libbb: speed up error_msg functions

function                                             old     new   delta
bb_verror_msg                                        386     466     +80

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 25 insertions, 4 deletions

diff --git a/libbb/verror_msg.c b/libbb/verror_msg.c
index 0ef2a311f..22c30357b 100644
--- a/libbb/verror_msg.c
+++ b/libbb/verror_msg.c
@@ -20,6 +20,7 @@ const char *msg_eol = "\n";
 void FAST_FUNC bb_verror_msg(const char *s, va_list p, const char* strerr)
 {
 	char *msg, *msg1;
+	char stack_msg[80];
 	int applet_len, strerr_len, msgeol_len, used;
 
 	if (!logmode)
@@ -28,6 +29,27 @@ void FAST_FUNC bb_verror_msg(const char *s, va_list p, const char* strerr)
 	if (!s) /* nomsg[_and_die] uses NULL fmt */
 		s = ""; /* some libc don't like printf(NULL) */
 
+	applet_len = strlen(applet_name) + 2; /* "applet: " */
+	strerr_len = strerr ? strlen(strerr) : 0;
+	msgeol_len = strlen(msg_eol);
+
+	/* This costs ~90 bytes of code, but avoids costly
+	 * malloc()[in vasprintf]+realloc()+memmove()+free() in 99% of cases.
+	 * ~40% speedup.
+	 */
+	if ((int)sizeof(stack_msg) - applet_len > 0) {
+		va_list p2;
+
+		/* It is not portable to use va_list twice, need to va_copy it */
+		va_copy(p2, p);
+		used = vsnprintf(stack_msg + applet_len, (int)sizeof(stack_msg) - applet_len, s, p2);
+		va_end(p2);
+		msg = stack_msg;
+		used += applet_len;
+		if (used < (int)sizeof(stack_msg) - 3 - msgeol_len - strerr_len)
+			goto add_pfx_and_sfx;
+	}
+
 	used = vasprintf(&msg, s, p);
 	if (used < 0)
 		return;
@@ -37,9 +59,6 @@ void FAST_FUNC bb_verror_msg(const char *s, va_list p, const char* strerr)
 	 * This is needed for e.g. httpd logging, when multiple
 	 * children can produce log messages simultaneously. */
 
-	applet_len = strlen(applet_name) + 2; /* "applet: " */
-	strerr_len = strerr ? strlen(strerr) : 0;
-	msgeol_len = strlen(msg_eol);
 	/* can't use xrealloc: it calls error_msg on failure,
 	 * that may result in a recursion */
 	/* +3 is for ": " before strerr and for terminating NUL */
@@ -52,6 +71,7 @@ void FAST_FUNC bb_verror_msg(const char *s, va_list p, const char* strerr)
 		/* TODO: maybe use writev instead of memmoving? Need full_writev? */
 		memmove(msg + applet_len, msg, used);
 		used += applet_len;
+ add_pfx_and_sfx:
 		strcpy(msg, applet_name);
 		msg[applet_len - 2] = ':';
 		msg[applet_len - 1] = ' ';
@@ -76,7 +96,8 @@ void FAST_FUNC bb_verror_msg(const char *s, va_list p, const char* strerr)
 		syslog(syslog_level, "%s", msg + applet_len);
 	}
 #endif
-	free(msg);
+	if (msg != stack_msg)
+		free(msg);
 }
 
 #ifdef VERSION_WITH_WRITEV