ebus-racket: cli interface

1 files changed, 98 insertions, 0 deletions

diff --git a/ebus-racket/parser.rkt b/ebus-racket/parser.rkt
new file mode 100644
index 0000000..1b9ed5b
--- /dev/null
+++ b/ebus-racket/parser.rkt
@@ -0,0 +1,98 @@
+#lang racket
+(require (planet bzlib/parseq:1:3))
+
+; Ebus SYN Byte-String
+(define ebus-const-syn (string->bytes/latin-1 "\xaa"))
+(define ebus-const-escape (string->bytes/latin-1 "\xa9"))
+(define ebus-const-ackok (string->bytes/latin-1 "\x00"))
+(define ebus-const-broadcastaddr 254)
+
+(struct ebus-header 
+  (source destination primaryCommand secondaryCommand payloadLength)
+  #:transparent)
+
+(struct ebus-body-broadcast (crc) #:transparent)
+
+(struct ebus-body-mastermaster (crc) #:transparent)
+
+(struct ebus-body-masterslave
+  (crc payloadSlaveLength payloadSlave crcSlave)
+  #:transparent)
+
+(struct ebus-paket (header body) #:transparent)
+
+(define parse-ebus-header (token (seq source <- any-byte
+                                      destination <- any-byte
+                                      primaryCommand <- any-byte
+                                      secondaryCommand <- any-byte
+                                      payloadLength <- any-byte
+                                      (return (ebus-header source 
+                                                           destination
+                                                           primaryCommand
+                                                           secondaryCommand
+                                                           payloadLength)) )))
+;; single, maybe escaped, payload data byte 
+(define ebus-payload (choice (seq escape-seq <- (bytes= ebus-const-escape)
+                                  escape-code <- (byte-in (list 0 1))
+                                  (return (cond
+                                            ((= escape-code 0) ebus-const-escape)
+                                            ((= escape-code 1) ebus-const-syn))))
+                             any-byte
+                             ))
+
+(define parse-ebus-broadcast (token (seq crc <- any-byte
+                                         syn <- (bytes= ebus-const-syn)
+                                         (return (ebus-body-broadcast crc)))))
+
+(define parse-ebus-mastermaster (token (seq  crc <- any-byte
+                                             ack <- (bytes= ebus-const-ackok) ; ACK des Empfängers
+                                             syn <- (bytes= ebus-const-syn)   ; SYN des Senders
+                                             (return (ebus-body-mastermaster crc)))))
+
+(define parse-ebus-masterslave (token (seq crc <- any-byte
+                                           ack <- (bytes= ebus-const-ackok) ;ACK des Empfängers
+                                           payloadSlaveLength <- any-byte
+                                           payloadSlave <- (repeat ebus-payload payloadSlaveLength payloadSlaveLength)
+                                           crcSlave <- any-byte
+                                           ackSlave <- (bytes= ebus-const-ackok) ;ACK des Senders
+                                           synSlave <- (bytes= ebus-const-syn)   ;SYN des Senders
+                                           (return (ebus-body-masterslave crc payloadSlaveLength payloadSlave crcSlave)))))
+
+(define parse-ebus-master-or-slave (token (choice parse-ebus-mastermaster parse-ebus-masterslave)))
+
+(define parse-ebus-paket (token (seq header <- parse-ebus-header
+                                     payload <- (repeat ebus-payload (ebus-header-payloadLength header) (ebus-header-payloadLength header))
+                                     body <- (cond ((= (ebus-header-destination header) ebus-const-broadcastaddr) parse-ebus-broadcast)
+                                                   (else parse-ebus-master-or-slave))
+                                     (return (ebus-paket header body)))))
+
+(define ebus-sync (tokens syncs <- (seq (repeat (string->bytes/latin-1 "\xaa")))
+                          (return (length syncs))))
+
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(define (read-ebus input-port)
+  (let ([syn   ((make-reader ebus-sync #:sof? #f #:eof? #f)  input-port)]
+        [paket   ((make-reader parse-ebus-paket #:sof? #f #:eof? #f) input-port)])
+    (cond ((not (false? syn))
+           (display (format "drop ~s x SYN (~s) ~n" syn ebus-const-syn))))
+    (cond ((not (false? paket))
+           paket)
+          ((eof-object? (peek-byte input-port))
+           eof)
+          (else
+           (display (format "drop ~s ~n" (peek-byte input-port)))
+           ; skip one byte
+           (read-byte input-port)
+           ;(file-position input-port (+ 1 (file-position input-port)))
+           (read-ebus input-port)))))
+
+(define (read-ebus-loop input-port)
+  (let ([paket (read-ebus (current-input-port))])
+    (display (format "Paket ~s~n" paket))
+    (cond ((not (eof-object? paket)) (read-ebus-loop input-port)))))
+
+(provide read-ebus
+         read-ebus-loop)
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