utils: Add 'decompressed-port' and 'compressed-port'.

* guix/utils.scm (decompressed-port, compressed-port): New procedures.
* guix/scripts/substitute-binary.scm (decompressed-port): Remove.
  (guix-substitute-binary): Pass a symbol or #f as the first argument to
  'decompress-port'.
* tests/utils.scm ("compressed-port, decompressed-port, non-file"): New
  test.

1 files changed, 24 insertions, 1 deletions

diff --git a/guix/utils.scm b/guix/utils.scm
index 15a4390074..f786c83f47 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -70,7 +70,10 @@
             call-with-temporary-output-file
             with-atomic-file-output
             fold2
-            filtered-port))
+
+            filtered-port
+            compressed-port
+            decompressed-port))
 
 
 ;;;
@@ -200,6 +203,26 @@ buffered data is lost."
               (close-port out)
               (loop in (cons child pids)))))))))
 
+(define (decompressed-port compression input)
+  "Return an input port where INPUT is decompressed according to COMPRESSION,
+a symbol such as 'xz."
+  (match compression
+    ((or #f 'none) (values input '()))
+    ('bzip2        (filtered-port `(,%bzip2 "-dc") input))
+    ('xz           (filtered-port `(,%xz "-dc") input))
+    ('gzip         (filtered-port `(,%gzip "-dc") input))
+    (else          (error "unsupported compression scheme" compression))))
+
+(define (compressed-port compression input)
+  "Return an input port where INPUT is decompressed according to COMPRESSION,
+a symbol such as 'xz."
+  (match compression
+    ((or #f 'none) (values input '()))
+    ('bzip2        (filtered-port `(,%bzip2 "-c") input))
+    ('xz           (filtered-port `(,%xz "-c") input))
+    ('gzip         (filtered-port `(,%gzip "-c") input))
+    (else          (error "unsupported compression scheme" compression))))
+
 
 ;;;
 ;;; Nixpkgs.