GString *response;
gint64 laststart;
unsigned int elapsed_ms;
- unsigned int offset = 0;
+ unsigned int offset;
int space;
- if (command)
+ /* Optionally send caller provided command. */
+ if (command) {
if (sr_scpi_send(scpi, command) != SR_OK)
return SR_ERR;
+ }
+ /* Initiate SCPI read operation. */
if (sr_scpi_read_begin(scpi) != SR_OK)
return SR_ERR;
+ /* Keep reading until completion or until timeout. */
laststart = g_get_monotonic_time();
response = *scpi_response;
-
offset = response->len;
while (!sr_scpi_read_complete(scpi)) {
+ /* Resize the buffer when free space drops below a threshold. */
space = response->allocated_len - response->len;
if (space < 128) {
g_string_set_size(response, response->len + 1024);
+ g_string_set_size(response, offset);
space = response->allocated_len - response->len;
}
+ /* Read another chunk of the response. */
len = sr_scpi_read_data(scpi, &response->str[offset], space);
if (len < 0) {
sr_err("Incompletely read SCPI response.");
return SR_ERR;
} else if (len > 0) {
laststart = g_get_monotonic_time();
+ offset += len;
+ g_string_set_size(response, offset);
}
- offset += len;
- g_string_set_size(response, offset);
+ /* Quit reading after a period of time without receive data. */
elapsed_ms = (g_get_monotonic_time() - laststart) / 1000;
if (elapsed_ms >= scpi->read_timeout_ms) {
sr_err("Timed out waiting for SCPI response.");
return ret;
}
+
/**
* Send a SCPI command, read the reply, parse it as binary data with a
* "definite length block" header and store the as an result in scpi_response.
{
int ret;
GString* response;
-
- char buf[10] = { 0 };
+ char buf[10];
long llen;
long datalen;
+ /*
+ * Assume an initial maximum length, optionally gets adjusted below.
+ * Prepare a NULL return value for when error paths will be taken.
+ */
response = g_string_sized_new(1024);
*scpi_response = NULL;
+ /* Get (the first chunk of) the response. */
ret = sr_scpi_get_data(scpi, command, &response);
if (ret != SR_OK) {
g_string_free(response, TRUE);
return ret;
}
+ /*
+ * SCPI protocol data blocks are preceeded with a length spec.
+ * The length spec consists of a '#' marker, one digit which
+ * specifies the character count of the length spec, and the
+ * respective number of characters which specify the data block's
+ * length. Raw data bytes follow (thus one must no longer assume
+ * that the received input stream would be an ASCIIZ string).
+ *
+ * Get the data block length, and strip off the length spec from
+ * the input buffer, leaving just the data bytes.
+ */
if (response->str[0] != '#') {
g_string_free(response, TRUE);
return SR_ERR_DATA;
}
-
buf[0] = response->str[1];
+ buf[1] = '\0';
ret = sr_atol(buf, &llen);
if ((ret != SR_OK) || (llen == 0)) {
g_string_free(response, TRUE);
return ret;
}
-
memcpy(buf, &response->str[2], llen);
+ buf[llen] = '\0';
ret = sr_atol(buf, &datalen);
if ((ret != SR_OK) || (datalen == 0)) {
g_string_free(response, TRUE);
return ret;
}
-
- // strip header
g_string_erase(response, 0, 2 + llen);
+ /*
+ * If the initially assumed length does not cover the data block
+ * length, then re-allocate the buffer size to the now known
+ * length, and keep reading more chunks of response data.
+ */
if (response->len < (unsigned long)(datalen)) {
int oldlen = response->len;
g_string_set_size(response, datalen);
g_string_set_size(response, oldlen);
}
-
while (response->len < (unsigned long)(datalen)) {
- if (sr_scpi_get_data(scpi, NULL, &response) != SR_OK) {
+ ret = sr_scpi_get_data(scpi, NULL, &response);
+ if (ret != SR_OK) {
g_string_free(response, TRUE);
return ret;
}
}
+ /* Convert received data to byte array. */
*scpi_response = g_byte_array_new_take(
(guint8*)g_string_free(response, FALSE), datalen);
return ret;
}
-
/**
* Send the *IDN? SCPI command, receive the reply, parse it and store the
* reply as a sr_scpi_hw_info structure in the supplied scpi_response pointer.