.\" Copyright (c) 2007-2013 Daniel Adler <dadler AT uni-goettingen DOT de>, 
.\"                         Tassilo Philipp <tphilipp AT potion-studios DOT com>
.\" 
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate$
.Dt dyncall 3
.Sh NAME
.Nm dyncall
.Nd encapsulation of architecture-, OS- and compiler-specific function call
semantics 
.Sh SYNOPSIS
.In dyncall.h
.Ft DCCallVM *
.Fn dcNewCallVM "DCsize size"
.Ft void
.Fn dcFree "DCCallVM * vm"
.Ft void
.Fn dcMode "DCCallVM * vm" "DCint mode"
.Ft void
.Fn dcReset "DCCallVM * vm"
.Ft void
.Fn dcArgBool "DCCallVM * vm" "DCbool arg"
.Ft void
.Fn dcArgChar "DCCallVM * vm" "DCchar arg"
.Ft void
.Fn dcArgShort "DCCallVM * vm" "DCshort arg"
.Ft void
.Fn dcArgInt "DCCallVM * vm" "DCint arg"
.Ft void
.Fn dcArgLong "DCCallVM * vm" "DClong arg"
.Ft void
.Fn dcArgLongLong "DCCallVM * vm" "DClonglong arg"
.Ft void
.Fn dcArgFloat "DCCallVM * vm" "DCfloat arg"
.Ft void
.Fn dcArgDouble "DCCallVM * vm" "DCdouble arg"
.Ft void
.Fn dcArgPointer "DCCallVM * vm" "DCpointer arg"
.Ft DCvoid
.Fn dcCallVoid "DCCallVM * vm" "DCpointer funcptr"
.Ft DCbool
.Fn dcCallBool "DCCallVM * vm" "DCpointer funcptr"
.Ft DCchar
.Fn dcCallChar "DCCallVM * vm" "DCpointer funcptr"
.Ft DCshort
.Fn dcCallShort "DCCallVM * vm" "DCpointer funcptr"
.Ft DCint
.Fn dcCallInt "DCCallVM * vm" "DCpointer funcptr"
.Ft DClong
.Fn dcCallLong "DCCallVM * vm" "DCpointer funcptr"
.Ft DClonglong
.Fn dcCallLongLong "DCCallVM * vm" "DCpointer funcptr"
.Ft DCfloat
.Fn dcCallFloat "DCCallVM * vm" "DCpointer funcptr"
.Ft DCdouble
.Fn dcCallDouble "DCCallVM * vm" "DCpointer funcptr"
.Ft DCpointer
.Fn dcCallPointer "DCCallVM * vm" "DCpointer funcptr"
.Ft void
.Fn dcArgF "DCCallVM * vm" "const DCsigchar * signature" "..."
.Ft void
.Fn dcVArgF "DCCallVM * vm" "const DCsigchar * signature" "va_list args"
.Ft void
.Fn dcCallF "DCCallVM * vm" "DCValue * result" "DCpointer funcptr" "const DCsigchar * signature" "..."
.Ft void
.Fn dcVCallF "DCCallVM * vm" "DCValue * result" "DCpointer funcptr" "const DCsigchar * signature" "va_list args"
.Sh DESCRIPTION
The
.Nm
library encapsulates architecture-, OS- and compiler-specific function call
semantics in a virtual "bind argument parameters from left to right and then
call" interface allowing programmers to call C functions in a completely
dynamic manner.
.Pp
In other words, instead of calling a function directly, the
.Nm
library provides a mechanism to push the function parameters manually and to
issue the call afterwards.
.Pp
Since the idea behind this concept is similar to call dispatching mechanisms
of virtual machines, the object that can be dynamically loaded with arguments,
and then used to actually invoke the call, is called CallVM. It is possible to
change the calling convention used by the CallVM at run-time. Due to the fact
that nearly every platform comes with one or more distinct calling conventions, the
.Nm
library project intends to be a portable and open-source approach to the variety of
compiler-specific binary interfaces, platform specific subtleties, and so on...
.Pp
.Fn dcNewCallVM
creates a new CallVM object, where
.Ar size
specifies the max size of the internal stack that will be allocated and used to
bind the arguments to. Use
.Fn dcFree
to destroy the CallVM object.
.Pp
.Fn dcMode
sets the calling convention to use. See dyncall.h for a list of
available modes. Note that some mode/platform combinations don't make any
sense (e.g. using a PowerPC calling convention on a MIPS platform) and are
silently ignored.
.Pp
.Fn dcReset
resets the internal stack of arguments and prepares it for a new call.
This function should be called after setting the call mode (using dcMode), but
prior to binding arguments to the CallVM. Use it also when reusing a CallVM, as
arguments don't get flushed automatically after a function call invocation.
Note: you should also call this function after initial creation of the a CallVM
object, as dcNewCallVM doesn't do this, implicitly.
.Pp
.Fn dcArgBool ,
.Fn dcArgChar ,
.Fn dcArgShort ,
.Fn dcArgInt ,
.Fn dcArgLong ,
.Fn dcArgLongLong ,
.Fn dcArgFloat ,
.Fn dcArgDouble
and
.Fn dcArgPointer
are used to bind arguments of the named types to the CallVM object. Arguments should
be bound in
.Em "left to right"
order regarding the C function prototype.
.Pp
.Fn dcCallVoid ,
.Fn dcCallBool ,
.Fn dcCallChar ,
.Fn dcCallShort ,
.Fn dcCallInt ,
.Fn dcCallLong ,
.Fn dcCallLongLong ,
.Fn dcCallFloat ,
.Fn dcCallDouble
and
.Fn dcCallPointer
call the function with the bound arguments and returning the named type, where
.Ar funcptr
is a pointer to the function to call. After the invocation of the function
call, the argument values are still bound to the CallVM and a second call
using the same arguments can be issued. Call
.Fn reset
to clear the internal argument stack.
.Pp
.Fn dcArgF ,
.Fn dcVArgF ,
.Fn dcCallF
and
.Fn dcVCallF
can be used to bind arguments in a printf-style call, using a signature
string encoding the argument types and return type. The former 2 only bind
the arguments to the
.Ar vm
object (and ignore return types specified in the
signature), whereas the latter two issue a call to the given function pointer,
afterwards. The return value will be stored in
.Ar result .
For information about the signature format, refer to the
.Nm
manual in PDF format.
.Sh EXAMPLE
Let's say, we want to make a call to the function:
.Bd -literal -offset indent
	double sqrt(double x); 
.Ed
.Pp
Using the
.Nm
library, this function would be called as follows: 
.Bd -literal -offset indent
	double r;
	DCCallVM* vm = dcNewCallVM(4096);
	dcMode(vm, DC_CALL_C_DEFAULT);
	dcReset(vm);
	dcArgDouble(vm, 4.2373);
	r = dcCallDouble(vm, (DCpointer)&sqrt);
	dcFree(vm);
.Ed
.Sh CONFORMING TO
The dyncall library needs at least a c99 compiler with additional support for
anonymous structs/unions (which were introduced officially in c11). Given that
those are generally supported by pretty much all major c99 conforming compilers
(as default extension), it should build fine with a c99 toolchain. Strictly
speaking, dyncall conforms to c11, though.
.Ed
.Sh SEE ALSO
.Xr dyncallback 3 ,
.Xr dynload 3
and the
.Nm
manual (available in HTML and PDF format) for more information.
.Sh AUTHORS
.An "Daniel Adler" Aq dadler@uni-goettingen.de
.An "Tassilo Philipp" Aq tphilipp@potion-studios.com