X-Git-Url: http://sigrok.org/gitweb/?a=blobdiff_plain;f=src%2Fscpi%2Fscpi.c;h=f6865c37dc846d809a016b0627cb4fb44630813d;hb=9ea4018f2f7c3bac99f738334ebd57b1e6ae0a2c;hp=efa839de748972052898156ecd1d4f087be3d3b6;hpb=904401e8fe8175252d68fcf6e0c0edae902c1c17;p=libsigrok.git

diff --git a/src/scpi/scpi.c b/src/scpi/scpi.c
index efa839de..f6865c37 100644
--- a/src/scpi/scpi.c
+++ b/src/scpi/scpi.c
@@ -190,7 +190,7 @@ SR_PRIV struct sr_scpi_dev_inst *scpi_dev_inst_new(struct drv_context *drvc,
 			scpi = g_malloc(sizeof(*scpi));
 			*scpi = *scpi_dev;
 			scpi->priv = g_malloc0(scpi->priv_size);
-			scpi->read_timeout_ms = 1000;
+			scpi->read_timeout_us = 1000 * 1000;
 			params = g_strsplit(resource, "/", 0);
 			if (scpi->dev_inst_new(scpi->priv, drvc, resource,
 			                       params, serialcomm) != SR_OK) {
@@ -417,44 +417,51 @@ SR_PRIV int sr_scpi_get_data(struct sr_scpi_dev_inst *scpi,
 {
 	int len;
 	GString *response;
-	gint64 laststart;
-	unsigned int elapsed_ms;
+	gint64 laststart, now;
 	unsigned int offset;
 	int space;
 
+	/* 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();
+		}
+
+		now = g_get_monotonic_time();
+
+		if (len > 0) {
+			laststart = now;
 			offset += len;
 			g_string_set_size(response, offset);
-		}
-		elapsed_ms = (g_get_monotonic_time() - laststart) / 1000;
-		if (elapsed_ms >= scpi->read_timeout_ms) {
+		} else if ((now - laststart) >= scpi->read_timeout_us) {
+			/* Quit reading after a period of time without receiving data. */
 			sr_err("Timed out waiting for SCPI response.");
-			return SR_ERR;
+			return SR_ERR_TIMEOUT;
 		}
 	}
 
@@ -743,55 +750,74 @@ SR_PRIV int sr_scpi_get_block(struct sr_scpi_dev_inst *scpi,
 {
 	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);