store: Add store path computation procedures.

* guix/derivations.scm (compressed-hash, store-path)
(output-path, fixed-output-path): Move to...
* guix/store.scm: ... here.

guix/derivations.scm

@@ -76,7 +76,6 @@
             derivation-name
             derivation-output-names
             fixed-output-derivation?
-            fixed-output-path
             offloadable-derivation?
             substitutable-derivation?
             substitution-oracle
@@ -614,20 +613,6 @@ list of name/path pairs of its outputs."
 ;;; Derivation primitive.
 ;;;
 
-(define (compressed-hash bv size)                 ; `compressHash'
-  "Given the hash stored in BV, return a compressed version thereof that fits
-in SIZE bytes."
-  (define new (make-bytevector size 0))
-  (define old-size (bytevector-length bv))
-  (let loop ((i 0))
-    (if (= i old-size)
-        new
-        (let* ((j (modulo i size))
-               (o (bytevector-u8-ref new j)))
-          (bytevector-u8-set! new j
-                              (logxor o (bytevector-u8-ref bv i)))
-          (loop (+ 1 i))))))
-
 (define derivation-path->base16-hash
   (mlambda (file)
     "Return a string containing the base16 representation of the hash of the
@@ -674,43 +659,6 @@ derivation at FILE."
          ;; character.
          (sha256 (derivation->bytevector drv)))))))
 
-(define (store-path type hash name)               ; makeStorePath
-  "Return the store path for NAME/HASH/TYPE."
-  (let* ((s (string-append type ":sha256:"
-                           (bytevector->base16-string hash) ":"
-                           (%store-prefix) ":" name))
-         (h (sha256 (string->utf8 s)))
-         (c (compressed-hash h 20)))
-    (string-append (%store-prefix) "/"
-                   (bytevector->nix-base32-string c) "-"
-                   name)))
-
-(define (output-path output hash name)            ; makeOutputPath
-  "Return an output path for OUTPUT (the name of the output as a string) of
-the derivation called NAME with hash HASH."
-  (store-path (string-append "output:" output) hash
-              (if (string=? output "out")
-                  name
-                  (string-append name "-" output))))
-
-(define* (fixed-output-path name hash
-                            #:key
-                            (output "out")
-                            (hash-algo 'sha256)
-                            (recursive? #t))
-  "Return an output path for the fixed output OUTPUT defined by HASH of type
-HASH-ALGO, of the derivation NAME.  RECURSIVE? has the same meaning as for
-'add-to-store'."
-  (if (and recursive? (eq? hash-algo 'sha256))
-      (store-path "source" hash name)
-      (let ((tag (string-append "fixed:" output ":"
-                                (if recursive? "r:" "")
-                                (symbol->string hash-algo) ":"
-                                (bytevector->base16-string hash) ":")))
-        (store-path (string-append "output:" output)
-                    (sha256 (string->utf8 tag))
-                    name))))
-
 (define* (derivation store name builder args
                      #:key
                      (system (%current-system)) (env-vars '())

guix/store.scm

@@ -23,7 +23,8 @@
   #:use-module (guix serialization)
   #:use-module (guix monads)
   #:use-module (guix base16)
-  #:autoload   (guix base32) (bytevector->base32-string)
+  #:use-module (guix base32)
+  #:use-module (guix hash)
   #:autoload   (guix build syscalls) (terminal-columns)
   #:use-module (rnrs bytevectors)
   #:use-module (ice-9 binary-ports)
@@ -133,6 +134,9 @@
             interned-file
 
             %store-prefix
+            store-path
+            output-path
+            fixed-output-path
             store-path?
             direct-store-path?
             derivation-path?
@@ -1347,6 +1351,57 @@ connection, and return the result."
   ;; Absolute path to the Nix store.
   (make-parameter %store-directory))
 
+(define (compressed-hash bv size)                 ; `compressHash'
+  "Given the hash stored in BV, return a compressed version thereof that fits
+in SIZE bytes."
+  (define new (make-bytevector size 0))
+  (define old-size (bytevector-length bv))
+  (let loop ((i 0))
+    (if (= i old-size)
+        new
+        (let* ((j (modulo i size))
+               (o (bytevector-u8-ref new j)))
+          (bytevector-u8-set! new j
+                              (logxor o (bytevector-u8-ref bv i)))
+          (loop (+ 1 i))))))
+
+(define (store-path type hash name)               ; makeStorePath
+  "Return the store path for NAME/HASH/TYPE."
+  (let* ((s (string-append type ":sha256:"
+                           (bytevector->base16-string hash) ":"
+                           (%store-prefix) ":" name))
+         (h (sha256 (string->utf8 s)))
+         (c (compressed-hash h 20)))
+    (string-append (%store-prefix) "/"
+                   (bytevector->nix-base32-string c) "-"
+                   name)))
+
+(define (output-path output hash name)            ; makeOutputPath
+  "Return an output path for OUTPUT (the name of the output as a string) of
+the derivation called NAME with hash HASH."
+  (store-path (string-append "output:" output) hash
+              (if (string=? output "out")
+                  name
+                  (string-append name "-" output))))
+
+(define* (fixed-output-path name hash
+                            #:key
+                            (output "out")
+                            (hash-algo 'sha256)
+                            (recursive? #t))
+  "Return an output path for the fixed output OUTPUT defined by HASH of type
+HASH-ALGO, of the derivation NAME.  RECURSIVE? has the same meaning as for
+'add-to-store'."
+  (if (and recursive? (eq? hash-algo 'sha256))
+      (store-path "source" hash name)
+      (let ((tag (string-append "fixed:" output ":"
+                                (if recursive? "r:" "")
+                                (symbol->string hash-algo) ":"
+                                (bytevector->base16-string hash) ":")))
+        (store-path (string-append "output:" output)
+                    (sha256 (string->utf8 tag))
+                    name))))
+
 (define (store-path? path)
   "Return #t if PATH is a store path."
   ;; This is a lightweight check, compared to using a regexp, but this has to