X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=doc%2Fmanual%2Fffi.texinfo;h=0c4eb4945875a66264c11a3be5ea49e4c3b3d2b0;hb=43df38a2fe89c376ee6791899ec52736054dcfb0;hp=0b1f2c0f89751e78c27ad4ec532969d30585676f;hpb=53f4147704fbe48c03dd73d7b6a9f92c0a066ed8;p=sbcl.git diff --git a/doc/manual/ffi.texinfo b/doc/manual/ffi.texinfo index 0b1f2c0..0c4eb49 100644 --- a/doc/manual/ffi.texinfo +++ b/doc/manual/ffi.texinfo @@ -3,7 +3,7 @@ @chapter Foreign Function Interface This chapter describes SBCL's interface to C programs and -libraries (and, since C interfaces are a sort of @emph{ingua +libraries (and, since C interfaces are a sort of @emph{lingua franca} of the Unix world, to other programs and libraries in general.) @@ -49,12 +49,11 @@ by the Lisp implementation. This can require a considerable amount of dependent on the internal implementation details of the Lisp system. @item -The Lisp system can automatically convert objects back and forth -between the Lisp and foreign representations. This is convenient, but +The Lisp system can automatically convert objects back and forth between +the Lisp and foreign representations. This is convenient, but translation becomes prohibitively slow when large or complex data structures must be shared. This approach is supported by the SBCL -@acronym{FFI}, and used automatically by the when passing integers and -strings. +@acronym{FFI}, and used automatically when passing integers and strings. @item The Lisp program can directly manipulate foreign objects through the @@ -64,7 +63,7 @@ use of extensions to the Lisp language. SBCL, like CMUCL before it, relies primarily on the automatic conversion and direct manipulation approaches. The @code{SB-ALIEN} -package provices a facility wherein foreign values of simple scalar +package provides a facility wherein foreign values of simple scalar types are automatically converted and complex types are directly manipulated in their foreign representation. Additionally the lower-level System Area Pointers (or @acronym{SAP}s) can be used where @@ -196,8 +195,10 @@ variables. Dynamic arrays can only be allocated using The foreign type specifier @code{(sb-alien:struct @var{name} &rest @var{fields})} describes a structure type with the specified @var{name} and @var{fields}. Fields are allocated at the same offsets -used by the implementation's C compiler. If @var{name} is @code{nil} -then the structure is anonymous. +used by the implementation's C compiler, as guessed by the SBCL +internals. An optional @code{:alignment} keyword argument can be +specified for each field to explicitly control the alignment of a +field. If @var{name} is @code{nil} then the structure is anonymous. If a named foreign @code{struct} specifier is passed to @code{define-alien-type} or @code{with-alien}, then this defines, @@ -216,9 +217,9 @@ determine which field is active from context. @item The foreign type specifier @code{(sb-alien:enum @var{name} &rest @var{specs})} describes an enumeration type that maps between integer -values and keywords. If @var{name} is @code{nil}, then the type is +values and symbols. If @var{name} is @code{nil}, then the type is anonymous. Each element of the @var{specs} list is either a Lisp -keyword, or a list @code{(@var{keyword} @var{value})}. @var{value} is +symbol, or a list @code{(@var{symbol} @var{value})}. @var{value} is an integer. If @var{value} is not supplied, then it defaults to one greater than the value for the preceding spec (or to zero if it is the first spec). @@ -281,13 +282,40 @@ types to declare that no useful value is returned. Using return zero values. @item -The foreign type specifier @code{sb-alien:c-string} is similar to +@cindex External formats +The foreign type specifier @code{(sb-alien:c-string &key +external-format element-type not-null)} is similar to @code{(* char)}, but is interpreted as a null-terminated string, and is automatically converted into a Lisp string when accessed; or if the pointer is C @code{NULL} or @code{0}, then accessing it gives Lisp -@code{nil}. Lisp strings are stored with a trailing NUL -termination, so no copying (either by the user or the implementation) -is necessary when passing them to foreign code. +@code{nil} unless @code{not-null} is true, in which case a type-error +is signalled. + +External format conversion is automatically done when Lisp strings are +passed to foreign code, or when foreign strings are passed to Lisp code. +If the type specifier has an explicit @code{external-format}, that +external format will be used. Otherwise a default external format that +has been determined at SBCL startup time based on the current locale +settings will be used. For example, when the following alien routine is +called, the Lisp string given as argument is converted to an +@code{ebcdic} octet representation. + +@lisp +(define-alien-routine test int (str (c-string :external-format :ebcdic-us))) +@end lisp + +Lisp strings of type @code{base-string} are stored with a trailing NUL +termination, so no copying (either by the user or the implementation) is +necessary when passing them to foreign code, assuming that the +@code{external-format} and @code{element-type} of the @code{c-string} +type are compatible with the internal representation of the string. For +an SBCL built with Unicode support that means an @code{external-format} +of @code{:ascii} and an @code{element-type} of @code{base-char}. Without +Unicode support the @code{external-format} can also be +@code{:iso-8859-1}, and the @code{element-type} can also be +@code{character}. If the @code{external-format} or @code{element-type} +is not compatible, or the string is a @code{(simple-array character +(*))}, this data is copied by the implementation as required. Assigning a Lisp string to a @code{c-string} structure field or variable stores the contents of the string to the memory already @@ -313,13 +341,17 @@ the variable. @item @code{sb-alien} also exports translations of these C type -specifiers as foreign type specifiers: @code{sb-alien:char}, -@code{sb-alien:short}, @code{sb-alien:int}, -@code{sb-alien:long}, @code{sb-alien:unsigned-char}, -@code{sb-alien:unsigned-short}, -@code{sb-alien:unsigned-int}, -@code{sb-alien:unsigned-long}, @code{sb-alien:float}, and -@code{sb-alien:double}. +specifiers as foreign type specifiers: +@code{char}, +@code{short}, +@code{int}, +@code{long}, +@code{unsigned-char}, +@code{unsigned-short}, +@code{unsigned-int}, +@code{unsigned-long}, +@code{float}, @code{double}, +@code{size-t}, and @code{off-t}. @end itemize @@ -342,8 +374,7 @@ to dynamically allocate and free foreign variables. @comment node-name, next, previous, up @subsection Accessing Foreign Values -@defun sb-alien:deref @var{pointer-or-array} &rest @var{indices} -@findex deref +@defun @sbalien{deref} @var{pointer-or-array} &rest @var{indices} The @code{sb-alien:deref} function returns the value pointed to by a foreign pointer, or the value of a foreign array element. When @@ -355,8 +386,7 @@ array type. @code{deref} can be set with @code{setf} to assign a new value. @end defun -@defun sb-alien:slot @var{struct-or-union} &rest @var{slot-names} -@findex slot +@defun @sbalien{slot} @var{struct-or-union} @var{slot-name} The @code{sb-alien:slot} function extracts the value of the slot named @var{slot-name} from a foreign @code{struct} or @code{union}. If @@ -378,23 +408,20 @@ to and from integers - raw machine addresses. They should thus be used with caution; corrupting the Lisp heap or other memory with @acronym{SAP}s is trivial. -@defun sb-sys:int-sap @var{machine-address} -@findex int-sap +@defun @sbsys{int-sap} @var{machine-address} Creates a @acronym{SAP} pointing at the virtual address @var{machine-address}. @end defun -@defun sb-sys:sap-ref-32 @var{sap} @var{offset} -@findex sap-ref-32 +@defun @sbsys{sap-ref-32} @var{sap} @var{offset} Access the value of the memory location at @var{offset} bytes from @var{sap}. This form may also be used with @code{setf} to alter the memory at that location. @end defun -@defun sb-sys:sap= @var{sap1} @var{sap2} -@findex sap= +@defun @sbsys{sap=} @var{sap1} @var{sap2} Compare @var{sap1} and @var{sap2} for equality. @end defun @@ -412,37 +439,33 @@ use @code{apropos} and @code{describe} for more details @comment node-name, next, previous, up @subsection Coercing Foreign Values -@defun sb-alien:addr @var{alien-expr} -@findex addr +@defmac @sbalien{addr} @var{alien-expr} The @code{sb-alien:addr} macro returns a pointer to the location specified by @var{alien-expr}, which must be either a foreign variable, a use of @code{sb-alien:deref}, a use of @code{sb-alien:slot}, or a use of @code{sb-alien:extern-alien}. -@end defun +@end defmac -@defun sb-alien:cast @var{foreign-value} @var{new-type} -@findex cast +@defmac @sbalien{cast} @var{foreign-value} @var{new-type} The @code{sb-alien:cast} macro converts @var{foreign-value} to a new foreign value with the specified @var{new-type}. Both types, old and new, must be foreign pointer, array or function types. Note that the resulting Lisp foreign variable object is not @code{eq} to the argument, but it does refer to the same foreign data bits. -@end defun +@end defmac -@defun sb-alien:sap-alien @var{sap} @var{type} -@findex sap-alien +@defmac @sbalien{sap-alien} @var{sap} @var{type} -The @code{sb-alien:sap-alien} function converts @var{sap} (a system +The @code{sb-alien:sap-alien} macro converts @var{sap} (a system area pointer) to a foreign value with the specified -@var{type}. @var{type} is not evaluated. +@var{type}. @var{type} is not evaluated. The @var{type} must be some foreign pointer, array, or record type. -@end defun +@end defmac -@defun sb-alien:alien-sap @var{foreign-value} @var{type} -@findex alien-sap +@defun @sbalien{alien-sap} @var{foreign-value} The @code{sb-alien:alien-sap} function returns the @acronym{SAP} which points to @var{alien-value}'s data. @@ -457,62 +480,15 @@ record type. @subsection Foreign Dynamic Allocation Lisp code can call the C standard library functions @code{malloc} and -@code{free} to dynamically allocate and deallocate foreign -variables. The Lisp code shares the same allocator with foreign C -code, so it's OK for foreign code to call @code{free} on the result of -Lisp @code{sb-alien:make-alien}, or for Lisp code to call -@code{sb-alien:free-alien} on foreign objects allocated by C -code. - -@defmac sb-alien:make-alien @var{type} @var{size} -@findex make-alien - -The @code{sb-alien:make-alien} macro -returns a dynamically allocated foreign value of the specified -@var{type} (which is not evaluated.) The allocated memory is not -initialized, and may contain arbitrary junk. If supplied, -@var{size} is an expression to evaluate to compute the size of the -allocated object. There are two major cases: - -@itemize -@item -When @var{type} is a foreign array type, an array of that type is -allocated and a pointer to it is returned. Note that you must use -@code{deref} to change the result to an array before you can use -@code{deref} to read or write elements: - -@lisp -(cl:in-package "CL-USER") ; which USEs package "SB-ALIEN" -(defvar *foo* (make-alien (array char 10))) -(type-of *foo*) @result{} (alien (* (array (signed 8) 10))) -(setf (deref (deref foo) 0) 10) @result{} 10 -@end lisp - -If supplied, @var{size} is used as the first dimension for the - array. - -@item -When @var{type} is any other foreign type, then an object for that -type is allocated, and a pointer to it is returned. So -@code{(make-alien int)} returns a @code{(* int)}. If @var{size} is -specified, then a block of that many objects is allocated, with the -result pointing to the first one. - -@end itemize - -@end defmac - -@defun sb-alien:free-alien @var{foreign-value} -@findex free-alien +@code{free} to dynamically allocate and deallocate foreign variables. +The Lisp code shares the same allocator with foreign C code, so it's +OK for foreign code to call @code{free} on the result of Lisp +@code{sb-alien:make-alien}, or for Lisp code to call +@code{sb-alien:free-alien} on foreign objects allocated by C code. -The @code{sb-alien:free-alien} function -frees the storage for @var{foreign-value}, -which must have been allocated with Lisp @code{make-alien} -or C @code{malloc}. - -See also the @code{sb-alien:with-alien} macro, which allocates foreign -values on the stack. -@end defun +@include macro-sb-alien-make-alien.texinfo +@include fun-sb-alien-make-alien-string.texinfo +@include fun-sb-alien-free-alien.texinfo @node Foreign Variables @comment node-name, next, previous, up @@ -531,8 +507,7 @@ are supported. @comment node-name, next, previous, up @subsection Local Foreign Variables -@defmac sb-alien:with-alien @var{var-definitions} &body @var{body} -@findex with-alien +@defmac @sbalien{with-alien} @var{var-definitions} &body @var{body} The @code{with-alien} macro establishes local foreign variables with the specified alien types and names. This form is analogous to @@ -590,8 +565,7 @@ specified by using a list of the form @end itemize -@defmac sb-alien:define-alien-variable @var{name} @var{type} -@findex define-alien-variable +@defmac @sbalien{define-alien-variable} @var{name} @var{type} The @code{define-alien-variable} macro defines @var{name} as an external foreign variable of the specified foreign @code{type}. @@ -617,8 +591,7 @@ For example, to access a C-level counter @var{foo}, one could write @end lisp @end defmac -@defun sb-alien:get-errno -@findex get-errno +@defun @sbalien{get-errno} Since in modern C libraries, the @code{errno} ``variable'' is typically no longer a variable, but some bizarre artificial construct @@ -628,8 +601,7 @@ it can no longer reliably be accessed through the ordinary the operator @code{sb-alien:get-errno} to allow Lisp code to read it. @end defun -@defmac sb-alien:extern-alien @var{name} @var{type} -@findex extern-alien +@defmac @sbalien{extern-alien} @var{name} @var{type} The @code{extern-alien} macro returns an alien with the specified @var{type} which points to an externally defined value. @var{name} is @@ -720,6 +692,8 @@ calling @code{load-shared-object}. @include fun-sb-alien-load-shared-object.texinfo +@include fun-sb-alien-unload-shared-object.texinfo + @node Foreign Function Calls @comment node-name, next, previous, up @section Foreign Function Calls @@ -751,8 +725,7 @@ the only documentation. Users of a Lisp built with the @comment node-name, next, previous, up @subsection The @code{alien-funcall} Primitive -@defun sb-alien:alien-funcall @var{alien-function} &rest @var{arguments} -@findex alien-funcall +@defun @sbalien{alien-funcall} @var{alien-function} &rest @var{arguments} The @code{alien-funcall} function is the foreign function call primitive: @var{alien-function} is called with the supplied @@ -805,8 +778,7 @@ the @code{(* (struct foo))} objects filled in by the foreign call: @comment node-name, next, previous, up @subsection The @code{define-alien-routine} Macro -@defmac sb-alien:define-alien-routine @var{name} @var{result-type} &rest @var{arg-specifiers} -@findex define-alien-routine +@defmac @sbalien{define-alien-routine} @var{name} @var{result-type} &rest @var{arg-specifiers} The @code{define-alien-routine} macro is a convenience for automatically generating Lisp interfaces to simple foreign functions. @@ -943,8 +915,7 @@ other ports it is implemented by turning off GC for the duration (so could be said to have a whole-world granularity). @item -Disable GC, using the @code{without-gcing} macro or @code{gc-off} -call. +Disable GC, using the @code{without-gcing} macro. @end enumerate @c