gnuplot output: Optimize by only storing changes.

[libsigrok.git] / output / output_gnuplot.c

diff --git a/output/output_gnuplot.c b/output/output_gnuplot.c
index c3417c45173f8d5962878a862f890880838dddca..dfa91eb78b39f8a8db1638cba7409bf497684572 100644 (file)
--- a/output/output_gnuplot.c
+++ b/output/output_gnuplot.c
@@ -195,7 +195,7 @@ static int data(struct sr_output *o, const char *data_in, uint64_t length_in,
        struct context *ctx;
        unsigned int max_linelen, outsize, p, curbit, i;
        uint64_t sample;
-       static uint64_t samplecount = 0;
+       static uint64_t samplecount = 0, old_sample = 0;
        char *outbuf, *c;
 
        if (!o) {
@@ -243,8 +243,19 @@ static int data(struct sr_output *o, const char *data_in, uint64_t length_in,
        }
 
        for (i = 0; i <= length_in - ctx->unitsize; i += ctx->unitsize) {
+
                memcpy(&sample, data_in + i, ctx->unitsize);
 
+               /*
+                * Don't output the same samples multiple times. However, make
+                * sure to output at least the first and last sample.
+                */
+               if (samplecount++ != 0 && sample == old_sample) {
+                       if (i != (length_in - ctx->unitsize))
+                               continue;
+               }
+               old_sample = sample;
+
                /* The first column is a counter (needed for gnuplot). */
                c = outbuf + strlen(outbuf);
                sprintf(c, "%" PRIu64 "\t", samplecount++);