Add TYPE_CONST_STRING and SIZEOF_CONST_STRING for "const char *"

Add rb_fiddle_ prefix to conversion functions.h to keep backward
compatibility but value_to_generic() isn't safe for TYPE_CONST_STRING
and not String src. Use rb_fiddle_value_to_generic() instead.

ext/fiddle/conversions.c

@@ -1,7 +1,7 @@
 #include <fiddle.h>
 
 ffi_type *
-int_to_ffi_type(int type)
+rb_fiddle_int_to_ffi_type(int type)
 {
     int signed_p = 1;
 
@@ -33,66 +33,90 @@ int_to_ffi_type(int type)
 	return &ffi_type_float;
       case TYPE_DOUBLE:
 	return &ffi_type_double;
+      case TYPE_CONST_STRING:
+	return &ffi_type_pointer;
       default:
 	rb_raise(rb_eRuntimeError, "unknown type %d", type);
     }
     return &ffi_type_pointer;
 }
 
+ffi_type *
+int_to_ffi_type(int type)
+{
+    return rb_fiddle_int_to_ffi_type(type);
+}
+
 void
-value_to_generic(int type, VALUE src, fiddle_generic * dst)
+rb_fiddle_value_to_generic(int type, VALUE *src, fiddle_generic *dst)
 {
     switch (type) {
       case TYPE_VOID:
 	break;
       case TYPE_VOIDP:
-	dst->pointer = NUM2PTR(rb_Integer(src));
+	dst->pointer = NUM2PTR(rb_Integer(*src));
 	break;
       case TYPE_CHAR:
-	dst->schar = (signed char)NUM2INT(src);
+	dst->schar = (signed char)NUM2INT(*src);
 	break;
       case -TYPE_CHAR:
-	dst->uchar = (unsigned char)NUM2UINT(src);
+	dst->uchar = (unsigned char)NUM2UINT(*src);
 	break;
       case TYPE_SHORT:
-	dst->sshort = (unsigned short)NUM2INT(src);
+	dst->sshort = (unsigned short)NUM2INT(*src);
 	break;
       case -TYPE_SHORT:
-	dst->sshort = (signed short)NUM2UINT(src);
+	dst->sshort = (signed short)NUM2UINT(*src);
 	break;
       case TYPE_INT:
-	dst->sint = NUM2INT(src);
+	dst->sint = NUM2INT(*src);
 	break;
       case -TYPE_INT:
-	dst->uint = NUM2UINT(src);
+	dst->uint = NUM2UINT(*src);
 	break;
       case TYPE_LONG:
-	dst->slong = NUM2LONG(src);
+	dst->slong = NUM2LONG(*src);
 	break;
       case -TYPE_LONG:
-	dst->ulong = NUM2ULONG(src);
+	dst->ulong = NUM2ULONG(*src);
 	break;
 #if HAVE_LONG_LONG
       case TYPE_LONG_LONG:
-	dst->slong_long = NUM2LL(src);
+	dst->slong_long = NUM2LL(*src);
 	break;
       case -TYPE_LONG_LONG:
-	dst->ulong_long = NUM2ULL(src);
+	dst->ulong_long = NUM2ULL(*src);
 	break;
 #endif
       case TYPE_FLOAT:
-	dst->ffloat = (float)NUM2DBL(src);
+	dst->ffloat = (float)NUM2DBL(*src);
 	break;
       case TYPE_DOUBLE:
-	dst->ddouble = NUM2DBL(src);
+	dst->ddouble = NUM2DBL(*src);
+	break;
+      case TYPE_CONST_STRING:
+        if (NIL_P(*src)) {
+            dst->pointer = NULL;
+        }
+        else {
+            dst->pointer = rb_string_value_cstr(src);
+        }
 	break;
       default:
 	rb_raise(rb_eRuntimeError, "unknown type %d", type);
     }
 }
 
+void
+value_to_generic(int type, VALUE src, fiddle_generic *dst)
+{
+    /* src isn't safe from GC when type is TYPE_CONST_STRING and src
+     * isn't String. */
+    return rb_fiddle_value_to_generic(type, &src, dst);
+}
+
 VALUE
-generic_to_value(VALUE rettype, fiddle_generic retval)
+rb_fiddle_generic_to_value(VALUE rettype, fiddle_generic retval)
 {
     int type = NUM2INT(rettype);
     VALUE cPointer;
@@ -131,11 +155,24 @@ generic_to_value(VALUE rettype, fiddle_generic retval)
 	return rb_float_new(retval.ffloat);
       case TYPE_DOUBLE:
 	return rb_float_new(retval.ddouble);
+      case TYPE_CONST_STRING:
+        if (retval.pointer) {
+            return rb_str_new_cstr(retval.pointer);
+        }
+        else {
+            return Qnil;
+        }
       default:
 	rb_raise(rb_eRuntimeError, "unknown type %d", type);
     }
 
     UNREACHABLE;
 }
 
+VALUE
+generic_to_value(VALUE rettype, fiddle_generic retval)
+{
+    return rb_fiddle_generic_to_value(rettype, retval);
+}
+
 /* vim: set noet sw=4 sts=4 */

ext/fiddle/conversions.h

@@ -24,13 +24,22 @@ typedef union
     void * pointer;        /* ffi_type_pointer */
 } fiddle_generic;
 
+/* Deprecated. Use rb_fiddle_*() version. */
+ffi_type * rb_fiddle_int_to_ffi_type(int type);
+void rb_fiddle_value_to_generic(int type, VALUE *src, fiddle_generic *dst);
+VALUE rb_fiddle_generic_to_value(VALUE rettype, fiddle_generic retval);
+
+/* Deprecated. Use rb_fiddle_*() version. */
 ffi_type * int_to_ffi_type(int type);
-void value_to_generic(int type, VALUE src, fiddle_generic * dst);
+void value_to_generic(int type, VALUE src, fiddle_generic *dst);
 VALUE generic_to_value(VALUE rettype, fiddle_generic retval);
 
-#define VALUE2GENERIC(_type, _src, _dst) value_to_generic((_type), (_src), (_dst))
-#define INT2FFI_TYPE(_type) int_to_ffi_type(_type)
-#define GENERIC2VALUE(_type, _retval) generic_to_value((_type), (_retval))
+#define VALUE2GENERIC(_type, _src, _dst)        \
+    rb_fiddle_value_to_generic((_type), &(_src), (_dst))
+#define INT2FFI_TYPE(_type)                     \
+    rb_fiddle_int_to_ffi_type(_type)
+#define GENERIC2VALUE(_type, _retval)           \
+    rb_fiddle_generic_to_value((_type), (_retval))
 
 #if SIZEOF_VOIDP == SIZEOF_LONG
 # define PTR2NUM(x)   (LONG2NUM((long)(x)))

ext/fiddle/fiddle.c

@@ -235,6 +235,12 @@ Init_fiddle(void)
     rb_define_const(mFiddle, "TYPE_VARIADIC",  INT2NUM(TYPE_VARIADIC));
 #endif
 
+    /* Document-const: TYPE_CONST_STRING
+     *
+     * C type - const char* ('\0' terminated const char*)
+     */
+    rb_define_const(mFiddle, "TYPE_CONST_STRING",  INT2NUM(TYPE_CONST_STRING));
+
     /* Document-const: TYPE_SIZE_T
      *
      * C type - size_t
@@ -435,6 +441,12 @@ Init_fiddle(void)
      */
     rb_define_const(mFiddle, "SIZEOF_UINTPTR_T",  INT2NUM(sizeof(uintptr_t)));
 
+    /* Document-const: SIZEOF_CONST_STRING
+     *
+     * size of a const char*
+     */
+    rb_define_const(mFiddle, "SIZEOF_CONST_STRING", INT2NUM(sizeof(const char*)));
+
     /* Document-const: RUBY_FREE
      *
      * Address of the ruby_xfree() function

ext/fiddle/fiddle.h

@@ -116,6 +116,7 @@
 #define TYPE_FLOAT 7
 #define TYPE_DOUBLE 8
 #define TYPE_VARIADIC 9
+#define TYPE_CONST_STRING 10
 
 #define ALIGN_OF(type) offsetof(struct {char align_c; type align_x;}, align_x)
 

ext/fiddle/function.c

@@ -207,6 +207,7 @@ function_call(int argc, VALUE argv[], VALUE self)
     int n_call_args = 0;
     int i;
     int i_call;
+    VALUE converted_args = Qnil;
     VALUE alloc_buffer = 0;
 
     cfunc    = rb_iv_get(self, "@ptr");
@@ -313,6 +314,7 @@ function_call(int argc, VALUE argv[], VALUE self)
          i++, i_call++) {
         VALUE arg_type;
         int c_arg_type;
+        VALUE original_src;
         VALUE src;
         arg_type = RARRAY_AREF(arg_types, i_call);
         c_arg_type = FIX2INT(arg_type);
@@ -327,11 +329,22 @@ function_call(int argc, VALUE argv[], VALUE self)
             }
             else if (cPointer != CLASS_OF(src)) {
                 src = rb_funcall(cPointer, rb_intern("[]"), 1, src);
+                if (NIL_P(converted_args)) {
+                    converted_args = rb_ary_new();
+                }
+                rb_ary_push(converted_args, src);
             }
             src = rb_Integer(src);
         }
 
+        original_src = src;
         VALUE2GENERIC(c_arg_type, src, &generic_args[i_call]);
+        if (src != original_src) {
+            if (NIL_P(converted_args)) {
+                converted_args = rb_ary_new();
+            }
+            rb_ary_push(converted_args, src);
+        }
         args.values[i_call] = (void *)&generic_args[i_call];
     }
     args.values[i_call] = NULL;

lib/fiddle/import.rb

@@ -121,6 +121,8 @@ def sizeof(ty)
           return SIZEOF_DOUBLE
         when TYPE_VOIDP
           return SIZEOF_VOIDP
+        when TYPE_CONST_STRING
+          return SIZEOF_CONST_STRING
         else
           if defined?(TYPE_LONG_LONG) and
             ty == TYPE_LONG_LONG

test/fiddle/test_func.rb

@@ -98,7 +98,7 @@ def test_snprintf
                               [
                                 TYPE_VOIDP,
                                 TYPE_SIZE_T,
-                                TYPE_VOIDP,
+                                TYPE_CONST_STRING,
                                 TYPE_VARIADIC,
                               ],
                               TYPE_INT)
@@ -107,20 +107,31 @@ def test_snprintf
 
       written = snprintf.call(output,
                               output.size,
-                              "int: %d, string: %.*s\n",
+                              "int: %d, string: %.*s, const string: %s\n",
                               TYPE_INT, -29,
                               TYPE_INT, 4,
-                              TYPE_VOIDP, "Hello")
-      assert_equal("int: -29, string: Hell\n",
+                              TYPE_VOIDP, "Hello",
+                              TYPE_CONST_STRING, "World")
+      assert_equal("int: -29, string: Hell, const string: World\n",
                    output_buffer[0, written])
 
+      string_like_class = Class.new do
+        def initialize(string)
+          @string = string
+        end
+
+        def to_str
+          @string
+        end
+      end
       written = snprintf.call(output,
                               output.size,
-                              "string: %.*s, uint: %u\n",
+                              "string: %.*s, const string: %s, uint: %u\n",
                               TYPE_INT, 2,
                               TYPE_VOIDP, "Hello",
+                              TYPE_CONST_STRING, string_like_class.new("World"),
                               TYPE_INT, 29)
-      assert_equal("string: He, uint: 29\n",
+      assert_equal("string: He, const string: World, uint: 29\n",
                    output_buffer[0, written])
     end
   end

test/fiddle/test_import.rb

@@ -97,10 +97,17 @@ def test_sizeof()
 
     Fiddle.constants.grep(/\ATYPE_(?!VOID|VARIADIC\z)(.*)/) do
       type = $&
-      size = Fiddle.const_get("SIZEOF_#{$1}")
-      name = $1.sub(/P\z/,"*").gsub(/_(?!T\z)/, " ").downcase
+      const_type_name = $1
+      size = Fiddle.const_get("SIZEOF_#{const_type_name}")
+      if const_type_name == "CONST_STRING"
+        name = "const_string"
+        type_name = "const char*"
+      else
+        name = $1.sub(/P\z/,"*").gsub(/_(?!T\z)/, " ").downcase
+        type_name = name
+      end
       define_method("test_sizeof_#{name}") do
-        assert_equal(size, Fiddle::Importer.sizeof(name), type)
+        assert_equal(size, Fiddle::Importer.sizeof(type_name), type)
       end
     end