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minor but worthwhile optimization in printf: avoid expensive strspn

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the strspn call was made for every format specifier and end-of-string,
even though the expected return value was 1-2 for normal usage.
replace with simple loop.
This commit is contained in:
Rich Felker
2012-08-10 23:39:32 -04:00
parent 4c346919a9
commit 2b964b010e
1 changed files with 2 additions and 4 deletions
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src/stdio/vfprintf.c
+2 -4
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@@ -430,7 +430,7 @@ static int getint(char **s) {
static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg, int *nl_type) static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg, int *nl_type)
{ {
char *a, *z, *s=(char *)fmt; char *a, *z, *s=(char *)fmt;
unsigned l10n=0, litpct, fl; unsigned l10n=0, fl;
int w, p; int w, p;
union arg arg; union arg arg;
int argpos; int argpos;
@@ -455,9 +455,7 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
/* Handle literal text and %% format specifiers */ /* Handle literal text and %% format specifiers */
for (a=s; *s && *s!='%'; s++); for (a=s; *s && *s!='%'; s++);
litpct = strspn(s, "%")/2; /* Optimize %%%% runs */ for (z=s; s[0]=='%' && s[1]=='%'; z++, s+=2);
z = s+litpct;
s += 2*litpct;
l = z-a; l = z-a;
if (f) out(f, a, l); if (f) out(f, a, l);
if (l) continue; if (l) continue;