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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.
This commit is contained in:
Stefan Brüns 2017-01-08 18:32:05 +01:00 committed by Uwe Hermann
parent 37ef582d08
commit 9ea4018f2f
1 changed files with 18 additions and 45 deletions
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63
src/scpi/scpi_serial.c
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@ -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;
int ret;
len = BUFFER_SIZE - sscpi->count;
/* Try to read new data into the buffer. */
ret = serial_read_nonblocking(sscpi->serial, buf, maxlen);
/* 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);
if (ret < 0)
return ret;
if (ret < 0)
return ret;
if (ret > 0) {
sr_spew("Read %d bytes into buffer.", ret);
sscpi->count += 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)