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