Merge pull request #97 from joshtriplett/remove-more-generated-files
Remove more generated files
This commit is contained in:
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doc/libffi.info
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doc/libffi.info
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This is libffi.info, produced by makeinfo version 5.1 from libffi.texi.
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This manual is for Libffi, a portable foreign-function interface
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library.
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Copyright (C) 2008, 2010, 2011 Red Hat, Inc.
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Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU General Public License as
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||||||
published by the Free Software Foundation; either version 2, or (at
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your option) any later version. A copy of the license is included
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||||||
in the section entitled "GNU General Public License".
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INFO-DIR-SECTION Development
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START-INFO-DIR-ENTRY
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* libffi: (libffi). Portable foreign-function interface library.
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END-INFO-DIR-ENTRY
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File: libffi.info, Node: Top, Next: Introduction, Up: (dir)
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libffi
|
|
||||||
******
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|
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||||||
This manual is for Libffi, a portable foreign-function interface
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|
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library.
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|
||||||
|
|
||||||
Copyright (C) 2008, 2010, 2011 Red Hat, Inc.
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||||||
Permission is granted to copy, distribute and/or modify this
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|
||||||
document under the terms of the GNU General Public License as
|
|
||||||
published by the Free Software Foundation; either version 2, or (at
|
|
||||||
your option) any later version. A copy of the license is included
|
|
||||||
in the section entitled "GNU General Public License".
|
|
||||||
|
|
||||||
* Menu:
|
|
||||||
|
|
||||||
* Introduction:: What is libffi?
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|
||||||
* Using libffi:: How to use libffi.
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||||||
* Missing Features:: Things libffi can't do.
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|
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* Index:: Index.
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File: libffi.info, Node: Introduction, Next: Using libffi, Prev: Top, Up: Top
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1 What is libffi?
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*****************
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|
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Compilers for high level languages generate code that follow certain
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|
||||||
conventions. These conventions are necessary, in part, for separate
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compilation to work. One such convention is the "calling convention".
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||||||
The calling convention is a set of assumptions made by the compiler
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||||||
about where function arguments will be found on entry to a function. A
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calling convention also specifies where the return value for a function
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is found. The calling convention is also sometimes called the "ABI" or
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"Application Binary Interface".
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Some programs may not know at the time of compilation what arguments
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are to be passed to a function. For instance, an interpreter may be
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told at run-time about the number and types of arguments used to call a
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given function. 'Libffi' can be used in such programs to provide a
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bridge from the interpreter program to compiled code.
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The 'libffi' library provides a portable, high level programming
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interface to various calling conventions. This allows a programmer to
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call any function specified by a call interface description at run time.
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FFI stands for Foreign Function Interface. A foreign function
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interface is the popular name for the interface that allows code written
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in one language to call code written in another language. The 'libffi'
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library really only provides the lowest, machine dependent layer of a
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fully featured foreign function interface. A layer must exist above
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'libffi' that handles type conversions for values passed between the two
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languages.
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File: libffi.info, Node: Using libffi, Next: Missing Features, Prev: Introduction, Up: Top
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2 Using libffi
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**************
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* Menu:
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||||||
|
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||||||
* The Basics:: The basic libffi API.
|
|
||||||
* Simple Example:: A simple example.
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|
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* Types:: libffi type descriptions.
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||||||
* Multiple ABIs:: Different passing styles on one platform.
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||||||
* The Closure API:: Writing a generic function.
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|
||||||
* Closure Example:: A closure example.
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||||||
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File: libffi.info, Node: The Basics, Next: Simple Example, Up: Using libffi
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2.1 The Basics
|
|
||||||
==============
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'Libffi' assumes that you have a pointer to the function you wish to
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|
||||||
call and that you know the number and types of arguments to pass it, as
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|
||||||
well as the return type of the function.
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|
||||||
|
|
||||||
The first thing you must do is create an 'ffi_cif' object that
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|
||||||
matches the signature of the function you wish to call. This is a
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|
||||||
separate step because it is common to make multiple calls using a single
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'ffi_cif'. The "cif" in 'ffi_cif' stands for Call InterFace. To
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|
||||||
prepare a call interface object, use the function 'ffi_prep_cif'.
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||||||
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-- Function: ffi_status ffi_prep_cif (ffi_cif *CIF, ffi_abi ABI,
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||||||
unsigned int NARGS, ffi_type *RTYPE, ffi_type **ARGTYPES)
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||||||
This initializes CIF according to the given parameters.
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||||||
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||||||
ABI is the ABI to use; normally 'FFI_DEFAULT_ABI' is what you want.
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|
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*note Multiple ABIs:: for more information.
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NARGS is the number of arguments that this function accepts.
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||||||
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RTYPE is a pointer to an 'ffi_type' structure that describes the
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return type of the function. *Note Types::.
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ARGTYPES is a vector of 'ffi_type' pointers. ARGTYPES must have
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|
||||||
NARGS elements. If NARGS is 0, this argument is ignored.
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'ffi_prep_cif' returns a 'libffi' status code, of type
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||||||
'ffi_status'. This will be either 'FFI_OK' if everything worked
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||||||
properly; 'FFI_BAD_TYPEDEF' if one of the 'ffi_type' objects is
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||||||
incorrect; or 'FFI_BAD_ABI' if the ABI parameter is invalid.
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If the function being called is variadic (varargs) then
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'ffi_prep_cif_var' must be used instead of 'ffi_prep_cif'.
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-- Function: ffi_status ffi_prep_cif_var (ffi_cif *CIF, ffi_abi varabi,
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||||||
unsigned int NFIXEDARGS, unsigned int varntotalargs, ffi_type
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||||||
*RTYPE, ffi_type **ARGTYPES)
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This initializes CIF according to the given parameters for a call
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to a variadic function. In general it's operation is the same as
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||||||
for 'ffi_prep_cif' except that:
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NFIXEDARGS is the number of fixed arguments, prior to any variadic
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|
||||||
arguments. It must be greater than zero.
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||||||
|
|
||||||
NTOTALARGS the total number of arguments, including variadic and
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||||||
fixed arguments.
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|
||||||
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||||||
Note that, different cif's must be prepped for calls to the same
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|
||||||
function when different numbers of arguments are passed.
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||||||
|
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||||||
Also note that a call to 'ffi_prep_cif_var' with
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|
||||||
NFIXEDARGS=NOTOTALARGS is NOT equivalent to a call to
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|
||||||
'ffi_prep_cif'.
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|
||||||
|
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||||||
To call a function using an initialized 'ffi_cif', use the 'ffi_call'
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||||||
function:
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||||||
|
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||||||
-- Function: void ffi_call (ffi_cif *CIF, void *FN, void *RVALUE, void
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||||||
**AVALUES)
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||||||
This calls the function FN according to the description given in
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|
||||||
CIF. CIF must have already been prepared using 'ffi_prep_cif'.
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||||||
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RVALUE is a pointer to a chunk of memory that will hold the result
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|
||||||
of the function call. This must be large enough to hold the
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||||||
result, no smaller than the system register size (generally 32 or
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||||||
64 bits), and must be suitably aligned; it is the caller's
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|
||||||
responsibility to ensure this. If CIF declares that the function
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|
||||||
returns 'void' (using 'ffi_type_void'), then RVALUE is ignored.
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||||||
AVALUES is a vector of 'void *' pointers that point to the memory
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|
||||||
locations holding the argument values for a call. If CIF declares
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||||||
that the function has no arguments (i.e., NARGS was 0), then
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|
||||||
AVALUES is ignored. Note that argument values may be modified by
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||||||
the callee (for instance, structs passed by value); the burden of
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||||||
copying pass-by-value arguments is placed on the caller.
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File: libffi.info, Node: Simple Example, Next: Types, Prev: The Basics, Up: Using libffi
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2.2 Simple Example
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||||||
==================
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||||||
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||||||
Here is a trivial example that calls 'puts' a few times.
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#include <stdio.h>
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#include <ffi.h>
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int main()
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{
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ffi_cif cif;
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||||||
ffi_type *args[1];
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||||||
void *values[1];
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||||||
char *s;
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ffi_arg rc;
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||||||
|
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||||||
/* Initialize the argument info vectors */
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||||||
args[0] = &ffi_type_pointer;
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|
||||||
values[0] = &s;
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||||||
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||||||
/* Initialize the cif */
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||||||
if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1,
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&ffi_type_sint, args) == FFI_OK)
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{
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s = "Hello World!";
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||||||
ffi_call(&cif, puts, &rc, values);
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|
||||||
/* rc now holds the result of the call to puts */
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||||||
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||||||
/* values holds a pointer to the function's arg, so to
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||||||
call puts() again all we need to do is change the
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||||||
value of s */
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s = "This is cool!";
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||||||
ffi_call(&cif, puts, &rc, values);
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}
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return 0;
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}
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File: libffi.info, Node: Types, Next: Multiple ABIs, Prev: Simple Example, Up: Using libffi
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2.3 Types
|
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||||||
=========
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||||||
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* Menu:
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||||||
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||||||
* Primitive Types:: Built-in types.
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||||||
* Structures:: Structure types.
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||||||
* Type Example:: Structure type example.
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File: libffi.info, Node: Primitive Types, Next: Structures, Up: Types
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2.3.1 Primitive Types
|
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||||||
---------------------
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'Libffi' provides a number of built-in type descriptors that can be used
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||||||
to describe argument and return types:
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||||||
|
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||||||
'ffi_type_void'
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The type 'void'. This cannot be used for argument types, only for
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return values.
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'ffi_type_uint8'
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An unsigned, 8-bit integer type.
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'ffi_type_sint8'
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A signed, 8-bit integer type.
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'ffi_type_uint16'
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An unsigned, 16-bit integer type.
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||||||
'ffi_type_sint16'
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||||||
A signed, 16-bit integer type.
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'ffi_type_uint32'
|
|
||||||
An unsigned, 32-bit integer type.
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||||||
|
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||||||
'ffi_type_sint32'
|
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A signed, 32-bit integer type.
|
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||||||
|
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'ffi_type_uint64'
|
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An unsigned, 64-bit integer type.
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'ffi_type_sint64'
|
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||||||
A signed, 64-bit integer type.
|
|
||||||
|
|
||||||
'ffi_type_float'
|
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The C 'float' type.
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'ffi_type_double'
|
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||||||
The C 'double' type.
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|
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'ffi_type_uchar'
|
|
||||||
The C 'unsigned char' type.
|
|
||||||
|
|
||||||
'ffi_type_schar'
|
|
||||||
The C 'signed char' type. (Note that there is not an exact
|
|
||||||
equivalent to the C 'char' type in 'libffi'; ordinarily you should
|
|
||||||
either use 'ffi_type_schar' or 'ffi_type_uchar' depending on
|
|
||||||
whether 'char' is signed.)
|
|
||||||
|
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||||||
'ffi_type_ushort'
|
|
||||||
The C 'unsigned short' type.
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|
||||||
|
|
||||||
'ffi_type_sshort'
|
|
||||||
The C 'short' type.
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|
||||||
|
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'ffi_type_uint'
|
|
||||||
The C 'unsigned int' type.
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|
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'ffi_type_sint'
|
|
||||||
The C 'int' type.
|
|
||||||
|
|
||||||
'ffi_type_ulong'
|
|
||||||
The C 'unsigned long' type.
|
|
||||||
|
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||||||
'ffi_type_slong'
|
|
||||||
The C 'long' type.
|
|
||||||
|
|
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'ffi_type_longdouble'
|
|
||||||
On platforms that have a C 'long double' type, this is defined. On
|
|
||||||
other platforms, it is not.
|
|
||||||
|
|
||||||
'ffi_type_pointer'
|
|
||||||
A generic 'void *' pointer. You should use this for all pointers,
|
|
||||||
regardless of their real type.
|
|
||||||
|
|
||||||
Each of these is of type 'ffi_type', so you must take the address
|
|
||||||
when passing to 'ffi_prep_cif'.
|
|
||||||
|
|
||||||
|
|
||||||
File: libffi.info, Node: Structures, Next: Type Example, Prev: Primitive Types, Up: Types
|
|
||||||
|
|
||||||
2.3.2 Structures
|
|
||||||
----------------
|
|
||||||
|
|
||||||
Although 'libffi' has no special support for unions or bit-fields, it is
|
|
||||||
perfectly happy passing structures back and forth. You must first
|
|
||||||
describe the structure to 'libffi' by creating a new 'ffi_type' object
|
|
||||||
for it.
|
|
||||||
|
|
||||||
-- Data type: ffi_type
|
|
||||||
The 'ffi_type' has the following members:
|
|
||||||
'size_t size'
|
|
||||||
This is set by 'libffi'; you should initialize it to zero.
|
|
||||||
|
|
||||||
'unsigned short alignment'
|
|
||||||
This is set by 'libffi'; you should initialize it to zero.
|
|
||||||
|
|
||||||
'unsigned short type'
|
|
||||||
For a structure, this should be set to 'FFI_TYPE_STRUCT'.
|
|
||||||
|
|
||||||
'ffi_type **elements'
|
|
||||||
This is a 'NULL'-terminated array of pointers to 'ffi_type'
|
|
||||||
objects. There is one element per field of the struct.
|
|
||||||
|
|
||||||
|
|
||||||
File: libffi.info, Node: Type Example, Prev: Structures, Up: Types
|
|
||||||
|
|
||||||
2.3.3 Type Example
|
|
||||||
------------------
|
|
||||||
|
|
||||||
The following example initializes a 'ffi_type' object representing the
|
|
||||||
'tm' struct from Linux's 'time.h'.
|
|
||||||
|
|
||||||
Here is how the struct is defined:
|
|
||||||
|
|
||||||
struct tm {
|
|
||||||
int tm_sec;
|
|
||||||
int tm_min;
|
|
||||||
int tm_hour;
|
|
||||||
int tm_mday;
|
|
||||||
int tm_mon;
|
|
||||||
int tm_year;
|
|
||||||
int tm_wday;
|
|
||||||
int tm_yday;
|
|
||||||
int tm_isdst;
|
|
||||||
/* Those are for future use. */
|
|
||||||
long int __tm_gmtoff__;
|
|
||||||
__const char *__tm_zone__;
|
|
||||||
};
|
|
||||||
|
|
||||||
Here is the corresponding code to describe this struct to 'libffi':
|
|
||||||
|
|
||||||
{
|
|
||||||
ffi_type tm_type;
|
|
||||||
ffi_type *tm_type_elements[12];
|
|
||||||
int i;
|
|
||||||
|
|
||||||
tm_type.size = tm_type.alignment = 0;
|
|
||||||
tm_type.type = FFI_TYPE_STRUCT;
|
|
||||||
tm_type.elements = &tm_type_elements;
|
|
||||||
|
|
||||||
for (i = 0; i < 9; i++)
|
|
||||||
tm_type_elements[i] = &ffi_type_sint;
|
|
||||||
|
|
||||||
tm_type_elements[9] = &ffi_type_slong;
|
|
||||||
tm_type_elements[10] = &ffi_type_pointer;
|
|
||||||
tm_type_elements[11] = NULL;
|
|
||||||
|
|
||||||
/* tm_type can now be used to represent tm argument types and
|
|
||||||
return types for ffi_prep_cif() */
|
|
||||||
}
|
|
||||||
|
|
||||||
|
|
||||||
File: libffi.info, Node: Multiple ABIs, Next: The Closure API, Prev: Types, Up: Using libffi
|
|
||||||
|
|
||||||
2.4 Multiple ABIs
|
|
||||||
=================
|
|
||||||
|
|
||||||
A given platform may provide multiple different ABIs at once. For
|
|
||||||
instance, the x86 platform has both 'stdcall' and 'fastcall' functions.
|
|
||||||
|
|
||||||
'libffi' provides some support for this. However, this is
|
|
||||||
necessarily platform-specific.
|
|
||||||
|
|
||||||
|
|
||||||
File: libffi.info, Node: The Closure API, Next: Closure Example, Prev: Multiple ABIs, Up: Using libffi
|
|
||||||
|
|
||||||
2.5 The Closure API
|
|
||||||
===================
|
|
||||||
|
|
||||||
'libffi' also provides a way to write a generic function - a function
|
|
||||||
that can accept and decode any combination of arguments. This can be
|
|
||||||
useful when writing an interpreter, or to provide wrappers for arbitrary
|
|
||||||
functions.
|
|
||||||
|
|
||||||
This facility is called the "closure API". Closures are not supported
|
|
||||||
on all platforms; you can check the 'FFI_CLOSURES' define to determine
|
|
||||||
whether they are supported on the current platform.
|
|
||||||
|
|
||||||
Because closures work by assembling a tiny function at runtime, they
|
|
||||||
require special allocation on platforms that have a non-executable heap.
|
|
||||||
Memory management for closures is handled by a pair of functions:
|
|
||||||
|
|
||||||
-- Function: void *ffi_closure_alloc (size_t SIZE, void **CODE)
|
|
||||||
Allocate a chunk of memory holding SIZE bytes. This returns a
|
|
||||||
pointer to the writable address, and sets *CODE to the
|
|
||||||
corresponding executable address.
|
|
||||||
|
|
||||||
SIZE should be sufficient to hold a 'ffi_closure' object.
|
|
||||||
|
|
||||||
-- Function: void ffi_closure_free (void *WRITABLE)
|
|
||||||
Free memory allocated using 'ffi_closure_alloc'. The argument is
|
|
||||||
the writable address that was returned.
|
|
||||||
|
|
||||||
Once you have allocated the memory for a closure, you must construct
|
|
||||||
a 'ffi_cif' describing the function call. Finally you can prepare the
|
|
||||||
closure function:
|
|
||||||
|
|
||||||
-- Function: ffi_status ffi_prep_closure_loc (ffi_closure *CLOSURE,
|
|
||||||
ffi_cif *CIF, void (*FUN) (ffi_cif *CIF, void *RET, void
|
|
||||||
**ARGS, void *USER_DATA), void *USER_DATA, void *CODELOC)
|
|
||||||
Prepare a closure function.
|
|
||||||
|
|
||||||
CLOSURE is the address of a 'ffi_closure' object; this is the
|
|
||||||
writable address returned by 'ffi_closure_alloc'.
|
|
||||||
|
|
||||||
CIF is the 'ffi_cif' describing the function parameters.
|
|
||||||
|
|
||||||
USER_DATA is an arbitrary datum that is passed, uninterpreted, to
|
|
||||||
your closure function.
|
|
||||||
|
|
||||||
CODELOC is the executable address returned by 'ffi_closure_alloc'.
|
|
||||||
|
|
||||||
FUN is the function which will be called when the closure is
|
|
||||||
invoked. It is called with the arguments:
|
|
||||||
CIF
|
|
||||||
The 'ffi_cif' passed to 'ffi_prep_closure_loc'.
|
|
||||||
|
|
||||||
RET
|
|
||||||
A pointer to the memory used for the function's return value.
|
|
||||||
FUN must fill this, unless the function is declared as
|
|
||||||
returning 'void'.
|
|
||||||
|
|
||||||
ARGS
|
|
||||||
A vector of pointers to memory holding the arguments to the
|
|
||||||
function.
|
|
||||||
|
|
||||||
USER_DATA
|
|
||||||
The same USER_DATA that was passed to 'ffi_prep_closure_loc'.
|
|
||||||
|
|
||||||
'ffi_prep_closure_loc' will return 'FFI_OK' if everything went ok,
|
|
||||||
and something else on error.
|
|
||||||
|
|
||||||
After calling 'ffi_prep_closure_loc', you can cast CODELOC to the
|
|
||||||
appropriate pointer-to-function type.
|
|
||||||
|
|
||||||
You may see old code referring to 'ffi_prep_closure'. This function
|
|
||||||
is deprecated, as it cannot handle the need for separate writable and
|
|
||||||
executable addresses.
|
|
||||||
|
|
||||||
|
|
||||||
File: libffi.info, Node: Closure Example, Prev: The Closure API, Up: Using libffi
|
|
||||||
|
|
||||||
2.6 Closure Example
|
|
||||||
===================
|
|
||||||
|
|
||||||
A trivial example that creates a new 'puts' by binding 'fputs' with
|
|
||||||
'stdin'.
|
|
||||||
|
|
||||||
#include <stdio.h>
|
|
||||||
#include <ffi.h>
|
|
||||||
|
|
||||||
/* Acts like puts with the file given at time of enclosure. */
|
|
||||||
void puts_binding(ffi_cif *cif, void *ret, void* args[],
|
|
||||||
void *stream)
|
|
||||||
{
|
|
||||||
*(ffi_arg *)ret = fputs(*(char **)args[0], (FILE *)stream);
|
|
||||||
}
|
|
||||||
|
|
||||||
typedef int (*puts_t)(char *);
|
|
||||||
|
|
||||||
int main()
|
|
||||||
{
|
|
||||||
ffi_cif cif;
|
|
||||||
ffi_type *args[1];
|
|
||||||
ffi_closure *closure;
|
|
||||||
|
|
||||||
void *bound_puts;
|
|
||||||
int rc;
|
|
||||||
|
|
||||||
/* Allocate closure and bound_puts */
|
|
||||||
closure = ffi_closure_alloc(sizeof(ffi_closure), &bound_puts);
|
|
||||||
|
|
||||||
if (closure)
|
|
||||||
{
|
|
||||||
/* Initialize the argument info vectors */
|
|
||||||
args[0] = &ffi_type_pointer;
|
|
||||||
|
|
||||||
/* Initialize the cif */
|
|
||||||
if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1,
|
|
||||||
&ffi_type_sint, args) == FFI_OK)
|
|
||||||
{
|
|
||||||
/* Initialize the closure, setting stream to stdout */
|
|
||||||
if (ffi_prep_closure_loc(closure, &cif, puts_binding,
|
|
||||||
stdout, bound_puts) == FFI_OK)
|
|
||||||
{
|
|
||||||
rc = ((puts_t)bound_puts)("Hello World!");
|
|
||||||
/* rc now holds the result of the call to fputs */
|
|
||||||
}
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
/* Deallocate both closure, and bound_puts */
|
|
||||||
ffi_closure_free(closure);
|
|
||||||
|
|
||||||
return 0;
|
|
||||||
}
|
|
||||||
|
|
||||||
|
|
||||||
File: libffi.info, Node: Missing Features, Next: Index, Prev: Using libffi, Up: Top
|
|
||||||
|
|
||||||
3 Missing Features
|
|
||||||
******************
|
|
||||||
|
|
||||||
'libffi' is missing a few features. We welcome patches to add support
|
|
||||||
for these.
|
|
||||||
|
|
||||||
* Variadic closures.
|
|
||||||
|
|
||||||
* There is no support for bit fields in structures.
|
|
||||||
|
|
||||||
* The closure API is
|
|
||||||
|
|
||||||
* The "raw" API is undocumented.
|
|
||||||
|
|
||||||
Note that variadic support is very new and tested on a relatively
|
|
||||||
small number of platforms.
|
|
||||||
|
|
||||||
|
|
||||||
File: libffi.info, Node: Index, Prev: Missing Features, Up: Top
|
|
||||||
|
|
||||||
Index
|
|
||||||
*****
|
|
||||||
|
|
||||||
| |||||||