implement mrb_format and mrb_vformat

include/mruby/array.h

@@ -54,6 +54,7 @@ mrb_value mrb_assoc_new(mrb_state *mrb, mrb_value car, mrb_value cdr);
 mrb_value mrb_ary_entry(mrb_value ary, mrb_int offset);
 mrb_value mrb_ary_shift(mrb_state *mrb, mrb_value self);
 mrb_value mrb_ary_clear(mrb_state *mrb, mrb_value self);
+mrb_value mrb_ary_join(mrb_state *mrb, mrb_value ary, mrb_value sep);
 
 #if defined(__cplusplus)
 }  /* extern "C" { */

src/error.c

@@ -13,6 +13,7 @@
 #include "error.h"
 #include "mruby/variable.h"
 #include "mruby/string.h"
+#include "mruby/array.h"
 #include "mruby/class.h"
 #include "mruby/proc.h"
 #include "mruby/irep.h"
@@ -228,6 +229,54 @@ mrb_raise(mrb_state *mrb, struct RClass *c, const char *msg)
   mrb_exc_raise(mrb, mrb_exc_new3(mrb, c, mesg));
 }
 
+mrb_value
+mrb_vformat(mrb_state *mrb, const char *format, va_list ap)
+{
+  const char *p = format;
+  const char *b = p;
+  ptrdiff_t size;
+  mrb_value ary = mrb_ary_new_capa(mrb, 4);
+
+  while (*p) {
+    const char c = *p++;
+
+    if (c == '%') {
+      if (*p == 'S') {
+        size = p - b - 1;
+        mrb_ary_push(mrb, ary, mrb_str_new(mrb, b, size));
+        mrb_ary_push(mrb, ary, va_arg(ap, mrb_value));
+        b = p + 1;
+      }
+    }
+    else if (c == '\\') {
+      if (!*p) break;
+      p++;
+    }
+    p++;
+  }
+  if (b == format) {
+    return mrb_str_new_cstr(mrb, format);
+  }
+  else {
+    size = p - b;
+    mrb_ary_push(mrb, ary, mrb_str_new(mrb, b, size));
+    return mrb_ary_join(mrb, ary, mrb_str_new(mrb,NULL,0));
+  }
+}
+
+mrb_value
+mrb_format(mrb_state *mrb, const char *format, ...)
+{
+  va_list ap;
+  mrb_value str;
+
+  va_start(ap, format);
+  str = mrb_vformat(mrb, format, ap);
+  va_end(ap);
+
+  return str;
+}
+
 void
 mrb_raisef(mrb_state *mrb, struct RClass *c, const char *fmt, ...)
 {