From 87b82b5822ca54228cfa6df29be3ad9d4bc47d16 Mon Sep 17 00:00:00 2001
From: Bryan Newbold <bnewbold@robocracy.org>
Date: Mon, 20 Feb 2017 00:05:28 -0800
Subject: Import Upstream version 2d2

---
 makcrc.scm | 49 +++++++++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 20 deletions(-)

(limited to 'makcrc.scm')

diff --git a/makcrc.scm b/makcrc.scm
index 3ea80d5..debd5c9 100644
--- a/makcrc.scm
+++ b/makcrc.scm
@@ -1,9 +1,9 @@
 ;;;; "makcrc.scm" Compute Cyclic Checksums
-;;; Copyright (C) 1995, 1996, 1997 Aubrey Jaffer.
+;;; Copyright (C) 1995, 1996, 1997, 2001 Aubrey Jaffer
 ;
-;Permission to copy this software, to redistribute it, and to use it
-;for any purpose is granted, subject to the following restrictions and
-;understandings.
+;Permission to copy this software, to modify it, to redistribute it,
+;to distribute modified versions, and to use it for any purpose is
+;granted, subject to the following restrictions and understandings.
 ;
 ;1.  Any copy made of this software must include this copyright notice
 ;in full.
@@ -17,27 +17,39 @@
 ;promotional, or sales literature without prior written consent in
 ;each case.
 
+(require 'byte)
 (require 'logical)
 
-;;;(define crc (eval (make-port-crc 16 #o010013)))
-;;;(define crc (eval (make-port-crc 08 #o053)))
-;;;(define (file-check-sum file) (call-with-input-file file crc32))
-
 (define (make-port-crc . margs)
   (define (make-mask hibit)
     (+ (ash (+ -1 (ash 1 (+ 1 (- hibit 2)))) 1) 1))
-  (define accum-bits 32)
   (define chunk-bits (integer-length (+ -1 char-code-limit)))
+  (define accum-bits #f)
   (define generator #f)
-  (cond ((pair? margs)
-	 (set! accum-bits (car margs))
-	 (cond ((pair? (cdr margs))
-		(set! generator (cadr margs))))))
+  (case (length margs)
+    ((0) #t)
+    ((1) (if (< (car margs) 128)
+	     (set! accum-bits (car margs))
+	     (set! generator (car margs))))
+    ((2)
+     (set! accum-bits (car margs))
+     (set! generator (cadr margs)))
+    (else  (slib:error 'make-port-crc 'args margs)))
   (cond ((not generator)
 	 (case accum-bits
-	   ((32) (set! generator #b00000100110000010001110110110111))
+	   ((#f 32) (set! accum-bits 32)
+	    (set! generator #b00000100110000010001110110110111)) ; CRC-32
+	   ((16) (set! generator #b0001000000001011)) ; CRC-16
+	   ;;((16) (set! generator #b0001000000100001)) ; CRC-CCIT
+	   ;;((08) (set! generator #b101011))
 	   (else (slib:error 'make-port-crc "no default polynomial for"
-			     accum-bits "bits")))))
+			     accum-bits "bits"))))
+	((not accum-bits)
+	 (set! accum-bits (+ -1 (integer-length generator)))))
+  (set! generator (logand generator (lognot (ash 1 accum-bits))))
+  (cond ((>= (integer-length generator) accum-bits)
+	 (slib:error 'make-port-crc
+		     "generator longer than" accum-bits "bits")))
   (let* ((chunk-mask (make-mask chunk-bits))
 	 (crctab (make-vector (+ 1 chunk-mask))))
     (define (accum src)
@@ -69,17 +81,14 @@
 	(do ((i 0 (+ 1 i)))
 	    ((> i chunk-mask))
 	  (vector-set! crctab i (remd i)))))
-    (cond ((>= (integer-length generator) accum-bits)
-	   (slib:error 'make-port-crc
-		       "generator longer than" accum-bits "bits")))
     (make-crc-table)
     `(lambda (port)
        (define crc 0)
        (define byte-count 0)
        (define crctab ',crctab)
-       (do ((ci (read-char port) (read-char port)))
+       (do ((ci (read-byte port) (read-byte port)))
 	   ((eof-object? ci))
-	 ,(accum '(char->integer ci))
+	 ,(accum 'ci)
 	 (set! byte-count (+ 1 byte-count)))
        (do ((byte-count byte-count (ash byte-count ,(- chunk-bits))))
 	   ((zero? byte-count))
-- 
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