Define slice-copy! and slice-zero!.

These will be used for the ancillary message parsing code,
which will be used to generate more detailed network error
messages than what can be interferenced from the errno.

* tests/bv-slice.scm: New test file, testing slice-copy!
  and slice-zero!
* gnu/gnunet/utils/bv-slice.scm (slice-zero!, slice-copy!):
  New procedures.  Also comment the module more.
* Makefile.am (SCM_TESTS): Register tests/bv-slice.scm.

1 files changed, 38 insertions, 8 deletions

diff --git a/gnu/gnunet/utils/bv-slice.scm b/gnu/gnunet/utils/bv-slice.scm
index 4dfbc2c..a4156b9 100644
--- a/gnu/gnunet/utils/bv-slice.scm
+++ b/gnu/gnunet/utils/bv-slice.scm
@@ -1,5 +1,5 @@
 ;;   This file is part of scheme-GNUnet, a partial Scheme port of GNUnet.
-;;   Copyright (C) 2020 Maxime Devos <maxime.devos@student.kuleuven.be>
+;;   Copyright (C) 2020, 2021 Maxime Devos <maximedevos@telenet.be>
 ;;
 ;;   scheme-GNUnet is free software: you can redistribute it and/or modify it
 ;;   under the terms of the GNU Affero General Public License as published
@@ -15,11 +15,6 @@
 ;;   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ;;
 ;;   SPDX-License-Identifier: AGPL-3.0-or-later
-;;
-;;   As a special exception to the GNU Affero General Public License,
-;;   the file may be relicensed under any license used for
-;;   most source code of GNUnet 0.13.1, or later versions, as published by
-;;   GNUnet e.V.
 
 ;; Author: Maxime Devos
 ;; Source: gnu/gnunet/utils/bv-slice.scm
@@ -28,6 +23,7 @@
 
 (library (gnu gnunet utils bv-slice)
   (export slice?
+          ;; Slicing
           slice-bv
           slice-offset
           slice-length
@@ -39,6 +35,7 @@
           slice/read-only
           slice/write-only
           slice/read-write
+          ;; Small operations
           slice-u8-ref
           slice-u16-ref
           slice-u32-ref
@@ -46,13 +43,18 @@
           slice-u8-set!
           slice-u16-set!
           slice-u32-set!
-          slice-u64-set!)
+          slice-u64-set!
+          ;; Large operations
+          slice-copy!
+          slice-zero!)
   (import (rnrs arithmetic bitwise)
           (rnrs base)
           (rnrs bytevectors)
           (rnrs control)
           (rnrs records syntactic)
           (srfi srfi-31))
+  
+  ;; Slicing
 
   (define-record-type (<slice> %make-slice slice?)
     ;; TODO: perhaps use pointer->bytevector
@@ -150,6 +152,9 @@ the bytevector in place."
   (define slice/read-write
     (make-select-capabilities (bitwise-ior CAP_READ CAP_WRITE)))
 
+  
+  ;; ‘Small’ operations
+
   (define (wrap-rnrs-ref rnrs-ref ok? size)
     (lambda (slice index . rest)
       (assert (and (exact? index)
@@ -177,4 +182,29 @@ the bytevector in place."
   (define slice-u32-set!
     (wrap-rnrs-ref bytevector-u32-set! slice-writable? 4))
   (define slice-u64-set!
-    (wrap-rnrs-ref bytevector-u64-set! slice-writable? 8)))
+    (wrap-rnrs-ref bytevector-u64-set! slice-writable? 8))
+
+  
+  ;; ‘Large’ operations.
+
+  (define (slice-zero! slice)
+    "Zero out the writable slice @var{slice}."
+    (assert (slice-writable? slice))
+    ;; TODO optimise this and/or optimise guile's compiler
+    ;; w.r.t. bytevectors, structs and type inference.
+    (let loop ((i 0))
+      (when (< i (slice-length slice))
+        (slice-u8-set! slice i 0)
+        (loop (+ i 1))))
+    (values))
+
+  (define (slice-copy! from to)
+    "Copy the contents of the readable slice @var{from} to
+the writable slice @var{slice}.  The slices may overlap."
+    (assert (slice-readable? from))
+    (assert (slice-writable? to))
+    (assert (= (slice-length from) (slice-length to)))
+    (bytevector-copy! (slice-bv from) (slice-offset from)
+                      (slice-bv to) (slice-offset to)
+                      (slice-length from))
+    (values)))