Revise SCPI read API to allow backend-independent data handling.

[libsigrok.git] / hardware / common / scpi_usbtmc.c

diff --git a/hardware/common/scpi_usbtmc.c b/hardware/common/scpi_usbtmc.c
index 298e3ab52012a7ade0ce810658dddc3c4372c56a..5aa0dbbd335d323dd20615984a59f9294069f7c5 100644 (file)
--- a/hardware/common/scpi_usbtmc.c
+++ b/hardware/common/scpi_usbtmc.c
@@ -28,9 +28,19 @@
 
 #define LOG_PREFIX "scpi_usbtmc"
 
+#define MAX_READ_LENGTH 2048
+
+struct usbtmc_scpi {
+       struct sr_usbtmc_dev_inst *usbtmc;
+       char response_buffer[MAX_READ_LENGTH];
+       int response_length;
+       int response_bytes_read;
+};
+
 SR_PRIV int scpi_usbtmc_open(void *priv)
 {
-       struct sr_usbtmc_dev_inst *usbtmc = priv;
+       struct usbtmc_scpi *uscpi = priv;
+       struct sr_usbtmc_dev_inst *usbtmc = uscpi->usbtmc;
 
        if ((usbtmc->fd = open(usbtmc->device, O_RDWR)) < 0)
                return SR_ERR;
@@ -41,21 +51,24 @@ SR_PRIV int scpi_usbtmc_open(void *priv)
 SR_PRIV int scpi_usbtmc_source_add(void *priv, int events, int timeout,
                        sr_receive_data_callback_t cb, void *cb_data)
 {
-       struct sr_usbtmc_dev_inst *usbtmc = priv;
+       struct usbtmc_scpi *uscpi = priv;
+       struct sr_usbtmc_dev_inst *usbtmc = uscpi->usbtmc;
 
        return sr_source_add(usbtmc->fd, events, timeout, cb, cb_data);
 }
 
 SR_PRIV int scpi_usbtmc_source_remove(void *priv)
 {
-       struct sr_usbtmc_dev_inst *usbtmc = priv;
+       struct usbtmc_scpi *uscpi = priv;
+       struct sr_usbtmc_dev_inst *usbtmc = uscpi->usbtmc;
 
        return sr_source_remove(usbtmc->fd);
 }
 
 SR_PRIV int scpi_usbtmc_send(void *priv, const char *command)
 {
-       struct sr_usbtmc_dev_inst *usbtmc = priv;
+       struct usbtmc_scpi *uscpi = priv;
+       struct sr_usbtmc_dev_inst *usbtmc = uscpi->usbtmc;
        int len, out;
 
        len = strlen(command);
@@ -76,53 +89,56 @@ SR_PRIV int scpi_usbtmc_send(void *priv, const char *command)
        return SR_OK;
 }
 
-SR_PRIV int scpi_usbtmc_receive(void *priv, char **scpi_response)
+SR_PRIV int scpi_usbtmc_read_begin(void *priv)
 {
-       struct sr_usbtmc_dev_inst *usbtmc = priv;
-       GString *response;
-       char buf[256];
+       struct usbtmc_scpi *uscpi = priv;
+       struct sr_usbtmc_dev_inst *usbtmc = uscpi->usbtmc;
        int len;
 
-       response = g_string_sized_new(1024);
-
-       len = read(usbtmc->fd, buf, sizeof(buf));
+       len = read(usbtmc->fd, uscpi->response_buffer, MAX_READ_LENGTH);
 
        if (len < 0) {
                sr_err("Read error: %s", strerror(errno));
-               g_string_free(response, TRUE);
                return SR_ERR;
        }
 
-       response = g_string_append_len(response, buf, len);
-
-       *scpi_response = response->str;
-
-       sr_dbg("SCPI response received (length %d): '%.50s'",
-              response->len, response->str);
-
-       g_string_free(response, FALSE);
+       uscpi->response_length = len;
+       uscpi->response_bytes_read = 0;
 
        return SR_OK;
 }
 
-SR_PRIV int scpi_usbtmc_read(void *priv, char *buf, int maxlen)
+SR_PRIV int scpi_usbtmc_read_data(void *priv, char *buf, int maxlen)
 {
-       struct sr_usbtmc_dev_inst *usbtmc = priv;
-       int len;
-
-       len = read(usbtmc->fd, buf, maxlen);
+       struct usbtmc_scpi *uscpi = priv;
+       int read_length;
 
-       if (len < 0) {
-               sr_err("Read error: %s", strerror(errno));
+       if (uscpi->response_bytes_read >= uscpi->response_length)
                return SR_ERR;
-       }
 
-       return len;
+       read_length = uscpi->response_length - uscpi->response_bytes_read;
+
+       if (read_length > maxlen)
+               read_length = maxlen;
+
+       memcpy(buf, uscpi->response_buffer + uscpi->response_bytes_read, read_length);
+
+       uscpi->response_bytes_read += read_length;
+
+       return read_length;
+}
+
+SR_PRIV int scpi_usbtmc_read_complete(void *priv)
+{
+       struct usbtmc_scpi *uscpi = priv;
+
+       return (uscpi->response_bytes_read >= uscpi->response_length);
 }
 
 SR_PRIV int scpi_usbtmc_close(void *priv)
 {
-       struct sr_usbtmc_dev_inst *usbtmc = priv;
+       struct usbtmc_scpi *uscpi = priv;
+       struct sr_usbtmc_dev_inst *usbtmc = uscpi->usbtmc;
 
        if (close(usbtmc->fd) < 0)
                return SR_ERR;
@@ -132,31 +148,38 @@ SR_PRIV int scpi_usbtmc_close(void *priv)
 
 static void scpi_usbtmc_free(void *priv)
 {
-       return sr_usbtmc_dev_inst_free(priv);
+       struct usbtmc_scpi *uscpi = priv;
+       struct sr_usbtmc_dev_inst *usbtmc = uscpi->usbtmc;
+
+       g_free(uscpi);
+       sr_usbtmc_dev_inst_free(usbtmc);
 }
 
 SR_PRIV struct sr_scpi_dev_inst *scpi_usbtmc_dev_inst_new(const char *device)
 {
        struct sr_scpi_dev_inst *scpi;
+       struct usbtmc_scpi *uscpi;
        struct sr_usbtmc_dev_inst *usbtmc;
 
-       scpi = g_try_malloc(sizeof(struct sr_scpi_dev_inst));
-
        if (!(usbtmc = sr_usbtmc_dev_inst_new(device)))
-       {
-               g_free(scpi);
                return NULL;
-       }
+
+       uscpi = g_malloc(sizeof(struct usbtmc_scpi));
+
+       uscpi->usbtmc = usbtmc;
+
+       scpi = g_malloc(sizeof(struct sr_scpi_dev_inst));
 
        scpi->open = scpi_usbtmc_open;
        scpi->source_add = scpi_usbtmc_source_add;
        scpi->source_remove = scpi_usbtmc_source_remove;
        scpi->send = scpi_usbtmc_send;
-       scpi->receive = scpi_usbtmc_receive;
-       scpi->read = scpi_usbtmc_read;
+       scpi->read_begin = scpi_usbtmc_read_begin;
+       scpi->read_data = scpi_usbtmc_read_data;
+       scpi->read_complete = scpi_usbtmc_read_complete;
        scpi->close = scpi_usbtmc_close;
        scpi->free = scpi_usbtmc_free;
-       scpi->priv = usbtmc;
+       scpi->priv = uscpi;
 
        return scpi;
 }