;;;; string-hexadecimal.scm  -*- Scheme -*-
;;;; Kon Lovett, Jul '18
;;;; Kon Lovett, Aug '17
;;;; Kon Lovett, Aug '10

(declare
  (bound-to-procedure
    ##sys#signal-hook
    ##sys#make-string))

(module string-hexadecimal

(;export
  string->hex *string->hex
  hex->string *hex->string)

(import scheme)
(import (chicken base))
(import (chicken type))
(import (chicken foreign))
(import (chicken memory representation))
(import to-hex)
(import (only type-checks check-natural-fixnum check-string))

;;

(: string->hex (string #!optional fixnum (or boolean fixnum) --> string))
(: hex->string (string #!optional fixnum --> string))
(: *string->hex (string fixnum fixnum --> string))
(: *hex->string (string fixnum fixnum --> string))

;;

(define (check-subvector-indexes loc start end)
  (unless
    (<=
      (check-natural-fixnum loc start 'start)
      (check-natural-fixnum loc end 'end))
    (##sys#signal-hook #:bounds-error loc "illegal subvector specification" start end) ) )

;;

(define (string->hex str #!optional (start 0) (end #f))
  (let* (
    (len (number-of-bytes (check-string 'string->hex str)))
    (end (or end len)) )
    (check-subvector-indexes 'string->hex start end)
    (*string->hex str start end) ) )

(define (hex->string str #!optional (start 0) (end #f))
  (let* (
    (len (number-of-bytes (check-string 'hex->string str)))
    (end (or end len)) )
    (unless (zero? (modulo end 2))
      (error 'hex->string "too few characters" str) )
    (check-subvector-indexes 'hex->string start end)
    (*hex->string str start end) ) )

;;

(define (*string->hex str start end)
  (let (
    (len (- end start)) )
    (if (zero? len)
      ""
      (str_to_hex (##sys#make-string (* len 2)) str start len) ) ) )

(define (*hex->string str start end)
  (let (
    (len (- end start)) )
    (if (zero? len)
      ""
      (hex_to_str (##sys#make-string (quotient len 2)) str start len) ) ) )

#|
(import
  (only (srfi 1) drop drop-right)
  (only (srfi 13) string-pad string-concatenate  reverse-list->string))

(define ( ch)
  (string-pad (number->string (char->integer ch) 16) 2 #\0) )

(define (*string->hex str start end)
  (let* (
    (ls (string->list str))
    (ls (drop ls start))
    (strlen (string-length str))
    (ls (drop-right ls (- strlen end))) )
    (string-concatenate
      (map
        (lambda (c)
          (string-pad (number->string (char->integer c) 16) 2 #\0))
      ls)) ) )

(define (*hex->string str)
  (let (
    (len (string-length str)) )
    (let loop ((i 0) (ls '()))
      (if (<= len i)
        (reverse-list->string ls)
        (let (
          (ni (+ i 2)) )
          (loop ni (cons (integer->char (string->number (substring str i ni) 16)) ls)) ) ) ) ) )
|#

) ;module string-hexadecimal