## gtypelib

gtypelib — Layout and accessors for typelib

## Stability Level

Stable, unless otherwise indicated

## Synopsis

    #define             G_IR_MAGIC
    enum                GTypelibBlobType;
                        Header;
                        DirEntry;
                        ArgBlob;
                        SignatureBlob;
                        CommonBlob;
                        FunctionBlob;
                        CallbackBlob;
                        InterfaceTypeBlob;
                        ParamTypeBlob;
                        ErrorTypeBlob;
                        ValueBlob;
                        FieldBlob;
                        RegisteredTypeBlob;
                        StructBlob;
                        UnionBlob;
                        EnumBlob;
                        PropertyBlob;
                        SignalBlob;
                        VFuncBlob;
                        ObjectBlob;
                        InterfaceBlob;
                        ConstantBlob;
                        AttributeBlob;
    DirEntry *          g_typelib_get_dir_entry             (GITypelib *typelib,
                                                             guint16 index);
    void                g_typelib_check_sanity              (void);
    #define             g_typelib_get_string                (typelib,
                                                             offset)
    #define             G_TYPELIB_ERROR
    gboolean            g_typelib_validate                  (GITypelib *typelib,
                                                             GError **error);
    #define             BLOB_IS_REGISTERED_TYPE             (blob)

## Description

The "typelib" is a binary, readonly, memory-mappable database containing reflective information about a GObject library.

The format of GObject typelib is strongly influenced by the Mozilla XPCOM format.

Some of the differences to XPCOM include:

- Type information is stored not quite as compactly (XPCOM stores it inline in function descriptions in variable-sized blobs of 1 to n bytes. We store 16 bits of type information for each parameter, which is enough to encode simple types inline. Complex (e.g. recursive) types are stored out of line in a separate list of types.

- String and complex type data is stored outside of typelib entry blobs, references are stored as offsets relative to the start of the typelib. One possibility is to store the strings and types in a pools at the end of the typelib.

The typelib has the following general format.

typelib ::= header, section-index, directory, blobs, attributes, attributedata

directory ::= list of entries

entry ::= blob type, name, namespace, offset blob ::= function|callback|struct|boxed|enum|flags|object|interface|constant|union attributes ::= list of attributes, sorted by offset attribute ::= offset, key, value attributedata ::= string data for attributes

Details

We describe the fragments that make up the typelib in the form of C structs (although some fall short of being valid C structs since they contain multiple flexible arrays).

## Details

### G_IR_MAGIC

    #define G_IR_MAGIC "GOBJ\nMETADATA\r\n\032"

Identifying prefix for the typelib. This was inspired by XPCOM, which in turn borrowed from PNG.

### enum GTypelibBlobType

    typedef enum {
      BLOB_TYPE_INVALID,
      BLOB_TYPE_FUNCTION,
      BLOB_TYPE_CALLBACK,
      BLOB_TYPE_STRUCT,
      BLOB_TYPE_BOXED,
      BLOB_TYPE_ENUM,
      BLOB_TYPE_FLAGS,
      BLOB_TYPE_OBJECT,
      BLOB_TYPE_INTERFACE,
      BLOB_TYPE_CONSTANT,
      BLOB_TYPE_INVALID_0, /* DELETED - used to be ErrorDomain */
      BLOB_TYPE_UNION
    } GTypelibBlobType;

The integral value of this enumeration appears in each "Blob" component of a typelib to identify its type.

`BLOB_TYPE_INVALID` | Should not appear in code
`BLOB_TYPE_FUNCTION` | A FunctionBlob
`BLOB_TYPE_CALLBACK` | A CallbackBlob
`BLOB_TYPE_STRUCT` | A StructBlob
`BLOB_TYPE_BOXED` | Can be either a StructBlob or UnionBlob
`BLOB_TYPE_ENUM` | An EnumBlob
`BLOB_TYPE_FLAGS` | An EnumBlob
`BLOB_TYPE_OBJECT` | An ObjectBlob
`BLOB_TYPE_INTERFACE` | An InterfaceBlob
`BLOB_TYPE_CONSTANT` | A ConstantBlob
`BLOB_TYPE_INVALID_0` |
`BLOB_TYPE_UNION` | A UnionBlob

### Header

    typedef struct {
      gchar   magic[16];
      guint8  major_version;
      guint8  minor_version;
      guint16 n_entries;
      guint16 n_local_entries;
      guint32 directory;
      guint32 n_attributes;
      guint32 attributes;

      guint32 dependencies;

      guint32 size;
      guint32 namespace;
      guint32 nsversion;
      guint32 shared_library;
      guint32 c_prefix;

      guint16 entry_blob_size;
      guint16 function_blob_size;
      guint16 callback_blob_size;
      guint16 signal_blob_size;
      guint16 vfunc_blob_size;
      guint16 arg_blob_size;
      guint16 property_blob_size;
      guint16 field_blob_size;
      guint16 value_blob_size;
      guint16 attribute_blob_size;
      guint16 constant_blob_size;
      guint16 error_domain_blob_size;

      guint16 signature_blob_size;
      guint16 enum_blob_size;
      guint16 struct_blob_size;
      guint16 object_blob_size;
      guint16 interface_blob_size;
      guint16 union_blob_size;

      guint32 sections;
    } Header;

The header structure appears exactly once at the beginning of a typelib. It is a collection of meta-information, such as the number of entries and dependencies.

gchar `magic`[16]; | See G_IR_MAGIC.
guint8 `major_version`; | The version of the typelib format. Minor version changes indicate compatible changes and should still allow the typelib to be parsed by a parser designed for the same major_version.
guint8 `minor_version`; | See major_version.
guint16 `n_entries`; | The number of entries in the directory.
guint16 `n_local_entries`; | The number of entries referring to blobs in this typelib. The local entries must occur before the unresolved entries.
guint32 `directory`; | Offset of the directory in the typelib.
guint32 `n_attributes`; | Number of attribute blocks
guint32 `attributes`; | Offset of the list of attributes in the typelib.
guint32 `dependencies`; | Offset of a single string, which is the list of dependencies, separated by the '|' character. The dependencies are required in order to avoid having programs consuming a typelib check for an "Unresolved" type return from every API call.
guint32 `size`; | The size in bytes of the typelib.
guint32 `namespace`; | Offset of the namespace string in the typelib.
guint32 `nsversion`; | Offset of the namespace version string in the typelib.
guint32 `shared_library`; | This field is the set of shared libraries associated with the typelib. The entries are separated by the '|' (pipe) character.
guint32 `c_prefix`; | The prefix for the function names of the library
guint16 `entry_blob_size`; | The sizes of fixed-size blobs. Recording this information here allows to write parser which continue to work if the format is extended by adding new fields to the end of the fixed-size blobs.
guint16 `function_blob_size`; | See above.
guint16 `callback_blob_size`; | See above.
guint16 `signal_blob_size`; | See above.
guint16 `vfunc_blob_size`; | See above.
guint16 `arg_blob_size`; | See above.
guint16 `property_blob_size`; | See above.
guint16 `field_blob_size`; | See above.
guint16 `value_blob_size`; | See above.
guint16 `attribute_blob_size`; | See above.
guint16 `constant_blob_size`; | See above.
guint16 `error_domain_blob_size`; | See above.
guint16 `signature_blob_size`; | See above.
guint16 `enum_blob_size`; | See above.
guint16 `struct_blob_size`; | See above.
guint16 `object_blob_size`; | See above.
guint16 `interface_blob_size`; | For variable-size blobs, the size of the struct up to the first flexible array member. Recording this information here allows to write parser which continue to work if the format is extended by adding new fields before the first flexible array member in variable-size blobs.
guint16 `union_blob_size`; | See above.
guint32 `sections`; | Offset of section blob array

### DirEntry

    typedef struct {
      guint16 blob_type;

      guint16 local    : 1;
      guint32 name;
      guint32 offset;
    } DirEntry;

References to directory entries are stored as 1-based 16-bit indexes.

All blobs pointed to by a directory entry start with the same layout for the first 8 bytes (the reserved flags may be used by some blob types)

guint16 `blob_type`; | A GTypelibBlobType
guint16 `local` : 1; | Whether this entry refers to a blob in this typelib.
guint32 `name`; | The name of the entry.
guint32 `offset`; | If is_local is set, this is the offset of the blob in the typelib. Otherwise, it is the offset of the namespace in which the blob has to be looked up by name.

### ArgBlob

    typedef struct {
      guint32        name;

      guint          in                           : 1;
      guint          out                          : 1;
      guint          caller_allocates             : 1;
      guint          allow_none                   : 1;
      guint          optional                     : 1;
      guint          transfer_ownership           : 1;
      guint          transfer_container_ownership : 1;
      guint          return_value                 : 1;
      guint          scope                        : 3;
      guint          skip                         : 1;
      gint8        closure;
      gint8        destroy;

      SimpleTypeBlob arg_type;
    } ArgBlob;

Types are specified by four bytes. If the three high bytes are zero, the low byte describes a basic type, otherwise the 32bit number is an offset which points to a TypeBlob.

guint32 `name`; | A suggested name for the parameter.
guint `in` : 1; | The parameter is an input to the function
guint `out` : 1; | The parameter is used to return an output of the function. Parameters can be both in and out. Out parameters implicitly add another level of indirection to the parameter type. Ie if the type is uint32 in an out parameter, the function actually takes an uint32*.
guint `caller_allocates` : 1; | The parameter is a pointer to a struct or object that will receive an output of the function.
guint `allow_none` : 1; | Only meaningful for types which are passed as pointers. For an in parameter, indicates if it is ok to pass NULL in, for an out parameter, whether it may return NULL. Note that NULL is a valid GList and GSList value, thus allow_none will normally be set for parameters of these types.
guint `optional` : 1; | For an out parameter, indicates that NULL may be passed in if the value is not needed.
guint `transfer_ownership` : 1; | For an in parameter, indicates that the function takes over ownership of the parameter value. For an out parameter, it indicates that the caller is responsible for freeing the return value.
guint `transfer_container_ownership` : 1; | For container types, indicates that the ownership of the container, but not of its contents is transferred. This is typically the case for out parameters returning lists of statically allocated things.
guint `return_value` : 1; | The parameter should be considered the return value of the function. Only out parameters can be marked as return value, and there can be at most one per function call. If an out parameter is marked as return value, the actual return value of the function should be either void or a boolean indicating the success of the call.
guint `scope` : 3; | A GIScopeType. If the parameter is of a callback type, this denotes the scope of the user_data and the callback function pointer itself (for languages that emit code at run-time).
guint `skip` : 1; | Indicates that the parameter is only useful in C and should be skipped.
gint8 `closure`; | Index of the closure (user_data) parameter associated with the callback, or -1.
gint8 `destroy`; | Index of the destroy notfication callback parameter associated with the callback, or -1.
SimpleTypeBlob `arg_type`; | Describes the type of the parameter. See details below.

### SignatureBlob

    typedef struct {
      SimpleTypeBlob return_type;

      guint16        may_return_null              : 1;
      guint16        caller_owns_return_value     : 1;
      guint16        caller_owns_return_container : 1;
      guint16        skip_return                  : 1;
      guint16        reserved                     :12;

      guint16        n_arguments;

      ArgBlob        arguments[];
    } SignatureBlob;

SimpleTypeBlob `return_type`; | Describes the type of the return value. See details below.
guint16 `may_return_null` : 1; | Only relevant for pointer types. Indicates whether the caller must expect NULL as a return value.
guint16 `caller_owns_return_value` : 1; | If set, the caller is responsible for freeing the return value if it is no longer needed.
guint16 `caller_owns_return_container` : 1; | This flag is only relevant if the return type is a container type. If the flag is set, the caller is resonsible for freeing the container, but not its contents.
guint16 `skip_return` : 1; | Indicates that the return value is only useful in C and should be skipped.
guint16 `reserved` :12; |
guint16 `n_arguments`; | The number of arguments that this function expects, also the length of the array of ArgBlobs.
ArgBlob `arguments`[]; | An array of ArgBlob for the arguments of the function.

### CommonBlob

    typedef struct {
      guint16 blob_type;  /* 1 */

      guint16 deprecated : 1;
      guint32 name;
    } CommonBlob;

The CommonBlob is shared between FunctionBlob, CallbackBlob, SignalBlob.

guint16 `blob_type`; | A GTypelibBlobType
guint16 `deprecated` : 1; | Whether the blob is deprecated.
guint32 `name`; | The name of the blob.

### FunctionBlob

    typedef struct {
      guint16 blob_type;  /* 1 */

      guint16 deprecated  : 1;
      guint16 setter      : 1;
      guint16 getter      : 1;
      guint16 constructor : 1;
      guint16 wraps_vfunc : 1;
      guint16 throws      : 1;
      guint16 index       :10;
      /* Note the bits above need to match CommonBlob
       * and are thus exhausted, extend things using
       * the reserved block below. */

      guint32 name;
      guint32 symbol;
      guint32 signature;

      guint16 is_static   : 1;
      guint16 reserved    : 15;
      guint16 reserved2   : 16;
    } FunctionBlob;

guint16 `blob_type`; |
guint16 `deprecated` : 1; | The function is deprecated.
guint16 `setter` : 1; | The function is a setter for a property. Language bindings may prefer to not bind individual setters and rely on the generic `g_object_set()`.
guint16 `getter` : 1; | The function is a getter for a property. Language bindings may prefer to not bind individual getters and rely on the generic `g_object_get()`.
guint16 `constructor` : 1; | The function acts as a constructor for the object it is contained in.
guint16 `wraps_vfunc` : 1; | The function is a simple wrapper for a virtual function.
guint16 `throws` : 1; |
guint16 `index` :10; | Index of the property that this function is a setter or getter of in the array of properties of the containing interface, or index of the virtual function that this function wraps.
guint32 `name`; |
guint32 `symbol`; | The symbol which can be used to obtain the function pointer with `dlsym()`.
guint32 `signature`; | Offset of the SignatureBlob describing the parameter types and the return value type.
guint16 `is_static` : 1; | The function is a "static method"; in other words it's a pure function whose name is conceptually scoped to the object.
guint16 `reserved` : 15; |
guint16 `reserved2` : 16; |

### CallbackBlob

    typedef struct {
      guint16 blob_type;  /* 2 */

      guint16 deprecated : 1;
      guint32 name;
      guint32 signature;
    } CallbackBlob;

guint16 `blob_type`; |
guint16 `deprecated` : 1; |
guint32 `name`; |
guint32 `signature`; | Offset of the SignatureBlob describing the parameter types and the return value type.

### InterfaceTypeBlob

    typedef struct {
      guint8  pointer  :1;
      guint8  tag      :5;
      guint16 interface;
    } InterfaceTypeBlob;

If the interface is an enum of flags type, is_pointer is 0, otherwise it is 1.

guint8 `pointer` :1; | Whether this type represents an indirection
guint8 `tag` :5; | A GITypeTag
guint16 `interface`; | Index of the directory entry for the interface.

### ParamTypeBlob

    typedef struct {
      guint8	 pointer  :1;
      guint8	 reserved :2;
      guint8	 tag      :5;

      guint8	 reserved2;
      guint16	 n_types;

      SimpleTypeBlob type[];
    } ParamTypeBlob;

guint8 `pointer` :1; |
guint8 `reserved` :2; |
guint8 `tag` :5; |
guint8 `reserved2`; |
guint16 `n_types`; | The number of parameter types to follow.
SimpleTypeBlob `type`[]; | Describes the type of the list elements.

### ErrorTypeBlob

    typedef struct {
      guint8  pointer  :1;
      guint8  reserved :2;
      guint8  tag      :5;

      guint8  reserved2;

      guint16 n_domains; /* Must be 0 */
      guint16 domains[];
    } ErrorTypeBlob;

### ValueBlob

    typedef struct {
      guint32 deprecated : 1;
      guint32 unsigned_value : 1;
      guint32 name;
      gint32 value;
    } ValueBlob;

Values commonly occur in enums and flags.

guint32 `deprecated` : 1; | Whether this value is deprecated
guint32 `unsigned_value` : 1; | if set, value is a 32-bit unsigned integer cast to gint32
guint32 `name`; | Name of blob
gint32 `value`; | The numerical value

### FieldBlob

    typedef struct {
      guint32        name;

      guint8         readable :1;
      guint8         writable :1;
      guint8         has_embedded_type :1;
      guint8         reserved :5;
      guint8         bits;

      guint16        struct_offset;

      guint32        reserved2;

      SimpleTypeBlob type;
    } FieldBlob;

guint32 `name`; | The name of the field.
guint8 `readable` :1; |
guint8 `writable` :1; | How the field may be accessed.
guint8 `has_embedded_type` :1; | An anonymous type follows the FieldBlob.
guint8 `reserved` :5; |
guint8 `bits`; | If this field is part of a bitfield, the number of bits which it uses, otherwise 0.
guint16 `struct_offset`; | The offset of the field in the struct. The value 0xFFFF indicates that the struct offset is unknown.
guint32 `reserved2`; |
SimpleTypeBlob `type`; | The type of the field.

### RegisteredTypeBlob

    typedef struct {
      guint16 blob_type;
      guint16 deprecated   : 1;
      guint16 unregistered : 1;
      guint16 reserved :14;
      guint32 name;

      guint32 gtype_name;
      guint32 gtype_init;
    } RegisteredTypeBlob;

guint16 `blob_type`; |
guint16 `deprecated` : 1; |
guint16 `unregistered` : 1; |
guint16 `reserved` :14; |
guint32 `name`; |
guint32 `gtype_name`; | The name under which the type is registered with GType.
guint32 `gtype_init`; | The symbol name of the `get_type()` function which registers the type.

### StructBlob

    typedef struct {
      guint16   blob_type;

      guint16   deprecated   : 1;
      guint16   unregistered : 1;
      guint16   is_gtype_struct : 1;
      guint16   alignment    : 6;
      guint16   foreign      : 1;
      guint16   reserved     : 6;

      guint32   name;

      guint32   gtype_name;
      guint32   gtype_init;

      guint32   size;

      guint16   n_fields;
      guint16   n_methods;

      guint32   reserved2;
      guint32   reserved3;

    #if 0
      /* variable-length parts of the blob */
      FieldBlob    fields[];
      FunctionBlob methods[];
    #endif
    } StructBlob;

guint16 `blob_type`; | BLOB_TYPE_STRUCT
guint16 `deprecated` : 1; | Whether this structure is deprecated
guint16 `unregistered` : 1; | If this is set, the type is not registered with GType.
guint16 `is_gtype_struct` : 1; | Whether this structure is the class or interface layout for a GObject
guint16 `alignment` : 6; | The byte boundary that the struct is aligned to in memory
guint16 `foreign` : 1; | If the type is foreign, eg if it's expected to be overridden by a native language binding instead of relying of introspected bindings.
guint16 `reserved` : 6; |
guint32 `name`; |
guint32 `gtype_name`; | String name of the associated GType
guint32 `gtype_init`; | String naming the symbol which gets the runtime GType
guint32 `size`; | The size of the struct in bytes.
guint16 `n_fields`; |
guint16 `n_methods`; |
guint32 `reserved2`; |
guint32 `reserved3`; |
FieldBlob `fields`[]; | An array of n_fields FieldBlobs. should be considered as methods of the struct.
FunctionBlob `methods`[]; |

### UnionBlob

    typedef struct {
      guint16      blob_type;
      guint16      deprecated    : 1;
      guint16      unregistered  : 1;
      guint16      discriminated : 1;
      guint16      alignment     : 6;
      guint16      reserved      : 7;
      guint32      name;

      guint32      gtype_name;
      guint32      gtype_init;

      guint32      size;

      guint16      n_fields;
      guint16      n_functions;

      guint32      reserved2;
      guint32      reserved3;

      gint32       discriminator_offset;
      SimpleTypeBlob discriminator_type;

    #if 0
      FieldBlob    fields[];
      FunctionBlob functions[];
      ConstantBlob discriminator_values[]
    #endif
    } UnionBlob;

guint16 `blob_type`; |
guint16 `deprecated` : 1; |
guint16 `unregistered` : 1; | If this is set, the type is not registered with GType.
guint16 `discriminated` : 1; | Is set if the union is discriminated
guint16 `alignment` : 6; | The byte boundary that the union is aligned to in memory
guint16 `reserved` : 7; |
guint32 `name`; |
guint32 `gtype_name`; | String name of the associated GType
guint32 `gtype_init`; | String naming the symbol which gets the runtime GType
guint32 `size`; | The size of the union in bytes.
guint16 `n_fields`; | Length of the arrays
guint16 `n_functions`; |
guint32 `reserved2`; |
guint32 `reserved3`; |
gint32 `discriminator_offset`; | Offset from the beginning of the union where the discriminator of a discriminated union is located. The value 0xFFFF indicates that the discriminator offset is unknown.
SimpleTypeBlob `discriminator_type`; | Type of the discriminator
FieldBlob `fields`[]; | Array of FieldBlobs describing the alternative branches of the union
FunctionBlob `functions`[]; |

### EnumBlob

    typedef struct {
      guint16   blob_type;

      guint16   deprecated   : 1;
      guint16   unregistered : 1;
      guint16   storage_type : 5;
      guint16   reserved     : 9;

      guint32   name;

      guint32   gtype_name;
      guint32   gtype_init;

      guint16   n_values;
      guint16   n_methods;

      guint32   error_domain;

      ValueBlob values[];
    #if 0
      FunctionBlob methods[];
    #endif
    } EnumBlob;

guint16 `blob_type`; |
guint16 `deprecated` : 1; |
guint16 `unregistered` : 1; | If this is set, the type is not registered with GType.
guint16 `storage_type` : 5; | The tag of the type used for the enum in the C ABI (will be a signed or unsigned integral type)
guint16 `reserved` : 9; |
guint32 `name`; |
guint32 `gtype_name`; | String name of the associated GType
guint32 `gtype_init`; | String naming the symbol which gets the runtime GType
guint16 `n_values`; | The length of the values array.
guint16 `n_methods`; | The length of the methods array.
guint32 `error_domain`; | String naming the GError domain this enum is associated with
ValueBlob `values`[]; | Describes the enum values.
FunctionBlob `methods`[]; | Describes the enum methods.

### PropertyBlob

    typedef struct {
      guint32        name;

      guint32        deprecated                   : 1;
      guint32        readable                     : 1;
      guint32        writable                     : 1;
      guint32        construct                    : 1;
      guint32        construct_only               : 1;
      guint32        transfer_ownership           : 1;
      guint32        transfer_container_ownership : 1;
      guint32        reserved                     :25;

      guint32        reserved2;

      SimpleTypeBlob type;
    } PropertyBlob;

guint32 `name`; | The name of the property.
guint32 `deprecated` : 1; |
guint32 `readable` : 1; |
guint32 `writable` : 1; |
guint32 `construct` : 1; |
guint32 `construct_only` : 1; | The ParamFlags used when registering the property.
guint32 `transfer_ownership` : 1; | When writing, the type containing the property takes ownership of the value. When reading, the returned value needs to be released by the caller.
guint32 `transfer_container_ownership` : 1; | For container types indicates that the ownership of the container, but not of its contents, is transferred. This is typically the case when reading lists of statically allocated things.
guint32 `reserved` :25; |
guint32 `reserved2`; |
SimpleTypeBlob `type`; | Describes the type of the property.

### SignalBlob

    typedef struct {
      guint16 deprecated        : 1;
      guint16 run_first         : 1;
      guint16 run_last          : 1;
      guint16 run_cleanup       : 1;
      guint16 no_recurse        : 1;
      guint16 detailed          : 1;
      guint16 action            : 1;
      guint16 no_hooks          : 1;
      guint16 has_class_closure : 1;
      guint16 true_stops_emit   : 1;
      guint16 reserved          : 6;

      guint16 class_closure;

      guint32 name;

      guint32 reserved2;

      guint32 signature;
    } SignalBlob;

guint16 `deprecated` : 1; |
guint16 `run_first` : 1; |
guint16 `run_last` : 1; |
guint16 `run_cleanup` : 1; |
guint16 `no_recurse` : 1; |
guint16 `detailed` : 1; |
guint16 `action` : 1; |
guint16 `no_hooks` : 1; | The flags used when registering the signal.
guint16 `has_class_closure` : 1; | Set if the signal has a class closure.
guint16 `true_stops_emit` : 1; | Whether the signal has true-stops-emit semantics
guint16 `reserved` : 6; |
guint16 `class_closure`; | The index of the class closure in the list of virtual functions of the object or interface on which the signal is defined.
guint32 `name`; | The name of the signal.
guint32 `reserved2`; |
guint32 `signature`; | Offset of the SignatureBlob describing the parameter types and the return value type.

### VFuncBlob

    typedef struct {
      guint32 name;

      guint16 must_chain_up           : 1;
      guint16 must_be_implemented     : 1;
      guint16 must_not_be_implemented : 1;
      guint16 class_closure           : 1;
      guint16 throws                  : 1;
      guint16 reserved                :11;
      guint16 signal;

      guint16 struct_offset;
      guint16 invoker : 10; /* Number of bits matches @index in FunctionBlob */
      guint16 reserved2 : 6;

      guint32 reserved3;
      guint32 signature;
    } VFuncBlob;

guint32 `name`; | The name of the virtual function.
guint16 `must_chain_up` : 1; | If set, every implementation of this virtual function must chain up to the implementation of the parent class.
guint16 `must_be_implemented` : 1; | If set, every derived class must override this virtual function.
guint16 `must_not_be_implemented` : 1; | If set, derived class must not override this virtual function.
guint16 `class_closure` : 1; | Set if this virtual function is the class closure of a signal.
guint16 `throws` : 1; |
guint16 `reserved` :11; |
guint16 `signal`; | The index of the signal in the list of signals of the object or interface to which this virtual function belongs.
guint16 `struct_offset`; | The offset of the function pointer in the class struct. The value 0xFFFF indicates that the struct offset is unknown.
guint16 `invoker` : 10; | If a method invoker for this virtual exists, this is the offset in the class structure of the method. If no method is known, this value will be 0x3ff.
guint16 `reserved2` : 6; |
guint32 `reserved3`; |
guint32 `signature`; | Offset of the SignatureBlob describing the parameter types and the return value type.

### ObjectBlob

    typedef struct {
      guint16   blob_type;  /* 7 */
      guint16   deprecated   : 1;
      guint16   abstract     : 1;
      guint16   fundamental  : 1;
      guint16   reserved     :13;
      guint32   name;

      guint32   gtype_name;
      guint32   gtype_init;

      guint16   parent;
      guint16   gtype_struct;

      guint16   n_interfaces;
      guint16   n_fields;
      guint16   n_properties;
      guint16   n_methods;
      guint16   n_signals;
      guint16   n_vfuncs;
      guint16   n_constants;
      guint16   reserved2;

      guint32   ref_func;
      guint32   unref_func;
      guint32   set_value_func;
      guint32   get_value_func;

      guint32   reserved3;
      guint32   reserved4;

      guint16   interfaces[];

    #if 0
      /* variable-length parts of the blob */
      FieldBlob           fields[];
      PropertyBlob        properties[];
      FunctionBlob        methods[];
      SignalBlob          signals[];
      VFuncBlob           vfuncs[];
      ConstantBlob        constants[];
    #endif
    } ObjectBlob;

guint16 `blob_type`; | BLOB_TYPE_OBJECT
guint16 `deprecated` : 1; |
guint16 `abstract` : 1; |
guint16 `fundamental` : 1; | this object is not a GObject derived type, instead it's an additional fundamental type.
guint16 `reserved` :13; |
guint32 `name`; |
guint32 `gtype_name`; | String name of the associated GType
guint32 `gtype_init`; | String naming the symbol which gets the runtime GType
guint16 `parent`; | The directory index of the parent type. This is only set for objects. If an object does not have a parent, it is zero.
guint16 `gtype_struct`; |
guint16 `n_interfaces`; |
guint16 `n_fields`; |
guint16 `n_properties`; |
guint16 `n_methods`; |
guint16 `n_signals`; |
guint16 `n_vfuncs`; |
guint16 `n_constants`; | The lengths of the arrays.Up to 16bits of padding may be inserted between the arrays to ensure that they start on a 32bit boundary.
guint16 `reserved2`; |
guint32 `ref_func`; | String pointing to a function which can be called to increase the reference count for an instance of this object type.
guint32 `unref_func`; | String pointing to a function which can be called to decrease the reference count for an instance of this object type.
guint32 `set_value_func`; | String pointing to a function which can be called to convert a pointer of this object to a GValue
guint32 `get_value_func`; | String pointing to a function which can be called to convert extract a pointer to this object from a GValue
guint32 `reserved3`; |
guint32 `reserved4`; |
guint16 `interfaces`[]; | An array of indices of directory entries for the implemented interfaces.
FieldBlob `fields`[]; | Describes the fields.
PropertyBlob `properties`[]; | Describes the properties.
FunctionBlob `methods`[]; | Describes the methods, constructors, setters and getters.
SignalBlob `signals`[]; | Describes the signals.
VFuncBlob `vfuncs`[]; | Describes the virtual functions.
ConstantBlob `constants`[]; | Describes the constants.

### InterfaceBlob

    typedef struct {
      guint16 blob_type;
      guint16 deprecated   : 1;
      guint16 reserved     :15;
      guint32 name;

      guint32 gtype_name;
      guint32 gtype_init;
      guint16 gtype_struct;

      guint16 n_prerequisites;
      guint16 n_properties;
      guint16 n_methods;
      guint16 n_signals;
      guint16 n_vfuncs;
      guint16 n_constants;

      guint16 padding;

      guint32 reserved2;
      guint32 reserved3;

      guint16 prerequisites[];

    #if 0
      /* variable-length parts of the blob */
      PropertyBlob        properties[];
      FunctionBlob        methods[];
      SignalBlob          signals[];
      VFuncBlob           vfuncs[];
      ConstantBlob        constants[];
    #endif
    } InterfaceBlob;

guint16 `blob_type`; |
guint16 `deprecated` : 1; |
guint16 `reserved` :15; |
guint32 `name`; |
guint32 `gtype_name`; |
guint32 `gtype_init`; |
guint16 `gtype_struct`; | Name of the interface "class" C structure
guint16 `n_prerequisites`; | Number of prerequisites
guint16 `n_properties`; | Number of properties
guint16 `n_methods`; | Number of methods
guint16 `n_signals`; | Number of signals
guint16 `n_vfuncs`; | Number of virtual functions
guint16 `n_constants`; | The lengths of the arrays. Up to 16bits of padding may be inserted between the arrays to ensure that they start on a 32bit boundary.
guint16 `padding`; |
guint32 `reserved2`; |
guint32 `reserved3`; |
guint16 `prerequisites`[]; | An array of indices of directory entries for required interfaces.
PropertyBlob `properties`[]; | Describes the properties.
FunctionBlob `methods`[]; | Describes the methods, constructors, setters and getters.
SignalBlob `signals`[]; | Describes the signals.
VFuncBlob `vfuncs`[]; | Describes the virtual functions.
ConstantBlob `constants`[]; | Describes the constants.

### ConstantBlob

    typedef struct {
      guint16        blob_type;
      guint16        deprecated   : 1;
      guint16        reserved     :15;
      guint32        name;

      SimpleTypeBlob type;

      guint32        size;
      guint32        offset;

      guint32        reserved2;
    } ConstantBlob;

guint16 `blob_type`; |
guint16 `deprecated` : 1; |
guint16 `reserved` :15; |
guint32 `name`; |
SimpleTypeBlob `type`; | The type of the value. In most cases this should be a numeric type or string.
guint32 `size`; | The size of the value in bytes.
guint32 `offset`; | The offset of the value in the typelib.
guint32 `reserved2`; |

### AttributeBlob

    typedef struct {
      guint32 offset;
      guint32 name;
      guint32 value;
    } AttributeBlob;

guint32 `offset`; | The offset of the typelib entry to which this attribute refers. Attributes are kept sorted by offset, so that the attributes of an entry can be found by a binary search.
guint32 `name`; | The name of the attribute, a string.
guint32 `value`; | The value of the attribute (also a string)

### g_typelib_get_dir_entry ()

    DirEntry *          g_typelib_get_dir_entry             (GITypelib *typelib,
                                                             guint16 index);

### g_typelib_check_sanity ()

    void                g_typelib_check_sanity              (void);

### g_typelib_get_string()

    #define             g_typelib_get_string(typelib,offset)

### G_TYPELIB_ERROR

    #define G_TYPELIB_ERROR (g_typelib_error_quark ())

### g_typelib_validate ()

    gboolean            g_typelib_validate                  (GITypelib *typelib,
                                                             GError **error);

### BLOB_IS_REGISTERED_TYPE()

    #define             BLOB_IS_REGISTERED_TYPE(blob)