Re: [PATCH] mailsplit and mailinfo: gracefully handle NUL characters

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Fri, 16 May 2008, Avery Pennarun wrote:

> On 5/16/08, Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:
> > Hmpf.  I hoped to get more definitive information here.  Especially given
> >  that fgetc() is nothing more than a glorified fread() into a buffer, and
> >  then access the buffer.
> >
> >  Well, at least you kind of pointed me to the _unlocked() function family.
> 
> Point taken.
> 
> /tmp $ for d in test1 test2 test3 test3u; do echo -n "$d: ";
> /usr/bin/time ./$d </dev/zero; done
> test1: 0.09user 0.05system 0:00.14elapsed 94%CPU
> test2: 2.50user 0.05system 0:02.54elapsed 100%CPU
> test3: 2.48user 0.06system 0:02.53elapsed 100%CPU
> test3u: 1.05user 0.05system 0:01.10elapsed 99%CPU
> 
> fread is about 18x faster than fgetc().  getc() is the same speed as
> fgetc().  getc_unlocked() is definitely faster than getc, but still at
> least 7x slower than fread().

Well, my question was more about fgetc() vs fgets().

If you feel like it, you might benchmark this patch:

-- snipsnap --
diff --git a/builtin-mailsplit.c b/builtin-mailsplit.c
index 021dc16..5d8defd 100644
--- a/builtin-mailsplit.c
+++ b/builtin-mailsplit.c
@@ -45,13 +45,32 @@ static int is_from_line(const char *line, int len)
 /* Could be as small as 64, enough to hold a Unix "From " line. */
 static char buf[4096];
 
+/*
+ *  This is an ugly hack to avoid fgetc(), which is slow, as it is locking.
+ *  The argument "in" must be the same for all calls to this function!
+ */
+static int fast_fgetc(FILE *in)
+{
+	static char buf[4096];
+	static int offset = 0, len = 0;
+
+	if (offset >= len) {
+		len = fread(buf, 1, sizeof(buf), in);
+		offset = 0;
+		if (!len && feof(in))
+			return EOF;
+	}
+
+	return buf[offset++];
+}
+
 /* We cannot use fgets() because our lines can contain NULs */
 int read_line_with_nul(char *buf, int size, FILE *in)
 {
 	int len = 0, c;
 
 	for (;;) {
-		c = fgetc(in);
+		c = fast_fgetc(in);
 		buf[len++] = c;
 		if (c == EOF || c == '\n' || len + 1 >= size)
 			break;