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-rw-r--r--guix/zlib.scm19
1 files changed, 15 insertions, 4 deletions
diff --git a/guix/zlib.scm b/guix/zlib.scm
index 40f5294ceb..74420129f6 100644
--- a/guix/zlib.scm
+++ b/guix/zlib.scm
@@ -168,9 +168,18 @@ closed even if closing GZFILE triggers an exception."
"Return an input port that decompresses data read from PORT, a file port.
PORT is automatically closed when the resulting port is closed. BUFFER-SIZE
is the size in bytes of the internal buffer, 8 KiB by default; using a larger
-buffer increases decompression speed."
+buffer increases decompression speed. An error is thrown if PORT contains
+buffered input, which would be lost (and is lost anyway)."
(define gzfile
- (gzdopen (fileno port) "r"))
+ (match (drain-input port)
+ ("" ;PORT's buffer is empty
+ (gzdopen (fileno port) "r"))
+ (_
+ ;; This is unrecoverable but it's better than having the buffered input
+ ;; be lost, leading to unclear end-of-file or corrupt-data errors down
+ ;; the path.
+ (throw 'zlib-error 'make-gzip-input-port
+ "port contains buffered input" port))))
(define (read! bv start count)
(gzread! gzfile bv start count))
@@ -189,8 +198,10 @@ buffer increases decompression speed."
a file port, as its sink. PORT is automatically closed when the resulting
port is closed."
(define gzfile
- (gzdopen (fileno port)
- (string-append "w" (number->string level))))
+ (begin
+ (force-output port) ;empty PORT's buffer
+ (gzdopen (fileno port)
+ (string-append "w" (number->string level)))))
(define (write! bv start count)
(gzwrite gzfile bv start count))