Table of Contents
*****************

cffi-sys
1 Introduction
2 Built-In Foreign Types
3 Operations on Built-in Foreign Types
4 Basic Pointer Operations
5 Foreign Memory Allocation
6 Memory Access
7 Foreign Function Calling
8 Loading Foreign Libraries
9 Foreign Globals
Symbol Index


cffi-sys
********

Copyright (C) 2005-2006, James Bielman  <jamesjb at jamesjb.com>

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1 Introduction
**************

CFFI, the Common Foreign Function Interface, purports to be a portable
foreign function interface for Common Lisp.

   This specification defines a set of low-level primitives that must be
defined for each Lisp implementation supported by CFFI.  These
operators are defined in the `CFFI-SYS' package.

   The `CFFI' package uses the `CFFI-SYS' interface to implement an
extensible foreign type system with support for typedefs, structures,
and unions, a declarative interface for defining foreign function
calls, and automatic conversion of foreign function arguments to/from
Lisp types.

   Please note the following conventions that apply to everything in
`CFFI-SYS':

   * Functions in `CFFI-SYS' that are low-level versions of functions
     exported from the `CFFI' package begin with a leading percent-sign
     (eg. `%mem-ref').

   * Where "foreign type" is mentioned as the kind of an argument, the
     meaning is restricted to that subset of all foreign types defined
     in *Note Built-In Foreign Types::.  Support for higher-level types
     is always defined in terms of those lower-level types in `CFFI'
     proper.

2 Built-In Foreign Types
************************

 -- Foreign Type: :char
 -- Foreign Type: :unsigned-char
 -- Foreign Type: :short
 -- Foreign Type: :unsigned-short
 -- Foreign Type: :int
 -- Foreign Type: :unsigned-int
 -- Foreign Type: :long
 -- Foreign Type: :unsigned-long
 -- Foreign Type: :long-long
 -- Foreign Type: :unsigned-long-long
     These types correspond to the native C integer types according to
     the ABI of the system the Lisp implementation is compiled against.

 -- Foreign Type: :int8
 -- Foreign Type: :uint8
 -- Foreign Type: :int16
 -- Foreign Type: :uint16
 -- Foreign Type: :int32
 -- Foreign Type: :uint32
 -- Foreign Type: :int64
 -- Foreign Type: :uint64
     Foreign integer types of specific sizes, corresponding to the C
     types defined in `stdint.h'.

 -- Foreign Type: :size
 -- Foreign Type: :ssize
 -- Foreign Type: :ptrdiff
 -- Foreign Type: :time
     Foreign integer types corresponding to the standard C types
     (without the `_t' suffix).

   _Implementor's note: I'm sure there are more of these that could be
useful, let's add any types that can't be defined portably to this list
as necessary._

 -- Foreign Type: :float
 -- Foreign Type: :double
     The `:float' type represents a C `float' and a Lisp
     `single-float'. `:double' represents a C `double' and a Lisp
     `double-float'.

 -- Foreign Type: :pointer
     A foreign pointer to an object of any type, corresponding to `void
     *'.

 -- Foreign Type: :void
     No type at all. Only valid as the return type of a function.

3 Operations on Built-in Foreign Types
**************************************

 -- Function: %foreign-type-size type => size
     Return the SIZE, in bytes, of objects having foreign type TYPE. An
     error is signalled if TYPE is not a known built-in foreign type.

 -- Function: %foreign-type-alignment type => alignment
     Return the default alignment in bytes for structure members of
     foreign type TYPE. An error is signalled if TYPE is not a known
     built-in foreign type.

     _Implementor's note: Maybe this should take an optional keyword
     argument specifying an alternate alignment system, eg. :mac68k for
     68000-compatible alignment on Darwin._

4 Basic Pointer Operations
**************************

 -- Function: pointerp ptr => boolean
     Return true if PTR is a foreign pointer.

 -- Function: null-pointer => pointer
     Return a null foreign pointer.

 -- Function: null-pointer-p ptr => boolean
     Return true if PTR is a null foreign pointer.

 -- Function: make-pointer address => pointer
     Return a pointer corresponding to the numeric integer ADDRESS.

 -- Function: inc-pointer ptr offset => pointer
     Return the result of numerically incrementing PTR by OFFSET.

5 Foreign Memory Allocation
***************************

 -- Function: foreign-alloc size => pointer
     Allocate SIZE bytes of foreign-addressable memory and return a
     POINTER to the allocated block. An implementation-specific error
     is signalled if the memory cannot be allocated.

 -- Function: foreign-free ptr => unspecified
     Free a pointer PTR allocated by `foreign-alloc'. The results are
     undefined if PTR is used after being freed.

 -- Macro: with-foreign-pointer (var size &optional size-var) &body body
     Bind VAR to a pointer to SIZE bytes of foreign-accessible memory
     during BODY.  Both PTR and the memory block it points to have
     dynamic extent and may be stack allocated if supported by the
     implementation. If SIZE-VAR is supplied, it will be bound to SIZE
     during BODY.

6 Memory Access
***************

 -- Accessor: %mem-ref ptr type &optional offset
     Dereference a pointer OFFSET bytes from PTR to an object for
     reading (or writing when used with `setf') of built-in type TYPE.

Example
=======

     ;; An impractical example, since time returns the time as well,
     ;; but it demonstrates %MEM-REF. Better (simple) examples wanted!
     (with-foreign-pointer (p (foreign-type-size :time))
       (foreign-funcall "time" :pointer p :time)
       (%mem-ref p :time))

7 Foreign Function Calling
**************************

 -- Macro: %foreign-funcall name {arg-type arg}* &optional result-type
          => object
 -- Macro: %foreign-funcall-pointer ptr {arg-type arg}* &optional
          result-type => object
     Invoke a foreign function called NAME in the foreign source code.

     Each ARG-TYPE is a foreign type specifier, followed by ARG, Lisp
     data to be converted to foreign data of type ARG-TYPE.
     RESULT-TYPE is the foreign type of the function's return value,
     and is assumed to be `:void' if not supplied.

     `%foreign-funcall-pointer' takes a pointer PTR to the function, as
     returned by `foreign-symbol-pointer', rather than a string NAME.

Examples
========

     ;; Calling a standard C library function:
     (%foreign-funcall "sqrtf" :float 16.0 :float) => 4.0

     ;; Dynamic allocation of a buffer and passing to a function:
     (with-foreign-ptr (buf 255 buf-size)
       (%foreign-funcall "gethostname" :pointer buf :size buf-size :int)
       ;; Convert buf to a Lisp string using MAKE-STRING and %MEM-REF or
       ;; a portable CFFI function such as CFFI:FOREIGN-STRING-TO-LISP.
       )

8 Loading Foreign Libraries
***************************

 -- Function: %load-foreign-library name => unspecified
     Load the foreign shared library NAME.

     _Implementor's note: There is a lot of behavior to decide here.
     Currently I lean toward not requiring NAME to be a full path to
     the library so we can search the system library directories (maybe
     even get LD_LIBRARY_PATH from the environment) as necessary._

9 Foreign Globals
*****************

 -- Function: foreign-symbol-pointer name => pointer
     Return a pointer to a foreign symbol NAME.

Symbol Index
************

%foreign-funcall:                              See 7.         (line 196)
%foreign-funcall-pointer:                      See 7.         (line 198)
%foreign-type-alignment:                       See 3.         (line 130)
%foreign-type-size:                            See 3.         (line 126)
%load-foreign-library:                         See 8.         (line 225)
%mem-ref:                                      See 6.         (line 179)
:char:                                         See 2.         (line  75)
:double:                                       See 2.         (line 111)
:float:                                        See 2.         (line 110)
:int:                                          See 2.         (line  79)
:int16:                                        See 2.         (line  90)
:int32:                                        See 2.         (line  92)
:int64:                                        See 2.         (line  94)
:int8:                                         See 2.         (line  88)
:long:                                         See 2.         (line  81)
:long-long:                                    See 2.         (line  83)
:pointer:                                      See 2.         (line 116)
:ptrdiff:                                      See 2.         (line 101)
:short:                                        See 2.         (line  77)
:size:                                         See 2.         (line  99)
:ssize:                                        See 2.         (line 100)
:time:                                         See 2.         (line 102)
:uint16:                                       See 2.         (line  91)
:uint32:                                       See 2.         (line  93)
:uint64:                                       See 2.         (line  95)
:uint8:                                        See 2.         (line  89)
:unsigned-char:                                See 2.         (line  76)
:unsigned-int:                                 See 2.         (line  80)
:unsigned-long:                                See 2.         (line  82)
:unsigned-long-long:                           See 2.         (line  84)
:unsigned-short:                               See 2.         (line  78)
:void:                                         See 2.         (line 120)
foreign-alloc:                                 See 5.         (line 160)
foreign-free:                                  See 5.         (line 165)
foreign-symbol-pointer:                        See 9.         (line 236)
inc-pointer:                                   See 4.         (line 154)
make-pointer:                                  See 4.         (line 151)
null-pointer:                                  See 4.         (line 145)
null-pointer-p:                                See 4.         (line 148)
pointerp:                                      See 4.         (line 142)
with-foreign-pointer:                          See 5.         (line 169)
