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Diffstat (limited to 'ebus-racket/parser.rkt')
| -rw-r--r-- | ebus-racket/parser.rkt | 98 |
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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