transform/scale: Use a rational rather than floating point factor.

[libsigrok.git] / src / transform / scale.c

diff --git a/src/transform/scale.c b/src/transform/scale.c
index e0ecd3de72907b56aa408f672d73eff312c28a84..b4dd13cb90e028423cd11b5e959db8a2b0d0ceb3 100644 (file)
--- a/src/transform/scale.c
+++ b/src/transform/scale.c
@@ -26,7 +26,7 @@
 #define LOG_PREFIX "transform/scale"
 
 struct context {
-       double factor;
+       struct sr_rational factor;
 };
 
 static int init(struct sr_transform *t, GHashTable *options)
@@ -38,7 +38,8 @@ static int init(struct sr_transform *t, GHashTable *options)
 
        t->priv = ctx = g_malloc0(sizeof(struct context));
 
-       ctx->factor = g_variant_get_double(g_hash_table_lookup(options, "factor"));
+       g_variant_get(g_hash_table_lookup(options, "factor"), "(xt)",
+                       &ctx->factor.p, &ctx->factor.q);
 
        return SR_OK;
 }
@@ -52,6 +53,7 @@ static int receive(const struct sr_transform *t,
        struct sr_channel *ch;
        GSList *l;
        float *fdata;
+       float factor;
        int i, num_channels, c;
 
        if (!t || !t->sdi || !packet_in || !packet_out)
@@ -63,12 +65,13 @@ static int receive(const struct sr_transform *t,
                analog = packet_in->payload;
                fdata = (float *)analog->data;
                num_channels = g_slist_length(analog->channels);
+               factor = (float) ctx->factor.p / ctx->factor.q;
                for (i = 0; i < analog->num_samples; i++) {
                        /* For now scale all values in all channels. */
                        for (l = analog->channels, c = 0; l; l = l->next, c++) {
                                ch = l->data;
                                (void)ch;
-                               fdata[i * num_channels + c] *= ctx->factor;
+                               fdata[i * num_channels + c] *= factor;
                        }
                }
                break;
@@ -104,9 +107,12 @@ static struct sr_option options[] = {
 
 static const struct sr_option *get_options(void)
 {
+       int64_t p = 1;
+       uint64_t q = 1;
+
        /* Default to a scaling factor of 1.0. */
        if (!options[0].def)
-               options[0].def = g_variant_ref_sink(g_variant_new_double(1.0));
+               options[0].def = g_variant_ref_sink(g_variant_new(("(xt"), &p, &q));
 
        return options;
 }