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266 lines
8.5 KiB
Text
266 lines
8.5 KiB
Text
=begin
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= Ruby/DL
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Ruby/DL provides an interface to the dynamic linker such as dlopen() on UNIX
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and LoadLibrary() on Windows.
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= Building and Installing
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$ ruby extconf.rb # to create the Makefile
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$ make # to build the library 'dl.so'
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$ make libtest.so # to build the C library 'libtest.so' for the test script
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$ make test # to run the test script
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$ make install # to install the library
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$ make clean # to remove the created files without Makefile
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$ make distclean # to remove the all created files
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= Using Ruby/DL
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We should usually use DL::Importable module provided by "dl/import.rb".
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It has high-level functions to access library functions. We use
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DL::Importable module to extend a module as follows:
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require "dl/import"
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module LIBC
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extend DL::Importable
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end
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Now we can use methods dlload and extern in this module. We load the
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libraries using dlload, and define wrapper methods to library functions
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using extern respectively as follows:
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module LIBC
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extend DL::Importable
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dlload "libc.so.6","libm.so.6"
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extern "int strlen(char*)"
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end
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# Note that we should not include the module LIBC from some reason.
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We can call the library function strlen() using LIBC.strlen. If the first
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character of given function name is an uppercase, the first character of the
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defined method name becomes lowercase.
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We can also construct memory images of structures and unions using functions
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struct and union which are defined in "dl/struct.rb" as follows:
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require "dl/import"
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require "dl/struct"
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module LIBC
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extend DL::Importable
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Timeval = struct [ # define timeval structure.
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"long tv_sec",
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"long tv_uses",
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]
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end
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val = LIBC::Timeval.malloc # allocate memory.
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Notice that the above example takes LIBC::Timeval.malloc to allocate memory,
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rather than LIBC::Timeval.new. It is because DL::Timeval.new is for wrapping
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an object, PtrData, which has already been created.
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We can define a callback using the module function "callback" as follows:
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module Foo
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extend DL::Importable
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def my_comp(str1,str2)
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str1 <=> str2
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end
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COMPARE = callback "int my_comp(char*,char*)"
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end
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where Foo::COMPARE is a Symbol object which invokes the method "my_comp".
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DL::Importable module is very useful. However, we sometimes encounter a case
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that we must directly use low-level functions such as dlsym(). In such case,
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we would use DL module functions. They are described in next section.
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= DL module
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Module DL consists of three classes, a few module functions and constants.
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The class Symbol represents the symbol we can call. The class PtrData
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indicates a memory block such as a pointer in C. An object instantiated from
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the class Handle keeps a handle to opened library.
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== Constants
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* VERSION
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* MAJOR_VERSION
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* MINOR_VERSION
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* PATCH_VERSION
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* RTLD_GLOBAL
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* RTLD_LAZY
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* RTLD_NOW
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* MAX_ARG
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* MAX_CBARG
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* MAX_CBENT
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== Functions
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* handle = dlopen(lib){|handle| ... }
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* is quite equal to `Handle.new(lib)'
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* sym = set_callback(cbtype, entry){|args| ... }
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* sym = set_callback(cbtype, entry, proc)
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* makes entry-th pre-defined function to call the proc or given block. the
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entry-th pre-defined function is specified by cbtype and entry. cbtype is a
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prototype of the callback. see also the section `Type specifiers' about
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cbtype.
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* sym = get_callback(cbtype, entry)
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* returns the Proc object which is given by the above function
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`set_callback'.
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* ptr = malloc(size, [free = nil])
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* allocates the size bytes, and returns the pointer as a PtrData object ptr.
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* ptr = strdup(str)
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* returns a PtrData object ptr which represents the pointer to a new string
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which is a duplicate of the string str.
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* size = sizeof(type)
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* returns the size of type. `sizeof("C") + sizeof("L")' is not equal to
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`sizeof("CL")'. the latter is assumed to returns the enough size of the
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structure `struct foo { char c; long l; }', but the size may not equal to
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`sizeof(foo)' of C.
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== Handle class
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* handle = Handle.new(lib){|handle| ... }
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* opens a library lib and returns a Handle object handle. if a block is
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given, the handle is automatically closed as the block ends.
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* Handle#close
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* closes the handle opened by the above Handle.new(lib).
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* sym = Handle#sym(func, prototype = "0"),
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sym = Handle#[func, prototype = nil]
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* obtains the pointer to a function called func and returns a Symbol object
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or a DataPtr object. prototype is a string which consists of type
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specifiers, it indicates the function's prototype. see also the section
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`Type specifiers'.
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== Symbol class
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* sym = Symbol.new(addr, type = nil, name = nil)
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* creates the Symbol object sym with the type type if type is not nil. addr
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is the address where the function is allocated. If type is nil, it returns
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a DataPtr object.
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* Symbol::char2type(char)
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* takes a character char that represents a type and returns the type
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specifier of the C language.
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* str = Symbol#proto()
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* returns the function prototype.
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* str = Symbol#name()
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* Returns the function name.
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* str = Symbol#cproto(),
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str = Symbol#to_s()
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* returns the prototype of the C language.
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* str = Symbol#inspect()
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* returns the inspectable string.
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* r,rs = Symbol#call(arg1,arg2,...,argN),
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r,rs = Symbol#[](arg1,arg2,...,argN)
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* calls the function with parameters arg1, arg2, ..., argN. and the result
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consists of the return value r and parameters rs. rs is an array.
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* ptr = Symbol#to_ptr
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* returns the corresponding PtrData object ptr.
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== PtrData class
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* ptr = PtrData.new(addr, [size = 0, free = nil])
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* returns the PtrData object representing the pointer which indicates the
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address addr. GC frees the memory using the free function.
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* PtrData#free=(sym)
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* If you specify a symbol object sym, GC frees the memory using the function
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represented by sym.
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* sym = PtrData#free
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* returns a symbol object sym which is used when GC frees the memory. it
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usually configured by `PtrData#free=' or `PtrData.new'.
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* size = PtrData#size, PtrData#size=(size)
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* gets and sets allocated size of the memory.
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* ary = PtrData#to_a(type, [size])
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* returns an array of the type which specified with type. type must be one of
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'S','P','I','L','D' and 'F'.
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* str = PtrData#to_s([len])
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* returns a string which length is len. if len is omitted, the end of the
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string is '\0'.
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* ptr = PtrData#ptr,+@
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* returns the pointed value as a PtrData object ptr.
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* ptr = PtrData#ref,-@
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* returns the reference as a PtrData object ptr.
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* ptr = PtrData#+
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* returns the PtrData object
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* ptr = PtrData#-
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* returns the PtrData object
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* PtrData#struct!(type, *members)
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* defines the data type to get access to a structure member with a symbol.
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(see also PtrData#[])
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* PtrData#union!(type, *members)
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* defines the data type to get access to a union member with a symbol. (see
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also PtrData#[])
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* val = PtrData#[key], PtrData#[key, num = 0]
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* if the key is a string or symbol, this method returns the value of the
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structure/union member which has the type defined by PtrData#
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{struct!,union!}. if the key is a integer value and this object represents
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the pointer ptr, it returns the value of `(ptr + key).to_s(num)'
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* PtrData#[key,num]=val, PtrData#[key]=val
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* if the key is a string or symbol, this method substitute the value of the
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structure/union member with val. if the key is a integer value and val is a
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string, this method copies num bytes of val to the memory area ptr using
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memcpy(3).
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== Type specifiers
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the prototype consists of the following type specifiers, first element of
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prototype represents the type of return value, and remaining elements represent
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the type of each argument.
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C : a character (char)
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c : a pointer to a character (char *)
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H : a short integer (short)
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h : a pointer to a short integer (short *)
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I : an integer (char, short, int)
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i : a pointer to an integer (char *, short *, int *)
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L : a long integer (long)
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l : a pointer to a long integer (long *)
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F : a real (float)
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f : a pointer to a real (float *)
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D : a real (double)
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d : a pointer to a real (double *)
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S : an immutable string (const char *)
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s : a mutable string (char *)
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A : an array (const type[])
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a : a mutable array (type[])
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P : a pointer (void *)
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p : a mutable object (void *)
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0 : void function (this must be a first character of the prototype)
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the cbtype consists of type specifiers 0, C, I, H, L, F, D, S and P.
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for example:
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DL.callback('IPP'){|ptr1,ptr2|
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str1 = ptr1.ptr.to_s
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str2 = ptr2.ptr.to_s
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str1 <=> str2
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}
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=end
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