The signatures element

signatures is the top-level, or root, element of a BridgeSupport XML file.

Mandatory attributes:

version

The version number of the BridgeSupport format. The only possible value is “1.0” which means the format delivered with Mac OS X 10.5.

Possible children elements: depends_on, struct, cftype, opaque, constant, string_constant, enum, function, function_alias, informal_protocol, class.

The depends_on element

This element describes a dependency on other frameworks. This element is deprecated and no longer provided.

Mandatory attributes:

path

The path of the dependency.

The struct element

This element describes a C structure.

Mandatory attributes:

name

The name of the C structure.

type, type64

The complete type of the C structure, including the field names, as a string of Objective-C runtime encoding types. If the element has a different type on a 64-bit environment, the type64 attribute will contain it. If the element does not exist on a 32-bit environment, only the type64 attribute will be used.

Optional attributes:

opaque

Indicates whether the fields of the structure should be exposed. The default value is “false”.

The cftype element

This element describes a Core Foundation-based type.

Mandatory attributes:

name

The name of the Core Foundation type.

type, type64

The type of the Core Foundation type as a string of Objective-C runtime encoding types. If the element has a different type on a 64-bit environment, the type64 attribute will contain it. If the element does not exist on a 32-bit environment, only the type64 attribute will be used.

Optional attributes:

tollfree

The name of the tollfree-bridged Objective-C class, if any.

gettypeid_func

The name of the function that retrieves the TypeID value of the given Core Foundation type, if any. This name usually ends with “GetTypeID”.

The opaque element

This element describes an opaque type, most generally a C pointer to a C opaque structure.

Mandatory attributes:

name

The name of the opaque type.

type, type64

The type of the opaque type, as a string of Objective-C runtime encoding types. If the element has a different type on a 64-bit environment, the type64 attribute will contain it. If the element does not exist on a 32-bit environment, only the type64 attribute will be used.

The constant element

This element describes a C constant.

Mandatory attributes:

name

The name of the C constant.

type, type64

The type of the C constant, as a string of Objective-C runtime encoding types. If the element has a different type on a 64-bit environment, the type64 attribute will contain it. If the element does not exist on a 32-bit environment, only the type64 attribute will be used.

Optional attributes:

magic_cookie

Indicates whether the C constant has a “magic” or fixed value and should not be converted at runtime to the given type. The default value is “false”.

The string_constant element

This element describes a string constant. The string can either be a C string or an Objective-C string (an NSString object). string_constant elements are usually created from C preprocessor macros.

Mandatory attributes:

name

The name of the string constant.

value

The value of the string constant.

Optional attributes:

nsstring

Indicates whether the string constant has an Objective-C value, and should be converted to an NSString object. The default value is “false”.

The enum element

This element describes a C enumeration.

Mandatory attributes:

name

The name of the C enumeration.

value, value64

The value of the C enumeration, as an integer. The value can be negative. If the enumeration has a different value on a 64-bit environment, the value64 attribute will contain it. If the enumeration does not exist on a 32-bit environment, only the value64 attribute will be used. (The le_value and be_value values for little and big endian platforms are no longer supported; only native, little endian order is now used.)

Optional attributes:

ignore

Indicates whether the C enumeration should be ignored by the bridges. The default value is “false”.

suggestion

If the ignore attribute is “true” , this attribute may contain a textual message that the bridges can deliver as an exception or error message to be delivered to the user. By default there is no suggestion.

The function element

This element describes a C function.

Mandatory attributes:

name

The name of the C function.

Optional attributes:

variadic

Indicates whether the C function accepts a variable number of arguments. The default value is “false”.

sentinel

An integer value that specifies which argument (counting backwards from the end of the argument list) must be a NULL value to indicate the end of a variable length argument list (thus, this is only legal for variadic functions). (The __attribute__((sentinel)) compiler attribute will be automatically recognized by the new parser, and the given sentinel value (defaulting to zero), will be assigned to the sentinel attribute.)

inline

Indicates whether the C function is inline. In that case, the symbol can be found in the respective .dylib file that comes with the BridgeSupport file. Consult gen_bridge_metadata(1) to know how the dylib files are generated. The default value is “false”.

Possible children: arg (zero or more), retval (zero or one).

The function_alias element

This element defines an alias or shortcut to a C function.

Mandatory attributes:

name

The name of the C function alias.

original

The name of the original C function the alias points to.

The class element

This element defines an Objective-C class. Only classes where additional metadata is needed are described.

Mandatory attributes:

name

The name of the Objective-C class.

Possible children: method (zero or more).

The informal_protocol element

This element defines an Objective-C informal protocol.

Mandatory attributes:

name

The name of the Objective-C informal protocol.

Possible children: method (zero or more).

The method element

This element defines an Objective-C method. Only methods where additional metadata is needed are described.

Mandatory attributes:

selector

The selector of the Objective-C method.

Mandatory attributes (only when declared under informal_protocol) :

type, type64

The type of the Objective-C method, as a string of Objective-C runtime encoding types. If the element has a different type on a 64-bit environment, the type64 attribute will contain it. If the element does not exist on a 32-bit environment, only the type64 attribute will be used.

Optional attributes:

class_method

Whether this is a class method or not. The default value is “false”.

Optional attributes (only when not declared under informal_protocol) :

variadic

Indicates whether the method accepts a variable number of arguments. The default value is “false”.

sentinel

An integer value that specifies which argument (counting backwards from the end of the argument list) must be a NULL value to indicate the end of a variable length argument list (thus, this is only legal for variadic methods). (The __attribute__((sentinel)) compiler attribute will be automatically recognized by the new parser, and the given sentinel value (defaulting to zero), will be assigned to the sentinel attribute.)

ignore

Indicates whether the method should be ignored by the bridges. The default value is “false”.

suggestion

If the ignore attribute is “true” , this attribute may contain a textual message that the bridges can deliver as an exception or error message to be delivered to the user. By default there is no suggestion.

Possible children (only when not declared under informal_protocol) : arg (zero or more), retval (zero or one).

The arg and retval elements

These elements describe respectively an argument and a return value. They should be defined within both function and method elements, and their attributes depend under which element they are defined under.

Optional attributes:

c_array_length_in_arg

Defines the argument or return value as a C array whose length is defined by the value of the given argument. The value of this attribute is the index position of the argument that should contain the array size. The value can also be two integers separated by a comma, which in that case means that the first value is used when converting to C / Objective-C, and the second when converting back to the scripting language. This attribute cannot be used with another “c_array_” attribute.

c_array_of_fixed_length

Defines the argument or return value as a C array of a fixed length. The value of this attribute is the array size. This attribute cannot be used with another “c_array_” attribute.

c_array_delimited_by_null

Defines the argument or return value as a C array that ends with a NULL value, if the value of this attribute is “true”. The default value of this attribute is “false”. This attribute cannot be used with another “c_array_” attribute.

c_array_of_variable_length

Defines the argument or return value as a C array of a variable length, if the value of this attribute is “true”. The default value of this attribute is “false”. This attribute cannot be used with another “c_array_” attribute.

function_pointer

Indicates whether the argument or return value is a function or block pointer. If “true”, the type attribute will be '^?' for functions and '@?' for blocks, and the current element should have a set of complete arg and retval child elements to define both the argument and the return value types of the function or block pointer.

sel_of_type, sel_of_type64

This attribute, used for arguments or return value of the type “SEL” (an Objective-C selector), is used to provide the signature of the method the selector should point to, as a string of Objective-C runtime encoding types. If the selector has a different type on a 64-bit environment, the sel_of_type64 attribute will contain it. There is no default value. This attribute can be used to give a hint to the bridges when their default behavior isn't sufficient.

Optional attributes (arg only):

c_array_length_in_retval

Defines the argument as a C like array whose length is defined by the value of the return value, if “true”. The default value of this attribute is “false”. This attribute cannot be used with another “c_array_” attribute.

type_modifier

The type modifier of the argument. Possible values are “n” (in), “o” (out) and “N” (inout). There is no default value. (For Objective C methods arguments, the in, out and inout type modifiers will be automatically recognized by the new parser, and the appropriate type_modifier attribute will be set.)

null_accepted

Indicates whether a NULL value can be passed to this argument. The default value is “true”. (The __attribute__((nonnull)) compiler attribute will be automatically recognized by the new parser, and the corresponding argument's null_accepted attribute will set to “false”.)

printf_format

Indicates whether this argument accepts a printf(3) format string value. The default value is “false”. (The __attribute__((format(printf, m, n))) compiler attribute will be automatically recognized by the new parser, and the m-th argument's printf_format attribute will be set to “true”.)

Optional attributes (retval only):

already_retained

A value of “true” indicates that the return value should not be retained by the bridges. The default value is “false”.

Mandatory attributes (when declared under function):

type, type64

The type of the argument or return value, as a string of Objective-C runtime encoding types. If the element has a different type on a 64-bit environment, the type64 attribute will contain it. If the element does not exist on a 32-bit environment, only the type64 attribute will be used.

Mandatory attributes (when declared under method, arg only):

index

The index position of the argument.

Optional attributes (when declared under method):

type, type64

The type of the argument or return value, as a string of Objective-C runtime encoding types. If the element has a different type on a 64-bit environment, the type64 attribute will contain it. If the element does not exist on a 32-bit environment, only the type64 attribute will be used. This attribute is optional for methods as the bridges can retrieve the type by asking the runtime, but it is possible to override the default type using this attribute. There is no default value.