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byte access to foreigns via bytevectors

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* libguile/foreign.h:
* libguile/foreign.c (scm_foreign_ref, scm_foreign_set_x): Remove all
  bits about offsets and aliasing; bytevectors are much better at that.
  (scm_foreign_to_bytevector, scm_bytevector_to_foreign): New functions
  for getting at the bytes of a memory region.

* module/system/foreign.scm (foreign->bytevector, bytevector->foreign):
  Export these.
This commit is contained in:
Andy Wingo 2010-01-18 14:36:23 +01:00
parent ab4779ffcf
commit 20aafae22a
3 changed files with 161 additions and 111 deletions
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260
libguile/foreign.c
View file

@ -22,6 +22,7 @@
#include <string.h>
#include "libguile/_scm.h"
#include "libguile/bytevectors.h"
#include "libguile/foreign.h"
@ -38,6 +39,14 @@ SCM_SYMBOL (sym_int32, "int32");
SCM_SYMBOL (sym_uint64, "uint64");
SCM_SYMBOL (sym_int64, "int64");
static SCM foreign_weak_refs = SCM_BOOL_F;
static void
register_weak_reference (SCM from, SCM to)
{
scm_hashq_set_x (foreign_weak_refs, from, to);
}
static void
foreign_finalizer_trampoline (GC_PTR ptr, GC_PTR data)
{
@ -77,23 +86,10 @@ scm_take_foreign_pointer (scm_t_foreign_type type, void *ptr, size_t len,
return ret;
}
static void
keepalive (GC_PTR obj, GC_PTR data)
{
}
SCM_DEFINE (scm_foreign_ref, "foreign-ref", 1, 3, 0,
(SCM foreign, SCM type, SCM offset, SCM len),
SCM_DEFINE (scm_foreign_ref, "foreign-ref", 1, 0, 0,
(SCM foreign),
"Reference the foreign value wrapped by @var{foreign}.\n\n"
"The value will be referenced according to its type.\n"
"If and only if the type of the foreign value is @code{void},\n"
"this function accepts optional @var{type} and @var{offset}\n"
"arguments, indicating that the pointer wrapped by\n"
"@var{foreign} should be incremented by @var{offset} bytes,\n"
"and treated as a pointer to a value of the given @var{type}.\n"
"@var{offset} defaults to 0.\n\n"
"If @var{type} itself is @code{void}, @var{len} will be used\n"
"to specify the size of the resulting @code{void} pointer.")
"The value will be referenced according to its type.")
#define FUNC_NAME s_scm_foreign_ref
{
scm_t_foreign_type ftype;
@ -101,25 +97,14 @@ SCM_DEFINE (scm_foreign_ref, "foreign-ref", 1, 3, 0,
SCM_VALIDATE_FOREIGN (1, foreign);
ptr = SCM_FOREIGN_POINTER (foreign, scm_t_uint8);
ftype = SCM_FOREIGN_TYPE (foreign);
if (ftype == SCM_FOREIGN_TYPE_VOID)
{
if (SCM_UNBNDP (type))
scm_error_num_args_subr (FUNC_NAME);
ftype = scm_to_unsigned_integer (type, 0, SCM_FOREIGN_TYPE_LAST);
if (!SCM_UNBNDP (offset))
ptr += scm_to_ssize_t (offset);
}
else
{
if (!SCM_UNBNDP (type))
scm_error_num_args_subr (FUNC_NAME);
}
/* FIXME: is there a window in which we can see ptr but not foreign? */
/* FIXME: accessing unaligned pointers */
switch (ftype)
{
case SCM_FOREIGN_TYPE_VOID:
return scm_from_ulong ((unsigned long)ptr);
case SCM_FOREIGN_TYPE_FLOAT:
return scm_from_double (*(float*)ptr);
case SCM_FOREIGN_TYPE_DOUBLE:
@ -140,35 +125,16 @@ SCM_DEFINE (scm_foreign_ref, "foreign-ref", 1, 3, 0,
return scm_from_uint64 (*(scm_t_uint64*)ptr);
case SCM_FOREIGN_TYPE_INT64:
return scm_from_int64 (*(scm_t_int64*)ptr);
case SCM_FOREIGN_TYPE_VOID:
/* seems we're making a new pointer, woo */
{
GC_finalization_proc prev_finalizer;
GC_PTR prev_finalizer_data;
SCM ret = scm_take_foreign_pointer
(ftype, ptr, SCM_UNBNDP (len) ? 0 : scm_to_size_t (len), NULL);
/* while the kid is alive, keep the parent alive */
if (SCM_FOREIGN_HAS_FINALIZER (foreign))
GC_REGISTER_FINALIZER_NO_ORDER (SCM2PTR (ret), keepalive, foreign,
&prev_finalizer, &prev_finalizer_data);
return ret;
}
default:
abort ();
}
}
#undef FUNC_NAME
SCM_DEFINE (scm_foreign_set_x, "foreign-set!", 2, 2, 0,
(SCM foreign, SCM val, SCM type, SCM offset),
SCM_DEFINE (scm_foreign_set_x, "foreign-set!", 2, 0, 0,
(SCM foreign, SCM val),
"Set the foreign value wrapped by @var{foreign}.\n\n"
"The value will be set according to its type.\n"
"If and only if the type of the foreign value is @code{void},\n"
"this function accepts optional @var{type} and @var{offset}\n"
"arguments, indicating that the pointer wrapped by\n"
"@var{foreign} should be incremented by @var{offset} bytes,\n"
"and treated as a pointer to a value of the given @var{type}.\n"
"@var{offset} defaults to 0.")
"The value will be set according to its type.")
#define FUNC_NAME s_scm_foreign_set_x
{
scm_t_foreign_type ftype;
@ -176,25 +142,15 @@ SCM_DEFINE (scm_foreign_set_x, "foreign-set!", 2, 2, 0,
SCM_VALIDATE_FOREIGN (1, foreign);
ptr = SCM_FOREIGN_POINTER (foreign, scm_t_uint8);
ftype = SCM_FOREIGN_TYPE (foreign);
if (ftype == SCM_FOREIGN_TYPE_VOID)
{
if (SCM_UNBNDP (type))
scm_error_num_args_subr (FUNC_NAME);
ftype = scm_to_unsigned_integer (type, 0, SCM_FOREIGN_TYPE_LAST);
if (!SCM_UNBNDP (offset))
ptr += scm_to_ssize_t (offset);
}
else
{
if (!SCM_UNBNDP (type))
scm_error_num_args_subr (FUNC_NAME);
}
/* FIXME: is there a window in which we can see ptr but not foreign? */
/* FIXME: unaligned access */
switch (ftype)
{
case SCM_FOREIGN_TYPE_VOID:
SCM_SET_CELL_WORD_1 (foreign, scm_to_ulong (val));
break;
case SCM_FOREIGN_TYPE_FLOAT:
*(float*)ptr = scm_to_double (val);
break;
@ -225,15 +181,6 @@ SCM_DEFINE (scm_foreign_set_x, "foreign-set!", 2, 2, 0,
case SCM_FOREIGN_TYPE_INT64:
*(scm_t_int64*)ptr = scm_to_int64 (val);
break;
case SCM_FOREIGN_TYPE_VOID:
SCM_VALIDATE_FOREIGN (2, val);
if (SCM_FOREIGN_HAS_FINALIZER (val))
/* setting a pointer inside one foreign value to the pointer of another?
that is asking for trouble */
scm_wrong_type_arg_msg (FUNC_NAME, 2, val,
"foreign value without finalizer");
*(void**)ptr = SCM_FOREIGN_POINTER (val, void*);
break;
default:
abort ();
}
@ -242,6 +189,134 @@ SCM_DEFINE (scm_foreign_set_x, "foreign-set!", 2, 2, 0,
}
#undef FUNC_NAME
SCM_DEFINE (scm_foreign_to_bytevector, "foreign->bytevector", 1, 3, 0,
(SCM foreign, SCM uvec_type, SCM offset, SCM len),
"Return a bytevector aliasing the memory pointed to by\n"
"@var{foreign}.\n\n"
"@var{foreign} must be a void pointer, a foreign whose type is\n"
"@var{void}. By default, the resulting bytevector will alias\n"
"all of the memory pointed to by @var{foreign}, from beginning\n"
"to end, treated as a @code{vu8} array.\n\n"
"The user may specify an alternate default interpretation for\n"
"the memory by passing the @var{uvec_type} argument, to indicate\n"
"that the memory is an array of elements of that type.\n"
"@var{uvec_type} should be something that\n"
"@code{uniform-vector-element-type} would return, like @code{f32}\n"
"or @code{s16}.\n\n"
"Users may also specify that the bytevector should only alias a\n"
"subset of the memory, by specifying @var{offset} and @var{len}\n"
"arguments.")
#define FUNC_NAME s_scm_foreign_to_bytevector
{
SCM ret;
scm_t_int8 *ptr;
size_t boffset, blen;
scm_t_array_element_type btype;
SCM_VALIDATE_FOREIGN_TYPED (1, foreign, VOID);
ptr = SCM_FOREIGN_POINTER (foreign, scm_t_int8);
if (SCM_UNBNDP (uvec_type))
btype = SCM_ARRAY_ELEMENT_TYPE_VU8;
else
{
int i;
for (i = 0; i <= SCM_ARRAY_ELEMENT_TYPE_LAST; i++)
if (scm_is_eq (uvec_type, scm_i_array_element_types[i]))
break;
switch (i)
{
case SCM_ARRAY_ELEMENT_TYPE_VU8:
case SCM_ARRAY_ELEMENT_TYPE_U8:
case SCM_ARRAY_ELEMENT_TYPE_S8:
case SCM_ARRAY_ELEMENT_TYPE_U16:
case SCM_ARRAY_ELEMENT_TYPE_S16:
case SCM_ARRAY_ELEMENT_TYPE_U32:
case SCM_ARRAY_ELEMENT_TYPE_S32:
case SCM_ARRAY_ELEMENT_TYPE_U64:
case SCM_ARRAY_ELEMENT_TYPE_S64:
case SCM_ARRAY_ELEMENT_TYPE_F32:
case SCM_ARRAY_ELEMENT_TYPE_F64:
case SCM_ARRAY_ELEMENT_TYPE_C32:
case SCM_ARRAY_ELEMENT_TYPE_C64:
btype = i;
break;
default:
scm_wrong_type_arg_msg (FUNC_NAME, SCM_ARG1, uvec_type,
"uniform vector type");
}
}
if (SCM_UNBNDP (offset))
boffset = 0;
else if (SCM_FOREIGN_LEN (foreign))
boffset = scm_to_unsigned_integer (offset, 0,
SCM_FOREIGN_LEN (foreign) - 1);
else
boffset = scm_to_size_t (offset);
if (SCM_UNBNDP (len))
{
if (SCM_FOREIGN_LEN (foreign))
blen = SCM_FOREIGN_LEN (foreign) - boffset;
else
scm_misc_error (FUNC_NAME,
"length needed to convert foreign pointer to bytevector",
SCM_EOL);
}
else
{
if (SCM_FOREIGN_LEN (foreign))
blen = scm_to_unsigned_integer (len, 0,
SCM_FOREIGN_LEN (foreign) - boffset);
else
blen = scm_to_size_t (len);
}
ret = scm_c_take_typed_bytevector (ptr + boffset, blen, btype);
register_weak_reference (ret, foreign);
return ret;
}
#undef FUNC_NAME
SCM_DEFINE (scm_bytevector_to_foreign, "bytevector->foreign", 1, 2, 0,
(SCM bv, SCM offset, SCM len),
"Return a foreign pointer aliasing the memory pointed to by\n"
"@var{bv}.\n\n"
"The resulting foreign will be a void pointer, a foreign whose\n"
"type is @code{void}. By default it will alias all of the\n"
"memory pointed to by @var{bv}, from beginning to end.\n\n"
"Users may explicily specify that the foreign should only alias a\n"
"subset of the memory, by specifying @var{offset} and @var{len}\n"
"arguments.")
#define FUNC_NAME s_scm_bytevector_to_foreign
{
SCM ret;
scm_t_int8 *ptr;
size_t boffset, blen;
SCM_VALIDATE_BYTEVECTOR (1, bv);
ptr = SCM_BYTEVECTOR_CONTENTS (bv);
if (SCM_UNBNDP (offset))
boffset = 0;
else
boffset = scm_to_unsigned_integer (offset, 0,
SCM_BYTEVECTOR_LENGTH (bv) - 1);
if (SCM_UNBNDP (len))
blen = SCM_BYTEVECTOR_LENGTH (bv) - boffset;
else
blen = scm_to_unsigned_integer (len, 0,
SCM_BYTEVECTOR_LENGTH (bv) - boffset);
ret = scm_take_foreign_pointer (SCM_FOREIGN_TYPE_VOID, ptr + boffset, blen,
NULL);
register_weak_reference (ret, bv);
return ret;
}
#undef FUNC_NAME
void
scm_i_foreign_print (SCM foreign, SCM port, scm_print_state *pstate)
{
@ -250,71 +325,41 @@ scm_i_foreign_print (SCM foreign, SCM port, scm_print_state *pstate)
{
case SCM_FOREIGN_TYPE_FLOAT:
scm_puts ("float ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_DOUBLE:
scm_puts ("double ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_UINT8:
scm_puts ("uint8 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_INT8:
scm_puts ("int8 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_UINT16:
scm_puts ("uint16 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_INT16:
scm_puts ("int16 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_UINT32:
scm_puts ("uint32 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_INT32:
scm_puts ("int32 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_UINT64:
scm_puts ("uint64 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_INT64:
scm_puts ("int64 ", port);
scm_display (scm_foreign_ref (foreign, SCM_UNDEFINED, SCM_UNDEFINED,
SCM_UNDEFINED),
port);
break;
case SCM_FOREIGN_TYPE_VOID:
scm_puts ("pointer 0x", port);
scm_uintprint ((scm_t_bits)SCM_FOREIGN_POINTER (foreign, void), 16, port);
scm_puts ("pointer ", port);
break;
default:
abort ();
}
scm_display (scm_foreign_ref (foreign), port);
scm_putc ('>', port);
}
@ -345,6 +390,7 @@ scm_register_foreign (void)
scm_c_register_extension ("libguile", "scm_init_foreign",
(scm_t_extension_init_func)scm_init_foreign,
NULL);
foreign_weak_refs = scm_make_weak_key_hash_table (SCM_UNDEFINED);
}
/*

7
libguile/foreign.h
View file

@ -90,8 +90,11 @@ SCM_API SCM scm_take_foreign_pointer (scm_t_foreign_type type, void *ptr,
scm_t_foreign_finalizer finalizer);
SCM_API SCM scm_foreign_type (SCM foreign);
SCM_API SCM scm_foreign_ref (SCM foreign, SCM type, SCM offset, SCM len);
SCM_API SCM scm_foreign_set_x (SCM foreign, SCM val, SCM type, SCM offset);
SCM_API SCM scm_foreign_ref (SCM foreign);
SCM_API SCM scm_foreign_set_x (SCM foreign, SCM val);
SCM_API SCM scm_foreign_to_bytevector (SCM foreign, SCM type,
SCM offset, SCM len);
SCM_API SCM scm_bytevector_to_foreign (SCM bv, SCM offset, SCM len);
SCM_INTERNAL void scm_i_foreign_print (SCM foreign, SCM port,
scm_print_state *pstate);

3
module/system/foreign.scm
View file

@ -24,6 +24,7 @@
uint32 int32
uint64 int64
foreign-ref foreign-set!))
foreign-ref foreign-set!
foreign->bytevector bytevector->foreign))
(load-extension "libguile" "scm_init_foreign")