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>

diff --git a/libbb/verror_msg.c b/libbb/verror_msg.c
index 0ef2a311fd2ca7345c91c1b38d9a35c8031949fa..22c30357b267325add97dd24946f899b6ca3b174 100644 (file)
--- 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