fel: extend progress display with transfer rate and ETA

Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>
Reviewed-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>

progress.c

@@ -28,16 +28,48 @@ inline double gettime(void)
 	return tv.tv_sec + (double)tv.tv_usec / 1000000.;
 }
 
+/* Calculate transfer rate (in bytes per second) */
+inline double rate(size_t transferred, double elapsed)
+{
+	if (elapsed > 0)
+		return (double)transferred / elapsed;
+	return 0.;
+}
+
+/* Estimate remaining time ("ETA") for given transfer rate */
+inline double estimate(size_t remaining, double rate)
+{
+	if (rate > 0)
+		return (double)remaining / rate;
+	return 0.;
+}
+
+/* Return ETA (in seconds) as string, formatted to minutes and seconds */
+const char *format_ETA(double remaining)
+{
+	static char result[6] = "";
+
+	int seconds = remaining + 0.5; /* simplistic round() */
+	if (seconds >= 0 && seconds < 6000) {
+		snprintf(result, sizeof(result),
+			 "%02d:%02d", seconds / 60, seconds % 60);
+		return result;
+	}
+	return "--:--";
+}
+
 /* Private progress state variable */
 
 typedef struct {
 	progress_cb_t callback;
 	size_t total;
 	size_t done;
+	double start; /* start point (timestamp) for rate and ETA calculation */
 } progress_private_t;
 
 static progress_private_t progress = {
 	.callback = NULL,
+	.start = 0.
 };
 
 /* 'External' API */
@@ -47,6 +79,7 @@ void progress_start(progress_cb_t callback, size_t expected_total)
 	progress.callback = callback;
 	progress.total = expected_total;
 	progress.done = 0;
+	progress.start = gettime(); /* reset start time */
 }
 
 /* Update progress status, passing information to the callback function. */
@@ -57,19 +90,32 @@ void progress_update(size_t bytes_done)
 		progress.callback(progress.total, progress.done);
 }
 
+/* Return relative / "elapsed" time, since progress_start() */
+static inline double progress_elapsed(void)
+{
+	if (progress.start != 0.)
+		return gettime() - progress.start;
+	return 0.;
+}
+
 /* Callback function implementing a simple progress bar written to stdout */
 void progress_bar(size_t total, size_t done)
 {
-	static const int WIDTH = 60; /* # of characters to use for progress bar */
+	static const int WIDTH = 48; /* # of characters to use for progress bar */
 
 	float ratio = total > 0 ? (float)done / total : 0;
 	int i, pos = WIDTH * ratio;
+	double speed = rate(done, progress_elapsed());
+	double eta = estimate(total - done, speed);
 
 	printf("\r%3.0f%% [", ratio * 100); /* current percentage */
 	for (i = 0; i < pos; i++) putchar('=');
 	for (i = pos; i < WIDTH; i++) putchar(' ');
-	printf("] ");
+	if (done < total)
+		printf("]%6.1f kB/s, ETA %s ", kilo(speed), format_ETA(eta));
+	else
+		/* transfer complete, output totals plus a newline */
+		printf("] %5.0f kB, %6.1f kB/s\n", kilo(done), kilo(speed));
 
-	if (done >= total) putchar('\n'); /* output newline when complete */
 	fflush(stdout);
 }

progress.h

@@ -27,6 +27,8 @@ typedef void (*progress_cb_t)(size_t total, size_t done);
 #define kibi(value)	((double)(value) / 1024.) /* binary prefix "Ki", "K" */
 
 double gettime(void);
+double rate(size_t transferred, double elapsed);
+double estimate(size_t remaining, double rate);
 
 void progress_start(progress_cb_t callback, size_t expected_total);
 void progress_update(size_t bytes_done);