Adding initial bytevector library.

lib/chibi/bytevector.scm

@@ -0,0 +1,68 @@
+
+;; Additional accessors
+
+(define (bytevector-u16-ref-le str i)
+  (+ (bytevector-u8-ref str i)
+     (arithmetic-shift (bytevector-u8-ref str (+ i 1)) 8)))
+
+(define (bytevector-u16-ref-be str i)
+  (+ (arithmetic-shift (bytevector-u8-ref str i) 8)
+     (bytevector-u8-ref str (+ i 1))))
+
+(define (bytevector-u32-ref-le str i)
+  (+ (bytevector-u8-ref str i)
+     (arithmetic-shift (bytevector-u8-ref str (+ i 1)) 8)
+     (arithmetic-shift (bytevector-u8-ref str (+ i 2)) 16)
+     (arithmetic-shift (bytevector-u8-ref str (+ i 3)) 24)))
+
+(define (bytevector-u32-ref-be str i)
+  (+ (arithmetic-shift (bytevector-u8-ref str i) 24)
+     (arithmetic-shift (bytevector-u8-ref str (+ i 1)) 16)
+     (arithmetic-shift (bytevector-u8-ref str (+ i 2)) 8)
+     (bytevector-u8-ref str (+ i 3))))
+
+;; Integer conversion
+
+(define (integer->bytevector n)
+  (cond
+   ((zero? n)
+    (make-bytevector 1 0))
+   ((negative? n)
+    (error "can't convert a negative integer to bytevector" n))
+   (else
+    (let lp ((n n) (res '()))
+      (if (zero? n)
+          (let* ((len (length res))
+                 (bv (make-bytevector len 0)))
+            (do ((i 0 (+ i 1))
+                 (ls res (cdr ls)))
+                ((= i len) bv)
+              (bytevector-u8-set! bv i (car ls))))
+          (lp (quotient n 256) (cons (remainder n 256) res)))))))
+
+(define (bytevector->integer bv)
+  (let ((len (bytevector-length bv)))
+    (let lp ((i 0) (n 0))
+      (if (>= i len)
+          n
+          (lp (+ i 1)
+              (+ (arithmetic-shift n 8)
+                 (bytevector-u8-ref bv i)))))))
+
+;; Hex string conversion (big-endian, guaranteed padded to even length)
+
+(define (integer->hex-string n)
+  (let* ((res (number->string n 16))
+         (len (string-length res)))
+    (if (even? len)
+        res
+        (string-append "0" res))))
+
+(define (hex-string->integer str)
+  (string->number str 16))
+
+(define (bytevector->hex-string bv)
+  (integer->hex-string (bytevector->integer bv)))
+
+(define (hex-string->bytevector str)
+  (integer->bytevector (hex-string->integer str)))

lib/chibi/bytevector.sld

@@ -0,0 +1,10 @@
+
+(define-library (chibi bytevector)
+  (export
+   bytevector-u16-ref-le bytevector-u16-ref-be
+   bytevector-u32-ref-le bytevector-u32-ref-be
+   integer->bytevector bytevector->integer
+   integer->hex-string hex-string->integer
+   bytevector->hex-string hex-string->bytevector)
+  (import (chibi) (srfi 33))
+  (include "bytevector.scm"))