From: Chris Hanson <org/chris-hanson/cph>
Date: Fri, 28 Apr 2017 04:48:09 +0000 (-0700)
Subject: Implement conversions between integers and bytevectors.
X-Git-Tag: mit-scheme-pucked-9.2.12~14^2~125
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=3d355e87bd00f3beed13cb073c235122ce79e439;p=mit-scheme.git

Implement conversions between integers and bytevectors.
---

diff --git a/src/runtime/bytevector.scm b/src/runtime/bytevector.scm
index 95c310b24..422f5ae3f 100644
--- a/src/runtime/bytevector.scm
+++ b/src/runtime/bytevector.scm
@@ -46,6 +46,7 @@ USA.
   (bytevector-u8-ref 2)
   (bytevector-u8-set! 3)
   (bytevector? 1)
+  (integer-length-in-bits 1)
   (legacy-string-allocate string-allocate 1)
   (legacy-string? string? 1))
 
@@ -435,4 +436,21 @@ USA.
 	(builder
 	 (fix:+ (fix:lsh (hex-digit (string-ref string i)) 4)
 		(hex-digit (string-ref string (fix:+ i 1))))))
-      (builder))))
\ No newline at end of file
+      (builder))))
+
+(define (bytevector->exact-nonnegative-integer bytes)
+  (let ((len (bytevector-length bytes)))
+    (do ((i 0 (fix:+ i 1))
+	 (n 0 (+ (* n #x100) (bytevector-u8-ref bytes i))))
+	((not (fix:< i len)) n))))
+
+(define (exact-nonnegative-integer->bytevector n)
+  (guarantee exact-nonnegative-integer? n
+	     'exact-nonnegative-integer->bytevector)
+  (let* ((n-bytes (quotient (+ (integer-length-in-bits n) #xFF) #x100))
+	 (result (make-bytevector n-bytes)))
+    (do ((n n (quotient n #x100))
+	 (i 0 (fix:+ i 1)))
+	((not (> n 0)))
+      (bytevector-u8-set! result i (remainder n #x100)))
+    result))
\ No newline at end of file
diff --git a/src/runtime/runtime.pkg b/src/runtime/runtime.pkg
index ac938e528..342dea51e 100644
--- a/src/runtime/runtime.pkg
+++ b/src/runtime/runtime.pkg
@@ -1075,6 +1075,7 @@ USA.
   (export ()
 	  (byte? u8?)
 	  bytevector
+	  bytevector->exact-nonnegative-integer
 	  bytevector->hexadecimal
 	  bytevector->list
 	  bytevector->vector
@@ -1097,6 +1098,7 @@ USA.
 	  bytevector-u8-set!
 	  bytevector=?
 	  bytevector?
+	  exact-nonnegative-integer->bytevector
 	  hexadecimal->bytevector
 	  list->bytevector
 	  make-bytevector