[gnunet-scheme] 02/324: Define hashcodes

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maxime-devos pushed a commit to branch master
in repository gnunet-scheme.

commit 525d153dfef3925887f0beb649223bd2d3ccf00d
Author: Maxime Devos <maximedevos@telenet.be>
AuthorDate: Mon Nov 2 14:10:01 2020 +0100

    Define hashcodes
---
 gnu/gnunet/hashcode.scm | 84 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)

diff --git a/gnu/gnunet/hashcode.scm b/gnu/gnunet/hashcode.scm
new file mode 100644
index 0000000..de68267
--- /dev/null
+++ b/gnu/gnunet/hashcode.scm
@@ -0,0 +1,84 @@
+;;   This file is part of scheme-GNUnet, a partial Scheme port of GNUnet.
+;;   Copyright (C) 2006--2020 GNUnet e.V.
+;;   Copyright (C) 2020 Maxime Devos <maxime.devos@student.kuleuven.be>
+;;
+;;   GNUnet is free software: you can redistribute it and/or modify it
+;;   under the terms of the GNU Affero General Public License as published
+;;   by the Free Software Foundation, either version 3 of the License,
+;;   or (at your option) any later version.
+;;
+;;   GNUnet is distributed in the hope that it will be useful, but
+;;   WITHOUT ANY WARRANTY; without even the implied warranty of
+;;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;   Affero General Public License for more details.
+;;
+;;   You should have received a copy of the GNU Affero General Public License
+;;   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.
+
+;; Extracted from src/include/gnunet_common.h
+
+(library (gnu gnunet hashcode)
+  (export hashcode-bit-length hashcode-u8-length
+          short-hashcode-bit-length short-hashcode-u8-length
+          hashcode? short-hashcode?
+          bv->hashcode bv->short-hashcode
+          hashcode->bv short-hashcode->bv)
+  (import (rnrs base)
+         (rnrs control)
+          (rnrs records syntactic)
+         (rnrs bytevectors))
+
+  (define hashcode-bit-length 512)
+  (define short-hashcode-bit-length 256)
+  (define hashcode-u8-length (/ hashcode-bit-length 8))
+  (define short-hashcode-u8-length (/ short-hashcode-bit-length 8))
+
+  ;; A 512-bit hashcode.  These are the default length for GNUnet,
+  ;; using SHA-512.
+  (define-record-type (<hashcode> %make-hashcode hashcode?)
+    (fields (immutable bv %hashcode-bv))
+    (opaque #t)
+    (sealed #t))
+
+  ;; A 256-bit hashcode.  Used under special conditions, like when space
+  ;; is critical and security is not impacted by it.
+  (define-record-type (<short-hashcode> %make-short-hashcode short-hashcode?)
+    (fields (immutable bv %short-hashcode-bv))
+    (opaque #t)
+    (sealed #t))
+
+  (define (bv->something %wrap length)
+    (case-lambda
+      "Read something from a bytevector"
+      ((bv) ; whole bytevector
+       (assert (= (bytevector-length bv) length))
+       (%wrap (bytevector-copy bv)))
+      ((bv offset) ; part of a bytevector, starting at some offset
+       (assert (<= (+ offset length) (bytevector-length bv)))
+       (let ((bv-new (make-bytevector length)))
+         (bytevector-copy! bv 0 bv-new 0 length)
+         (%wrap bv-new)))))
+
+  (define bv->hashcode
+    (bv->something %make-hashcode hashcode-u8-length))
+  (define bv->short-hashcode
+    (bv->something %make-short-hashcode short-hashcode-u8-length))
+
+  (define (hashcode->bv hashcode)
+    "Extract the bytevector corresponding to @var{hashcode}
+(read-only)"
+    (bytevector-copy (%hashcode-bv hashcode)))
+
+  (define (short-hashcode->bv hashcode)
+    "Extract the bytevector corresponding to @var{short-hashcode}
+(read-only)"
+    (bytevector-copy (%short-hashcode-bv hashcode))))
+
+

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