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;; This file is part of scheme-GNUnet, a partial Scheme port of GNUnet.
;; 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
;; by the Free Software Foundation, either version 3 of the License,
;; or (at your option) any later version.
;;
;; scheme-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
;; Author: Maxime Devos
;; Source: gnu/gnunet/utils/bv-slice.scm
;; Brief: parts of bytevectors, with read/write restricted
;; (TODO: parts of vectors, uniform vectors ...)
(library (gnu gnunet utils bv-slice)
(export slice?
;; Slicing
slice-bv
slice-offset
slice-length
slice-slice
bv-slice/read-write
make-slice/read-write
slice-readable?
slice-writable?
slice/read-only
slice/write-only
slice/read-write
;; Small operations
slice-u8-ref
slice-u16-ref
slice-u32-ref
slice-u64-ref
slice-u8-set!
slice-u16-set!
slice-u32-set!
slice-u64-set!
slice-ieee-double-ref
slice-ieee-double-set!
;; Large operations
slice-copy!
slice-zero!)
(import (rnrs arithmetic bitwise)
(rnrs base)
(rnrs bytevectors)
(rnrs control)
(rnrs records syntactic)
(srfi srfi-31)
;; only for printing records
(only (rnrs io ports)
put-char put-string)
(only (srfi srfi-9 gnu)
set-record-type-printer!))
;; Slicing
(define-record-type (<slice> %make-slice slice?)
;; TODO: perhaps use pointer->bytevector
;; and bytevector->pointer when available
;; to remove the use of offset and length
(fields (immutable bv slice-bv) ;; unsafe: bounds may be ignored
(immutable offset slice-offset) ;; unsafe: implementation details
(immutable length slice-length)
(immutable cap-bits slice-capability-bits))
(opaque #t)
(sealed #t))
;; Not set in stone. Override the record printer to
;; avoid printing large bytevectors and instead only
;; print the sliced part.
(define (print-slice slice port)
(put-string port "#<slice (")
(put-string port
(cond ((and (slice-readable? slice)
(slice-writable? slice))
"CAP_READ | CAP_WRITE")
((slice-readable? slice)
"CAP_READ")
((slice-writable? slice)
"CAP_WRITE")
(#t
"0")))
(put-string port "):")
(let ((bv (slice-bv slice))
(end (+ (slice-offset slice)
(slice-length slice))))
(let loop ((i (slice-offset slice)))
(if (< i end)
(let ((val (bytevector-u8-ref bv i)))
(put-char port #\ )
(put-string port (number->string val))
(loop (+ i 1))))))
(put-char port #\>))
(set-record-type-printer! <slice> print-slice)
(define slice-slice
(case-lambda
"Select a part of the slice, preserving capabilities"
((slice)
(assert (slice? slice))
slice)
((slice offset)
(assert (slice? slice))
(assert (and (integer? offset)
(exact? offset)
(<= 0 offset)
(<= offset (slice-length slice))))
(%make-slice (slice-bv slice)
(+ offset (slice-offset slice))
(- (slice-length slice) offset)
(slice-capability-bits slice)))
((slice offset length)
(assert (slice? slice))
(assert (and (integer? offset)
(exact? offset)
(<= 0 offset)))
(assert (and (integer? length)
(exact? length)
(<= 0 length)))
(assert (<= (+ offset length)
(slice-length slice)))
(%make-slice (slice-bv slice)
(+ offset (slice-offset slice))
length
(slice-capability-bits slice)))))
(define CAP_READ #b1)
(define CAP_WRITE #b10)
(define CAP_ALL (bitwise-ior CAP_READ CAP_WRITE))
(define (slice-as-well process-first-arg)
(case-lambda
"Do @var{process-first-arg}, and then perhaps slice"
((obj)
(process-first-arg obj))
((obj offset)
(slice-slice (process-first-arg obj) offset))
((obj offset length)
(slice-slice (process-first-arg obj) offset length))))
(define bv-slice/read-write
(slice-as-well
(lambda (bv)
"Construct a read-write bytevector slice. Mutations will change
the bytevector in place."
(assert (bytevector? bv))
(%make-slice bv 0 (bytevector-length bv)
(bitwise-ior CAP_READ CAP_WRITE)))))
(define (make-slice/read-write length)
"Make a fresh, zero-initialised, read-write slice"
(bv-slice/read-write (make-bytevector length 0)))
(define (make-slice-cap-p required-cap-bits)
(assert (= (bitwise-and required-cap-bits CAP_ALL)
required-cap-bits))
(lambda (slice)
"Does @var{slice} have the capabilities @var{required-cap-bits}?"
(= (bitwise-and (slice-capability-bits slice) required-cap-bits)
required-cap-bits)))
(define slice-readable? (make-slice-cap-p CAP_READ))
(define slice-writable? (make-slice-cap-p CAP_WRITE))
(define (make-select-capabilities desired-cap-bits)
(let ((ok? (make-slice-cap-p desired-cap-bits)))
(slice-as-well
(lambda (slice)
(assert (ok? slice))
(%make-slice (slice-bv slice)
(slice-offset slice)
(slice-length slice)
desired-cap-bits)))))
(define slice/read-only
(make-select-capabilities CAP_READ))
(define slice/write-only
(make-select-capabilities CAP_WRITE))
(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)
(integer? index)
(<= 0 index)
(<= (+ index size) (slice-length slice))))
(assert (ok? slice))
(apply rnrs-ref (slice-bv slice)
(+ (slice-offset slice) index)
rest)))
(define slice-u8-ref
(wrap-rnrs-ref bytevector-u8-ref slice-readable? 1))
(define slice-u16-ref
(wrap-rnrs-ref bytevector-u16-ref slice-readable? 2))
(define slice-u32-ref
(wrap-rnrs-ref bytevector-u32-ref slice-readable? 4))
(define slice-u64-ref
(wrap-rnrs-ref bytevector-u64-ref slice-readable? 8))
(define slice-ieee-double-ref
(wrap-rnrs-ref bytevector-ieee-double-ref slice-readable? 8))
(define slice-u8-set!
(wrap-rnrs-ref bytevector-u8-set! slice-writable? 1))
(define slice-u16-set!
(wrap-rnrs-ref bytevector-u16-set! slice-writable? 2))
(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))
(define slice-ieee-double-set!
(wrap-rnrs-ref bytevector-ieee-double-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)))
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