ffi: Implement ffivar.get()/set() methods.

Done by introducing another factored out helper API in binary.c. This API
can be reused also by array and struct modules.

examples/unix/ffi_example.py

@@ -19,6 +19,7 @@ print()
 perror("ffi before error")
 open("somethingnonexistent__", 0)
 print(errno)
+print(errno.get())
 perror("ffi after error")
 print()
 

py/binary.c

+#include <stdlib.h>
+#include <stdint.h>
+#include <assert.h>
+
+#include "misc.h"
+#include "mpconfig.h"
+#include "qstr.h"
+#include "obj.h"
+#include "objint.h"
+#include "binary.h"
+
+// Helpers to work with binary-encoded data
+
+mp_obj_t mp_binary_get_val(char typecode, void *p, int index) {
+    int val = 0;
+    switch (typecode) {
+        case 'b':
+            val = ((int8_t*)p)[index];
+            break;
+        case BYTEARRAY_TYPECODE:
+        case 'B':
+            val = ((uint8_t*)p)[index];
+            break;
+        case 'h':
+            val = ((int16_t*)p)[index];
+            break;
+        case 'H':
+            val = ((uint16_t*)p)[index];
+            break;
+        case 'i':
+        case 'l':
+            return mp_obj_new_int(((int32_t*)p)[index]);
+        case 'I':
+        case 'L':
+            return mp_obj_new_int_from_uint(((uint32_t*)p)[index]);
+#if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
+        case 'q':
+        case 'Q':
+            // TODO: Explode API more to cover signedness
+            return mp_obj_new_int_from_ll(((long long*)p)[index]);
+#endif
+#if MICROPY_ENABLE_FLOAT
+        case 'f':
+            return mp_obj_new_float(((float*)p)[index]);
+        case 'd':
+            return mp_obj_new_float(((double*)p)[index]);
+#endif
+    }
+    return MP_OBJ_NEW_SMALL_INT(val);
+}
+
+void mp_binary_set_val(char typecode, void *p, int index, mp_obj_t val_in) {
+    machine_int_t val = 0;
+    if (MP_OBJ_IS_INT(val_in)) {
+        val = mp_obj_int_get(val_in);
+    }
+
+    switch (typecode) {
+        case 'b':
+            ((int8_t*)p)[index] = val;
+            break;
+        case BYTEARRAY_TYPECODE:
+        case 'B':
+            val = ((uint8_t*)p)[index] = val;
+            break;
+        case 'h':
+            val = ((int16_t*)p)[index] = val;
+            break;
+        case 'H':
+            val = ((uint16_t*)p)[index] = val;
+            break;
+        case 'i':
+        case 'l':
+            ((int32_t*)p)[index] = val;
+            break;
+        case 'I':
+        case 'L':
+            ((uint32_t*)p)[index] = val;
+            break;
+#if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
+        case 'q':
+        case 'Q':
+            assert(0);
+            ((long long*)p)[index] = val;
+            break;
+#endif
+#if MICROPY_ENABLE_FLOAT
+        case 'f':
+            ((float*)p)[index] = mp_obj_float_get(val_in);
+            break;
+        case 'd':
+            ((double*)p)[index] = mp_obj_float_get(val_in);
+            break;
+#endif
+    }
+}

py/binary.h

+// Use special typecode to differentiate repr() of bytearray vs array.array('B')
+// (underlyingly they're same).
+#define BYTEARRAY_TYPECODE 0
+
+int mp_binary_get_size(char typecode);
+mp_obj_t mp_binary_get_val(char typecode, void *p, int index);
+void mp_binary_set_val(char typecode, void *p, int index, mp_obj_t val_in);

py/objint.h

@@ -8,3 +8,7 @@ typedef struct _mp_obj_int_t {
 void int_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind);
 mp_obj_t int_unary_op(int op, mp_obj_t o_in);
 mp_obj_t int_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in);
+
+#if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
+mp_obj_t mp_obj_new_int_from_ll(long long val);
+#endif

py/objint_longlong.c

@@ -13,8 +13,6 @@
 
 #if MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_LONGLONG
 
-STATIC mp_obj_t mp_obj_new_int_from_ll(long long val);
-
 // Python3 no longer has "l" suffix for long ints. We allow to use it
 // for debugging purpose though.
 #ifdef DEBUG

py/py.mk

@@ -63,6 +63,7 @@ PY_O_BASENAME = \
 	objzip.o \
 	sequence.o \
 	stream.o \
+	binary.o \
 	builtin.o \
 	builtinimport.o \
 	builtinevex.o \

unix/ffi.c

@@ -10,6 +10,7 @@
 #include "qstr.h"
 #include "obj.h"
 #include "runtime.h"
+#include "binary.h"
 
 typedef struct _mp_obj_opaque_t {
     mp_obj_base_t base;
@@ -295,10 +296,30 @@ static void ffivar_print(void (*print)(void *env, const char *fmt, ...), void *e
     print(env, "<ffivar @%p: 0x%x>", self->var, *(int*)self->var);
 }
 
+static mp_obj_t ffivar_get(mp_obj_t self_in) {
+    mp_obj_ffivar_t *self = self_in;
+    return mp_binary_get_val(self->type, self->var, 0);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(ffivar_get_obj, ffivar_get);
+
+static mp_obj_t ffivar_set(mp_obj_t self_in, mp_obj_t val_in) {
+    mp_obj_ffivar_t *self = self_in;
+    mp_binary_set_val(self->type, self->var, 0, val_in);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(ffivar_set_obj, ffivar_set);
+
+static const mp_method_t ffivar_type_methods[] = {
+        { "get", &ffivar_get_obj },
+        { "set", &ffivar_set_obj },
+        { NULL, NULL },
+};
+
 static const mp_obj_type_t ffivar_type = {
     { &mp_const_type },
     "ffivar",
     .print = ffivar_print,
+    .methods = ffivar_type_methods,
 };
 
 // Generic opaque storage object