output_vcd: Remember samples between packets.

Fixes two bugs in vcd output:
1) Waveform did not match original input when viewed in gtkwave.
2) No vcd output when using 1 MHz sampling on Sigma.

diff --git a/output/output_vcd.c b/output/output_vcd.c
index 2157c1ba5c1cd4ab1fa4cba9109e7d2799991dad..2ea64538ddbd53c26de7893551f557ccc3256e89 100644 (file)
--- a/output/output_vcd.c
+++ b/output/output_vcd.c
@@ -31,6 +31,7 @@ struct context {
        char *probelist[65];
        int *prevbits;
        GString *header;
+       uint64_t prevsample;
 };
 
 const char *vcd_header = "\
@@ -169,9 +170,10 @@ static int data(struct output *o, char *data_in, uint64_t length_in,
        struct context *ctx;
        unsigned int i;
        int p, curbit, prevbit;
-       uint64_t sample, prevsample;
+       uint64_t sample;
        static uint64_t samplecount = 0;
        GString *out;
+       int first_sample = 0;
 
        ctx = o->internal;
        out = g_string_sized_new(512);
@@ -181,19 +183,24 @@ static int data(struct output *o, char *data_in, uint64_t length_in,
                g_string_append(out, ctx->header->str);
                g_string_free(ctx->header, TRUE);
                ctx->header = NULL;
+               first_sample = 1;
        }
 
        for (i = 0; i <= length_in - ctx->unitsize; i += ctx->unitsize) {
                samplecount++;
+
                memcpy(&sample, data_in + i, ctx->unitsize);
-               if (i == 0)
-                       prevsample = sample;
-               else
-                       memcpy(&prevsample, data_in + i - 1, ctx->unitsize);
+
+               if (first_sample) {
+                       /* First packet. We neg to make sure sample is stored. */
+                       ctx->prevsample = ~sample;
+                       first_sample = 0;
+               }
+
 
                for (p = 0; p < ctx->num_enabled_probes; p++) {
                        curbit = (sample & ((uint64_t) (1 << p))) >> p;
-                       prevbit = (prevsample & ((uint64_t) (1 << p))) >> p;
+                       prevbit = (ctx->prevsample & ((uint64_t) (1 << p))) >> p;
 
                        /* VCD only contains deltas/changes of signals. */
                        if (prevbit == curbit)
@@ -203,6 +210,8 @@ static int data(struct output *o, char *data_in, uint64_t length_in,
                        g_string_append_printf(out, "#%" PRIu64 "\n%i%c\n", samplecount,
                                        curbit, (char)('!' + p));
                }
+
+               ctx->prevsample = sample;
        }
 
        *data_out = out->str;