scpi: Rephrase buffer resize for free space during SCPI read, add comments

[libsigrok.git] / src / scpi / scpi.c

diff --git a/src/scpi/scpi.c b/src/scpi/scpi.c
index f87bf9eba239325107a1903eb6d682bd6f282028..8e7e4d74af6702b7b59ba1cd87f163a7468bee3c 100644 (file)
--- a/src/scpi/scpi.c
+++ b/src/scpi/scpi.c
@@ -422,26 +422,31 @@ SR_PRIV int sr_scpi_get_data(struct sr_scpi_dev_inst *scpi,
        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.");
@@ -451,6 +456,7 @@ SR_PRIV int sr_scpi_get_data(struct sr_scpi_dev_inst *scpi,
                }
                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.");