input/vcd: add channel list checks for file re-read

[libsigrok.git] / src / input / vcd.c

diff --git a/src/input/vcd.c b/src/input/vcd.c
index 95092cb2e5bf5363697a933051ad4cb4bf1dc391..e3c2347ac0875ff6f44f99f000077a691ce3a455 100644 (file)
--- a/src/input/vcd.c
+++ b/src/input/vcd.c
@@ -85,6 +85,7 @@ struct context {
        size_t samples_in_buffer;
        uint8_t *buffer;
        uint8_t *current_levels;
+       GSList *prev_sr_channels;
 };
 
 struct vcd_channel {
@@ -175,6 +176,56 @@ static void remove_empty_parts(gchar **parts)
        *dest = NULL;
 }
 
+/*
+ * Keep track of a previously created channel list, in preparation of
+ * re-reading the input file. Gets called from reset()/cleanup() paths.
+ */
+static void keep_header_for_reread(const struct sr_input *in)
+{
+       struct context *inc;
+
+       inc = in->priv;
+       g_slist_free_full(inc->prev_sr_channels, sr_channel_free_cb);
+       inc->prev_sr_channels = in->sdi->channels;
+       in->sdi->channels = NULL;
+}
+
+/*
+ * Check whether the input file is being re-read, and refuse operation
+ * when essential parameters of the acquisition have changed in ways
+ * that are unexpected to calling applications. Gets called after the
+ * file header got parsed (again).
+ *
+ * Changing the channel list across re-imports of the same file is not
+ * supported, by design and for valid reasons, see bug #1215 for details.
+ * Users are expected to start new sessions when they change these
+ * essential parameters in the acquisition's setup. When we accept the
+ * re-read file, then make sure to keep using the previous channel list,
+ * applications may still reference them.
+ */
+static int check_header_in_reread(const struct sr_input *in)
+{
+       struct context *inc;
+
+       if (!in)
+               return FALSE;
+       inc = in->priv;
+       if (!inc)
+               return FALSE;
+       if (!inc->prev_sr_channels)
+               return TRUE;
+
+       if (sr_channel_lists_differ(inc->prev_sr_channels, in->sdi->channels)) {
+               sr_err("Channel list change not supported for file re-read.");
+               return FALSE;
+       }
+       g_slist_free_full(in->sdi->channels, sr_channel_free_cb);
+       in->sdi->channels = inc->prev_sr_channels;
+       inc->prev_sr_channels = NULL;
+
+       return TRUE;
+}
+
 /*
  * Parse VCD header to get values for context structure.
  * The context structure should be zeroed before calling this.
@@ -265,6 +316,8 @@ static gboolean parse_header(const struct sr_input *in, GString *buf)
        inc->current_levels = g_malloc0(inc->bytes_per_sample);
 
        inc->got_header = status;
+       if (status)
+               status = check_header_in_reread(in);
 
        return status;
 }
@@ -618,8 +671,10 @@ static void cleanup(struct sr_input *in)
        struct context *inc;
 
        inc = in->priv;
+       keep_header_for_reread(in);
        g_slist_free_full(inc->channels, free_channel);
        inc->channels = NULL;
+
        g_free(inc->buffer);
        inc->buffer = NULL;
        g_free(inc->current_levels);