bytevectors: Add a C-friendly API.

* doc/ref/api-data.texi (Bytevector Manipulation): Add
  `scm_is_bytevector ()', `scm_c_bytevector_length ()',
  `scm_c_bytevector_length ()', and `scm_c_bytevector_set_x ()'.

* libguile/bytevectors.c (scm_is_bytevector, scm_c_bytevector_length,
  scm_c_bytevector_ref, scm_c_bytevector_set_x): New functions.
  (scm_bytevector_p): Use `scm_is_bytevector ()'.
  (scm_bytevector_length): Use `scm_c_bytevector_length ()'.

* libguile/bytevectors.h (scm_is_bytevector, scm_c_bytevector_length,
  scm_c_bytevector_ref, scm_c_bytevector_set_x): New declarations.

doc/ref/api-data.texi

@@ -3833,7 +3833,7 @@ The objects denoting big (resp. little) endianness.
 @subsubsection Manipulating Bytevectors
 
 Bytevectors can be created, copied, and analyzed with the following
-procedures.
+procedures and C functions.
 
 @deffn {Scheme Procedure} make-bytevector len [fill]
 @deffnx {C Function} scm_make_bytevector (len, fill)
@@ -3848,11 +3848,19 @@ is given, fill it with @var{fill}; @var{fill} must be in the range
 Return true if @var{obj} is a bytevector.
 @end deffn
 
+@deftypefn {C Function} int scm_is_bytevector (SCM obj)
+Equivalent to @code{scm_is_true (scm_bytevector_p (obj))}.
+@end deftypefn
+
 @deffn {Scheme Procedure} bytevector-length bv
 @deffnx {C Function} scm_bytevector_length (bv)
 Return the length in bytes of bytevector @var{bv}.
 @end deffn
 
+@deftypefn {C Function} size_t scm_c_bytevector_length (SCM bv)
+Likewise, return the length in bytes of bytevector @var{bv}.
+@end deftypefn
+
 @deffn {Scheme Procedure} bytevector=? bv1 bv2
 @deffnx {C Function} scm_bytevector_eq_p (bv1, bv2)
 Return is @var{bv1} equals to @var{bv2}---i.e., if they have the same
@@ -3876,6 +3884,14 @@ and start writing at @var{target-start}.
 Return a newly allocated copy of @var{bv}.
 @end deffn
 
+@deftypefn {C Function} scm_t_uint8 scm_c_bytevector_ref (SCM bv, size_t index)
+Return the byte at @var{index} in bytevector @var{bv}.
+@end deftypefn
+
+@deftypefn {C Function} void scm_c_bytevector_set_x (SCM bv, size_t index, scm_t_uint8 value)
+Set the byte at @var{index} in @var{bv} to @var{value}.
+@end deftypefn
+
 Low-level C macros are available.  They do not perform any
 type-checking; as such they should be used with care.
 

libguile/bytevectors.c

@@ -274,6 +274,60 @@ scm_i_shrink_bytevector (SCM bv, size_t c_new_len)
   return bv;
 }
 
+int
+scm_is_bytevector (SCM obj)
+{
+  return SCM_SMOB_PREDICATE (scm_tc16_bytevector, obj);
+}
+
+size_t
+scm_c_bytevector_length (SCM bv)
+#define FUNC_NAME "scm_c_bytevector_length"
+{
+  SCM_VALIDATE_BYTEVECTOR (1, bv);
+
+  return SCM_BYTEVECTOR_LENGTH (bv);
+}
+#undef FUNC_NAME
+
+scm_t_uint8
+scm_c_bytevector_ref (SCM bv, size_t index)
+#define FUNC_NAME "scm_c_bytevector_ref"
+{
+  size_t c_len;
+  const scm_t_uint8 *c_bv;
+
+  SCM_VALIDATE_BYTEVECTOR (1, bv);
+
+  c_len = SCM_BYTEVECTOR_LENGTH (bv);
+  c_bv = (scm_t_uint8 *) SCM_BYTEVECTOR_CONTENTS (bv);
+
+  if (SCM_UNLIKELY (index >= c_len))
+    scm_out_of_range (FUNC_NAME, scm_from_size_t (index));
+
+  return c_bv[index];
+}
+#undef FUNC_NAME
+
+void
+scm_c_bytevector_set_x (SCM bv, size_t index, scm_t_uint8 value)
+#define FUNC_NAME "scm_c_bytevector_set_x"
+{
+  size_t c_len;
+  scm_t_uint8 *c_bv;
+
+  SCM_VALIDATE_BYTEVECTOR (1, bv);
+
+  c_len = SCM_BYTEVECTOR_LENGTH (bv);
+  c_bv = (scm_t_uint8 *) SCM_BYTEVECTOR_CONTENTS (bv);
+
+  if (SCM_UNLIKELY (index >= c_len))
+    scm_out_of_range (FUNC_NAME, scm_from_size_t (index));
+
+  c_bv[index] = value;
+}
+#undef FUNC_NAME
+
 SCM_SMOB_PRINT (scm_tc16_bytevector, print_bytevector,
 		bv, port, pstate)
 {
@@ -357,8 +411,7 @@ SCM_DEFINE (scm_bytevector_p, "bytevector?", 1, 0, 0,
 	    "Return true if @var{obj} is a bytevector.")
 #define FUNC_NAME s_scm_bytevector_p
 {
-  return (scm_from_bool (SCM_SMOB_PREDICATE (scm_tc16_bytevector,
+  return scm_from_bool (scm_is_bytevector (obj));
-					     obj)));
 }
 #undef FUNC_NAME
 
@@ -403,9 +456,7 @@ SCM_DEFINE (scm_bytevector_length, "bytevector-length", 1, 0, 0,
 	    "Return the length (in bytes) of @var{bv}.")
 #define FUNC_NAME s_scm_bytevector_length
 {
-  SCM_VALIDATE_BYTEVECTOR (1, bv);
+  return scm_from_uint (scm_c_bytevector_length (bv));
-
-  return (scm_from_uint (SCM_BYTEVECTOR_LENGTH (bv)));
 }
 #undef FUNC_NAME
 

libguile/bytevectors.h

@@ -37,8 +37,13 @@
 SCM_API SCM scm_endianness_big;
 SCM_API SCM scm_endianness_little;
 
-SCM_API SCM scm_make_bytevector (SCM, SCM);
 SCM_API SCM scm_c_make_bytevector (size_t);
+SCM_API int scm_is_bytevector (SCM);
+SCM_API size_t scm_c_bytevector_length (SCM);
+SCM_API scm_t_uint8 scm_c_bytevector_ref (SCM, size_t);
+SCM_API void scm_c_bytevector_set_x (SCM, size_t, scm_t_uint8);
+
+SCM_API SCM scm_make_bytevector (SCM, SCM);
 SCM_API SCM scm_native_endianness (void);
 SCM_API SCM scm_bytevector_p (SCM);
 SCM_API SCM scm_bytevector_length (SCM);