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authorStefan BrĂ¼ns <stefan.bruens@rwth-aachen.de>2017-01-08 18:32:05 +0100
committerUwe Hermann <uwe@hermann-uwe.de>2017-01-21 15:08:21 +0100
commit9ea4018f2f7c3bac99f738334ebd57b1e6ae0a2c (patch)
tree8e0343258026e902fd50695729b8b0f3d41999f8
parent37ef582d088190ffcf5f8a649ca622cfc52f289a (diff)
scpi_serial: Get rid of intermediate buffer, do not strip newline
Lowlevel access functions should not alter the data. sr_scpi_get_string(), which is called by most highlevel access functions, strips newlines in a central place, and is only fed with data which contains newlines as a final terminator. IEEE 488.2 definite length blocks may contain arbitrary data, thus the payload up to the provided length should be passed unaltered. Track if the last received character is a newline, which can be used by sr_scpi_get_string() and its callers to determine if the response is complete.
-rw-r--r--src/scpi/scpi_serial.c63
1 files changed, 18 insertions, 45 deletions
diff --git a/src/scpi/scpi_serial.c b/src/scpi/scpi_serial.c
index 02242ef..6811ad3 100644
--- a/src/scpi/scpi_serial.c
+++ b/src/scpi/scpi_serial.c
@@ -28,13 +28,9 @@
#define LOG_PREFIX "scpi_serial"
-#define BUFFER_SIZE 1024
-
struct scpi_serial {
struct sr_serial_dev_inst *serial;
- char buffer[BUFFER_SIZE];
- size_t count;
- size_t read;
+ char got_newline;
};
static const struct {
@@ -97,8 +93,7 @@ static int scpi_serial_open(struct sr_scpi_dev_inst *scpi)
if (serial_flush(serial) != SR_OK)
return SR_ERR;
- sscpi->count = 0;
- sscpi->read = 0;
+ sscpi->got_newline = 0;
return SR_OK;
}
@@ -145,7 +140,8 @@ static int scpi_serial_send(void *priv, const char *command)
static int scpi_serial_read_begin(void *priv)
{
- (void) priv;
+ struct scpi_serial *sscpi = priv;
+ sscpi->got_newline = 0;
return SR_OK;
}
@@ -153,56 +149,33 @@ static int scpi_serial_read_begin(void *priv)
static int scpi_serial_read_data(void *priv, char *buf, int maxlen)
{
struct scpi_serial *sscpi = priv;
- int len, ret;
-
- len = BUFFER_SIZE - sscpi->count;
+ int ret;
- /* Try to read new data into the buffer if there is space. */
- if (len > 0) {
- ret = serial_read_nonblocking(sscpi->serial, sscpi->buffer + sscpi->count,
- BUFFER_SIZE - sscpi->count);
+ /* Try to read new data into the buffer. */
+ ret = serial_read_nonblocking(sscpi->serial, buf, maxlen);
- if (ret < 0)
- return ret;
+ if (ret < 0)
+ return ret;
- sscpi->count += ret;
+ if (ret > 0) {
+ sr_spew("Read %d bytes into buffer.", ret);
- if (ret > 0)
- sr_spew("Read %d bytes into buffer.", ret);
- }
-
- /* Return as many bytes as possible from buffer, excluding any trailing newline. */
- if (sscpi->read < sscpi->count) {
- len = sscpi->count - sscpi->read;
- if (len > maxlen)
- len = maxlen;
- if (sscpi->buffer[sscpi->read + len - 1] == '\n')
- len--;
- sr_spew("Returning %d bytes from buffer.", len);
- memcpy(buf, sscpi->buffer + sscpi->read, len);
- sscpi->read += len;
- if (sscpi->read == BUFFER_SIZE) {
- sr_spew("Resetting buffer.");
- sscpi->count = 0;
- sscpi->read = 0;
+ if (buf[ret - 1] == '\n') {
+ sscpi->got_newline = 1;
+ sr_spew("Received terminator");
+ } else {
+ sscpi->got_newline = 0;
}
- return len;
}
- return 0;
+ return ret;
}
static int scpi_serial_read_complete(void *priv)
{
struct scpi_serial *sscpi = priv;
- /* If the next character is a newline, discard it and report complete. */
- if (sscpi->read < sscpi->count && sscpi->buffer[sscpi->read] == '\n') {
- sscpi->read++;
- return 1;
- } else {
- return 0;
- }
+ return sscpi->got_newline;
}
static int scpi_serial_close(struct sr_scpi_dev_inst *scpi)