strbuf: create strbuf_humanise_bytes() to show byte sizes

Humanization of downloaded size is done in the same function as text
formatting in 'process.c'. The code cannot be reused easily elsewhere.

Separate text formatting from size simplification and make the
function public in strbuf so that it can easily be used by other
callers.

We now can use strbuf_humanise_bytes() for both downloaded size and
download speed calculation. One of the drawbacks is that speed will
now look like this when download is stalled: "0 bytes/s" instead of
"0 KiB/s".

Signed-off-by: Antoine Pelisse <apelisse@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-strbuf.txt

@@ -230,6 +230,11 @@ which can be used by the programmer of the callback as she sees fit.
 	destination. This is useful for literal data to be fed to either
 	strbuf_expand or to the *printf family of functions.
 
+`strbuf_humanise_bytes`::
+
+	Append the given byte size as a human-readable string (i.e. 12.23 KiB,
+	3.50 MiB).
+
 `strbuf_addf`::
 
 	Add a formatted string to the buffer.

progress.c

@@ -10,6 +10,7 @@
 
 #include "git-compat-util.h"
 #include "progress.h"
+#include "strbuf.h"
 
 #define TP_IDX_MAX      8
 
@@ -112,34 +113,14 @@ static int display(struct progress *progress, unsigned n, const char *done)
 	return 0;
 }
 
-static void throughput_string(struct throughput *tp, off_t total,
+static void throughput_string(struct strbuf *buf, off_t total,
 			      unsigned int rate)
 {
-	int l = sizeof(tp->display);
-	if (total > 1 << 30) {
-		l -= snprintf(tp->display, l, ", %u.%2.2u GiB",
-			      (int)(total >> 30),
-			      (int)(total & ((1 << 30) - 1)) / 10737419);
-	} else if (total > 1 << 20) {
-		int x = total + 5243;  /* for rounding */
-		l -= snprintf(tp->display, l, ", %u.%2.2u MiB",
-			      x >> 20, ((x & ((1 << 20) - 1)) * 100) >> 20);
-	} else if (total > 1 << 10) {
-		int x = total + 5;  /* for rounding */
-		l -= snprintf(tp->display, l, ", %u.%2.2u KiB",
-			      x >> 10, ((x & ((1 << 10) - 1)) * 100) >> 10);
-	} else {
-		l -= snprintf(tp->display, l, ", %u bytes", (int)total);
-	}
-
-	if (rate > 1 << 10) {
-		int x = rate + 5;  /* for rounding */
-		snprintf(tp->display + sizeof(tp->display) - l, l,
-			 " | %u.%2.2u MiB/s",
-			 x >> 10, ((x & ((1 << 10) - 1)) * 100) >> 10);
-	} else if (rate)
-		snprintf(tp->display + sizeof(tp->display) - l, l,
-			 " | %u KiB/s", rate);
+	strbuf_addstr(buf, ", ");
+	strbuf_humanise_bytes(buf, total);
+	strbuf_addstr(buf, " | ");
+	strbuf_humanise_bytes(buf, rate * 1024);
+	strbuf_addstr(buf, "/s");
 }
 
 void display_throughput(struct progress *progress, off_t total)
@@ -183,6 +164,7 @@ void display_throughput(struct progress *progress, off_t total)
 	misecs += (int)(tv.tv_usec - tp->prev_tv.tv_usec) / 977;
 
 	if (misecs > 512) {
+		struct strbuf buf = STRBUF_INIT;
 		unsigned int count, rate;
 
 		count = total - tp->prev_total;
@@ -197,7 +179,9 @@ void display_throughput(struct progress *progress, off_t total)
 		tp->last_misecs[tp->idx] = misecs;
 		tp->idx = (tp->idx + 1) % TP_IDX_MAX;
 
-		throughput_string(tp, total, rate);
+		throughput_string(&buf, total, rate);
+		strncpy(tp->display, buf.buf, sizeof(tp->display));
+		strbuf_release(&buf);
 		if (progress->last_value != -1 && progress_update)
 			display(progress, progress->last_value, NULL);
 	}
@@ -253,9 +237,12 @@ void stop_progress_msg(struct progress **p_progress, const char *msg)
 
 		bufp = (len < sizeof(buf)) ? buf : xmalloc(len + 1);
 		if (tp) {
+			struct strbuf strbuf = STRBUF_INIT;
 			unsigned int rate = !tp->avg_misecs ? 0 :
 					tp->avg_bytes / tp->avg_misecs;
-			throughput_string(tp, tp->curr_total, rate);
+			throughput_string(&strbuf, tp->curr_total, rate);
+			strncpy(tp->display, strbuf.buf, sizeof(tp->display));
+			strbuf_release(&strbuf);
 		}
 		progress_update = 1;
 		sprintf(bufp, ", %s.\n", msg);

strbuf.c

@@ -528,6 +528,25 @@ void strbuf_addstr_urlencode(struct strbuf *sb, const char *s,
 	strbuf_add_urlencode(sb, s, strlen(s), reserved);
 }
 
+void strbuf_humanise_bytes(struct strbuf *buf, off_t bytes)
+{
+	if (bytes > 1 << 30) {
+		strbuf_addf(buf, "%u.%2.2u GiB",
+			    (int)(bytes >> 30),
+			    (int)(bytes & ((1 << 30) - 1)) / 10737419);
+	} else if (bytes > 1 << 20) {
+		int x = bytes + 5243;  /* for rounding */
+		strbuf_addf(buf, "%u.%2.2u MiB",
+			    x >> 20, ((x & ((1 << 20) - 1)) * 100) >> 20);
+	} else if (bytes > 1 << 10) {
+		int x = bytes + 5;  /* for rounding */
+		strbuf_addf(buf, "%u.%2.2u KiB",
+			    x >> 10, ((x & ((1 << 10) - 1)) * 100) >> 10);
+	} else {
+		strbuf_addf(buf, "%u bytes", (int)bytes);
+	}
+}
+
 int printf_ln(const char *fmt, ...)
 {
 	int ret;

strbuf.h

@@ -170,6 +170,7 @@ extern int strbuf_check_branch_ref(struct strbuf *sb, const char *name);
 
 extern void strbuf_addstr_urlencode(struct strbuf *, const char *,
 				    int reserved);
+extern void strbuf_humanise_bytes(struct strbuf *buf, off_t bytes);
 
 __attribute__((format (printf,1,2)))
 extern int printf_ln(const char *fmt, ...);