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 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. 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. 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)