if string precision is set, don't let the strlen loop run past the sp…

…ecified precision (#234)

* if string precision is set, don't let the strlen loop run past the specified precision

* rewrite to one loop, see if it's smaller

* remove npf_min

nanoprintf.h

@@ -283,7 +283,6 @@ static int npf_bin_len(npf_uint_t i);
   #include <intrin.h>
 #endif
 
-static int npf_min(int x, int y) { return (x < y) ? x : y; }
 static int npf_max(int x, int y) { return (x > y) ? x : y; }
 
 int npf_parse_format_spec(char const *format, npf_format_spec_t *out_spec) {
@@ -762,11 +761,11 @@ int npf_vpprintf(npf_putc pc, void *pc_ctx, char const *format, va_list args) {
 
       case NPF_FMT_SPEC_CONV_STRING: {
         cbuf = va_arg(args, char *);
-        for (char const *s = cbuf; *s; ++s, ++cbuf_len); // strlen
 #if NANOPRINTF_USE_PRECISION_FORMAT_SPECIFIERS == 1
-        if (fs.prec_opt == NPF_FMT_SPEC_OPT_LITERAL) {
-          cbuf_len = npf_min(fs.prec, cbuf_len); // prec truncates strings
-        }
+        int const n = (fs.prec_opt == NPF_FMT_SPEC_OPT_NONE) ? -1 : fs.prec;
+        for (char const *s = cbuf; *s && ((n == -1) || (cbuf_len < n)); ++s, ++cbuf_len);
+#else
+        for (char const *s = cbuf; *s; ++s, ++cbuf_len); // strlen
 #endif
       } break;