jsonfmt: Move arg parsing into XS

Going to need a way to pass arguments into the XS function anyway, so
might as well do the entire arg parsing step in XS while we're at it.
Provides a significant speedup for tiny inputs as well, but I don't find
that too interesting.

FU.xs

@@ -10,10 +10,6 @@ MODULE = FU   PACKAGE = FU::XS
 
 PROTOTYPES: DISABLE
 
-void json_format(SV *val)
+void json_format(SV *val, ...)
   CODE:
-    fustr buf;
-    fustr_init(&buf, 128);
-    fujson_fmt(aTHX_ &buf, val);
-    ST(0) = fustr_done(&buf);
-    SvUTF8_on(ST(0));
+    ST(0) = fujson_fmt_xs(aTHX_ ax, items, val);

FU/Benchmarks.pod

@@ -43,8 +43,7 @@ The following module versions were used:
 
 These benchmarks run on large-ish arrays with repeated values. JSON encoding is
 sufficiently fast that Perl function calling overhead tends to dominate for
-smaller inputs, but I don't find that overhead very interesting. Other modules
-will likely do better in benchmarks on small inputs.
+smaller inputs, but I don't find that overhead very interesting.
 
 Also worth noting that JSON::SIMD formatting code is forked from JSON::XS, the
 SIMD parts are only used for parsing.

FU/Util.pm

@@ -6,12 +6,6 @@ use Exporter 'import';
 
 our @EXPORT_OK = qw/json_format/;
 
-
-sub json_format($val, %opt) {
-    my $r = FU::XS::json_format($val);
-    # XXX: Does this go over the bytes? If so, not setting SvUTF8_on() in the first place would be much faster.
-    utf8::encode($r) if $opt{utf8};
-    $r
-}
+*json_format = *FU::XS::json_format;
 
 1;

bench.PL

@@ -159,8 +159,7 @@ The following module versions were used:
 
 These benchmarks run on large-ish arrays with repeated values. JSON encoding is
 sufficiently fast that Perl function calling overhead tends to dominate for
-smaller inputs, but I don't find that overhead very interesting. Other modules
-will likely do better in benchmarks on small inputs.
+smaller inputs, but I don't find that overhead very interesting.
 
 Also worth noting that JSON::SIMD formatting code is forked from JSON::XS, the
 SIMD parts are only used for parsing.

c/jsonfmt.c

@@ -172,6 +172,35 @@ static void fujson_fmt(pTHX_ fustr *out, SV *val) {
     }
 }
 
+
+static SV *fujson_fmt_xs(pTHX_ I32 ax, I32 argc, SV *val) {
+    I32 i = 1;
+    int encutf8 = 0;
+    char *arg;
+    SV *r;
+
+    while (i < argc) {
+        arg = SvPV_nolen(ST(i));
+        i++;
+        if (i == argc) croak("Odd name/value argument for json_format()");
+        r = ST(i);
+        i++;
+
+        if (strcmp(arg, "utf8") == 0) {
+            encutf8 = SvPVXtrue(r);
+        } else {
+            croak("Unknown flag: '%s'", arg);
+        }
+    }
+
+    fustr buf;
+    fustr_init(&buf, 128);
+    fujson_fmt(aTHX_ &buf, val);
+    r = fustr_done(&buf);
+    if (!encutf8) SvUTF8_on(r);
+    return r;
+}
+
 /* TODO: canonical */
 /* TODO: pretty */
 /* TODO: max depth? */

t/json_format.t

@@ -58,12 +58,17 @@ my @errors = (
     do { no warnings 'portable'; "\x{ffffffff}" }, qr/invalid codepoint encountered in string/,
 );
 
-plan tests => @tests + @errors/2 + 6;
+plan tests => @tests*2 + @errors/2 + 6;
 
 for my($in, $exp) (@tests) {
     my $out = json_format $in;
     is $out, $exp;
     ok utf8::is_utf8($out);
+
+    $out = json_format $in, utf8 => 1;
+    utf8::encode(my $uexp = $exp);
+    is $out, $uexp;
+    ok !utf8::is_utf8($out);
 }
 
 for my ($in, $exp) (@errors) {