serial: introduce local receive data buffer

[libsigrok.git] / src / serial.c

diff --git a/src/serial.c b/src/serial.c
index aca99d9988b725830a9251472231341be54c626c..b1e21eecbcbd69a3e21ffcd28620f76d122be444 100644 (file)
--- a/src/serial.c
+++ b/src/serial.c
@@ -96,6 +96,14 @@ SR_PRIV int serial_open(struct sr_serial_dev_inst *serial, int flags)
        if (!serial->lib_funcs)
                return SR_ERR_NA;
 
+       /*
+        * Note that use of the 'rcv_buffer' is optional, and the buffer's
+        * size heavily depends on the specific transport. That's why the
+        * buffer's content gets accessed and the buffer is released here in
+        * common code, but the buffer gets allocated in libraries' open()
+        * routines.
+        */
+
        /*
         * Run the transport's open routine. Setup the bitrate and the
         * UART frame format.
@@ -124,6 +132,8 @@ SR_PRIV int serial_open(struct sr_serial_dev_inst *serial, int flags)
  */
 SR_PRIV int serial_close(struct sr_serial_dev_inst *serial)
 {
+       int rc;
+
        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
@@ -134,7 +144,13 @@ SR_PRIV int serial_close(struct sr_serial_dev_inst *serial)
        if (!serial->lib_funcs || !serial->lib_funcs->close)
                return SR_ERR_NA;
 
-       return serial->lib_funcs->close(serial);
+       rc = serial->lib_funcs->close(serial);
+       if (rc == SR_OK && serial->rcv_buffer) {
+               g_string_free(serial->rcv_buffer, TRUE);
+               serial->rcv_buffer = NULL;
+       }
+
+       return rc;
 }
 
 /**
@@ -156,6 +172,8 @@ SR_PRIV int serial_flush(struct sr_serial_dev_inst *serial)
 
        sr_spew("Flushing serial port %s.", serial->port);
 
+       sr_ser_discard_queued_data(serial);
+
        if (!serial->lib_funcs || !serial->lib_funcs->flush)
                return SR_ERR_NA;
 
@@ -187,6 +205,113 @@ SR_PRIV int serial_drain(struct sr_serial_dev_inst *serial)
        return serial->lib_funcs->drain(serial);
 }
 
+/*
+ * Provide an internal RX data buffer for the serial port. This is not
+ * supposed to be used directly by applications. Instead optional and
+ * alternative transports for serial communication can use this buffer
+ * if their progress is driven from background activity, and is not
+ * (directly) driven by external API calls.
+ *
+ * BEWARE! This implementation assumes that data which gets communicated
+ * via UART can get stored in a GString (which is a char array). Since
+ * the API hides this detail, we can address this issue later when needed.
+ * Callers use the API which communicates bytes.
+ */
+
+/**
+ * Discard previously queued RX data. Internal to the serial subsystem,
+ * coordination between common and transport specific support code.
+ *
+ * @param[in] serial Previously opened serial port instance.
+ *
+ * @internal
+ */
+SR_PRIV void sr_ser_discard_queued_data(struct sr_serial_dev_inst *serial)
+{
+       if (!serial)
+               return;
+       if (!serial->rcv_buffer)
+               return;
+
+       g_string_truncate(serial->rcv_buffer, 0);
+}
+
+/**
+ * Get amount of queued RX data. Internal to the serial subsystem,
+ * coordination between common and transport specific support code.
+ *
+ * @param[in] serial Previously opened serial port instance.
+ *
+ * @internal
+ */
+SR_PRIV size_t sr_ser_has_queued_data(struct sr_serial_dev_inst *serial)
+{
+       if (!serial)
+               return 0;
+       if (!serial->rcv_buffer)
+               return 0;
+
+       return serial->rcv_buffer->len;
+}
+
+/**
+ * Queue received data. Internal to the serial subsystem, coordination
+ * between common and transport specific support code.
+ *
+ * @param[in] serial Previously opened serial port instance.
+ * @param[in] data Pointer to data bytes to queue.
+ * @param[in] len Number of data bytes to queue.
+ *
+ * @internal
+ */
+SR_PRIV void sr_ser_queue_rx_data(struct sr_serial_dev_inst *serial,
+       const uint8_t *data, size_t len)
+{
+       if (!serial)
+               return;
+       if (!data || !len)
+               return;
+
+       if (serial->rcv_buffer)
+               g_string_append_len(serial->rcv_buffer, (const gchar *)data, len);
+}
+
+/**
+ * Retrieve previously queued RX data. Internal to the serial subsystem,
+ * coordination between common and transport specific support code.
+ *
+ * @param[in] serial Previously opened serial port instance.
+ * @param[out] data Pointer to store retrieved data bytes into.
+ * @param[in] len Number of data bytes to retrieve.
+ *
+ * @internal
+ */
+SR_PRIV size_t sr_ser_unqueue_rx_data(struct sr_serial_dev_inst *serial,
+       uint8_t *data, size_t len)
+{
+       size_t qlen;
+       GString *buf;
+
+       if (!serial)
+               return 0;
+       if (!data || !len)
+               return 0;
+
+       qlen = sr_ser_has_queued_data(serial);
+       if (!qlen)
+               return 0;
+
+       buf = serial->rcv_buffer;
+       if (len > buf->len)
+               len = buf->len;
+       if (len) {
+               memcpy(data, buf->str, len);
+               g_string_erase(buf, 0, len);
+       }
+
+       return len;
+}
+
 /**
  * Check for available receive data.
  *
@@ -199,7 +324,7 @@ SR_PRIV int serial_drain(struct sr_serial_dev_inst *serial)
  */
 SR_PRIV size_t serial_has_receive_data(struct sr_serial_dev_inst *serial)
 {
-       size_t lib_count;
+       size_t lib_count, buf_count;
 
        if (!serial)
                return 0;
@@ -208,7 +333,9 @@ SR_PRIV size_t serial_has_receive_data(struct sr_serial_dev_inst *serial)
        if (serial->lib_funcs && serial->lib_funcs->get_rx_avail)
                lib_count = serial->lib_funcs->get_rx_avail(serial);
 
-       return lib_count;
+       buf_count = sr_ser_has_queued_data(serial);
+
+       return lib_count + buf_count;
 }
 
 static int _serial_write(struct sr_serial_dev_inst *serial,