* doc/extention.rdoc: move from toplevel document and added extname.

* doc/extention.ja.rdoc: ditto.

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-# README.EXT -  -*- RDoc -*- created at: Mon Aug  7 16:45:54 JST 1995
-
-This document explains how to make extension libraries for Ruby.
-
-= Basic Knowledge
-
-In C, variables have types and data do not have types.  In contrast,
-Ruby variables do not have a static type, and data themselves have
-types, so data will need to be converted between the languages.
-
-Data in Ruby are represented by the C type `VALUE'.  Each VALUE data
-has its data-type.
-
-To retrieve C data from a VALUE, you need to:
-
-1. Identify the VALUE's data type
-2. Convert the VALUE into C data
-
-Converting to the wrong data type may cause serious problems.
-
-== Data-Types
-
-The Ruby interpreter has the following data types:
-
-T_NIL       :: nil
-T_OBJECT    :: ordinary object
-T_CLASS     :: class
-T_MODULE    :: module
-T_FLOAT     :: floating point number
-T_STRING    :: string
-T_REGEXP    :: regular expression
-T_ARRAY     :: array
-T_HASH      :: associative array
-T_STRUCT    :: (Ruby) structure
-T_BIGNUM    :: multi precision integer
-T_FIXNUM    :: Fixnum(31bit or 63bit integer)
-T_COMPLEX   :: complex number
-T_RATIONAL  :: rational number
-T_FILE      :: IO
-T_TRUE      :: true
-T_FALSE     :: false
-T_DATA      :: data
-T_SYMBOL    :: symbol
-
-In addition, there are several other types used internally:
-
-T_ICLASS    :: included module
-T_MATCH     :: MatchData object
-T_UNDEF     :: undefined
-T_NODE      :: syntax tree node
-T_ZOMBIE    :: object awaiting finalization
-
-Most of the types are represented by C structures.
-
-== Check Data Type of the VALUE
-
-The macro TYPE() defined in ruby.h shows the data type of the VALUE.
-TYPE() returns the constant number T_XXXX described above.  To handle
-data types, your code will look something like this:
-
-  switch (TYPE(obj)) {
-    case T_FIXNUM:
-      /* process Fixnum */
-      break;
-    case T_STRING:
-      /* process String */
-      break;
-    case T_ARRAY:
-      /* process Array */
-      break;
-    default:
-      /* raise exception */
-      rb_raise(rb_eTypeError, "not valid value");
-      break;
-  }
-
-There is the data-type check function
-
-  void Check_Type(VALUE value, int type)
-
-which raises an exception if the VALUE does not have the type
-specified.
-
-There are also faster check macros for fixnums and nil.
-
-  FIXNUM_P(obj)
-  NIL_P(obj)
-
-== Convert VALUE into C Data
-
-The data for type T_NIL, T_FALSE, T_TRUE are nil, false, true
-respectively.  They are singletons for the data type.
-The equivalent C constants are: Qnil, Qfalse, Qtrue.
-Note that Qfalse is false in C also (i.e. 0), but not Qnil.
-
-The T_FIXNUM data is a 31bit or 63bit length fixed integer.
-This size is depend on the size of long: if long is 32bit then
-T_FIXNUM is 31bit, if long is 64bit then T_FIXNUM is 63bit.
-T_FIXNUM can be converted to a C integer by using the
-FIX2INT() macro or FIX2LONG().  Though you have to check that the
-data is really FIXNUM before using them, they are faster.  FIX2LONG()
-never raises exceptions, but FIX2INT() raises RangeError if the
-result is bigger or smaller than the size of int.
-There are also NUM2INT() and NUM2LONG() which converts any Ruby
-numbers into C integers.  These macros includes a type check,
-so an exception will be raised if the conversion failed.  NUM2DBL()
-can be used to retrieve the double float value in the same way.
-
-You can use the macros
-StringValue() and StringValuePtr() to get a char* from a VALUE.
-StringValue(var) replaces var's value with the result of "var.to_str()".
-StringValuePtr(var) does same replacement and returns char*
-representation of var.  These macros will skip the replacement if var
-is a String.  Notice that the macros take only the lvalue as their
-argument, to change the value of var in place.
-
-You can also use the macro named StringValueCStr(). This is just
-like StringValuePtr(), but always add nul character at the end of
-the result. If the result contains nul character, this macro causes
-the ArgumentError exception.
-StringValuePtr() doesn't guarantee the existence of a nul at the end
-of the result, and the result may contain nul.
-
-Other data types have corresponding C structures, e.g. struct RArray
-for T_ARRAY etc. The VALUE of the type which has the corresponding
-structure can be cast to retrieve the pointer to the struct.  The
-casting macro will be of the form RXXXX for each data type; for
-instance, RARRAY(obj).  See "ruby.h".  However, we do not recommend
-to access RXXXX data directly because these data structure is complex.
-Use corresponding rb_xxx() functions to access internal struct.
-For example, to access an entry of array, use rb_ary_entry(ary, offset)
-and rb_ary_store(ary, offset, obj).
-
-There are some accessing macros for structure members, for example
-`RSTRING_LEN(str)' to get the size of the Ruby String object.  The
-allocated region can be accessed by `RSTRING_PTR(str)'.
-
-Notice: Do not change the value of the structure directly, unless you
-are responsible for the result.  This ends up being the cause of
-interesting bugs.
-
-== Convert C Data into VALUE
-
-To convert C data to Ruby values:
-
-FIXNUM ::
-
-  left shift 1 bit, and turn on LSB.
-
-Other pointer values::
-
-  cast to VALUE.
-
-You can determine whether a VALUE is pointer or not by checking its LSB.
-
-Notice Ruby does not allow arbitrary pointer values to be a VALUE.  They
-should be pointers to the structures which Ruby knows about.  The known
-structures are defined in <ruby.h>.
-
-To convert C numbers to Ruby values, use these macros.
-
-INT2FIX() :: for integers within 31bits.
-INT2NUM() :: for arbitrary sized integer.
-
-INT2NUM() converts an integer into a Bignum if it is out of the FIXNUM
-range, but is a bit slower.
-
-== Manipulating Ruby Data
-
-As I already mentioned, it is not recommended to modify an object's
-internal structure.  To manipulate objects, use the functions supplied
-by the Ruby interpreter. Some (not all) of the useful functions are
-listed below:
-
-=== String Functions
-
-rb_str_new(const char *ptr, long len) ::
-
-  Creates a new Ruby string.
-
-rb_str_new2(const char *ptr) ::
-rb_str_new_cstr(const char *ptr) ::
-
-  Creates a new Ruby string from a C string.  This is equivalent to
-  rb_str_new(ptr, strlen(ptr)).
-
-rb_str_new_literal(const char *ptr) ::
-
-  Creates a new Ruby string from a C string literal.
-
-rb_tainted_str_new(const char *ptr, long len) ::
-
-  Creates a new tainted Ruby string.  Strings from external data
-  sources should be tainted.
-
-rb_tainted_str_new2(const char *ptr) ::
-rb_tainted_str_new_cstr(const char *ptr) ::
-
-  Creates a new tainted Ruby string from a C string.
-
-rb_sprintf(const char *format, ...) ::
-rb_vsprintf(const char *format, va_list ap) ::
-
-  Creates a new Ruby string with printf(3) format.
-
-  Note: In the format string, "%"PRIsVALUE can be used for Object#to_s
-  (or Object#inspect if '+' flag is set) output (and related argument
-  must be a VALUE).  Since it conflicts with "%i", for integers in
-  format strings, use "%d".
-
-rb_str_cat(VALUE str, const char *ptr, long len) ::
-
-  Appends len bytes of data from ptr to the Ruby string.
-
-rb_str_cat2(VALUE str, const char* ptr) ::
-rb_str_cat_cstr(VALUE str, const char* ptr) ::
-
-  Appends C string ptr to Ruby string str.  This function is
-  equivalent to rb_str_cat(str, ptr, strlen(ptr)).
-
-rb_str_catf(VALUE str, const char* format, ...) ::
-rb_str_vcatf(VALUE str, const char* format, va_list ap) ::
-
-  Appends C string format and successive arguments to Ruby string
-  str according to a printf-like format.  These functions are
-  equivalent to rb_str_cat2(str, rb_sprintf(format, ...)) and
-  rb_str_cat2(str, rb_vsprintf(format, ap)), respectively.
-
-rb_enc_str_new(const char *ptr, long len, rb_encoding *enc) ::
-rb_enc_str_new_cstr(const char *ptr, rb_encoding *enc) ::
-
-  Creates a new Ruby string with the specified encoding.
-
-rb_enc_str_new_literal(const char *ptr) ::
-
-  Creates a new Ruby string from a C string literal with the specified
-  encoding.
-
-rb_usascii_str_new(const char *ptr, long len) ::
-rb_usascii_str_new_cstr(const char *ptr) ::
-
-  Creates a new Ruby string with encoding US-ASCII.
-
-rb_usascii_str_new_literal(const char *ptr) ::
-
-  Creates a new Ruby string from a C string literal with encoding
-  US-ASCII.
-
-rb_utf8_str_new(const char *ptr, long len) ::
-rb_utf8_str_new_cstr(const char *ptr) ::
-
-  Creates a new Ruby string with encoding UTF-8.
-
-rb_utf8_str_new_literal(const char *ptr) ::
-
-  Creates a new Ruby string from a C string literal with encoding
-  UTF-8.
-
-rb_str_resize(VALUE str, long len) ::
-
-  Resizes Ruby string to len bytes.  If str is not modifiable, this
-  function raises an exception.  The length of str must be set in
-  advance.  If len is less than the old length the content beyond
-  len bytes is discarded, else if len is greater than the old length
-  the content beyond the old length bytes will not be preserved but
-  will be garbage.  Note that RSTRING_PTR(str) may change by calling
-  this function.
-
-rb_str_set_len(VALUE str, long len) ::
-
-  Sets the length of Ruby string.  If str is not modifiable, this
-  function raises an exception.  This function preserves the content
-  upto len bytes, regardless RSTRING_LEN(str).  len must not exceed
-  the capacity of str.
-
-=== Array Functions
-
-rb_ary_new() ::
-
-  Creates an array with no elements.
-
-rb_ary_new2(long len) ::
-rb_ary_new_capa(long len) ::
-
-  Creates an array with no elements, allocating internal buffer
-  for len elements.
-
-rb_ary_new3(long n, ...) ::
-rb_ary_new_from_args(long n, ...) ::
-
-  Creates an n-element array from the arguments.
-
-rb_ary_new4(long n, VALUE *elts) ::
-rb_ary_new_from_values(long n, VALUE *elts) ::
-
-  Creates an n-element array from a C array.
-
-rb_ary_to_ary(VALUE obj) ::
-
-  Converts the object into an array.
-  Equivalent to Object#to_ary.
-
-There are many functions to operate an array.  They may dump core if other
-types are given.
-
-rb_ary_aref(argc, VALUE *argv, VALUE ary) ::
-
-  Equivalent to Array#[].
-
-rb_ary_entry(VALUE ary, long offset) ::
-
-  ary[offset]
-
-rb_ary_store(VALUE ary, long offset, VALUE obj) ::
-
-  ary[offset] = obj
-
-rb_ary_subseq(VALUE ary, long beg, long len) ::
-
-  ary[beg, len]
-
-rb_ary_push(VALUE ary, VALUE val) ::
-rb_ary_pop(VALUE ary) ::
-rb_ary_shift(VALUE ary) ::
-rb_ary_unshift(VALUE ary, VALUE val) ::
-
-rb_ary_cat(VALUE ary, const VALUE *ptr, long len) ::
-
-  Appends len elements of objects from ptr to the array.
-
-= Extending Ruby with C
-
-== Adding New Features to Ruby
-
-You can add new features (classes, methods, etc.) to the Ruby
-interpreter.  Ruby provides APIs for defining the following things:
-
-* Classes, Modules
-* Methods, Singleton Methods
-* Constants
-
-=== Class and Module Definition
-
-To define a class or module, use the functions below:
-
-  VALUE rb_define_class(const char *name, VALUE super)
-  VALUE rb_define_module(const char *name)
-
-These functions return the newly created class or module.  You may
-want to save this reference into a variable to use later.
-
-To define nested classes or modules, use the functions below:
-
-  VALUE rb_define_class_under(VALUE outer, const char *name, VALUE super)
-  VALUE rb_define_module_under(VALUE outer, const char *name)
-
-=== Method and Singleton Method Definition
-
-To define methods or singleton methods, use these functions:
-
-  void rb_define_method(VALUE klass, const char *name,
-		        VALUE (*func)(), int argc)
-
-  void rb_define_singleton_method(VALUE object, const char *name,
-			          VALUE (*func)(), int argc)
-
-The `argc' represents the number of the arguments to the C function,
-which must be less than 17.  But I doubt you'll need that many.
-
-If `argc' is negative, it specifies the calling sequence, not number of
-the arguments.
-
-If argc is -1, the function will be called as:
-
-  VALUE func(int argc, VALUE *argv, VALUE obj)
-
-where argc is the actual number of arguments, argv is the C array of
-the arguments, and obj is the receiver.
-
-If argc is -2, the arguments are passed in a Ruby array. The function
-will be called like:
-
-  VALUE func(VALUE obj, VALUE args)
-
-where obj is the receiver, and args is the Ruby array containing
-actual arguments.
-
-There are some more functions to define methods. One takes an ID
-as the name of method to be defined. See also ID or Symbol below.
-
-  void rb_define_method_id(VALUE klass, ID name,
-                           VALUE (*func)(ANYARGS), int argc)
-
-There are two functions to define private/protected methods:
-
-  void rb_define_private_method(VALUE klass, const char *name,
-			        VALUE (*func)(), int argc)
-  void rb_define_protected_method(VALUE klass, const char *name,
-			          VALUE (*func)(), int argc)
-
-At last, rb_define_module_function defines a module functions,
-which are private AND singleton methods of the module.
-For example, sqrt is the module function defined in Math module.
-It can be called in the following way:
-
-  Math.sqrt(4)
-
-or
-
-  include Math
-  sqrt(4)
-
-To define module functions, use:
-
-  void rb_define_module_function(VALUE module, const char *name,
-				 VALUE (*func)(), int argc)
-
-In addition, function-like methods, which are private methods defined
-in the Kernel module, can be defined using:
-
-  void rb_define_global_function(const char *name, VALUE (*func)(), int argc)
-
-To define an alias for the method,
-
-  void rb_define_alias(VALUE module, const char* new, const char* old);
-
-To define a reader/writer for an attribute,
-
-  void rb_define_attr(VALUE klass, const char *name, int read, int write)
-
-To define and undefine the `allocate' class method,
-
-  void rb_define_alloc_func(VALUE klass, VALUE (*func)(VALUE klass));
-  void rb_undef_alloc_func(VALUE klass);
-
-func has to take the klass as the argument and return a newly
-allocated instance.  This instance should be as empty as possible,
-without any expensive (including external) resources.
-
-If you are overriding an existing method of any ancestor of your class,
-you may rely on:
-
-  VALUE rb_call_super(int argc, const VALUE *argv)
-
-To achieve the receiver of the current scope (if no other way is
-available), you can use:
-
-  VALUE rb_current_receiver(void)
-
-=== Constant Definition
-
-We have 2 functions to define constants:
-
-  void rb_define_const(VALUE klass, const char *name, VALUE val)
-  void rb_define_global_const(const char *name, VALUE val)
-
-The former is to define a constant under specified class/module.  The
-latter is to define a global constant.
-
-== Use Ruby Features from C
-
-There are several ways to invoke Ruby's features from C code.
-
-=== Evaluate Ruby Programs in a String
-
-The easiest way to use Ruby's functionality from a C program is to
-evaluate the string as Ruby program.  This function will do the job:
-
-  VALUE rb_eval_string(const char *str)
-
-Evaluation is done under the current context, thus current local variables
-of the innermost method (which is defined by Ruby) can be accessed.
-
-Note that the evaluation can raise an exception. There is a safer
-function:
-
-  VALUE rb_eval_string_protect(const char *str, int *state)
-
-It returns nil when an error occur. Moreover, *state is zero if str was
-successfully evaluated, or nonzero otherwise.
-
-=== ID or Symbol
-
-You can invoke methods directly, without parsing the string.  First I
-need to explain about ID.  ID is the integer number to represent
-Ruby's identifiers such as variable names.  The Ruby data type
-corresponding to ID is Symbol.  It can be accessed from Ruby in the
-form:
-
-  :Identifier
-
-or
-
-  :"any kind of string"
-
-You can get the ID value from a string within C code by using
-
-  rb_intern(const char *name)
-  rb_intern_str(VALUE name)
-
-You can retrieve ID from Ruby object (Symbol or String) given as an
-argument by using
-
-  rb_to_id(VALUE symbol)
-  rb_check_id(volatile VALUE *name)
-  rb_check_id_cstr(const char *name, long len, rb_encoding *enc)
-
-These functions try to convert the argument to a String if it was not
-a Symbol nor a String.  The second function stores the converted
-result into *name, and returns 0 if the string is not a known symbol.
-After this function returned a non-zero value, *name is always a
-Symbol or a String, otherwise it is a String if the result is 0.
-The third function takes NUL-terminated C string, not Ruby VALUE.
-
-You can retrieve Symbol from Ruby object (Symbol or String) given as
-an argument by using
-
-  rb_to_symbol(VALUE name)
-  rb_check_symbol(volatile VALUE *namep)
-  rb_check_symbol_cstr(const char *ptr, long len, rb_encoding *enc)
-
-These functions are similar to above functions except that these
-return a Symbol instead of an ID.
-
-You can convert C ID to Ruby Symbol by using
-
-  VALUE ID2SYM(ID id)
-
-and to convert Ruby Symbol object to ID, use
-
-  ID SYM2ID(VALUE symbol)
-
-=== Invoke Ruby Method from C
-
-To invoke methods directly, you can use the function below
-
-  VALUE rb_funcall(VALUE recv, ID mid, int argc, ...)
-
-This function invokes a method on the recv, with the method name
-specified by the symbol mid.
-
-=== Accessing the Variables and Constants
-
-You can access class variables and instance variables using access
-functions.  Also, global variables can be shared between both
-environments.  There's no way to access Ruby's local variables.
-
-The functions to access/modify instance variables are below:
-
-  VALUE rb_ivar_get(VALUE obj, ID id)
-  VALUE rb_ivar_set(VALUE obj, ID id, VALUE val)
-
-id must be the symbol, which can be retrieved by rb_intern().
-
-To access the constants of the class/module:
-
-  VALUE rb_const_get(VALUE obj, ID id)
-
-See also Constant Definition above.
-
-= Information Sharing Between Ruby and C
-
-=== Ruby Constants That C Can Be Accessed From C
-
-As stated in section 1.3,
-the following Ruby constants can be referred from C.
-
-  Qtrue
-  Qfalse
-
-Boolean values.  Qfalse is false in C also (i.e. 0).
-
-  Qnil
-
-Ruby nil in C scope.
-
-== Global Variables Shared Between C and Ruby
-
-Information can be shared between the two environments using shared global
-variables.  To define them, you can use functions listed below:
-
-  void rb_define_variable(const char *name, VALUE *var)
-
-This function defines the variable which is shared by both environments.
-The value of the global variable pointed to by `var' can be accessed
-through Ruby's global variable named `name'.
-
-You can define read-only (from Ruby, of course) variables using the
-function below.
-
-  void rb_define_readonly_variable(const char *name, VALUE *var)
-
-You can defined hooked variables.  The accessor functions (getter and
-setter) are called on access to the hooked variables.
-
-  void rb_define_hooked_variable(const char *name, VALUE *var,
-				 VALUE (*getter)(), void (*setter)())
-
-If you need to supply either setter or getter, just supply 0 for the
-hook you don't need.  If both hooks are 0, rb_define_hooked_variable()
-works just like rb_define_variable().
-
-The prototypes of the getter and setter functions are as follows:
-
-  VALUE (*getter)(ID id, VALUE *var);
-  void (*setter)(VALUE val, ID id, VALUE *var);
-
-
-Also you can define a Ruby global variable without a corresponding C
-variable.  The value of the variable will be set/get only by hooks.
-
-  void rb_define_virtual_variable(const char *name,
-				  VALUE (*getter)(), void (*setter)())
-
-The prototypes of the getter and setter functions are as follows:
-
-  VALUE (*getter)(ID id);
-  void (*setter)(VALUE val, ID id);
-
-
-== Encapsulate C Data into a Ruby Object
-
-To wrap and objectify a C pointer as a Ruby object (so called
-DATA), use Data_Wrap_Struct().
-
-  Data_Wrap_Struct(klass, mark, free, sval)
-
-Data_Wrap_Struct() returns a created DATA object.  The klass argument
-is the class for the DATA object.  The mark argument is the function
-to mark Ruby objects pointed by this data.  The free argument is the
-function to free the pointer allocation.  If this is -1, the pointer
-will be just freed.  The functions mark and free will be called from
-garbage collector.
-
-These mark / free functions are invoked during GC execution.  No
-object allocations are allowed during it, so do not allocate ruby
-objects inside them.
-
-You can allocate and wrap the structure in one step.
-
-  Data_Make_Struct(klass, type, mark, free, sval)
-
-This macro returns an allocated Data object, wrapping the pointer to
-the structure, which is also allocated.  This macro works like:
-
-  (sval = ALLOC(type), Data_Wrap_Struct(klass, mark, free, sval))
-
-Arguments klass, mark, and free work like their counterparts in
-Data_Wrap_Struct().  A pointer to the allocated structure will be
-assigned to sval, which should be a pointer of the type specified.
-
-To retrieve the C pointer from the Data object, use the macro
-Data_Get_Struct().
-
-  Data_Get_Struct(obj, type, sval)
-
-A pointer to the structure will be assigned to the variable sval.
-
-See the example below for details.
-
-= Example - Creating dbm Extension
-
-OK, here's the example of making an extension library.  This is the
-extension to access DBMs.  The full source is included in the ext/
-directory in the Ruby's source tree.
-
-== Make the Directory
-
-  % mkdir ext/dbm
-
-Make a directory for the extension library under ext directory.
-
-== Design the Library
-
-You need to design the library features, before making it.
-
-== Write the C Code
-
-You need to write C code for your extension library.  If your library
-has only one source file, choosing ``LIBRARY.c'' as a file name is
-preferred.  On the other hand, in case your library has multiple source
-files, avoid choosing ``LIBRARY.c'' for a file name.  It may conflict
-with an intermediate file ``LIBRARY.o'' on some platforms.
-Note that some functions in mkmf library described below generate
-a file ``conftest.c'' for checking with compilation.  You shouldn't
-choose ``conftest.c'' as a name of a source file.
-
-Ruby will execute the initializing function named ``Init_LIBRARY'' in
-the library.  For example, ``Init_dbm()'' will be executed when loading
-the library.
-
-Here's the example of an initializing function.
-
-  void
-  Init_dbm(void)
-  {
-      /* define DBM class */
-      VALUE cDBM = rb_define_class("DBM", rb_cObject);
-      /* DBM includes Enumerable module */
-      rb_include_module(cDBM, rb_mEnumerable);
-
-      /* DBM has class method open(): arguments are received as C array */
-      rb_define_singleton_method(cDBM, "open", fdbm_s_open, -1);
-
-      /* DBM instance method close(): no args */
-      rb_define_method(cDBM, "close", fdbm_close, 0);
-      /* DBM instance method []: 1 argument */
-      rb_define_method(cDBM, "[]", fdbm_fetch, 1);
-
-      /* ... */
-
-      /* ID for a instance variable to store DBM data */
-      id_dbm = rb_intern("dbm");
-  }
-
-The dbm extension wraps the dbm struct in the C environment using
-Data_Make_Struct.
-
-  struct dbmdata {
-      int  di_size;
-      DBM *di_dbm;
-  };
-
-  obj = Data_Make_Struct(klass, struct dbmdata, 0, free_dbm, dbmp);
-
-This code wraps the dbmdata structure into a Ruby object.  We avoid
-wrapping DBM* directly, because we want to cache size information.
-
-To retrieve the dbmdata structure from a Ruby object, we define the
-following macro:
-
-  #define GetDBM(obj, dbmp) do {\
-      Data_Get_Struct(obj, struct dbmdata, dbmp);\
-      if (dbmp->di_dbm == 0) closed_dbm();\
-  } while (0)
-
-This sort of complicated macro does the retrieving and close checking for
-the DBM.
-
-There are three kinds of way to receive method arguments.  First,
-methods with a fixed number of arguments receive arguments like this:
-
-  static VALUE
-  fdbm_delete(VALUE obj, VALUE keystr)
-  {
-        /* ... */
-  }
-
-The first argument of the C function is the self, the rest are the
-arguments to the method.
-
-Second, methods with an arbitrary number of arguments receive
-arguments like this:
-
-  static VALUE
-  fdbm_s_open(int argc, VALUE *argv, VALUE klass)
-  {
-      /* ... */
-      if (rb_scan_args(argc, argv, "11", &file, &vmode) == 1) {
-          mode = 0666;		/* default value */
-      }
-      /* ... */
-  }
-
-The first argument is the number of method arguments, the second
-argument is the C array of the method arguments, and the third
-argument is the receiver of the method.
-
-You can use the function rb_scan_args() to check and retrieve the
-arguments.  The third argument is a string that specifies how to
-capture method arguments and assign them to the following VALUE
-references.
-
-
-The following is an example of a method that takes arguments by Ruby's
-array:
-
-  static VALUE
-  thread_initialize(VALUE thread, VALUE args)
-  {
-      /* ... */
-  }
-
-The first argument is the receiver, the second one is the Ruby array
-which contains the arguments to the method.
-
-*Notice*: GC should know about global variables which refer to Ruby's objects,
-but are not exported to the Ruby world.  You need to protect them by
-
-  void rb_global_variable(VALUE *var)
-
-== Prepare extconf.rb
-
-If the file named extconf.rb exists, it will be executed to generate
-Makefile.
-
-extconf.rb is the file for checking compilation conditions etc.  You
-need to put
-
-  require 'mkmf'
-
-at the top of the file.  You can use the functions below to check
-various conditions.
-
-  have_macro(macro[, headers[, opt]]): check whether macro is defined
-  have_library(lib[, func[, headers[, opt]]]): check whether library containing function exists
-  find_library(lib[, func, *paths]): find library from paths
-  have_func(func[, headers[, opt]): check whether function exists
-  have_var(var[, headers[, opt]]): check whether variable exists
-  have_header(header[, preheaders[, opt]]): check whether header file exists
-  find_header(header, *paths): find header from paths
-  have_framework(fw): check whether framework exists (for MacOS X)
-  have_struct_member(type, member[, headers[, opt]]): check whether struct has member
-  have_type(type[, headers[, opt]]): check whether type exists
-  find_type(type, opt, *headers): check whether type exists in headers
-  have_const(const[, headers[, opt]]): check whether constant is defined
-  check_sizeof(type[, headers[, opts]]): check size of type
-  check_signedness(type[, headers[, opts]]): check signedness of type
-  convertible_int(type[, headers[, opts]]): find convertible integer type
-  find_executable(bin[, path]): find executable file path
-  create_header(header): generate configured header
-  create_makefile(target[, target_prefix]): generate Makefile
-
-See MakeMakefile for full documentation of these functions.
-
-The value of the variables below will affect the Makefile.
-
-  $CFLAGS: included in CFLAGS make variable (such as -O)
-  $CPPFLAGS: included in CPPFLAGS make variable (such as -I, -D)
-  $LDFLAGS: included in LDFLAGS make variable (such as -L)
-  $objs: list of object file names
-
-Normally, the object files list is automatically generated by searching
-source files, but you must define them explicitly if any sources will
-be generated while building.
-
-If a compilation condition is not fulfilled, you should not call
-``create_makefile''.  The Makefile will not be generated, compilation will
-not be done.
-
-== Prepare Depend (Optional)
-
-If the file named depend exists, Makefile will include that file to
-check dependencies.  You can make this file by invoking
-
-  % gcc -MM *.c > depend
-
-It's harmless.  Prepare it.
-
-== Generate Makefile
-
-Try generating the Makefile by:
-
-  ruby extconf.rb
-
-If the library should be installed under vendor_ruby directory
-instead of site_ruby directory, use --vendor option as follows.
-
-  ruby extconf.rb --vendor
-
-You don't need this step if you put the extension library under the ext
-directory of the ruby source tree.  In that case, compilation of the
-interpreter will do this step for you.
-
-== Run make
-
-Type
-
-  make
-
-to compile your extension.  You don't need this step either if you have
-put the extension library under the ext directory of the ruby source tree.
-
-== Debug
-
-You may need to rb_debug the extension.  Extensions can be linked
-statically by adding the directory name in the ext/Setup file so that
-you can inspect the extension with the debugger.
-
-== Done! Now You Have the Extension Library
-
-You can do anything you want with your library.  The author of Ruby
-will not claim any restrictions on your code depending on the Ruby API.
-Feel free to use, modify, distribute or sell your program.
-
-= Appendix A. Ruby Source Files Overview
-
-== Ruby Language Core
-
-class.c    :: classes and modules
-error.c    :: exception classes and exception mechanism
-gc.c       :: memory management
-load.c     :: library loading
-object.c   :: objects
-variable.c :: variables and constants
-
-== Ruby Syntax Parser
-
-parse.y  :: grammar definition
-parse.c  :: automatically generated from parse.y
-keywords :: reserved keywords
-lex.c    :: automatically generated from keywords
-
-== Ruby Evaluator (a.k.a. YARV)
-
-  compile.c
-  eval.c
-  eval_error.c
-  eval_jump.c
-  eval_safe.c
-  insns.def           : definition of VM instructions
-  iseq.c              : implementation of VM::ISeq
-  thread.c            : thread management and context switching
-  thread_win32.c      : thread implementation
-  thread_pthread.c    : ditto
-  vm.c
-  vm_dump.c
-  vm_eval.c
-  vm_exec.c
-  vm_insnhelper.c
-  vm_method.c
-
-  opt_insns_unif.def  : instruction unification
-  opt_operand.def     : definitions for optimization
-
-    -> insn*.inc      : automatically generated
-    -> opt*.inc       : automatically generated
-    -> vm.inc         : automatically generated
-
-== Regular Expression Engine (Oniguruma)
-
-  regex.c
-  regcomp.c
-  regenc.c
-  regerror.c
-  regexec.c
-  regparse.c
-  regsyntax.c
-
-== Utility Functions
-
-debug.c    :: debug symbols for C debugger
-dln.c      :: dynamic loading
-st.c       :: general purpose hash table
-strftime.c :: formatting times
-util.c     :: misc utilities
-
-== Ruby Interpreter Implementation
-
-  dmyext.c
-  dmydln.c
-  dmyencoding.c
-  id.c
-  inits.c
-  main.c
-  ruby.c
-  version.c
-
-  gem_prelude.rb
-  prelude.rb
-
-== Class Library
-
-array.c      :: Array
-bignum.c     :: Bignum
-compar.c     :: Comparable
-complex.c    :: Complex
-cont.c       :: Fiber, Continuation
-dir.c        :: Dir
-enum.c       :: Enumerable
-enumerator.c :: Enumerator
-file.c       :: File
-hash.c       :: Hash
-io.c         :: IO
-marshal.c    :: Marshal
-math.c       :: Math
-numeric.c    :: Numeric, Integer, Fixnum, Float
-pack.c       :: Array#pack, String#unpack
-proc.c       :: Binding, Proc
-process.c    :: Process
-random.c     :: random number
-range.c      :: Range
-rational.c   :: Rational
-re.c         :: Regexp, MatchData
-signal.c     :: Signal
-sprintf.c    :: String#sprintf
-string.c     :: String
-struct.c     :: Struct
-time.c       :: Time
-
-defs/known_errors.def :: Errno::* exception classes
--> known_errors.inc   :: automatically generated
-
-== Multilingualization
-
-encoding.c  :: Encoding
-transcode.c :: Encoding::Converter
-enc/*.c     :: encoding classes
-enc/trans/* :: codepoint mapping tables
-
-== goruby Interpreter Implementation
-
-  goruby.c
-  golf_prelude.rb     : goruby specific libraries.
-    -> golf_prelude.c : automatically generated
-
-
-= Appendix B. Ruby Extension API Reference
-
-== Types
-
-VALUE ::
-
-  The type for the Ruby object.  Actual structures are defined in ruby.h,
-  such as struct RString, etc.  To refer the values in structures, use
-  casting macros like RSTRING(obj).
-
-== Variables and Constants
-
-Qnil::
-  nil object
-
-Qtrue::
-  true object (default true value)
-
-Qfalse::
-  false object
-
-== C Pointer Wrapping
-
-Data_Wrap_Struct(VALUE klass, void (*mark)(), void (*free)(), void *sval) ::
-
-  Wrap a C pointer into a Ruby object.  If object has references to other
-  Ruby objects, they should be marked by using the mark function during
-  the GC process.  Otherwise, mark should be 0.  When this object is no
-  longer referred by anywhere, the pointer will be discarded by free
-  function.
-
-Data_Make_Struct(klass, type, mark, free, sval) ::
-
-  This macro allocates memory using malloc(), assigns it to the variable
-  sval, and returns the DATA encapsulating the pointer to memory region.
-
-Data_Get_Struct(data, type, sval) ::
-
-  This macro retrieves the pointer value from DATA, and assigns it to
-  the variable sval.
-
-== Checking Data Types
-
-TYPE(value) ::
-
-  Internal type (T_NIL, T_FIXNUM, etc.)
-
-FIXNUM_P(value) ::
-
-  Is +value+ a Fixnum?
-
-NIL_P(value) ::
-
-  Is +value+ nil?
-
-void Check_Type(VALUE value, int type) ::
-
-  Ensures +value+ is of the given internal +type+ or raises a TypeError
-
-SaveStringValue(value) ::
-
-  Checks that +value+ is a String and is not tainted
-
-== Data Type Conversion
-
-FIX2INT(value), INT2FIX(i) ::
-
-  Fixnum <-> integer
-
-FIX2LONG(value), LONG2FIX(l) ::
-
-  Fixnum <-> long
-
-NUM2INT(value), INT2NUM(i) ::
-
-  Numeric <-> integer
-
-NUM2UINT(value), UINT2NUM(ui) ::
-
-  Numeric <-> unsigned integer
-
-NUM2LONG(value), LONG2NUM(l) ::
-
-  Numeric <-> long
-
-NUM2ULONG(value), ULONG2NUM(ul) ::
-
-  Numeric <-> unsigned long
-
-NUM2LL(value), LL2NUM(ll) ::
-
-  Numeric <-> long long
-
-NUM2ULL(value), ULL2NUM(ull) ::
-
-  Numeric <-> unsigned long long
-
-NUM2OFFT(value), OFFT2NUM(off) ::
-
-  Numeric <-> off_t
-
-NUM2SIZET(value), SIZET2NUM(size) ::
-
-  Numeric <-> size_t
-
-NUM2SSIZET(value), SSIZET2NUM(ssize) ::
-
-  Numeric <-> ssize_t
-
-rb_integer_pack(value, words, numwords, wordsize, nails, flags), rb_integer_unpack(words, numwords, wordsize, nails, flags) ::
-
-  Numeric <-> Arbitrary size integer buffer
-
-NUM2DBL(value) ::
-
-  Numeric -> double
-
-rb_float_new(f) ::
-
-  double -> Float
-
-RSTRING_LEN(str) ::
-
-  String -> length of String data in bytes
-
-RSTRING_PTR(str) ::
-
-  String -> pointer to String data
-  Note that the result pointer may not be NUL-terminated
-
-StringValue(value) ::
-
-  Object with #to_str -> String
-
-StringValuePtr(value) ::
-
-  Object with #to_str -> pointer to String data
-
-StringValueCStr(value) ::
-
-  Object with #to_str -> pointer to String data without NUL bytes
-  It is guaranteed that the result data is NUL-terminated
-
-rb_str_new2(s) ::
-
-  char * -> String
-
-== Defining Class and Module
-
-VALUE rb_define_class(const char *name, VALUE super) ::
-
-  Defines a new Ruby class as a subclass of super.
-
-VALUE rb_define_class_under(VALUE module, const char *name, VALUE super) ::
-
-  Creates a new Ruby class as a subclass of super, under the module's
-  namespace.
-
-VALUE rb_define_module(const char *name) ::
-
-  Defines a new Ruby module.
-
-VALUE rb_define_module_under(VALUE module, const char *name) ::
-
-  Defines a new Ruby module under the module's namespace.
-
-void rb_include_module(VALUE klass, VALUE module) ::
-
-  Includes module into class.  If class already includes it, just ignored.
-
-void rb_extend_object(VALUE object, VALUE module) ::
-
-  Extend the object with the module's attributes.
-
-== Defining Global Variables
-
-void rb_define_variable(const char *name, VALUE *var) ::
-
-  Defines a global variable which is shared between C and Ruby.  If name
-  contains a character which is not allowed to be part of the symbol,
-  it can't be seen from Ruby programs.
-
-void rb_define_readonly_variable(const char *name, VALUE *var) ::
-
-  Defines a read-only global variable.  Works just like
-  rb_define_variable(), except the defined variable is read-only.
-
-void rb_define_virtual_variable(const char *name, VALUE (*getter)(), VALUE (*setter)()) ::
-
-  Defines a virtual variable, whose behavior is defined by a pair of C
-  functions.  The getter function is called when the variable is
-  referenced.  The setter function is called when the variable is set to a
-  value.  The prototype for getter/setter functions are:
-
-    VALUE getter(ID id)
-    void setter(VALUE val, ID id)
-
-  The getter function must return the value for the access.
-
-void rb_define_hooked_variable(const char *name, VALUE *var, VALUE (*getter)(), VALUE (*setter)()) ::
-
-  Defines hooked variable.  It's a virtual variable with a C variable.
-  The getter is called as
-
-    VALUE getter(ID id, VALUE *var)
-
-  returning a new value.  The setter is called as
-
-    void setter(VALUE val, ID id, VALUE *var)
-
-  GC requires C global variables which hold Ruby values to be marked.
-
-void rb_global_variable(VALUE *var)
-
-  Tells GC to protect these variables.
-
-== Constant Definition
-
-void rb_define_const(VALUE klass, const char *name, VALUE val) ::
-
-  Defines a new constant under the class/module.
-
-void rb_define_global_const(const char *name, VALUE val) ::
-
-  Defines a global constant.  This is just the same as
-
-    rb_define_const(cKernal, name, val)
-
-== Method Definition
-
-rb_define_method(VALUE klass, const char *name, VALUE (*func)(), int argc) ::
-
-  Defines a method for the class.  func is the function pointer.  argc
-  is the number of arguments.  if argc is -1, the function will receive
-  3 arguments: argc, argv, and self.  if argc is -2, the function will
-  receive 2 arguments, self and args, where args is a Ruby array of
-  the method arguments.
-
-rb_define_private_method(VALUE klass, const char *name, VALUE (*func)(), int argc) ::
-
-  Defines a private method for the class.  Arguments are same as
-  rb_define_method().
-
-rb_define_singleton_method(VALUE klass, const char *name, VALUE (*func)(), int argc) ::
-
-  Defines a singleton method.  Arguments are same as rb_define_method().
-
-rb_scan_args(int argc, VALUE *argv, const char *fmt, ...) ::
-
-  Retrieve argument from argc and argv to given VALUE references
-  according to the format string.  The format can be described in ABNF
-  as follows:
-
-    scan-arg-spec  := param-arg-spec [option-hash-arg-spec] [block-arg-spec]
-
-    param-arg-spec := pre-arg-spec [post-arg-spec] / post-arg-spec /
-                      pre-opt-post-arg-spec
-    pre-arg-spec   := num-of-leading-mandatory-args [num-of-optional-args]
-    post-arg-spec  := sym-for-variable-length-args
-                      [num-of-trailing-mandatory-args]
-    pre-opt-post-arg-spec := num-of-leading-mandatory-args num-of-optional-args
-                             num-of-trailing-mandatory-args
-    option-hash-arg-spec := sym-for-option-hash-arg
-    block-arg-spec := sym-for-block-arg
-
-    num-of-leading-mandatory-args  := DIGIT ; The number of leading
-                                            ; mandatory arguments
-    num-of-optional-args           := DIGIT ; The number of optional
-                                            ; arguments
-    sym-for-variable-length-args   := "*"   ; Indicates that variable
-                                            ; length arguments are
-                                            ; captured as a ruby array
-    num-of-trailing-mandatory-args := DIGIT ; The number of trailing
-                                            ; mandatory arguments
-    sym-for-option-hash-arg        := ":"   ; Indicates that an option
-                                            ; hash is captured if the last
-                                            ; argument is a hash or can be
-                                            ; converted to a hash with
-                                            ; #to_hash.  When the last
-                                            ; argument is nil, it is
-                                            ; captured if it is not
-                                            ; ambiguous to take it as
-                                            ; empty option hash; i.e. '*'
-                                            ; is not specified and
-                                            ; arguments are given more
-                                            ; than sufficient.
-    sym-for-block-arg              := "&"   ; Indicates that an iterator
-                                            ; block should be captured if
-                                            ; given
-
-  For example, "12" means that the method requires at least one
-  argument, and at most receives three (1+2) arguments.  So, the format
-  string must be followed by three variable references, which are to be
-  assigned to captured arguments.  For omitted arguments, variables are
-  set to Qnil.  NULL can be put in place of a variable reference, which
-  means the corresponding captured argument(s) should be just dropped.
-
-  The number of given arguments, excluding an option hash or iterator
-  block, is returned.
-
-int rb_get_kwargs(VALUE keyword_hash, const ID *table, int required, int optional, VALUE *values)
-
-  Retrieves argument VALUEs bound to keywords, which directed by +table+
-  into +values+.  First +required+ number of IDs referred by +table+ are
-  mandatory, and succeeding +optional+ (- +optional+ - 1 if
-  +optional+ is negative) number of IDs are optional.  If a
-  mandatory key is not contained in +keyword_hash+, raises "missing
-  keyword" +ArgumentError+.  If an optional key is not present in
-  +keyword_hash+, the corresponding element in +values+ is not changed.
-  If +optional+ is negative, rest of +keyword_hash+ are stored in the
-  next to optional +values+ as a new Hash, otherwise raises "unknown
-  keyword" +ArgumentError+.
-
-VALUE rb_extract_keywords(VALUE *original_hash)
-
-  Extracts pairs whose key is a symbol into a new hash from a hash
-  object referred by +original_hash+.  If the original hash contains
-  non-symbol keys, then they are copied to another hash and the new hash
-  is stored through +original_hash+, else 0 is stored.
-
-== Invoking Ruby method
-
-VALUE rb_funcall(VALUE recv, ID mid, int narg, ...) ::
-
-  Invokes a method.  To retrieve mid from a method name, use rb_intern().
-  Able to call even private/protected methods.
-
-VALUE rb_funcall2(VALUE recv, ID mid, int argc, VALUE *argv) ::
-VALUE rb_funcallv(VALUE recv, ID mid, int argc, VALUE *argv) ::
-
-  Invokes a method, passing arguments as an array of values.
-  Able to call even private/protected methods.
-
-VALUE rb_funcallv_public(VALUE recv, ID mid, int argc, VALUE *argv) ::
-
-  Invokes a method, passing arguments as an array of values.
-  Able to call only public methods.
-
-VALUE rb_eval_string(const char *str) ::
-
-  Compiles and executes the string as a Ruby program.
-
-ID rb_intern(const char *name) ::
-
-  Returns ID corresponding to the name.
-
-char *rb_id2name(ID id) ::
-
-  Returns the name corresponding ID.
-
-char *rb_class2name(VALUE klass) ::
-
-  Returns the name of the class.
-
-int rb_respond_to(VALUE object, ID id) ::
-
-  Returns true if the object responds to the message specified by id.
-
-== Instance Variables
-
-VALUE rb_iv_get(VALUE obj, const char *name) ::
-
-  Retrieve the value of the instance variable.  If the name is not
-  prefixed by `@', that variable shall be inaccessible from Ruby.
-
-VALUE rb_iv_set(VALUE obj, const char *name, VALUE val) ::
-
-  Sets the value of the instance variable.
-
-== Control Structure
-
-VALUE rb_block_call(VALUE recv, ID mid, int argc, VALUE * argv, VALUE (*func) (ANYARGS), VALUE data2) ::
-
-  Calls a method on the recv, with the method name specified by the
-  symbol mid, with argc arguments in argv, supplying func as the
-  block. When func is called as the block, it will receive the value
-  from yield as the first argument, and data2 as the second argument.
-  When yielded with multiple values (in C, rb_yield_values(),
-  rb_yield_values2() and rb_yield_splat()), data2 is packed as an Array,
-  whereas yielded values can be gotten via argc/argv of the third/fourth
-  arguments.
-
-[OBSOLETE] VALUE rb_iterate(VALUE (*func1)(), void *arg1, VALUE (*func2)(), void *arg2) ::
-
-  Calls the function func1, supplying func2 as the block.  func1 will be
-  called with the argument arg1.  func2 receives the value from yield as
-  the first argument, arg2 as the second argument.
-
-  When rb_iterate is used in 1.9, func1 has to call some Ruby-level method.
-  This function is obsolete since 1.9; use rb_block_call instead.
-
-VALUE rb_yield(VALUE val) ::
-
-  Evaluates the block with value val.
-
-VALUE rb_rescue(VALUE (*func1)(), VALUE arg1, VALUE (*func2)(), VALUE arg2) ::
-
-  Calls the function func1, with arg1 as the argument.  If an exception
-  occurs during func1, it calls func2 with arg2 as the argument.  The
-  return value of rb_rescue() is the return value from func1 if no
-  exception occurs, from func2 otherwise.
-
-VALUE rb_ensure(VALUE (*func1)(), VALUE arg1, VALUE (*func2)(), VALUE arg2) ::
-
-  Calls the function func1 with arg1 as the argument, then calls func2
-  with arg2 if execution terminated.  The return value from
-  rb_ensure() is that of func1 when no exception occurred.
-
-VALUE rb_protect(VALUE (*func) (VALUE), VALUE arg, int *state) ::
-
-  Calls the function func with arg as the argument.  If no exception
-  occurred during func, it returns the result of func and *state is zero.
-  Otherwise, it returns Qnil and sets *state to nonzero.  If state is
-  NULL, it is not set in both cases.
-  You have to clear the error info with rb_set_errinfo(Qnil) when
-  ignoring the caught exception.
-
-void rb_jump_tag(int state) ::
-
-  Continues the exception caught by rb_protect() and rb_eval_string_protect().
-  state must be the returned value from those functions.  This function
-  never return to the caller.
-
-void rb_iter_break() ::
-
-  Exits from the current innermost block.  This function never return to
-  the caller.
-
-void rb_iter_break_value(VALUE value) ::
-
-  Exits from the current innermost block with the value.  The block will
-  return the given argument value.  This function never return to the
-  caller.
-
-== Exceptions and Errors
-
-void rb_warn(const char *fmt, ...) ::
-
-  Prints a warning message according to a printf-like format.
-
-void rb_warning(const char *fmt, ...) ::
-
-  Prints a warning message according to a printf-like format, if
-  $VERBOSE is true.
-
-void rb_raise(rb_eRuntimeError, const char *fmt, ...) ::
-
-  Raises RuntimeError.  The fmt is a format string just like printf().
-
-void rb_raise(VALUE exception, const char *fmt, ...) ::
-
-  Raises a class exception.  The fmt is a format string just like printf().
-
-void rb_fatal(const char *fmt, ...) ::
-
-  Raises a fatal error, terminates the interpreter.  No exception handling
-  will be done for fatal errors, but ensure blocks will be executed.
-
-void rb_bug(const char *fmt, ...) ::
-
-  Terminates the interpreter immediately.  This function should be
-  called under the situation caused by the bug in the interpreter.  No
-  exception handling nor ensure execution will be done.
-
-Note: In the format string, "%"PRIsVALUE can be used for Object#to_s
-(or Object#inspect if '+' flag is set) output (and related argument
-must be a VALUE).  Since it conflicts with "%i", for integers in
-format strings, use "%d".
-
-== Initialize and Start the Interpreter
-
-The embedding API functions are below (not needed for extension libraries):
-
-void ruby_init() ::
-
-  Initializes the interpreter.
-
-void *ruby_options(int argc, char **argv) ::
-
-  Process command line arguments for the interpreter.
-  And compiles the Ruby source to execute.
-  It returns an opaque pointer to the compiled source
-  or an internal special value.
-
-int ruby_run_node(void *n) ::
-
-  Runs the given compiled source and exits this process.
-  It returns EXIT_SUCCESS if successfully runs the source.
-  Otherwise, it returns other value.
-
-void ruby_script(char *name) ::
-
-  Specifies the name of the script ($0).
-
-== Hooks for the Interpreter Events
-
-  void rb_add_event_hook(rb_event_hook_func_t func, rb_event_flag_t events,
-                         VALUE data)
-
-Adds a hook function for the specified interpreter events.
-events should be OR'ed value of:
-
-  RUBY_EVENT_LINE
-  RUBY_EVENT_CLASS
-  RUBY_EVENT_END
-  RUBY_EVENT_CALL
-  RUBY_EVENT_RETURN
-  RUBY_EVENT_C_CALL
-  RUBY_EVENT_C_RETURN
-  RUBY_EVENT_RAISE
-  RUBY_EVENT_ALL
-
-The definition of rb_event_hook_func_t is below:
-
-  typedef void (*rb_event_hook_func_t)(rb_event_t event, VALUE data,
-                                       VALUE self, ID id, VALUE klass)
-
-The third argument `data' to rb_add_event_hook() is passed to the hook
-function as the second argument, which was the pointer to the current
-NODE in 1.8.  See RB_EVENT_HOOKS_HAVE_CALLBACK_DATA below.
-
-  int rb_remove_event_hook(rb_event_hook_func_t func)
-
-Removes the specified hook function.
-
-== Macros for Compatibility
-
-Some macros to check API compatibilities are available by default.
-
-NORETURN_STYLE_NEW ::
-
-  Means that NORETURN macro is functional style instead of prefix.
-
-HAVE_RB_DEFINE_ALLOC_FUNC ::
-
-  Means that function rb_define_alloc_func() is provided, that means the
-  allocation framework is used.  This is same as the result of
-  have_func("rb_define_alloc_func", "ruby.h").
-
-HAVE_RB_REG_NEW_STR ::
-
-  Means that function rb_reg_new_str() is provided, that creates Regexp
-  object from String object.  This is same as the result of
-  have_func("rb_reg_new_str", "ruby.h").
-
-HAVE_RB_IO_T ::
-
-  Means that type rb_io_t is provided.
-
-USE_SYMBOL_AS_METHOD_NAME ::
-
-  Means that Symbols will be returned as method names, e.g.,
-  Module#methods, #singleton_methods and so on.
-
-HAVE_RUBY_*_H ::
-
-  Defined in ruby.h and means corresponding header is available.  For
-  instance, when HAVE_RUBY_ST_H is defined you should use ruby/st.h not
-  mere st.h.
-
-RB_EVENT_HOOKS_HAVE_CALLBACK_DATA ::
-
-  Means that rb_add_event_hook() takes the third argument `data', to be
-  passed to the given event hook function.
-
-= Appendix C. Functions available for use in extconf.rb
-
-See documentation for {mkmf}[rdoc-ref:MakeMakefile].
-
-= Appendix D. Generational GC
-
-Ruby 2.1 introduced a generational garbage collector (called RGenGC).
-RGenGC (mostly) keeps compatibility.
-
-Generally, the use of the technique called write barriers is required in
-extension libraries for generational GC
-(http://en.wikipedia.org/wiki/Garbage_collection_%28computer_science%29).
-RGenGC works fine without write barriers in extension libraries.
-
-If your library adheres to the following tips, performance can
-be further improved. Especially, the "Don't touch pointers directly" section is
-important.
-
-== Incompatibility
-
-You can't write RBASIC(obj)->klass field directly because it is const
-value now.
-
-Basically you should not write this field because MRI expects it to be
-an immutable field, but if you want to do it in your extension you can
-use the following functions:
-
-VALUE rb_obj_hide(VALUE obj) ::
-
-  Clear RBasic::klass field. The object will be an internal object.
-  ObjectSpace::each_object can't find this object.
-
-VALUE rb_obj_reveal(VALUE obj, VALUE klass) ::
-
-  Reset RBasic::klass to be klass.
-  We expect the `klass' is hidden class by rb_obj_hide().
-
-== Write barriers
-
-RGenGC doesn't require write barriers to support generational GC.
-However, caring about write barrier can improve the performance of
-RGenGC. Please check the following tips.
-
-=== Don't touch pointers directly
-
-In MRI (include/ruby/ruby.h), some macros to acquire pointers to the
-internal data structures are supported such as RARRAY_PTR(),
-RSTRUCT_PTR() and so on.
-
-DO NOT USE THESE MACROS and instead use the corresponding C-APIs such as
-rb_ary_aref(), rb_ary_store() and so on.
-
-=== Consider whether to insert write barriers
-
-You don't need to care about write barriers if you only use built-in
-types.
-
-If you support T_DATA objects, you may consider using write barriers.
-
-Inserting write barriers into T_DATA objects only works with the
-following type objects: (a) long-lived objects, (b) when a huge number
-of objects are generated and (c) container-type objects that have
-references to other objects. If your extension provides such a type of
-T_DATA objects, consider inserting write barriers.
-
-(a): short-lived objects don't become old generation objects.
-(b): only a few oldgen objects don't have performance impact.
-(c): only a few references don't have performance impact.
-
-Inserting write barriers is a very difficult hack, it is easy to
-introduce critical bugs. And inserting write barriers has several areas
-of overhead. Basically we don't recommend you insert write barriers.
-Please carefully consider the risks.
-
-=== Combine with built-in types
-
-Please consider utilizing built-in types. Most built-in types support
-write barrier, so you can use them to avoid manually inserting write
-barriers.
-
-For example, if your T_DATA has references to other objects, then you
-can move these references to Array. A T_DATA object only has a reference
-to an array object. Or you can also use a Struct object to gather a
-T_DATA object (without any references) and an that Array contains
-references.
-
-With use of such techniques, you don't need to insert write barriers
-anymore.
-
-=== Insert write barriers
-
-[AGAIN] Inserting write barriers is a very difficult hack, and it is
-easy to introduce critical bugs. And inserting write barriers has
-several areas of overhead. Basically we don't recommend you insert write
-barriers. Please carefully consider the risks.
-
-Before inserting write barriers, you need to know about RGenGC algorithm
-(gc.c will help you). Macros and functions to insert write barriers are
-available in in include/ruby/ruby.h. An example is available in iseq.c.
-
-For a complete guide for RGenGC and write barriers, please refer to
-<https://bugs.ruby-lang.org/projects/ruby-trunk/wiki/RGenGC>.
-
-= Appendix E. RB_GC_GUARD to protect from premature GC
-
-C Ruby currently uses conservative garbage collection, thus VALUE
-variables must remain visible on the stack or registers to ensure any
-associated data remains usable.  Optimizing C compilers are not designed
-with conservative garbage collection in mind, so they may optimize away
-the original VALUE even if the code depends on data associated with that
-VALUE.
-
-The following example illustrates the use of RB_GC_GUARD to ensure
-the contents of sptr remain valid while the second invocation of
-rb_str_new_cstr is running.
-
-  VALUE s, w;
-  const char *sptr;
-
-  s = rb_str_new_cstr("hello world!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
-  sptr = RSTRING_PTR(s);
-  w = rb_str_new_cstr(sptr + 6); /* Possible GC invocation */
-
-  RB_GC_GUARD(s); /* ensure s (and thus sptr) do not get GC-ed */
-
-In the above example, RB_GC_GUARD must be placed _after_ the last use of
-sptr.  Placing RB_GC_GUARD before dereferencing sptr would be of no use.
-RB_GC_GUARD is only effective on the VALUE data type, not converted C
-data types.
-
-RB_GC_GUARD would not be necessary at all in the above example if
-non-inlined function calls are made on the `s' VALUE after sptr is
-dereferenced.  Thus, in the above example, calling any un-inlined
-function on `s' such as:
-
-  rb_str_modify(s);
-
-Will ensure `s' stays on the stack or register to prevent a
-GC invocation from prematurely freeing it.
-
-Using the RB_GC_GUARD macro is preferable to using the "volatile"
-keyword in C.  RB_GC_GUARD has the following advantages:
-
-1) the intent of the macro use is clear
-
-2) RB_GC_GUARD only affects its call site, "volatile" generates some
-   extra code every time the variable is used, hurting optimization.
-
-3) "volatile" implementations may be buggy/inconsistent in some
-   compilers and architectures. RB_GC_GUARD is customizable for broken
-   systems/compilers without those without negatively affecting other
-   systems.
-
-/*
- * Local variables:
- * fill-column: 70
- * end:
- */