\input texinfo   @c -*-texinfo-*-
@c %**start of header
@setfilename cffi-sys.info
@settitle CFFI-SYS Interface Specification

@c Show types in the same index as the functions.
@synindex tp fn

@copying
Copyright @copyright{} 2005-2006, James Bielman  <jamesjb at jamesjb.com>

@quotation
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the ``Software''), to deal in the Software without
restriction, including without limitation the rights to use, copy,
modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

@sc{The software is provided ``as is'', without warranty of any kind,
express or implied, including but not limited to the warranties of
merchantability, fitness for a particular purpose and
noninfringement.  In no event shall the authors or copyright
holders be liable for any claim, damages or other liability,
whether in an action of contract, tort or otherwise, arising from,
out of or in connection with the software or the use or other
dealings in the software.}
@end quotation
@end copying

@macro impnote {text}
@emph{Implementor's note: \text\}
@end macro
@c %**end of header

@dircategory Software development
@direntry
* CFFI Sys spec: (cffi-sys-spec).       CFFI Sys spec.
@end direntry

@titlepage
@title CFFI-SYS Interface Specification
@c @subtitle Version X.X
@c @author James Bielman

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top cffi-sys
@insertcopying
@end ifnottex

@menu
* Introduction::                
* Built-In Foreign Types::      
* Operations on Foreign Types::  
* Basic Pointer Operations::    
* Foreign Memory Allocation::   
* Memory Access::               
* Foreign Function Calling::    
* Loading Foreign Libraries::   
* Foreign Globals::             
* Symbol Index::                
@end menu

@node Introduction
@chapter Introduction

@acronym{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 @acronym{CFFI}.
These operators are defined in the @code{CFFI-SYS} package.

The @code{CFFI} package uses the @code{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
@code{CFFI-SYS}:

@itemize @bullet
@item
Functions in @code{CFFI-SYS} that are low-level versions of functions
exported from the @code{CFFI} package begin with a leading
percent-sign (eg. @code{%mem-ref}).

@item
Where ``foreign type'' is mentioned as the kind of an argument, the
meaning is restricted to that subset of all foreign types defined in
@ref{Built-In Foreign Types}.  Support for higher-level types is
always defined in terms of those lower-level types in @code{CFFI}
proper.
@end itemize


@node Built-In Foreign Types
@chapter Built-In Foreign Types

@deftp {Foreign Type} :char
@deftpx {Foreign Type} :unsigned-char
@deftpx {Foreign Type} :short
@deftpx {Foreign Type} :unsigned-short
@deftpx {Foreign Type} :int
@deftpx {Foreign Type} :unsigned-int
@deftpx {Foreign Type} :long
@deftpx {Foreign Type} :unsigned-long
@deftpx {Foreign Type} :long-long
@deftpx {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.
@end deftp

@deftp {Foreign Type} :int8
@deftpx {Foreign Type} :uint8
@deftpx {Foreign Type} :int16
@deftpx {Foreign Type} :uint16
@deftpx {Foreign Type} :int32
@deftpx {Foreign Type} :uint32
@deftpx {Foreign Type} :int64
@deftpx {Foreign Type} :uint64
Foreign integer types of specific sizes, corresponding to the C types
defined in @code{stdint.h}.
@end deftp

@deftp {Foreign Type} :size
@deftpx {Foreign Type} :ssize
@deftpx {Foreign Type} :ptrdiff
@deftpx {Foreign Type} :time
Foreign integer types corresponding to the standard C types (without
the @code{_t} suffix).
@end deftp

@impnote{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.}

@deftp {Foreign Type} :float
@deftpx {Foreign Type} :double
The @code{:float} type represents a C @code{float} and a Lisp
@code{single-float}. @code{:double} represents a C @code{double} and a
Lisp @code{double-float}.
@end deftp

@deftp {Foreign Type} :pointer
A foreign pointer to an object of any type, corresponding to
@code{void *}.
@end deftp

@deftp {Foreign Type} :void
No type at all. Only valid as the return type of a function.
@end deftp


@node Operations on Foreign Types
@chapter Operations on Built-in Foreign Types

@defun %foreign-type-size type @result{} size
Return the @var{size}, in bytes, of objects having foreign type
@var{type}. An error is signalled if @var{type} is not a known
built-in foreign type.
@end defun

@defun %foreign-type-alignment type @result{} alignment
Return the default alignment in bytes for structure members of foreign
type @var{type}. An error is signalled if @var{type} is not a known
built-in foreign type.

@impnote{Maybe this should take an optional keyword argument specifying an
alternate alignment system, eg. :mac68k for 68000-compatible alignment
on Darwin.}
@end defun


@node Basic Pointer Operations
@chapter Basic Pointer Operations

@defun pointerp ptr @result{} boolean
Return true if @var{ptr} is a foreign pointer.
@end defun

@defun null-pointer @result{} pointer
Return a null foreign pointer.
@end defun

@defun null-pointer-p ptr @result{} boolean
Return true if @var{ptr} is a null foreign pointer.
@end defun

@defun make-pointer address @result{} pointer
Return a pointer corresponding to the numeric integer @var{address}.
@end defun

@defun inc-pointer ptr offset @result{} pointer
Return the result of numerically incrementing @var{ptr} by @var{offset}.
@end defun


@node Foreign Memory Allocation
@chapter Foreign Memory Allocation

@defun foreign-alloc size @result{} pointer
Allocate @var{size} bytes of foreign-addressable memory and return
a @var{pointer} to the allocated block. An implementation-specific
error is signalled if the memory cannot be allocated.
@end defun

@defun foreign-free ptr @result{} unspecified
Free a pointer @var{ptr} allocated by @code{foreign-alloc}. The
results are undefined if @var{ptr} is used after being freed.
@end defun

@defmac with-foreign-pointer (var size &optional size-var) &body body
Bind @var{var} to a pointer to @var{size} bytes of
foreign-accessible memory during @var{body}.  Both @var{ptr} and the
memory block it points to have dynamic extent and may be stack
allocated if supported by the implementation. If @var{size-var} is
supplied, it will be bound to @var{size} during @var{body}.
@end defmac


@node Memory Access
@chapter Memory Access

@deffn {Accessor} %mem-ref ptr type &optional offset
Dereference a pointer @var{offset} bytes from @var{ptr} to an object
for reading (or writing when used with @code{setf}) of built-in type
@var{type}.
@end deffn

@heading Example

@lisp
;; 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))
@end lisp


@node Foreign Function Calling
@chapter Foreign Function Calling

@defmac %foreign-funcall name @{arg-type arg@}* &optional result-type @result{} object
@defmacx %foreign-funcall-pointer ptr @{arg-type arg@}* &optional result-type @result{} object
Invoke a foreign function called @var{name} in the foreign source code.

Each @var{arg-type} is a foreign type specifier, followed by
@var{arg}, Lisp data to be converted to foreign data of type
@var{arg-type}.  @var{result-type} is the foreign type of the
function's return value, and is assumed to be @code{:void} if not
supplied.

@code{%foreign-funcall-pointer} takes a pointer @var{ptr} to the
function, as returned by @code{foreign-symbol-pointer}, rather than a
string @var{name}.
@end defmac

@defmac %foreign-funcall-varargs name (@{fixed-type arg@}*) @{vararg-type arg@}* &optional result-type @result{} object
@defmacx %foreign-funcall-varargs-pointer ptr (@{fixed-type arg@}*) @{vararg-type arg@}* &optional result-type @result{} object
Invoke a foreign variadic function called @var{name} in the foreign
source code.

Each @var{fixed-type} and @var{vararg-type} is a foreign type
specifier, followed by @var{arg}, Lisp data to be converted to foreign
data of type @var{arg-type}.  @var{result-type} is the foreign type of
the function's return value, and is assumed to be @code{:void} if not
supplied.

@code{%foreign-funcall-pointer-varargs} takes a pointer @var{ptr} to
the variadic function, as returned by @code{foreign-symbol-pointer},
rather than a string @var{name}.

Both functions have default implementation which call
@code{%foreign-funcall} and @code{%foreign-funcall-pointer}
approprietly.
@end defmac

@heading Examples

@lisp
;; Calling a standard C library function:
(%foreign-funcall "sqrtf" :float 16.0 :float) @result{} 4.0
@end lisp

@lisp
;; 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.
  )
@end lisp


@node Loading Foreign Libraries
@chapter Loading Foreign Libraries

@defun %load-foreign-library name @result{} unspecified
Load the foreign shared library @var{name}.

@impnote{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.}
@end defun


@node Foreign Globals
@chapter Foreign Globals

@defun foreign-symbol-pointer name @result{} pointer
Return a pointer to a foreign symbol @var{name}.
@end defun

@node Symbol Index
@unnumbered Symbol Index
@printindex fn

@bye