From b9683af2da882d542208a15d67d8040bab8fa5c2 Mon Sep 17 00:00:00 2001
From: Billy Brown <druidofluhn@gmail.com>
Date: Thu, 21 Dec 2023 17:07:00 +0000
Subject: Corrected Range and Content-Range header handling

Corrected the handling of the Range request header and the Content-
Range response header. They now have separate parsers, to match the
standard, and the content-range unparser is now correctly named.

The Range header can be in one of three forms:
    Range: bytes=<start>-<end>
    Range: bytes=<start>-
    Range: bytes=-<end>

The Content-Range header can be in one of three forms:
    Content-Range: bytes <start>-<end>/<size>
    Content-Range: bytes <start>-<end>/*
    Content-Range: bytes */<size>

The unit tests were updated to reflect the changes.

Signed-off-by: Peter Bex <peter@more-magic.net>
---
 header-parsers.scm | 60 ++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 52 insertions(+), 8 deletions(-)

(limited to 'header-parsers.scm')

diff --git a/header-parsers.scm b/header-parsers.scm
index 89edeae..ac41a09 100644
--- a/header-parsers.scm
+++ b/header-parsers.scm
@@ -376,18 +376,42 @@
         (cons (substring/shared contents 0 idx) version)
         (cons contents #f))))
 
-;; bytes <start>-<end>/<total>
+;; Try getting a submatch from an irregex match and parse it, or return #f
+(define (try-parse-submatch match group-name parser)
+  (and-let* ((value (irregex-match-substring match group-name)))
+    (parser value)))
+
+;; bytes=<start>-<end>
+;; bytes=<start>-
+;; bytes=-<end>
 (define range-subparser
   (let ((range-regex
+         (irregex '(seq "bytes="
+                        (=> start (* digit)) "-" (=> end (* digit))))))
+    (lambda (s)
+      (and-let* ((m (irregex-match range-regex s)))
+        (let ((start (try-parse-submatch m 'start string->number))
+              (end (try-parse-submatch m 'end string->number)))
+          (if (or start end)
+            (list start end)
+            #f))))))
+
+;; bytes <start>-<end>/<total>
+;; bytes <start>-<end>/*
+;; bytes */<total>
+(define content-range-subparser
+  (let ((content-range-regex
          (irregex '(seq "bytes" (+ space)
-                        (=> start (+ digit)) "-" (=> end (+ digit))
-                        "/" (=> total (+ digit))))))
+                        (or (seq "*/" (=> total (+ digit)))
+                            (seq (=> start (+ digit)) "-" (=> end (+ digit))
+                                 "/" (or "*"
+                                         (=> total (+ digit)))))))))
     (lambda (s)
-      (and-let* ((m (irregex-match range-regex s))
-                 (start (string->number (irregex-match-substring m 'start)))
-                 (end (string->number (irregex-match-substring m 'end)))
-                 (total (string->number (irregex-match-substring m 'total))))
-        (list start end total)))))
+      (and-let* ((m (irregex-match content-range-regex s)))
+        (let ((start (try-parse-submatch m 'start string->number))
+              (end (try-parse-submatch m 'end string->number))
+              (total (try-parse-submatch m 'total string->number)))
+          (list start end total))))))
 
 ;; Accept *just* a filename, not a full path (simply strips directories)
 ;; This matches the content-disposition recommendation in RFC2616, 19.5.1:
@@ -724,6 +748,23 @@
    (if (eq? 'weak (car etag)) "W/" "")
    (quote-string (cdr etag)))) ;; Etags are _always_ quoted
 
+(define (unparse-content-range content-range)
+  ; False values are used to represent wildcards "*"
+  (let ((content-range-value-unparser (lambda (value)
+                                        (if value
+                                          (number->string value)
+                                          "*"))))
+    (string-append "bytes "
+                   ; If the start and end are wildcards, use only one
+                   (if (not (or (car content-range) (cadr content-range)))
+                     "*"
+                     (string-append
+                       (content-range-value-unparser (car content-range))
+                       "-"
+                       (content-range-value-unparser (cadr content-range))))
+                   "/"
+                   (content-range-value-unparser (caddr content-range)))))
+
 ;; There's no need to make a specific header unparser for every header type.
 ;; Usually, the Scheme value representing a header can unambiguously be
 ;; unparsed into a header just by checking its type.
@@ -772,6 +813,9 @@
                                   (read-date . ,rfc1123-time->string))
                                 value-unparser: unparser)))))
 
+(define (content-range-unparser header-contents)
+  (list (unparse-content-range (get-value (car header-contents)))))
+
 (define (etag-unparser header-contents)
   (list (unparse-etag (get-value (car header-contents)))))
 
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