ;; Backport of Guile commit 312e79f8 ("Add HTTP Chunked Encoding support to
- ;; web modules.").
+ ;; Backport of Guile commits 312e79f8 ("Add HTTP Chunked Encoding support to
+ ;; web modules.") and 00d3ecf2 ("http: Do not buffer HTTP chunks.")
 
  (use-modules (ice-9 rdelim))
 
@@ -81,53 +81,50 @@
                                 16)))
      size))
 
- (define (read-chunk port)
-   (let ((size (read-chunk-header port)))
-     (read-chunk-body port size)))
-
- (define (read-chunk-body port size)
-   (let ((bv (get-bytevector-n port size)))
-     (get-u8 port)                                ; CR
-     (get-u8 port)                                ; LF
-     bv))
-
  (define* (make-chunked-input-port port #:key (keep-alive? #f))
    "Returns a new port which translates HTTP chunked transfer encoded
 data from PORT into a non-encoded format. Returns eof when it has
 read the final chunk from PORT. This does not necessarily mean
 that there is no more data on PORT. When the returned port is
 closed it will also close PORT, unless the KEEP-ALIVE? is true."
-   (define (next-chunk)
-     (read-chunk port))
-   (define finished? #f)
    (define (close)
      (unless keep-alive?
        (close-port port)))
-   (define buffer #vu8())
-   (define buffer-size 0)
-   (define buffer-pointer 0)
+
+   (define chunk-size 0)     ;size of the current chunk
+   (define remaining 0)      ;number of bytes left from the current chunk
+   (define finished? #f)     ;did we get all the chunks?
+
    (define (read! bv idx to-read)
      (define (loop to-read num-read)
        (cond ((or finished? (zero? to-read))
               num-read)
-             ((<= to-read (- buffer-size buffer-pointer))
-              (bytevector-copy! buffer buffer-pointer
-                                bv (+ idx num-read)
-                                to-read)
-              (set! buffer-pointer (+ buffer-pointer to-read))
-              (loop 0 (+ num-read to-read)))
-             (else
-              (let ((n (- buffer-size buffer-pointer)))
-                (bytevector-copy! buffer buffer-pointer
-                                  bv (+ idx num-read)
-                                  n)
-                (set! buffer (next-chunk))
-                (set! buffer-pointer 0)
-                (set! buffer-size (bytevector-length buffer))
-                (set! finished? (= buffer-size 0))
-                (loop (- to-read n)
-                      (+ num-read n))))))
+             ((zero? remaining)                    ;get a new chunk
+              (let ((size (read-chunk-header port)))
+                (set! chunk-size size)
+                (set! remaining size)
+                (if (zero? size)
+                    (begin
+                      (set! finished? #t)
+                      num-read)
+                    (loop to-read num-read))))
+             (else                           ;read from the current chunk
+              (let* ((ask-for (min to-read remaining))
+                     (read    (get-bytevector-n! port bv (+ idx num-read)
+                                                 ask-for)))
+                (if (eof-object? read)
+                    (begin                         ;premature termination
+                      (set! finished? #t)
+                      num-read)
+                    (let ((left (- remaining read)))
+                      (set! remaining left)
+                      (when (zero? left)
+                        ;; We're done with this chunk; read CR and LF.
+                        (get-u8 port) (get-u8 port))
+                      (loop (- to-read read)
+                            (+ num-read read))))))))
      (loop to-read 0))
+
    (make-custom-binary-input-port "chunked input port" read! #f #f close))
 
  (define (read-response-body* r)