diff --git a/contrib/40.srfi/src/106.c b/contrib/40.srfi/src/106.c
index c8efc474..a52d161d 100644
--- a/contrib/40.srfi/src/106.c
+++ b/contrib/40.srfi/src/106.c
@@ -185,8 +185,7 @@ pic_socket_socket_accept(pic_state *pic)
 static pic_value
 pic_socket_socket_send(pic_state *pic)
 {
-  pic_value obj;
-  struct pic_blob *bv;
+  pic_value obj, bv;
   const unsigned char *cursor;
   int flags = 0, remain, written;
   struct pic_socket_t *sock;
@@ -223,7 +222,6 @@ static pic_value
 pic_socket_socket_recv(pic_state *pic)
 {
   pic_value obj;
-  struct pic_blob *bv;
   void *buf;
   int size;
   int flags = 0;
@@ -239,7 +237,7 @@ pic_socket_socket_recv(pic_state *pic)
   sock = pic_socket_data(pic, obj);
   ensure_socket_is_open(pic, sock);
 
-  buf = malloc(size);
+  buf = pic_blob(pic, pic_blob_value(pic, NULL, size), NULL);
   if (buf == NULL && size > 0) {
     /* XXX: Is it really OK? */
     pic_panic(pic, "memory exhausted");
@@ -251,14 +249,10 @@ pic_socket_socket_recv(pic_state *pic)
   } while (len < 0 && (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK));
 
   if (len < 0) {
-    free(buf);
     pic_errorf(pic, "%s", strerror(errno));
   }
 
-  bv = pic_blob_value(pic, buf, len);
-  free(buf);
-
-  return pic_obj_value(bv);
+  return pic_blob_value(pic, buf, len);
 }
 
 static pic_value
diff --git a/extlib/benz/blob.c b/extlib/benz/blob.c
index 6cc1eaac..125c3e74 100644
--- a/extlib/benz/blob.c
+++ b/extlib/benz/blob.c
@@ -5,7 +5,7 @@
 #include "picrin.h"
 #include "picrin/object.h"
 
-struct pic_blob *
+pic_value
 pic_blob_value(pic_state *pic, const unsigned char *buf, int len)
 {
   struct pic_blob *bv;
@@ -16,14 +16,16 @@ pic_blob_value(pic_state *pic, const unsigned char *buf, int len)
   if (buf) {
     memcpy(bv->data, buf, len);
   }
-  return bv;
+  return pic_obj_value(bv);
 }
 
 unsigned char *
-pic_blob(pic_state PIC_UNUSED(*pic), struct pic_blob *blob, int *len)
+pic_blob(pic_state PIC_UNUSED(*pic), pic_value blob, int *len)
 {
-  *len = blob->len;
-  return blob->data;
+  if (len) {
+    *len = pic_blob_ptr(pic, blob)->len;
+  }
+  return pic_blob_ptr(pic, blob)->data;
 }
 
 static pic_value
@@ -39,16 +41,15 @@ pic_blob_bytevector_p(pic_state *pic)
 static pic_value
 pic_blob_bytevector(pic_state *pic)
 {
-  pic_value *argv;
+  pic_value *argv, blob;
   int argc, i;
-  struct pic_blob *blob;
   unsigned char *data;
 
   pic_get_args(pic, "*", &argc, &argv);
 
   blob = pic_blob_value(pic, 0, argc);
 
-  data = blob->data;
+  data = pic_blob(pic, blob, NULL);
 
   for (i = 0; i < argc; ++i) {
     pic_assert_type(pic, argv[i], int);
@@ -60,91 +61,103 @@ pic_blob_bytevector(pic_state *pic)
     *data++ = (unsigned char)pic_int(pic, argv[i]);
   }
 
-  return pic_obj_value(blob);
+  return blob;
 }
 
 static pic_value
 pic_blob_make_bytevector(pic_state *pic)
 {
-  struct pic_blob *blob;
-  int k, i, b = 0;
+  pic_value blob;
+  int k, b = 0;
 
   pic_get_args(pic, "i|i", &k, &b);
 
   if (b < 0 || b > 255)
     pic_errorf(pic, "byte out of range");
 
-  blob = pic_blob_value(pic, 0, k);
-  for (i = 0; i < k; ++i) {
-    blob->data[i] = (unsigned char)b;
+  if (k < 0) {
+    pic_errorf(pic, "make-bytevector: negative length given %d", k);
   }
 
-  return pic_obj_value(blob);
+  blob = pic_blob_value(pic, 0, k);
+
+  memset(pic_blob(pic, blob, NULL), k, (unsigned char)b);
+
+  return blob;
 }
 
 static pic_value
 pic_blob_bytevector_length(pic_state *pic)
 {
-  struct pic_blob *bv;
+  pic_value bv;
+  int len;
 
   pic_get_args(pic, "b", &bv);
 
-  return pic_int_value(pic, bv->len);
+  pic_blob(pic, bv, &len);
+
+  return pic_int_value(pic, len);
 }
 
 static pic_value
 pic_blob_bytevector_u8_ref(pic_state *pic)
 {
-  struct pic_blob *bv;
-  int k;
+  pic_value bv;
+  unsigned char *buf;
+  int k, len;
 
   pic_get_args(pic, "bi", &bv, &k);
 
-  return pic_int_value(pic, bv->data[k]);
+  buf = pic_blob(pic, bv, &len);
+
+  VALID_INDEX(pic, len, k);
+
+  return pic_int_value(pic, buf[k]);
 }
 
 static pic_value
 pic_blob_bytevector_u8_set(pic_state *pic)
 {
-  struct pic_blob *bv;
-  int k, v;
+  pic_value bv;
+  unsigned char *buf;
+  int k, v, len;
 
   pic_get_args(pic, "bii", &bv, &k, &v);
 
   if (v < 0 || v > 255)
     pic_errorf(pic, "byte out of range");
 
-  bv->data[k] = (unsigned char)v;
+  buf = pic_blob(pic, bv, &len);
+
+  VALID_INDEX(pic, len, k);
+
+  buf[k] = (unsigned char)v;
+
   return pic_undef_value(pic);
 }
 
 static pic_value
 pic_blob_bytevector_copy_i(pic_state *pic)
 {
-  struct pic_blob *to, *from;
-  int n, at, start, end;
+  pic_value to, from;
+  unsigned char *tobuf, *frombuf;
+  int n, at, start, end, tolen, fromlen;
 
   n = pic_get_args(pic, "bib|ii", &to, &at, &from, &start, &end);
 
+  tobuf = pic_blob(pic, to, &tolen);
+  frombuf = pic_blob(pic, from, &fromlen);
+
   switch (n) {
   case 3:
     start = 0;
   case 4:
-    end = from->len;
+    end = fromlen;
   }
 
-  if (to == from && (start <= at && at < end)) {
-    /* copy in reversed order */
-    at += end - start;
-    while (start < end) {
-      to->data[--at] = from->data[--end];
-    }
-    return pic_undef_value(pic);
-  }
+  VALID_ATRANGE(pic, tolen, at, fromlen, start, end);
 
-  while (start < end) {
-    to->data[at++] = from->data[start++];
-  }
+  memmove(tobuf + at, frombuf + start, end - start);
 
   return pic_undef_value(pic);
 }
@@ -152,62 +165,59 @@ pic_blob_bytevector_copy_i(pic_state *pic)
 static pic_value
 pic_blob_bytevector_copy(pic_state *pic)
 {
-  struct pic_blob *from, *to;
-  int n, start, end, i = 0;
+  pic_value from;
+  unsigned char *buf;
+  int n, start, end, len;
 
   n = pic_get_args(pic, "b|ii", &from, &start, &end);
 
+  buf = pic_blob(pic, from, &len);
+
   switch (n) {
   case 1:
     start = 0;
   case 2:
-    end = from->len;
+    end = len;
   }
 
-  if (end < start) {
-    pic_errorf(pic, "make-bytevector: end index must not be less than start index");
-  }
+  VALID_RANGE(pic, len, start, end);
 
-  to = pic_blob_value(pic, 0, end - start);
-  while (start < end) {
-    to->data[i++] = from->data[start++];
-  }
-
-  return pic_obj_value(to);
+  return pic_blob_value(pic, buf + start, end - start);
 }
 
 static pic_value
 pic_blob_bytevector_append(pic_state *pic)
 {
-  int argc, i, j, len;
-  pic_value *argv;
-  struct pic_blob *blob;
+  int argc, i, l, len;
+  unsigned char *buf, *dst;
+  pic_value *argv, blob;
 
   pic_get_args(pic, "*", &argc, &argv);
 
   len = 0;
   for (i = 0; i < argc; ++i) {
     pic_assert_type(pic, argv[i], blob);
-    len += pic_blob_ptr(argv[i])->len;
+    pic_blob(pic, argv[i], &l);
+    len += l;
   }
 
-  blob = pic_blob_value(pic, 0, len);
+  blob = pic_blob_value(pic, NULL, len);
 
+  dst = pic_blob(pic, blob, NULL);
   len = 0;
   for (i = 0; i < argc; ++i) {
-    for (j = 0; j < pic_blob_ptr(argv[i])->len; ++j) {
-      blob->data[len + j] = pic_blob_ptr(argv[i])->data[j];
-    }
-    len += pic_blob_ptr(argv[i])->len;
+    buf = pic_blob(pic, argv[i], &l);
+    memcpy(dst + len, buf, l);
+    len += l;
   }
 
-  return pic_obj_value(blob);
+  return blob;
 }
 
 static pic_value
 pic_blob_list_to_bytevector(pic_state *pic)
 {
-  struct pic_blob *blob;
+  pic_value blob;
   unsigned char *data;
   pic_value list, e, it;
 
@@ -215,7 +225,7 @@ pic_blob_list_to_bytevector(pic_state *pic)
 
   blob = pic_blob_value(pic, 0, pic_length(pic, list));
 
-  data = blob->data;
+  data = pic_blob(pic, blob, NULL);
 
   pic_for_each (e, list, it) {
     pic_assert_type(pic, e, int);
@@ -225,29 +235,32 @@ pic_blob_list_to_bytevector(pic_state *pic)
 
     *data++ = (unsigned char)pic_int(pic, e);
   }
-  return pic_obj_value(blob);
+  return blob;
 }
 
 static pic_value
 pic_blob_bytevector_to_list(pic_state *pic)
 {
-  struct pic_blob *blob;
-  pic_value list;
-  int n, start, end, i;
+  pic_value blob, list;
+  unsigned char *buf;
+  int n, len, start, end, i;
 
   n = pic_get_args(pic, "b|ii", &blob, &start, &end);
 
+  buf = pic_blob(pic, blob, &len);
+
   switch (n) {
   case 1:
     start = 0;
   case 2:
-    end = blob->len;
+    end = len;
   }
 
-  list = pic_nil_value(pic);
+  VALID_RANGE(pic, len, start, end);
 
+  list = pic_nil_value(pic);
   for (i = start; i < end; ++i) {
-    pic_push(pic, pic_int_value(pic, blob->data[i]), list);
+    pic_push(pic, pic_int_value(pic, buf[i]), list);
   }
   return pic_reverse(pic, list);
 }
diff --git a/extlib/benz/bool.c b/extlib/benz/bool.c
index c5d47823..3e474e55 100644
--- a/extlib/benz/bool.c
+++ b/extlib/benz/bool.c
@@ -109,18 +109,17 @@ internal_equal_p(pic_state *pic, pic_value x, pic_value y, int depth, khash_t(m)
     return pic_str_cmp(pic, pic_str_ptr(x), pic_str_ptr(y)) == 0;
   }
   case PIC_TYPE_BLOB: {
-    struct pic_blob *blob1, *blob2;
-    int i;
+    int xlen, ylen;
+    const unsigned char *xbuf, *ybuf;
 
-    blob1 = pic_blob_ptr(x);
-    blob2 = pic_blob_ptr(y);
+    xbuf = pic_blob(pic, x, &xlen);
+    ybuf = pic_blob(pic, y, &ylen);
 
-    if (blob1->len != blob2->len) {
+    if (xlen != ylen) {
       return false;
     }
-    for (i = 0; i < blob1->len; ++i) {
-      if (blob1->data[i] != blob2->data[i])
-        return false;
+    if (memcmp(xbuf, ybuf, xlen) != 0) {
+      return false;
     }
     return true;
   }
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 84df7381..9e796dc3 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -54,7 +54,6 @@ typedef struct {
 struct pic_object;
 struct pic_symbol;
 struct pic_string;
-struct pic_blob;
 struct pic_proc;
 struct pic_port;
 struct pic_error;
@@ -120,13 +119,13 @@ pic_value pic_vcall(pic_state *, struct pic_proc *proc, int, va_list);
 pic_value pic_apply(pic_state *, struct pic_proc *proc, int n, pic_value *argv);
 pic_value pic_applyk(pic_state *, struct pic_proc *proc, int n, pic_value *argv);
 
-PIC_INLINE int pic_int(pic_state *, pic_value);
-PIC_INLINE double pic_float(pic_state *, pic_value);
-PIC_INLINE char pic_char(pic_state *, pic_value);
-#define pic_bool(pic,v) (! pic_false_p(pic, v))
+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);
+#define pic_bool(pic,b) (! pic_false_p(pic, b))
 const char *pic_str(pic_state *, struct pic_string *);
-unsigned char *pic_blob(pic_state *, struct pic_blob *, int *len);
-void *pic_data(pic_state *, pic_value);
+unsigned char *pic_blob(pic_state *, pic_value blob, int *len);
+void *pic_data(pic_state *, pic_value str);
 
 typedef struct {
   const char *type_name;
@@ -147,7 +146,7 @@ struct pic_string *pic_str_value(pic_state *, const char *str, int len);
 #define pic_lit_value(pic, lit) pic_str_value(pic, "" lit, -((int)sizeof lit - 1))
 struct pic_string *pic_strf_value(pic_state *, const char *fmt, ...);
 struct pic_string *pic_vstrf_value(pic_state *, const char *fmt, va_list ap);
-struct pic_blob *pic_blob_value(pic_state *, const unsigned char *buf, int len);
+pic_value pic_blob_value(pic_state *, const unsigned char *buf, int len);
 struct pic_data *pic_data_value(pic_state *, void *ptr, const pic_data_type *type);
 
 enum {
diff --git a/extlib/benz/include/picrin/compat.h b/extlib/benz/include/picrin/compat.h
index ba4d964e..e367a6ce 100644
--- a/extlib/benz/include/picrin/compat.h
+++ b/extlib/benz/include/picrin/compat.h
@@ -221,6 +221,18 @@ memmove(void *dst, const void *src, size_t n)
   return d;
 }
 
+PIC_INLINE int
+memcmp(const void *b1, const void *b2, size_t n)
+{
+  const char *s1 = b1, *s2 = b2;
+
+  while (*s1 == *s2 && n-- > 0) {
+    s1++;
+    s2++;
+  }
+  return (unsigned)*s1 - (unsigned)*s2;
+}
+
 PIC_INLINE char *
 strcpy(char *dst, const char *src)
 {
diff --git a/extlib/benz/include/picrin/object.h b/extlib/benz/include/picrin/object.h
index 7e71ef38..ff3cb20d 100644
--- a/extlib/benz/include/picrin/object.h
+++ b/extlib/benz/include/picrin/object.h
@@ -121,11 +121,11 @@ struct pic_port {
 };
 
 #define pic_pair_ptr(pic, o) ((struct pic_pair *)pic_obj_ptr(o))
+#define pic_blob_ptr(pic, v) ((struct pic_blob *)pic_obj_ptr(v))
 #define pic_vec_ptr(pic, o) ((struct pic_vector *)pic_obj_ptr(o))
 #define pic_dict_ptr(pic, v) ((struct pic_dict *)pic_obj_ptr(v))
 #define pic_sym_ptr(v) ((pic_sym *)pic_obj_ptr(v))
 #define pic_id_ptr(v) ((pic_id *)pic_obj_ptr(v))
-#define pic_blob_ptr(v) ((struct pic_blob *)pic_obj_ptr(v))
 #define pic_str_ptr(o) ((struct pic_string *)pic_obj_ptr(o))
 #define pic_weak_ptr(v) ((struct pic_weak *)pic_obj_ptr(v))
 #define pic_data_ptr(o) ((struct pic_data *)pic_obj_ptr(o))
diff --git a/extlib/benz/port.c b/extlib/benz/port.c
index 136de293..039dbf91 100644
--- a/extlib/benz/port.c
+++ b/extlib/benz/port.c
@@ -125,14 +125,15 @@ pic_port_close_port(pic_state *pic)
 static pic_value
 pic_port_open_input_bytevector(pic_state *pic)
 {
-  struct pic_blob *blob;
-  xFILE *file;
+  pic_value blob;
+  unsigned char *buf;
+  int len;
 
   pic_get_args(pic, "b", &blob);
 
-  file = xfopen_buf(pic, (const char *)blob->data, blob->len, "r");
+  buf = pic_blob(pic, blob, &len);
 
-  return pic_obj_value(pic_make_port(pic, file));
+  return pic_obj_value(pic_make_port(pic, xfopen_buf(pic, (char *)buf, len, "r")));
 }
 
 static pic_value
@@ -157,7 +158,7 @@ pic_port_get_output_bytevector(pic_state *pic)
   if (xfget_buf(pic, port->file, &buf, &len) < 0) {
     pic_errorf(pic, "port was not created by open-output-bytevector");
   }
-  return pic_obj_value(pic_blob_value(pic, (unsigned char *)buf, len));
+  return pic_blob_value(pic, (unsigned char *)buf, len);
 }
 
 static pic_value
@@ -211,63 +212,51 @@ static pic_value
 pic_port_read_bytevector(pic_state *pic)
 {
   struct pic_port *port = pic_stdin(pic);
-  struct pic_blob *blob;
+  unsigned char *buf;
   int k, i;
 
   pic_get_args(pic, "i|p", &k, &port);
 
   assert_port_profile(port, X_READ, "read-bytevector");
 
-  blob = pic_blob_value(pic, 0, k);
+  buf = pic_blob(pic, pic_blob_value(pic, NULL, k), NULL);
 
-  i = xfread(pic, blob->data, sizeof(char), k, port->file);
+  i = xfread(pic, buf, sizeof(char), k, port->file);
   if (i == 0) {
     return pic_eof_object(pic);
   }
-  else {
-    pic_realloc(pic, blob->data, i);
-    blob->len = i;
-    return pic_obj_value(blob);
-  }
+  return pic_blob_value(pic, buf, i);
 }
 
 static pic_value
 pic_port_read_bytevector_ip(pic_state *pic)
 {
   struct pic_port *port;
-  struct pic_blob *bv;
-  char *buf;
+  pic_value bv;
+  unsigned char *buf;
   int n, start, end, i, len;
 
   n = pic_get_args(pic, "b|pii", &bv, &port, &start, &end);
+
+  buf = pic_blob(pic, bv, &len);
+
   switch (n) {
   case 1:
     port = pic_stdin(pic);
   case 2:
     start = 0;
   case 3:
-    end = bv->len;
+    end = len;
   }
 
+  VALID_RANGE(pic, len, start, end);
   assert_port_profile(port, X_READ, "read-bytevector!");
 
-  if (end < start) {
-    pic_errorf(pic, "read-bytevector!: end index must be greater than or equal to start index");
-  }
-
-  len = end - start;
-
-  buf = pic_calloc(pic, len, sizeof(char));
-  i = xfread(pic, buf, sizeof(char), len, port->file);
-  memcpy(bv->data + start, buf, i);
-  pic_free(pic, buf);
-
+  i = xfread(pic, buf + start, 1, end - start, port->file);
   if (i == 0) {
     return pic_eof_object(pic);
   }
-  else {
-    return pic_int_value(pic, i);
-  }
+  return pic_int_value(pic, i);
 }
 
 static pic_value
@@ -287,24 +276,31 @@ pic_port_write_u8(pic_state *pic)
 static pic_value
 pic_port_write_bytevector(pic_state *pic)
 {
-  struct pic_blob *blob;
+  pic_value blob;
   struct pic_port *port;
-  int n, start, end, i;
+  unsigned char *buf;
+  int n, start, end, len, done;
 
   n = pic_get_args(pic, "b|pii", &blob, &port, &start, &end);
+
+  buf = pic_blob(pic, blob, &len);
+
   switch (n) {
   case 1:
     port = pic_stdout(pic);
   case 2:
     start = 0;
   case 3:
-    end = blob->len;
+    end = len;
   }
 
+  VALID_RANGE(pic, len, start, end);
   assert_port_profile(port, X_WRITE, "write-bytevector");
 
-  for (i = start; i < end; ++i) {
-    xfputc(pic, blob->data[i], port->file);
+  done = 0;
+  while (done < end - start) {
+    done += xfwrite(pic, buf + start + done, 1, end - start - done, port->file);
+    /* FIXME: error check... */
   }
   return pic_undef_value(pic);
 }
diff --git a/extlib/benz/proc.c b/extlib/benz/proc.c
index 712c26db..017d691f 100644
--- a/extlib/benz/proc.c
+++ b/extlib/benz/proc.c
@@ -23,7 +23,7 @@
  *  m   pic_sym **              symbol
  *  v   pic_value *             vector object
  *  s   struct pic_str **       string object
- *  b   struct pic_blob **      bytevector object
+ *  b   pic_value *             bytevector object
  *  l   struct pic_proc **      lambda object
  *  p   struct pic_port **      port object
  *  d   pic_value *             dictionary object
@@ -149,7 +149,6 @@ pic_get_args(pic_state *pic, const char *format, ...)
 
     PTR_CASE('m', sym, pic_sym *)
     PTR_CASE('s', str, struct pic_string *)
-    PTR_CASE('b', blob, struct pic_blob *)
     PTR_CASE('l', proc, struct pic_proc *)
     PTR_CASE('p', port, struct pic_port *)
     PTR_CASE('e', error, struct pic_error *)
@@ -157,6 +156,7 @@ pic_get_args(pic_state *pic, const char *format, ...)
 
 #define OBJ_CASE(c, type) VAL_CASE(c, type, pic_value, v)
 
+    OBJ_CASE('b', blob)
     OBJ_CASE('v', vec)
     OBJ_CASE('d', dict)
 
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index 4f26f86f..3cefa8a3 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -499,7 +499,7 @@ read_blob(pic_state *pic, xFILE *file, int c)
   int nbits, n;
   int len;
   unsigned char *dat;
-  struct pic_blob *blob;
+  pic_value blob;
 
   nbits = 0;
 
@@ -532,7 +532,7 @@ read_blob(pic_state *pic, xFILE *file, int c)
   blob = pic_blob_value(pic, dat, len);
 
   pic_free(pic, dat);
-  return pic_obj_value(blob);
+  return blob;
 }
 
 static pic_value
diff --git a/extlib/benz/write.c b/extlib/benz/write.c
index 228bc3d9..f5f8ceb6 100644
--- a/extlib/benz/write.c
+++ b/extlib/benz/write.c
@@ -48,14 +48,17 @@ writer_control_destroy(struct writer_control *p)
 }
 
 static void
-write_blob(pic_state *pic, struct pic_blob *blob, xFILE *file)
+write_blob(pic_state *pic, pic_value blob, xFILE *file)
 {
-  int i;
+  const unsigned char *buf;
+  int len, i;
+
+  buf = pic_blob(pic, blob, &len);
 
   xfprintf(pic, file, "#u8(");
-  for (i = 0; i < blob->len; ++i) {
-    xfprintf(pic, file, "%d", blob->data[i]);
-    if (i + 1 < blob->len) {
+  for (i = 0; i < len; ++i) {
+    xfprintf(pic, file, "%d", buf[i]);
+    if (i + 1 < len) {
       xfprintf(pic, file, " ");
     }
   }
@@ -303,7 +306,7 @@ write_core(struct writer_control *p, pic_value obj)
     xfprintf(pic, file, "%s", pic_str(pic, pic_sym_name(pic, pic_sym_ptr(obj))));
     break;
   case PIC_TYPE_BLOB:
-    write_blob(pic, pic_blob_ptr(obj), file);
+    write_blob(pic, obj, file);
     break;
   case PIC_TYPE_CHAR:
     write_char(pic, pic_char(pic, obj), file, p->mode);