diff --git a/contrib/20.r7rs/src/file.c b/contrib/20.r7rs/src/file.c
index 2c0b080e..5cb99ffc 100644
--- a/contrib/20.r7rs/src/file.c
+++ b/contrib/20.r7rs/src/file.c
@@ -20,7 +20,7 @@ open_file(pic_state *pic, const char *fname, const char *mode)
   if ((fp = fopen(fname, mode)) == NULL) {
     file_error(pic, "could not open file...");
   }
-  return pic_make_port(pic, xfopen_file(pic, fp, mode));
+  return pic_open_port(pic, xfopen_file(pic, fp, mode));
 }
 
 pic_value
diff --git a/contrib/20.r7rs/src/load.c b/contrib/20.r7rs/src/load.c
index cc02bb2c..b7459bb6 100644
--- a/contrib/20.r7rs/src/load.c
+++ b/contrib/20.r7rs/src/load.c
@@ -20,7 +20,7 @@ pic_load_load(pic_state *pic)
     pic_errorf(pic, "load: could not open file %s", fn);
   }
 
-  port = pic_make_port(pic, xfopen_file(pic, fp, "r"));
+  port = pic_open_port(pic, xfopen_file(pic, fp, "r"));
 
   pic_load(pic, port);
 
diff --git a/contrib/40.srfi/src/106.c b/contrib/40.srfi/src/106.c
index 0be9f6d9..73272825 100644
--- a/contrib/40.srfi/src/106.c
+++ b/contrib/40.srfi/src/106.c
@@ -331,7 +331,7 @@ make_socket_port(pic_state *pic, struct pic_socket_t *sock, const char *mode)
     fp = xfunopen(pic, sock, 0, xf_socket_write, xf_socket_seek, xf_socket_close);
   }
 
-  return pic_make_port(pic, fp);
+  return pic_open_port(pic, fp);
 }
 
 static pic_value
diff --git a/extlib/benz/file.c b/extlib/benz/file.c
index 5032b480..66ec825c 100644
--- a/extlib/benz/file.c
+++ b/extlib/benz/file.c
@@ -252,10 +252,6 @@ size_t xfwrite(pic_state *pic, const void *ptr, size_t size, size_t count, xFILE
   return count;
 }
 
-#define XSEEK_CUR 0
-#define XSEEK_END 1
-#define XSEEK_SET 2
-
 long xfseek(pic_state *pic, xFILE *fp, long offset, int whence) {
   long s;
 
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 961297fa..15604e5a 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -107,6 +107,12 @@ pic_value pic_vcall(pic_state *, pic_value proc, int, va_list);
 pic_value pic_apply(pic_state *, pic_value proc, int n, pic_value *argv);
 pic_value pic_applyk(pic_state *, pic_value proc, int n, pic_value *argv);
 
+typedef struct xFILE xFILE;
+
+pic_value pic_open_port(pic_state *, xFILE *file);
+xFILE *pic_fileno(pic_state *, pic_value port);
+void pic_close_port(pic_state *, pic_value port);
+
 PIC_INLINE int pic_int(pic_state *, pic_value i);
 PIC_INLINE double pic_float(pic_state *, pic_value f);
 PIC_INLINE char pic_char(pic_state *, pic_value c);
@@ -255,6 +261,35 @@ int pic_str_cmp(pic_state *, pic_value str1, pic_value str2);
 int pic_str_hash(pic_state *, pic_value str);
 
 
+
+/* External I/O */
+
+#define XSEEK_CUR 0
+#define XSEEK_END 1
+#define XSEEK_SET 2
+
+xFILE *xfunopen(pic_state *, void *cookie, int (*read)(pic_state *, void *, char *, int), int (*write)(pic_state *, void *, const char *, int), long (*seek)(pic_state *, void *, long, int), int (*close)(pic_state *, void *));
+size_t xfread(pic_state *, void *ptr, size_t size, size_t count, xFILE *fp);
+size_t xfwrite(pic_state *, const void *ptr, size_t size, size_t count, xFILE *fp);
+long xfseek(pic_state *, xFILE *fp, long offset, int whence);
+int xfclose(pic_state *, xFILE *fp);
+
+void xclearerr(pic_state *, xFILE *fp);
+int xfeof(pic_state *, xFILE *fp);
+int xferror(pic_state *, xFILE *fp);
+
+int xfputc(pic_state *, int c, xFILE *fp);
+int xfgetc(pic_state *, xFILE *fp);
+int xfputs(pic_state *, const char *s, xFILE *fp);
+char *xfgets(pic_state *, char *s, int size, xFILE *fp);
+int xungetc(pic_state *, int c, xFILE *fp);
+int xfflush(pic_state *, xFILE *fp);
+
+int xfprintf(pic_state *, xFILE *fp, const char *fmt, ...);
+int xvfprintf(pic_state *, xFILE *fp, const char *fmt, va_list);
+
+
+
 /* extra stuff */
 
 
@@ -272,15 +307,23 @@ void *pic_default_allocf(void *, void *, size_t);
     pic_errorf(pic, "expected " #type ", but got ~s", v);       \
   }
 
-pic_value pic_make_port(pic_state *, xFILE *file);
-void pic_close_port(pic_state *, pic_value port);
+#define xstdin  (&pic->files[0])
+#define xstdout (&pic->files[1])
+#define xstderr (&pic->files[2])
+
+#if PIC_ENABLE_STDIO
+xFILE *xfopen_file(pic_state *, FILE *, const char *mode);
+#endif
+xFILE *xfopen_buf(pic_state *, const char *buf, int len, const char *mode);
+int xfget_buf(pic_state *, xFILE *file, const char **buf, int *len);
+xFILE *xfopen_null(pic_state *, const char *mode);
 
 #define pic_void(exec)                          \
   pic_void_(PIC_GENSYM(ai), exec)
 #define pic_void_(ai,exec) do {                 \
-    size_t ai = pic_enter(pic);     \
+    size_t ai = pic_enter(pic);                 \
     exec;                                       \
-    pic_leave(pic, ai);              \
+    pic_leave(pic, ai);                         \
   } while (0)
 
 pic_value pic_read(pic_state *, pic_value port);
@@ -348,8 +391,6 @@ void pic_print_backtrace(pic_state *, xFILE *);
 #define pic_stdout(pic) pic_funcall(pic, "picrin.base", "current-output-port", 0)
 #define pic_stderr(pic) pic_funcall(pic, "picrin.base", "current-error-port", 0)
 
-xFILE *pic_fileno(pic_state *, pic_value port);
-
 pic_value pic_write(pic_state *, pic_value); /* returns given obj */
 pic_value pic_fwrite(pic_state *, pic_value, xFILE *);
 void pic_printf(pic_state *, const char *, ...);
diff --git a/extlib/benz/include/picrin/file.h b/extlib/benz/include/picrin/file.h
index 657fa2e6..7595d4fb 100644
--- a/extlib/benz/include/picrin/file.h
+++ b/extlib/benz/include/picrin/file.h
@@ -8,7 +8,7 @@ extern "C" {
 #define XBUFSIZ 1024
 #define XOPEN_MAX 1024
 
-typedef struct {
+struct xFILE {
   /* buffer */
   char buf[1];                  /* fallback buffer */
   long cnt;                     /* characters left */
@@ -23,7 +23,7 @@ typedef struct {
     int (*close)(pic_state *, void *);
   } vtable;
   int flag;                     /* mode of the file access */
-} xFILE;
+};
 
 enum {
   X_READ  = 01,
@@ -34,35 +34,6 @@ enum {
   X_LNBUF = 040
 };
 
-#define xstdin  (&pic->files[0])
-#define xstdout (&pic->files[1])
-#define xstderr (&pic->files[2])
-
-xFILE *xfunopen(pic_state *, void *cookie, int (*read)(pic_state *, void *, char *, int), int (*write)(pic_state *, void *, const char *, int), long (*seek)(pic_state *, void *, long, int), int (*close)(pic_state *, void *));
-size_t xfread(pic_state *, void *ptr, size_t size, size_t count, xFILE *fp);
-size_t xfwrite(pic_state *, const void *ptr, size_t size, size_t count, xFILE *fp);
-long xfseek(pic_state *, xFILE *fp, long offset, int whence); /* 0:cur, 1:end, 2:set */
-int xfclose(pic_state *, xFILE *fp);
-
-void xclearerr(pic_state *, xFILE *fp);
-int xfeof(pic_state *, xFILE *fp);
-int xferror(pic_state *, xFILE *fp);
-
-int xfputc(pic_state *, int c, xFILE *fp);
-int xfgetc(pic_state *, xFILE *fp);
-int xfputs(pic_state *, const char *s, xFILE *fp);
-char *xfgets(pic_state *, char *s, int size, xFILE *fp);
-int xungetc(pic_state *, int c, xFILE *fp);
-int xfflush(pic_state *, xFILE *fp);
-int xfprintf(pic_state *, xFILE *fp, const char *fmt, ...);
-int xvfprintf(pic_state *, xFILE *fp, const char *fmt, va_list);
-
-#if PIC_ENABLE_STDIO
-xFILE *xfopen_file(pic_state *, FILE *, const char *mode);
-#endif
-xFILE *xfopen_buf(pic_state *, const char *buf, int len, const char *mode);
-int xfget_buf(pic_state *, xFILE *file, const char **buf, int *len);
-xFILE *xfopen_null(pic_state *, const char *mode);
 
 #if defined(__cplusplus)
 }
diff --git a/extlib/benz/include/picrin/state.h b/extlib/benz/include/picrin/state.h
index a6db373d..5246797c 100644
--- a/extlib/benz/include/picrin/state.h
+++ b/extlib/benz/include/picrin/state.h
@@ -10,9 +10,9 @@ extern "C" {
 #endif
 
 #include "picrin/khash.h"
+#include "picrin/file.h"
 
 #include "picrin/irep.h"
-#include "picrin/file.h"
 #include "picrin/read.h"
 #include "picrin/gc.h"
 
diff --git a/extlib/benz/load.c b/extlib/benz/load.c
index 28ac61b0..2ceefa11 100644
--- a/extlib/benz/load.c
+++ b/extlib/benz/load.c
@@ -20,7 +20,7 @@ pic_load(pic_state *pic, pic_value port)
 void
 pic_load_cstr(pic_state *pic, const char *str)
 {
-  pic_value port = pic_make_port(pic, xfopen_buf(pic, str, strlen(str), "r"));
+  pic_value port = pic_open_port(pic, xfopen_buf(pic, str, strlen(str), "r"));
 
   pic_try {
     pic_load(pic, port);
diff --git a/extlib/benz/port.c b/extlib/benz/port.c
index 69a564ff..f410f44f 100644
--- a/extlib/benz/port.c
+++ b/extlib/benz/port.c
@@ -9,7 +9,7 @@
 #define EOF (-1)
 
 pic_value
-pic_make_port(pic_state *pic, xFILE *file)
+pic_open_port(pic_state *pic, xFILE *file)
 {
   struct pic_port *port;
 
@@ -142,7 +142,7 @@ pic_port_open_input_bytevector(pic_state *pic)
 
   buf = pic_blob(pic, blob, &len);
 
-  return pic_make_port(pic, xfopen_buf(pic, (char *)buf, len, "r"));
+  return pic_open_port(pic, xfopen_buf(pic, (char *)buf, len, "r"));
 }
 
 static pic_value
@@ -150,7 +150,7 @@ pic_port_open_output_bytevector(pic_state *pic)
 {
   pic_get_args(pic, "");
 
-  return pic_make_port(pic, xfopen_buf(pic, NULL, 0, "w"));
+  return pic_open_port(pic, xfopen_buf(pic, NULL, 0, "w"));
 }
 
 static pic_value
@@ -337,7 +337,7 @@ coerce_port(pic_state *pic)
 }
 
 #define DEFINE_PORT(pic, name, file)                                    \
-  pic_defvar(pic, name, pic_make_port(pic, file), coerce)
+  pic_defvar(pic, name, pic_open_port(pic, file), coerce)
 
 void
 pic_init_port(pic_state *pic)
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index 6d3803fa..b409264b 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -844,7 +844,7 @@ pic_read(pic_state *pic, pic_value port)
 pic_value
 pic_read_cstr(pic_state *pic, const char *str)
 {
-  pic_value port = pic_make_port(pic, xfopen_buf(pic, str, strlen(str), "r"));
+  pic_value port = pic_open_port(pic, xfopen_buf(pic, str, strlen(str), "r"));
   pic_value form;
 
   pic_try {