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\newpage
\section{\emph{Dyncall} C library API}

The library provides low-level functionality to make foreign function calls
from different run-time environments. The flexibility is constrained by the
set of supported types.

\paragraph{C interface style conventions}

This manual and the \product{dyncall} library's C interface {\tt "dyncall.h"}
use the following C source code style.


\begin{table}[h]
\begin{center}
\begin{tabular*}{0.8\textwidth}{llll}
Subject    & C symbol & Details & Example \\
\hline  
Types      
  & {\tt DC\group{type name}}      
  & lower-case & \capi{DCint}, \capi{DCfloat}, \capi{DClong}, \ldots\\
Structures 
  & {\tt DC\group{structure name}} 
  & camel-case 
  & \capi{DCCallVM}\\
Functions  & {\tt dc\group{function name}}  & camel-case & \capi{dcNewCallVM}, \capi{dcArgInt}, \ldots\\
\end{tabular*}
\caption{C interface conventions}
\label{sourcecode}
\end{center}
\end{table}

\subsection{Supported C/C++ argument and return types}

\begin{table}[h]
\begin{center}
\begin{tabular*}{0.75\textwidth}{ll}
Type alias & C/C++ data type\\
\hline
DCbool     & \_Bool, bool\\
DCchar     & char\\
DCshort    & short\\
DCint      & int\\
DClong     & long\\
DClonglong & long long\\
DCfloat    & float\\
DCdouble   & double\\
DCpointer  & void*\\
DCvoid     & void\\
\end{tabular*}
\caption{Supported C/C++ argument and return types}
\label{types}
\end{center}
\end{table}

\pagebreak

\subsection{Call Virtual Machine - CallVM}

This \emph{CallVM} is the main entry to the functionality of the library.

\paragraph{Types}

\begin{lstlisting}[language=c]
typedef void DCCallVM; /* abstract handle */
\end{lstlisting}

\paragraph{Details}
The \emph{CallVM} is a state machine that manages all aspects of a function 
call from configuration, argument passing up the actual function call on
the processor.

\subsection{Allocation}

\paragraph{Functions}

\begin{lstlisting}[language=c]
DCCallVM* dcNewCallVM (DCsize size);
void      dcFree(DCCallVM* vm);
\end{lstlisting}

\lstinline{dcNewCallVM} creates a new \emph{CallVM} object, where
\lstinline{size} specifies the max size of the internal stack that will be
allocated and used to bind arguments to. Use \lstinline{dcFree} to
destroy the \emph{CallVM} object.\\
\\
This will allocate memory using the system allocators or custom ones provided
custom \capi{dcAllocMem} and \capi{dcFreeMem} macros are defined to override the
default behaviour. See \capi{dyncall\_alloc.h} for defails.


\subsection{Error Reporting}

\paragraph{Function}

\begin{lstlisting}[language=c]
DCint dcGetError(DCCallVM* vm);
\end{lstlisting}

Returns the most recent error state code out of the following:

\paragraph{Errors}

\begin{table}[h]
\begin{center}
\begin{tabular*}{0.95\textwidth}{ll}
Constant & Description\\
\hline
\lstinline@DC_ERROR_NONE@             & No error occured. \\
\lstinline@DC_ERROR_UNSUPPORTED_MODE@ & Unsupported mode, caused by \lstinline@dcMode()@ \\
\end{tabular*}
\caption{CallVM calling convention modes}
\label{errorcodes}
\end{center}
\end{table}

\pagebreak

\subsection{Configuration}

\paragraph{Function}

\begin{lstlisting}[language=c]
void dcMode (DCCallVM* vm, DCint mode);
\end{lstlisting}

Sets the calling convention to use. Note that some mode/platform combination
don't make any sense (e.g. using a PowerPC calling convention on a MIPS
platform) and are silently ignored.

\paragraph{Modes}

\begin{table}[h]
\begin{center}
\begin{tabular*}{0.95\textwidth}{ll}
Constant & Description\\
\hline
\lstinline@DC_CALL_C_DEFAULT@            & C default function call for current platform\\
\lstinline@DC_CALL_C_ELLIPSIS@           & C ellipsis function call (named arguments (before '...'))\\
\lstinline@DC_CALL_C_ELLIPSIS_VARARGS@   & C ellipsis function call (variable/unnamed arguments (after '...'))\\
\lstinline@DC_CALL_C_X86_CDECL@          & C x86 platforms standard call\\
\lstinline@DC_CALL_C_X86_WIN32_STD@      & C x86 Windows standard call\\
\lstinline@DC_CALL_C_X86_WIN32_FAST_MS@  & C x86 Windows Microsoft fast call\\
\lstinline@DC_CALL_C_X86_WIN32_FAST_GNU@ & C x86 Windows GCC fast call\\
\lstinline@DC_CALL_C_X86_WIN32_THIS_MS@  & C x86 Windows Microsoft this call\\
\lstinline@DC_CALL_C_X86_WIN32_THIS_GNU@ & C x86 Windows GCC this call\\
\lstinline@DC_CALL_C_X86_PLAN9@          & C x86 Plan9 call\\
\lstinline@DC_CALL_C_X64_WIN64@          & C x64 Windows standard call\\
\lstinline@DC_CALL_C_X64_SYSV@           & C x64 System V standard call\\
\lstinline@DC_CALL_C_PPC32_DARWIN@       & C ppc32 Mac OS X standard call\\
\lstinline@DC_CALL_C_PPC32_OSX@          & alias for DC\_CALL\_C\_PPC32\_DARWIN\\
\lstinline@DC_CALL_C_PPC32_SYSV@         & C ppc32 SystemV standard call\\
\lstinline@DC_CALL_C_PPC32_LINUX@        & alias for DC\_CALL\_C\_PPC32\_SYSV\\
\lstinline@DC_CALL_C_PPC64@              & C ppc64 SystemV standard call\\
\lstinline@DC_CALL_C_PPC64_LINUX@        & alias for DC\_CALL\_C\_PPC64\\
\lstinline@DC_CALL_C_ARM_ARM@            & C arm call (arm mode)\\
\lstinline@DC_CALL_C_ARM_THUMB@          & C arm call (thumb mode)\\
\lstinline@DC_CALL_C_ARM_ARM_EABI@       & C arm eabi call (arm mode)\\
\lstinline@DC_CALL_C_ARM_THUMB_EABI@     & C arm eabi call (thumb mode)\\
\lstinline@DC_CALL_C_ARM_ARMHF@          & C arm call (arm hardfloat - e.g. raspberry pi)\\
\lstinline@DC_CALL_C_ARM64@              & C arm64 call (AArch64)\\
\lstinline@DC_CALL_C_MIPS32_EABI@        & C mips32 eabi call\\
\lstinline@DC_CALL_C_MIPS32_PSPSDK@      & alias for DC\_CALL\_C\_MIPS32\_EABI (deprecated)\\
\lstinline@DC_CALL_C_MIPS32_O32@         & C mips32 o32 call\\
\lstinline@DC_CALL_C_MIPS64_N64@         & C mips64 n64 call\\
\lstinline@DC_CALL_C_MIPS64_N32@         & C mips64 n32 call\\
\lstinline@DC_CALL_C_SPARC32@            & C sparc32 call\\
\lstinline@DC_CALL_C_SPARC64@            & C sparc64 call\\
\lstinline@DC_CALL_SYS_DEFAULT@          & C default syscall for current platform\\
\lstinline@DC_CALL_SYS_X86_INT80H_BSD@   & C syscall for x86 BSD platforms\\
\lstinline@DC_CALL_SYS_X86_INT80H_LINUX@ & C syscall for x86 Linux\\
\lstinline@DC_CALL_SYS_X64_SYSCALL_SYSV@ & C syscall for x64 System V platforms\\
\lstinline@DC_CALL_SYS_PPC32@            & C syscall for ppc32\\
\lstinline@DC_CALL_SYS_PPC64@            & C syscall for ppc64\\
\end{tabular*}
\caption{CallVM calling convention modes}
\label{callingconventionmodes}
\end{center}
\end{table}

\paragraph{Details}

\lstinline@DC_CALL_C_DEFAULT@ is the default standard C call on the target
platform. It uses the standard C calling convention.
\lstinline@DC_CALL_C_ELLIPSIS@ is used for C ellipsis calls which allow
to build up a variable argument list.
On many platforms, there is only one C calling convention. 
The X86 platform provides a rich family of different calling conventions.
\\


\subsection{Machine state reset}

\begin{lstlisting}[language=c]
void dcReset(DCCallVM* vm);
\end{lstlisting}


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.\\

\subsection{Argument binding}

\paragraph{Functions}

\begin{lstlisting}[language=c]
void dcArgBool    (DCCallVM* vm, DCbool     arg);
void dcArgChar    (DCCallVM* vm, DCchar     arg);
void dcArgShort   (DCCallVM* vm, DCshort    arg);
void dcArgInt     (DCCallVM* vm, DCint      arg);
void dcArgLong    (DCCallVM* vm, DClong     arg);
void dcArgLongLong(DCCallVM* vm, DClonglong arg);
void dcArgFloat   (DCCallVM* vm, DCfloat    arg);
void dcArgDouble  (DCCallVM* vm, DCdouble   arg);
void dcArgPointer (DCCallVM* vm, DCpointer  arg);
\end{lstlisting}

\paragraph{Details}

Used to bind arguments of the named types to the CallVM object.
Arguments should be bound in \emph{left-to-right} order regarding the C
function prototype.\\

\subsection{Call invocation}

\paragraph{Functions}

\begin{lstlisting}[language=c]
DCvoid     dcCallVoid    (DCCallVM* vm, DCpointer funcptr);
DCbool     dcCallBool    (DCCallVM* vm, DCpointer funcptr);
DCchar     dcCallChar    (DCCallVM* vm, DCpointer funcptr);
DCshort    dcCallShort   (DCCallVM* vm, DCpointer funcptr);
DCint      dcCallInt     (DCCallVM* vm, DCpointer funcptr);
DClong     dcCallLong    (DCCallVM* vm, DCpointer funcptr);
DClonglong dcCallLongLong(DCCallVM* vm, DCpointer funcptr);
DCfloat    dcCallFloat   (DCCallVM* vm, DCpointer funcptr);
DCdouble   dcCallDouble  (DCCallVM* vm, DCpointer funcptr);
DCpointer  dcCallPointer (DCCallVM* vm, DCpointer funcptr);
\end{lstlisting}

\paragraph{Details}
Calls the function specified by \emph{funcptr} with the arguments bound to
the \emph{CallVM} and returns. Use the function that corresponds to the
dynamically called function's return value.\\
\\
After the invocation of the foreign function call, the argument values are
still bound and a second call using the same arguments can be issued. If you
need to clear the argument bindings, you have to reset the \emph{CallVM}.

\subsection{Formatted argument binding and calls (ANSI C ellipsis interface)}

\paragraph{Functions}

\begin{lstlisting}[language=c]
void dcArgF  (DCCallVM* vm, const DCsigchar* signature, ...);
void dcVArgF (DCCallVM* vm, const DCsigchar* signature, va_list args);
void dcCallF (DCCallVM* vm, DCValue* result, DCpointer funcptr, 
              const DCsigchar* signature, ...);
void dcVCallF(DCCallVM* vm, DCValue* result, DCpointer funcptr, 
              const DCsigchar* signature, va_list args);
\end{lstlisting}

\paragraph{Details}

These functions can be used to operate \product{dyncall} via a printf-style
functional interface, using a signature string encoding the argument types and 
return type.
\capi{dcArgF()} and \capi{dcVArgF()} just bind arguments to the \capi{DCCallVM}
object, so any return value specified in the signature is ignored. \capi{dcCallF()}
and \capi{dcVCallF()} also take a function pointer to call after binding the arguments.
The return value will be stored in what \lstinline{result} points to.
For more information about the signature format, refer to \ref{sigchar}.

