From 97e4909d9e7c835b73c2eebdf4991d395c4ffb3f Mon Sep 17 00:00:00 2001 From: px4dev Date: Sun, 4 Aug 2013 19:40:57 -0700 Subject: [PATCH] Improvements to the HX stream protocol implementation. --- src/modules/systemlib/hx_stream.c | 191 ++++++++++++++++++++---------- src/modules/systemlib/hx_stream.h | 42 ++++++- 2 files changed, 167 insertions(+), 66 deletions(-) diff --git a/src/modules/systemlib/hx_stream.c b/src/modules/systemlib/hx_stream.c index 8d77f14a8d..8e9c2bfcf6 100644 --- a/src/modules/systemlib/hx_stream.c +++ b/src/modules/systemlib/hx_stream.c @@ -53,14 +53,26 @@ struct hx_stream { - uint8_t buf[HX_STREAM_MAX_FRAME + 4]; - unsigned frame_bytes; - bool escaped; - bool txerror; + /* RX state */ + uint8_t rx_buf[HX_STREAM_MAX_FRAME + 4]; + unsigned rx_frame_bytes; + bool rx_escaped; + hx_stream_rx_callback rx_callback; + void *rx_callback_arg; + /* TX state */ int fd; - hx_stream_rx_callback callback; - void *callback_arg; + bool tx_error; + uint8_t *tx_buf; + unsigned tx_resid; + uint32_t tx_crc; + enum { + TX_IDLE = 0, + TX_SEND_START, + TX_SEND_DATA, + TX_SENT_ESCAPE, + TX_SEND_END + } tx_state; perf_counter_t pc_tx_frames; perf_counter_t pc_rx_frames; @@ -81,21 +93,7 @@ static void hx_tx_raw(hx_stream_t stream, uint8_t c) { if (write(stream->fd, &c, 1) != 1) - stream->txerror = true; -} - -static void -hx_tx_byte(hx_stream_t stream, uint8_t c) -{ - switch (c) { - case FBO: - case CEO: - hx_tx_raw(stream, CEO); - c ^= 0x20; - break; - } - - hx_tx_raw(stream, c); + stream->tx_error = true; } static int @@ -105,11 +103,11 @@ hx_rx_frame(hx_stream_t stream) uint8_t b[4]; uint32_t w; } u; - unsigned length = stream->frame_bytes; + unsigned length = stream->rx_frame_bytes; /* reset the stream */ - stream->frame_bytes = 0; - stream->escaped = false; + stream->rx_frame_bytes = 0; + stream->rx_escaped = false; /* not a real frame - too short */ if (length < 4) { @@ -122,11 +120,11 @@ hx_rx_frame(hx_stream_t stream) length -= 4; /* compute expected CRC */ - u.w = crc32(&stream->buf[0], length); + u.w = crc32(&stream->rx_buf[0], length); /* compare computed and actual CRC */ for (unsigned i = 0; i < 4; i++) { - if (u.b[i] != stream->buf[length + i]) { + if (u.b[i] != stream->rx_buf[length + i]) { perf_count(stream->pc_rx_errors); return 0; } @@ -134,7 +132,7 @@ hx_rx_frame(hx_stream_t stream) /* frame is good */ perf_count(stream->pc_rx_frames); - stream->callback(stream->callback_arg, &stream->buf[0], length); + stream->rx_callback(stream->rx_callback_arg, &stream->rx_buf[0], length); return 1; } @@ -150,8 +148,8 @@ hx_stream_init(int fd, if (stream != NULL) { memset(stream, 0, sizeof(struct hx_stream)); stream->fd = fd; - stream->callback = callback; - stream->callback_arg = arg; + stream->rx_callback = callback; + stream->rx_callback_arg = arg; } return stream; @@ -179,49 +177,112 @@ hx_stream_set_counters(hx_stream_t stream, stream->pc_rx_errors = rx_errors; } +void +hx_stream_reset(hx_stream_t stream) +{ + stream->rx_frame_bytes = 0; + stream->rx_escaped = false; + + stream->tx_buf = NULL; + stream->tx_resid = 0; + stream->tx_state = TX_IDLE; +} + +int +hx_stream_start(hx_stream_t stream, + const void *data, + size_t count) +{ + if (count > HX_STREAM_MAX_FRAME) + return -EINVAL; + + stream->tx_buf = data; + stream->tx_resid = count; + stream->tx_state = TX_SEND_START; + stream->tx_crc = crc32(data, count); + return OK; +} + +int +hx_stream_send_next(hx_stream_t stream) +{ + int c; + + /* sort out what we're going to send */ + switch (stream->tx_state) { + + case TX_SEND_START: + stream->tx_state = TX_SEND_DATA; + return FBO; + + case TX_SEND_DATA: + c = *stream->tx_buf; + + switch (c) { + case FBO: + case CEO: + stream->tx_state = TX_SENT_ESCAPE; + return CEO; + } + break; + + case TX_SENT_ESCAPE: + c = *stream->tx_buf ^ 0x20; + stream->tx_state = TX_SEND_DATA; + break; + + case TX_SEND_END: + stream->tx_state = TX_IDLE; + return FBO; + + case TX_IDLE: + default: + return -1; + } + + /* if we are here, we have consumed a byte from the buffer */ + stream->tx_resid--; + stream->tx_buf++; + + /* buffer exhausted */ + if (stream->tx_resid == 0) { + uint8_t *pcrc = (uint8_t *)&stream->tx_crc; + + /* was the buffer the frame CRC? */ + if (stream->tx_buf == (pcrc + sizeof(stream->tx_crc))) { + stream->tx_state = TX_SEND_END; + } else { + /* no, it was the payload - switch to sending the CRC */ + stream->tx_buf = pcrc; + stream->tx_resid = sizeof(stream->tx_crc); + } + } + return c; +} + int hx_stream_send(hx_stream_t stream, const void *data, size_t count) { - union { - uint8_t b[4]; - uint32_t w; - } u; - const uint8_t *p = (const uint8_t *)data; - unsigned resid = count; + int result; - if (resid > HX_STREAM_MAX_FRAME) - return -EINVAL; + result = hx_stream_start(stream, data, count); + if (result != OK) + return result; - /* start the frame */ - hx_tx_raw(stream, FBO); - - /* transmit the data */ - while (resid--) - hx_tx_byte(stream, *p++); - - /* compute the CRC */ - u.w = crc32(data, count); - - /* send the CRC */ - p = &u.b[0]; - resid = 4; - - while (resid--) - hx_tx_byte(stream, *p++); - - /* and the trailing frame separator */ - hx_tx_raw(stream, FBO); + int c; + while ((c = hx_stream_send_next(stream)) >= 0) + hx_tx_raw(stream, c); /* check for transmit error */ - if (stream->txerror) { - stream->txerror = false; + if (stream->tx_error) { + stream->tx_error = false; return -EIO; } perf_count(stream->pc_tx_frames); - return 0; + return OK; } void @@ -234,17 +295,17 @@ hx_stream_rx(hx_stream_t stream, uint8_t c) } /* escaped? */ - if (stream->escaped) { - stream->escaped = false; + if (stream->rx_escaped) { + stream->rx_escaped = false; c ^= 0x20; } else if (c == CEO) { - /* now escaped, ignore the byte */ - stream->escaped = true; + /* now rx_escaped, ignore the byte */ + stream->rx_escaped = true; return; } /* save for later */ - if (stream->frame_bytes < sizeof(stream->buf)) - stream->buf[stream->frame_bytes++] = c; + if (stream->rx_frame_bytes < sizeof(stream->rx_buf)) + stream->rx_buf[stream->rx_frame_bytes++] = c; } diff --git a/src/modules/systemlib/hx_stream.h b/src/modules/systemlib/hx_stream.h index 128689953a..1f3927222a 100644 --- a/src/modules/systemlib/hx_stream.h +++ b/src/modules/systemlib/hx_stream.h @@ -58,7 +58,8 @@ __BEGIN_DECLS * Allocate a new hx_stream object. * * @param fd The file handle over which the protocol will - * communicate. + * communicate, or -1 if the protocol will use + * hx_stream_start/hx_stream_send_next. * @param callback Called when a frame is received. * @param callback_arg Passed to the callback. * @return A handle to the stream, or NULL if memory could @@ -80,6 +81,7 @@ __EXPORT extern void hx_stream_free(hx_stream_t stream); * * Any counter may be set to NULL to disable counting that datum. * + * @param stream A handle returned from hx_stream_init. * @param tx_frames Counter for transmitted frames. * @param rx_frames Counter for received frames. * @param rx_errors Counter for short and corrupt received frames. @@ -89,6 +91,44 @@ __EXPORT extern void hx_stream_set_counters(hx_stream_t stream, perf_counter_t rx_frames, perf_counter_t rx_errors); +/** + * Reset a stream. + * + * Forces the local stream state to idle. + * + * @param stream A handle returned from hx_stream_init. + */ +__EXPORT extern void hx_stream_reset(hx_stream_t stream); + +/** + * Prepare to send a frame. + * + * Use this in conjunction with hx_stream_send_next to + * set the frame to be transmitted. + * + * Use hx_stream_send() to write to the stream fd directly. + * + * @param stream A handle returned from hx_stream_init. + * @param data Pointer to the data to send. + * @param count The number of bytes to send. + * @return Zero on success, -errno on error. + */ +__EXPORT extern int hx_stream_start(hx_stream_t stream, + const void *data, + size_t count); + +/** + * Get the next byte to send for a stream. + * + * This requires that the stream be prepared for sending by + * calling hx_stream_start first. + * + * @param stream A handle returned from hx_stream_init. + * @return The byte to send, or -1 if there is + * nothing left to send. + */ +__EXPORT extern int hx_stream_send_next(hx_stream_t stream); + /** * Send a frame. *