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Improving (chibi bytevector) docs.

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Alex Shinn 2015-04-30 17:30:39 +09:00
parent 93730efceb
commit 0e83df3f91
2 changed files with 40 additions and 16 deletions
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54
lib/chibi/bytevector.scm
View file

@ -1,28 +1,43 @@
;;> \section{Additional accessors}
(define (bytevector-u16-ref-le str i)
(+ (bytevector-u8-ref str i)
(arithmetic-shift (bytevector-u8-ref str (+ i 1)) 8)))
;;> Retrieve a 16-bit unsigned integer value from the given bytevector
;;> \var{bv} at offset \var{i}, in little-endian order.
(define (bytevector-u16-ref-be str i)
(+ (arithmetic-shift (bytevector-u8-ref str i) 8)
(bytevector-u8-ref str (+ i 1))))
(define (bytevector-u16-ref-le bv i)
(+ (bytevector-u8-ref bv i)
(arithmetic-shift (bytevector-u8-ref bv (+ i 1)) 8)))
(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)))
;;> Retrieve a 16-bit unsigned integer value from the given bytevector
;;> \var{bv} at offset \var{i}, in big-endian order.
(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))))
(define (bytevector-u16-ref-be bv i)
(+ (arithmetic-shift (bytevector-u8-ref bv i) 8)
(bytevector-u8-ref bv (+ i 1))))
;;> Retrieve a 32-bit unsigned integer value from the given bytevector
;;> \var{bv} at offset \var{i}, in little-endian order.
(define (bytevector-u32-ref-le bv i)
(+ (bytevector-u8-ref bv i)
(arithmetic-shift (bytevector-u8-ref bv (+ i 1)) 8)
(arithmetic-shift (bytevector-u8-ref bv (+ i 2)) 16)
(arithmetic-shift (bytevector-u8-ref bv (+ i 3)) 24)))
;;> Retrieve a 32-bit unsigned integer value from the given bytevector
;;> \var{bv} at offset \var{i}, in big-endian order.
(define (bytevector-u32-ref-be bv i)
(+ (arithmetic-shift (bytevector-u8-ref bv i) 24)
(arithmetic-shift (bytevector-u8-ref bv (+ i 1)) 16)
(arithmetic-shift (bytevector-u8-ref bv (+ i 2)) 8)
(bytevector-u8-ref bv (+ i 3))))
;;> \section{Integer conversion}
;;> Convert an unsigned integer \var{n} to a bytevector representing
;;> the base-256 big-endian form (the zero index holds the MSB).
(define (integer->bytevector n)
(cond
((zero? n)
@ -40,6 +55,10 @@
(bytevector-u8-set! bv i (car ls))))
(lp (quotient n 256) (cons (remainder n 256) res)))))))
;;> The inverse of \scheme{integer->bytevector}. Convert a bytevector
;;> representing the base-256 big-endian form (the zero index holds
;;> the MSB) to the corresponding unsigned integer.
(define (bytevector->integer bv)
(let ((len (bytevector-length bv)))
(let lp ((i 0) (n 0))
@ -49,6 +68,9 @@
(+ (arithmetic-shift n 8)
(bytevector-u8-ref bv i)))))))
;;> Utility to pad a bytevector with zeros. Padding is added to the
;;> left so as not to change the big-endian value.
(define (bytevector-pad-left bv len)
(let ((diff (- len (bytevector-length bv))))
(if (positive? diff)

2
lib/chibi/bytevector.sld
View file

@ -1,4 +1,6 @@
;;> Additional bytevector utilities.
(define-library (chibi bytevector)
(export
bytevector-u16-ref-le bytevector-u16-ref-be