Add downsample and skip parameters to input/vcd.

diff --git a/input/vcd.c b/input/vcd.c
index 5ad9ad6ce979115db97dfe62ca76ad912682222c..b8b469791aaf617fe31955aec77dd8b7f11a73d1 100644 (file)
--- a/input/vcd.c
+++ b/input/vcd.c
@@ -1,7 +1,7 @@
 /*
  * This file is part of the sigrok project.
  *
- * Copyright (C) 2010-2012 Bert Vermeulen <bert@biot.com>
+ * Copyright (C) 2012 Petteri Aimonen <jpa@sr.mail.kapsi.fi>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,7 +17,40 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-/* Based on Verilog standard IEEE Std 1364-2001 Version C */
+/* The VCD input module has the following options:
+ *
+ * numprobes:   Maximum number of probes to use. The probes are
+ *              detected in the same order as they are listed
+ *              in the $var sections of the VCD file.
+ *
+ * skip:        Allows skipping until given timestamp in the file.
+ *              This can speed up analyzing of long captures.
+ *            
+ *              Value < 0: Skip until first timestamp listed in
+ *              the file. (default)
+ *
+ *              Value = 0: Do not skip, instead generate samples
+ *              beginning from timestamp 0.
+ *
+ *              Value > 0: Start at the given timestamp.
+ *
+ * downsample:  Divide the samplerate by the given factor.
+ *              This can speed up analyzing of long captures.
+ *
+ * Based on Verilog standard IEEE Std 1364-2001 Version C
+ *
+ * Supported features:
+ * - $var with 'wire' and 'reg' types of scalar variables
+ * - $timescale definition for samplerate
+ * - multiple character variable identifiers
+ *
+ * Most important unsupported features:
+ * - vector variables (bit vectors etc.)
+ * - analog, integer and real number variables
+ * - $dumpvars initial value declaration
+ */
+
+/*  */
 
 #include <stdlib.h>
 #include <glib.h>
@@ -131,6 +164,8 @@ struct context
        uint64_t samplerate;
        int maxprobes;
        int probecount;
+       int downsample;
+       int64_t skip;
        struct probe probes[SR_MAX_NUM_PROBES];
 };
 
@@ -192,7 +227,7 @@ static gboolean parse_header(FILE *file, struct context *ctx)
                                if (period.q % period.p != 0)
                                {
                                        /* Does not happen unless time value is non-standard */
-                                       sr_warn("Inexact rounding of samplerate, %" PRIu64 " / %" PRIu64 " to %" PRIu64 ".",
+                                       sr_warn("Inexact rounding of samplerate, %" PRIu64 " / %" PRIu64 " to %" PRIu64 " Hz.",
                                                period.q, period.p, ctx->samplerate);
                                }
                                
@@ -284,6 +319,8 @@ static int init(struct sr_input *in)
 
        num_probes = DEFAULT_NUM_PROBES;
        ctx->samplerate = 0;
+       ctx->downsample = 1;
+       ctx->skip = -1;
 
        if (in->param) {
                param = g_hash_table_lookup(in->param, "numprobes");
@@ -295,6 +332,20 @@ static int init(struct sr_input *in)
                                return SR_ERR;
                        }
                }
+               
+               param = g_hash_table_lookup(in->param, "downsample");
+               if (param) {
+                       ctx->downsample = strtoul(param, NULL, 10);
+                       if (ctx->downsample < 1)
+                       {
+                               ctx->downsample = 1;
+                       }
+               }
+               
+               param = g_hash_table_lookup(in->param, "skip");
+               if (param) {
+                       ctx->skip = strtoul(param, NULL, 10) / ctx->downsample;
+               }
        }
        
        /* Maximum number of probes to parse from the VCD */
@@ -329,7 +380,7 @@ static void send_samples(const struct sr_dev_inst *sdi, uint64_t sample, uint64_
        uint64_t buffer[CHUNKSIZE];
        uint64_t i;
        unsigned chunksize = CHUNKSIZE;
-       
+               
        if (count < chunksize)
                chunksize = count;
 
@@ -360,8 +411,8 @@ static void parse_contents(FILE *file, const struct sr_dev_inst *sdi, struct con
 {
        GString *token = g_string_sized_new(32);
        
-       gboolean first = TRUE;
        uint64_t prev_timestamp = 0;
+       uint64_t new_values = 0;
        uint64_t prev_values = 0;
        
        /* Read one space-delimited token at a time. */
@@ -373,19 +424,40 @@ static void parse_contents(FILE *file, const struct sr_dev_inst *sdi, struct con
                        uint64_t timestamp;
                        timestamp = strtoull(token->str + 1, NULL, 10);
                        
-                       if (first)
+                       if (ctx->downsample > 1)
+                               timestamp /= ctx->downsample;
+                       
+                       /* Skip < 0 => skip until first timestamp.
+                        * Skip = 0 => don't skip
+                        * Skip > 0 => skip until timestamp >= skip.
+                        */
+                       if (ctx->skip < 0)
+                       {
+                               ctx->skip = timestamp;
+                       }
+                       else if (ctx->skip > 0 && timestamp < (uint64_t)ctx->skip)
                        {
-                               first = FALSE;
+                               prev_timestamp = ctx->skip - 1;
+                       }
+                       else if (timestamp == prev_timestamp)
+                       {
+                               /* This only occurs when ctx->downsample > 1 */
+                               if (prev_values != new_values)
+                               {
+                                       sr_warn("VCD downsampling hides a glitch at %" PRIu64, timestamp);
+                                       prev_values = new_values;
+                               }
                        }
                        else
                        {
                                sr_dbg("New timestamp: %" PRIu64, timestamp);
                        
                                /* Generate samples from prev_timestamp up to timestamp - 1. */
-                               send_samples(sdi, prev_values, timestamp - prev_timestamp);
+                               send_samples(sdi, new_values, timestamp - prev_timestamp);
+
+                               prev_timestamp = timestamp;
+                               prev_values = new_values;
                        }
-                       
-                       prev_timestamp = timestamp;
                }
                else if (token->str[0] == '$')
                {
@@ -417,9 +489,9 @@ static void parse_contents(FILE *file, const struct sr_dev_inst *sdi, struct con
                                
                                        /* Found our probe */
                                        if (bit)
-                                               prev_values |= (1 << i);
+                                               new_values |= (1 << i);
                                        else
-                                               prev_values &= ~(1 << i);
+                                               new_values &= ~(1 << i);
                                        
                                        break;
                                }
@@ -467,7 +539,7 @@ static int loadfile(struct sr_input *in, const char *filename)
        /* Send metadata about the SR_DF_LOGIC packets to come. */
        packet.type = SR_DF_META_LOGIC;
        packet.payload = &meta;
-       meta.samplerate = ctx->samplerate;
+       meta.samplerate = ctx->samplerate / ctx->downsample;
        meta.num_probes = ctx->probecount;
        sr_session_send(in->sdi, &packet);