drivers/audio/iasiothiscallresolver.cpp

/*
        IASIOThiscallResolver.cpp see the comments in iasiothiscallresolver.h for
    the top level description - this comment describes the technical details of
    the implementation.

    The latest version of this file is available from:
    http://www.audiomulch.com/~rossb/code/calliasio

    please email comments to Ross Bencina <rossb@audiomulch.com>

    BACKGROUND

    The IASIO interface declared in the Steinberg ASIO 2 SDK declares
    functions with no explicit calling convention. This causes MSVC++ to default
    to using the thiscall convention, which is a proprietary convention not
    implemented by some non-microsoft compilers - notably borland BCC,
    C++Builder, and gcc. MSVC++ is the defacto standard compiler used by
    Steinberg. As a result of this situation, the ASIO sdk will compile with
    any compiler, however attempting to execute the compiled code will cause a
    crash due to different default calling conventions on non-Microsoft
    compilers.

    IASIOThiscallResolver solves the problem by providing an adapter class that
    delegates to the IASIO interface using the correct calling convention
    (thiscall). Due to the lack of support for thiscall in the Borland and GCC
    compilers, the calls have been implemented in assembly language.

    A number of macros are defined for thiscall function calls with different
    numbers of parameters, with and without return values - it may be possible
    to modify the format of these macros to make them work with other inline
    assemblers.


    THISCALL DEFINITION

    A number of definitions of the thiscall calling convention are floating
    around the internet. The following definition has been validated against
    output from the MSVC++ compiler:

    For non-vararg functions, thiscall works as follows: the object (this)
    pointer is passed in ECX. All arguments are passed on the stack in
    right to left order. The return value is placed in EAX. The callee
    clears the passed arguments from the stack.


    FINDING FUNCTION POINTERS FROM AN IASIO POINTER

    The first field of a COM object is a pointer to its vtble. Thus a pointer
    to an object implementing the IASIO interface also points to a pointer to
    that object's vtbl. The vtble is a table of function pointers for all of
    the virtual functions exposed by the implemented interfaces.

    If we consider a variable declared as a pointer to IASO:

    IASIO *theAsioDriver

    theAsioDriver points to:

    object implementing IASIO
    {
        IASIOvtbl *vtbl
        other data
    }

    in other words, theAsioDriver points to a pointer to an IASIOvtbl

    vtbl points to a table of function pointers:

    IASIOvtbl ( interface IASIO : public IUnknown )
    {
    (IUnknown functions)
    0   virtual HRESULT STDMETHODCALLTYPE (*QueryInterface)(REFIID riid, void **ppv) = 0;
    4   virtual ULONG STDMETHODCALLTYPE (*AddRef)() = 0;
    8   virtual ULONG STDMETHODCALLTYPE (*Release)() = 0;

    (IASIO functions)
    12  virtual ASIOBool (*init)(void *sysHandle) = 0;
    16  virtual void (*getDriverName)(char *name) = 0;
    20  virtual long (*getDriverVersion)() = 0;
    24  virtual void (*getErrorMessage)(char *string) = 0;
    28  virtual ASIOError (*start)() = 0;
    32  virtual ASIOError (*stop)() = 0;
    36  virtual ASIOError (*getChannels)(long *numInputChannels, long *numOutputChannels) = 0;
    40  virtual ASIOError (*getLatencies)(long *inputLatency, long *outputLatency) = 0;
    44  virtual ASIOError (*getBufferSize)(long *minSize, long *maxSize,
            long *preferredSize, long *granularity) = 0;
    48  virtual ASIOError (*canSampleRate)(ASIOSampleRate sampleRate) = 0;
    52  virtual ASIOError (*getSampleRate)(ASIOSampleRate *sampleRate) = 0;
    56  virtual ASIOError (*setSampleRate)(ASIOSampleRate sampleRate) = 0;
    60  virtual ASIOError (*getClockSources)(ASIOClockSource *clocks, long *numSources) = 0;
    64  virtual ASIOError (*setClockSource)(long reference) = 0;
    68  virtual ASIOError (*getSamplePosition)(ASIOSamples *sPos, ASIOTimeStamp *tStamp) = 0;
    72  virtual ASIOError (*getChannelInfo)(ASIOChannelInfo *info) = 0;
    76  virtual ASIOError (*createBuffers)(ASIOBufferInfo *bufferInfos, long numChannels,
            long bufferSize, ASIOCallbacks *callbacks) = 0;
    80  virtual ASIOError (*disposeBuffers)() = 0;
    84  virtual ASIOError (*controlPanel)() = 0;
    88  virtual ASIOError (*future)(long selector,void *opt) = 0;
    92  virtual ASIOError (*outputReady)() = 0;
    };

    The numbers in the left column show the byte offset of each function ptr
    from the beginning of the vtbl. These numbers are used in the code below
    to select different functions.

    In order to find the address of a particular function, theAsioDriver
    must first be dereferenced to find the value of the vtbl pointer:

    mov     eax, theAsioDriver
    mov     edx, [theAsioDriver]  // edx now points to vtbl[0]

    Then an offset must be added to the vtbl pointer to select a
    particular function, for example vtbl+44 points to the slot containing
    a pointer to the getBufferSize function.

    Finally vtbl+x must be dereferenced to obtain the value of the function
    pointer stored in that address:

    call    [edx+44]    // call the function pointed to by
                        // the value in the getBufferSize field of the vtbl


    SEE ALSO

    Martin Fay's OpenASIO DLL at http://www.martinfay.com solves the same
    problem by providing a new COM interface which wraps IASIO with an
    interface that uses portable calling conventions. OpenASIO must be compiled
    with MSVC, and requires that you ship the OpenASIO DLL with your
    application.


    ACKNOWLEDGEMENTS

    Ross Bencina: worked out the thiscall details above, wrote the original
    Borland asm macros, and a patch for asio.cpp (which is no longer needed).
    Thanks to Martin Fay for introducing me to the issues discussed here,
    and to Rene G. Ceballos for assisting with asm dumps from MSVC++.

    Antti Silvast: converted the original calliasio to work with gcc and NASM
    by implementing the asm code in a separate file.

        Fraser Adams: modified the original calliasio containing the Borland inline
    asm to add inline asm for gcc i.e. Intel syntax for Borland and AT&T syntax
    for gcc. This seems a neater approach for gcc than to have a separate .asm
    file and it means that we only need one version of the thiscall patch.

    Fraser Adams: rewrote the original calliasio patch in the form of the
    IASIOThiscallResolver class in order to avoid modifications to files from
    the Steinberg SDK, which may have had potential licence issues.

    Andrew Baldwin: contributed fixes for compatibility problems with more
    recent versions of the gcc assembler.
*/


// We only need IASIOThiscallResolver at all if we are on Win32. For other
// platforms we simply bypass the IASIOThiscallResolver definition to allow us
// to be safely #include'd whatever the platform to keep client code portable
#if defined(WIN32) || defined(_WIN32) || defined(__WIN32__)

// If microsoft compiler we can call IASIO directly so IASIOThiscallResolver
// is not used.
#if !defined(_MSC_VER)

#include <new>
#include <assert.h>

// We have a mechanism in iasiothiscallresolver.h to ensure that asio.h is
// #include'd before it in client code, we do NOT want to do this test here.
#define iasiothiscallresolver_sourcefile 1
#include "iasiothiscallresolver.h"
#undef iasiothiscallresolver_sourcefile

// iasiothiscallresolver.h redefines ASIOInit for clients, but we don't want
// this macro defined in this translation unit.
#undef ASIOInit

// theAsioDriver is a global pointer to the current IASIO instance which the
// ASIO SDK uses to perform all actions on the IASIO interface. We substitute
// our own forwarding interface into this pointer.
extern IASIO* theAsioDriver;

// The following macros define the inline assembler for BORLAND first then gcc

#if defined(__BCPLUSPLUS__) || defined(__BORLANDC__)

#define CALL_THISCALL_0( resultName, thisPtr, funcOffset )\
    void *this_ = (thisPtr);                                                \
    __asm {                                                                 \
        mov     ecx, this_            ;                                     \
        mov     eax, [ecx]            ;                                     \
        call    [eax+funcOffset]      ;                                     \
        mov     resultName, eax       ;                                     \
    }

#define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 )\
    void *this_ = (thisPtr);                                                \
    __asm {                                                                 \
        mov     eax, param1           ;                                     \
        push    eax                   ;                                     \
        mov     ecx, this_            ;                                     \
        mov     eax, [ecx]            ;                                     \
        call    [eax+funcOffset]      ;                                     \
    }

#define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 )\
    void *this_ = (thisPtr);                                                \
    __asm {                                                                 \
        mov     eax, param1           ;                                     \
        push    eax                   ;                                     \
        mov     ecx, this_            ;                                     \
        mov     eax, [ecx]            ;                                     \
        call    [eax+funcOffset]      ;                                     \
        mov     resultName, eax       ;                                     \
    }

#define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 )\
    void *this_ = (thisPtr);                                                \
    void *doubleParamPtr_ (&param1);                                        \
    __asm {                                                                 \
        mov     eax, doubleParamPtr_  ;                                     \
        push    [eax+4]               ;                                     \
        push    [eax]                 ;                                     \
        mov     ecx, this_            ;                                     \
        mov     eax, [ecx]            ;                                     \
        call    [eax+funcOffset]      ;                                     \
        mov     resultName, eax       ;                                     \
    }

#define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 )\
    void *this_ = (thisPtr);                                                \
    __asm {                                                                 \
        mov     eax, param2           ;                                     \
        push    eax                   ;                                     \
        mov     eax, param1           ;                                     \
        push    eax                   ;                                     \
        mov     ecx, this_            ;                                     \
        mov     eax, [ecx]            ;                                     \
        call    [eax+funcOffset]      ;                                     \
        mov     resultName, eax       ;                                     \
    }

#define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
    void *this_ = (thisPtr);                                                \
    __asm {                                                                 \
        mov     eax, param4           ;                                     \
        push    eax                   ;                                     \
        mov     eax, param3           ;                                     \
        push    eax                   ;                                     \
        mov     eax, param2           ;                                     \
        push    eax                   ;                                     \
        mov     eax, param1           ;                                     \
        push    eax                   ;                                     \
        mov     ecx, this_            ;                                     \
        mov     eax, [ecx]            ;                                     \
        call    [eax+funcOffset]      ;                                     \
        mov     resultName, eax       ;                                     \
    }

#elif defined(__GNUC__)

#define CALL_THISCALL_0( resultName, thisPtr, funcOffset )                  \
    __asm__ __volatile__ ("movl (%1), %%edx\n\t"                            \
                          "call *"#funcOffset"(%%edx)\n\t"                  \
                          :"=a"(resultName) /* Output Operands */           \
                          :"c"(thisPtr)     /* Input Operands */            \
                         );                                                 \

#define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 )                 \
    __asm__ __volatile__ ("pushl %0\n\t"                                    \
                          "movl (%1), %%edx\n\t"                            \
                          "call *"#funcOffset"(%%edx)\n\t"                  \
                          :                 /* Output Operands */           \
                          :"r"(param1),     /* Input Operands */            \
                           "c"(thisPtr)                                     \
                         );                                                 \

#define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 )          \
    __asm__ __volatile__ ("pushl %1\n\t"                                    \
                          "movl (%2), %%edx\n\t"                            \
                          "call *"#funcOffset"(%%edx)\n\t"                  \
                          :"=a"(resultName) /* Output Operands */           \
                          :"r"(param1),     /* Input Operands */            \
                           "c"(thisPtr)                                     \
                          );                                                \

#define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 )   \
    __asm__ __volatile__ ("pushl 4(%1)\n\t"                                 \
                          "pushl (%1)\n\t"                                  \
                          "movl (%2), %%edx\n\t"                            \
                          "call *"#funcOffset"(%%edx);\n\t"                 \
                          :"=a"(resultName) /* Output Operands */           \
                          :"a"(&param1),    /* Input Operands */            \
                           /* Note: Using "r" above instead of "a" fails */ \
                           /* when using GCC 3.3.3, and maybe later versions*/\
                           "c"(thisPtr)                                     \
                          );                                                \

#define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 )  \
    __asm__ __volatile__ ("pushl %1\n\t"                                    \
                          "pushl %2\n\t"                                    \
                          "movl (%3), %%edx\n\t"                            \
                          "call *"#funcOffset"(%%edx)\n\t"                  \
                          :"=a"(resultName) /* Output Operands */           \
                          :"r"(param2),     /* Input Operands */            \
                           "r"(param1),                                     \
                           "c"(thisPtr)                                     \
                          );                                                \

#define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
    __asm__ __volatile__ ("pushl %1\n\t"                                    \
                          "pushl %2\n\t"                                    \
                          "pushl %3\n\t"                                    \
                          "pushl %4\n\t"                                    \
                          "movl (%5), %%edx\n\t"                            \
                          "call *"#funcOffset"(%%edx)\n\t"                  \
                          :"=a"(resultName) /* Output Operands */           \
                          :"r"(param4),     /* Input Operands  */           \
                           "r"(param3),                                     \
                           "r"(param2),                                     \
                           "r"(param1),                                     \
                           "c"(thisPtr)                                     \
                          );                                                \

#endif

// Our static singleton instance.
IASIOThiscallResolver IASIOThiscallResolver::instance;

// Constructor called to initialize static Singleton instance above. Note that
// it is important not to clear that_ incase it has already been set by the call
// to placement new in ASIOInit().
IASIOThiscallResolver::IASIOThiscallResolver()
{
}

// Constructor called from ASIOInit() below
IASIOThiscallResolver::IASIOThiscallResolver(IASIO* that)
: that_( that )
{
}

// Implement IUnknown methods as assert(false). IASIOThiscallResolver is not
// really a COM object, just a wrapper which will work with the ASIO SDK.
// If you wanted to use ASIO without the SDK you might want to implement COM
// aggregation in these methods.
HRESULT STDMETHODCALLTYPE IASIOThiscallResolver::QueryInterface(REFIID riid, void **ppv)
{
    (void)riid;     // suppress unused variable warning

    assert( false ); // this function should never be called by the ASIO SDK.

    *ppv = NULL;
    return E_NOINTERFACE;
}

ULONG STDMETHODCALLTYPE IASIOThiscallResolver::AddRef()
{
    assert( false ); // this function should never be called by the ASIO SDK.

    return 1;
}

ULONG STDMETHODCALLTYPE IASIOThiscallResolver::Release()
{
    assert( false ); // this function should never be called by the ASIO SDK.

    return 1;
}

// Implement the IASIO interface methods by performing the vptr manipulation
// described above then delegating to the real implementation.
ASIOBool IASIOThiscallResolver::init(void *sysHandle)
{
    ASIOBool result;
    CALL_THISCALL_1( result, that_, 12, sysHandle );
    return result;
}

void IASIOThiscallResolver::getDriverName(char *name)
{
    CALL_VOID_THISCALL_1( that_, 16, name );
}

long IASIOThiscallResolver::getDriverVersion()
{
    ASIOBool result;
    CALL_THISCALL_0( result, that_, 20 );
    return result;
}

void IASIOThiscallResolver::getErrorMessage(char *string)
{
     CALL_VOID_THISCALL_1( that_, 24, string );
}

ASIOError IASIOThiscallResolver::start()
{
    ASIOBool result;
    CALL_THISCALL_0( result, that_, 28 );
    return result;
}

ASIOError IASIOThiscallResolver::stop()
{
    ASIOBool result;
    CALL_THISCALL_0( result, that_, 32 );
    return result;
}

ASIOError IASIOThiscallResolver::getChannels(long *numInputChannels, long *numOutputChannels)
{
    ASIOBool result;
    CALL_THISCALL_2( result, that_, 36, numInputChannels, numOutputChannels );
    return result;
}

ASIOError IASIOThiscallResolver::getLatencies(long *inputLatency, long *outputLatency)
{
    ASIOBool result;
    CALL_THISCALL_2( result, that_, 40, inputLatency, outputLatency );
    return result;
}

ASIOError IASIOThiscallResolver::getBufferSize(long *minSize, long *maxSize,
        long *preferredSize, long *granularity)
{
    ASIOBool result;
    CALL_THISCALL_4( result, that_, 44, minSize, maxSize, preferredSize, granularity );
    return result;
}

ASIOError IASIOThiscallResolver::canSampleRate(ASIOSampleRate sampleRate)
{
    ASIOBool result;
    CALL_THISCALL_1_DOUBLE( result, that_, 48, sampleRate );
    return result;
}

ASIOError IASIOThiscallResolver::getSampleRate(ASIOSampleRate *sampleRate)
{
    ASIOBool result;
    CALL_THISCALL_1( result, that_, 52, sampleRate );
    return result;
}

ASIOError IASIOThiscallResolver::setSampleRate(ASIOSampleRate sampleRate)
{
    ASIOBool result;
    CALL_THISCALL_1_DOUBLE( result, that_, 56, sampleRate );
    return result;
}

ASIOError IASIOThiscallResolver::getClockSources(ASIOClockSource *clocks, long *numSources)
{
    ASIOBool result;
    CALL_THISCALL_2( result, that_, 60, clocks, numSources );
    return result;
}

ASIOError IASIOThiscallResolver::setClockSource(long reference)
{
    ASIOBool result;
    CALL_THISCALL_1( result, that_, 64, reference );
    return result;
}

ASIOError IASIOThiscallResolver::getSamplePosition(ASIOSamples *sPos, ASIOTimeStamp *tStamp)
{
    ASIOBool result;
    CALL_THISCALL_2( result, that_, 68, sPos, tStamp );
    return result;
}

ASIOError IASIOThiscallResolver::getChannelInfo(ASIOChannelInfo *info)
{
    ASIOBool result;
    CALL_THISCALL_1( result, that_, 72, info );
    return result;
}

ASIOError IASIOThiscallResolver::createBuffers(ASIOBufferInfo *bufferInfos,
        long numChannels, long bufferSize, ASIOCallbacks *callbacks)
{
    ASIOBool result;
    CALL_THISCALL_4( result, that_, 76, bufferInfos, numChannels, bufferSize, callbacks );
    return result;
}

ASIOError IASIOThiscallResolver::disposeBuffers()
{
    ASIOBool result;
    CALL_THISCALL_0( result, that_, 80 );
    return result;
}

ASIOError IASIOThiscallResolver::controlPanel()
{
    ASIOBool result;
    CALL_THISCALL_0( result, that_, 84 );
    return result;
}

ASIOError IASIOThiscallResolver::future(long selector,void *opt)
{
    ASIOBool result;
    CALL_THISCALL_2( result, that_, 88, selector, opt );
    return result;
}

ASIOError IASIOThiscallResolver::outputReady()
{
    ASIOBool result;
    CALL_THISCALL_0( result, that_, 92 );
    return result;
}

// Implement our substitute ASIOInit() method
ASIOError IASIOThiscallResolver::ASIOInit(ASIODriverInfo *info)
{
    // To ensure that our instance's vptr is correctly constructed, even if
    // ASIOInit is called prior to main(), we explicitly call its constructor
    // (potentially over the top of an existing instance). Note that this is
    // pretty ugly, and is only safe because IASIOThiscallResolver has no
    // destructor and contains no objects with destructors.
    new((void*)&instance) IASIOThiscallResolver( theAsioDriver );

    // Interpose between ASIO client code and the real driver.
    theAsioDriver = &instance;

    // Note that we never need to switch theAsioDriver back to point to the
    // real driver because theAsioDriver is reset to zero in ASIOExit().

    // Delegate to the real ASIOInit
        return ::ASIOInit(info);
}

#endif /* !defined(_MSC_VER) */

#endif /* Win32 */
1	/*
2	IASIOThiscallResolver.cpp see the comments in iasiothiscallresolver.h for
3	the top level description - this comment describes the technical details of
4	the implementation.
5
6	The latest version of this file is available from:
7	http://www.audiomulch.com/~rossb/code/calliasio
8
9	please email comments to Ross Bencina <rossb@audiomulch.com>
10
11	BACKGROUND
12
13	The IASIO interface declared in the Steinberg ASIO 2 SDK declares
14	functions with no explicit calling convention. This causes MSVC++ to default
15	to using the thiscall convention, which is a proprietary convention not
16	implemented by some non-microsoft compilers - notably borland BCC,
17	C++Builder, and gcc. MSVC++ is the defacto standard compiler used by
18	Steinberg. As a result of this situation, the ASIO sdk will compile with
19	any compiler, however attempting to execute the compiled code will cause a
20	crash due to different default calling conventions on non-Microsoft
21	compilers.
22
23	IASIOThiscallResolver solves the problem by providing an adapter class that
24	delegates to the IASIO interface using the correct calling convention
25	(thiscall). Due to the lack of support for thiscall in the Borland and GCC
26	compilers, the calls have been implemented in assembly language.
27
28	A number of macros are defined for thiscall function calls with different
29	numbers of parameters, with and without return values - it may be possible
30	to modify the format of these macros to make them work with other inline
31	assemblers.
32
33
34	THISCALL DEFINITION
35
36	A number of definitions of the thiscall calling convention are floating
37	around the internet. The following definition has been validated against
38	output from the MSVC++ compiler:
39
40	For non-vararg functions, thiscall works as follows: the object (this)
41	pointer is passed in ECX. All arguments are passed on the stack in
42	right to left order. The return value is placed in EAX. The callee
43	clears the passed arguments from the stack.
44
45
46	FINDING FUNCTION POINTERS FROM AN IASIO POINTER
47
48	The first field of a COM object is a pointer to its vtble. Thus a pointer
49	to an object implementing the IASIO interface also points to a pointer to
50	that object's vtbl. The vtble is a table of function pointers for all of
51	the virtual functions exposed by the implemented interfaces.
52
53	If we consider a variable declared as a pointer to IASO:
54
55	IASIO *theAsioDriver
56
57	theAsioDriver points to:
58
59	object implementing IASIO
60	{
61	IASIOvtbl *vtbl
62	other data
63	}
64
65	in other words, theAsioDriver points to a pointer to an IASIOvtbl
66
67	vtbl points to a table of function pointers:
68
69	IASIOvtbl ( interface IASIO : public IUnknown )
70	{
71	(IUnknown functions)
72	0 virtual HRESULT STDMETHODCALLTYPE (QueryInterface)(REFIID riid, void *ppv) = 0;
73	4 virtual ULONG STDMETHODCALLTYPE (*AddRef)() = 0;
74	8 virtual ULONG STDMETHODCALLTYPE (*Release)() = 0;
75
76	(IASIO functions)
77	12 virtual ASIOBool (init)(void sysHandle) = 0;
78	16 virtual void (getDriverName)(char name) = 0;
79	20 virtual long (*getDriverVersion)() = 0;
80	24 virtual void (getErrorMessage)(char string) = 0;
81	28 virtual ASIOError (*start)() = 0;
82	32 virtual ASIOError (*stop)() = 0;
83	36 virtual ASIOError (getChannels)(long numInputChannels, long *numOutputChannels) = 0;
84	40 virtual ASIOError (getLatencies)(long inputLatency, long *outputLatency) = 0;
85	44 virtual ASIOError (getBufferSize)(long minSize, long *maxSize,
86	long preferredSize, long granularity) = 0;
87	48 virtual ASIOError (*canSampleRate)(ASIOSampleRate sampleRate) = 0;
88	52 virtual ASIOError (getSampleRate)(ASIOSampleRate sampleRate) = 0;
89	56 virtual ASIOError (*setSampleRate)(ASIOSampleRate sampleRate) = 0;
90	60 virtual ASIOError (getClockSources)(ASIOClockSource clocks, long *numSources) = 0;
91	64 virtual ASIOError (*setClockSource)(long reference) = 0;
92	68 virtual ASIOError (getSamplePosition)(ASIOSamples sPos, ASIOTimeStamp *tStamp) = 0;
93	72 virtual ASIOError (getChannelInfo)(ASIOChannelInfo info) = 0;
94	76 virtual ASIOError (createBuffers)(ASIOBufferInfo bufferInfos, long numChannels,
95	long bufferSize, ASIOCallbacks *callbacks) = 0;
96	80 virtual ASIOError (*disposeBuffers)() = 0;
97	84 virtual ASIOError (*controlPanel)() = 0;
98	88 virtual ASIOError (future)(long selector,void opt) = 0;
99	92 virtual ASIOError (*outputReady)() = 0;
100	};
101
102	The numbers in the left column show the byte offset of each function ptr
103	from the beginning of the vtbl. These numbers are used in the code below
104	to select different functions.
105
106	In order to find the address of a particular function, theAsioDriver
107	must first be dereferenced to find the value of the vtbl pointer:
108
109	mov eax, theAsioDriver
110	mov edx, [theAsioDriver] // edx now points to vtbl[0]
111
112	Then an offset must be added to the vtbl pointer to select a
113	particular function, for example vtbl+44 points to the slot containing
114	a pointer to the getBufferSize function.
115
116	Finally vtbl+x must be dereferenced to obtain the value of the function
117	pointer stored in that address:
118
119	call [edx+44] // call the function pointed to by
120	// the value in the getBufferSize field of the vtbl
121
122
123	SEE ALSO
124
125	Martin Fay's OpenASIO DLL at http://www.martinfay.com solves the same
126	problem by providing a new COM interface which wraps IASIO with an
127	interface that uses portable calling conventions. OpenASIO must be compiled
128	with MSVC, and requires that you ship the OpenASIO DLL with your
129	application.
130
131
132	ACKNOWLEDGEMENTS
133
134	Ross Bencina: worked out the thiscall details above, wrote the original
135	Borland asm macros, and a patch for asio.cpp (which is no longer needed).
136	Thanks to Martin Fay for introducing me to the issues discussed here,
137	and to Rene G. Ceballos for assisting with asm dumps from MSVC++.
138
139	Antti Silvast: converted the original calliasio to work with gcc and NASM
140	by implementing the asm code in a separate file.
141
142	Fraser Adams: modified the original calliasio containing the Borland inline
143	asm to add inline asm for gcc i.e. Intel syntax for Borland and AT&T syntax
144	for gcc. This seems a neater approach for gcc than to have a separate .asm
145	file and it means that we only need one version of the thiscall patch.
146
147	Fraser Adams: rewrote the original calliasio patch in the form of the
148	IASIOThiscallResolver class in order to avoid modifications to files from
149	the Steinberg SDK, which may have had potential licence issues.
150
151	Andrew Baldwin: contributed fixes for compatibility problems with more
152	recent versions of the gcc assembler.
153	*/
154
155
156	// We only need IASIOThiscallResolver at all if we are on Win32. For other
157	// platforms we simply bypass the IASIOThiscallResolver definition to allow us
158	// to be safely #include'd whatever the platform to keep client code portable
159	#if defined(WIN32) \|\| defined(_WIN32) \|\| defined(__WIN32__)
160
161	// If microsoft compiler we can call IASIO directly so IASIOThiscallResolver
162	// is not used.
163	#if !defined(_MSC_VER)
164
165	#include <new>
166	#include <assert.h>
167
168	// We have a mechanism in iasiothiscallresolver.h to ensure that asio.h is
169	// #include'd before it in client code, we do NOT want to do this test here.
170	#define iasiothiscallresolver_sourcefile 1
171	#include "iasiothiscallresolver.h"
172	#undef iasiothiscallresolver_sourcefile
173
174	// iasiothiscallresolver.h redefines ASIOInit for clients, but we don't want
175	// this macro defined in this translation unit.
176	#undef ASIOInit
177
178	// theAsioDriver is a global pointer to the current IASIO instance which the
179	// ASIO SDK uses to perform all actions on the IASIO interface. We substitute
180	// our own forwarding interface into this pointer.
181	extern IASIO* theAsioDriver;
182
183	// The following macros define the inline assembler for BORLAND first then gcc
184
185	#if defined(__BCPLUSPLUS__) \|\| defined(__BORLANDC__)
186
187	#define CALL_THISCALL_0( resultName, thisPtr, funcOffset )\
188	void *this_ = (thisPtr); \
189	__asm { \
190	mov ecx, this_ ; \
191	mov eax, [ecx] ; \
192	call [eax+funcOffset] ; \
193	mov resultName, eax ; \
194	}
195
196	#define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 )\
197	void *this_ = (thisPtr); \
198	__asm { \
199	mov eax, param1 ; \
200	push eax ; \
201	mov ecx, this_ ; \
202	mov eax, [ecx] ; \
203	call [eax+funcOffset] ; \
204	}
205
206	#define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 )\
207	void *this_ = (thisPtr); \
208	__asm { \
209	mov eax, param1 ; \
210	push eax ; \
211	mov ecx, this_ ; \
212	mov eax, [ecx] ; \
213	call [eax+funcOffset] ; \
214	mov resultName, eax ; \
215	}
216
217	#define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 )\
218	void *this_ = (thisPtr); \
219	void *doubleParamPtr_ (&param1); \
220	__asm { \
221	mov eax, doubleParamPtr_ ; \
222	push [eax+4] ; \
223	push [eax] ; \
224	mov ecx, this_ ; \
225	mov eax, [ecx] ; \
226	call [eax+funcOffset] ; \
227	mov resultName, eax ; \
228	}
229
230	#define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 )\
231	void *this_ = (thisPtr); \
232	__asm { \
233	mov eax, param2 ; \
234	push eax ; \
235	mov eax, param1 ; \
236	push eax ; \
237	mov ecx, this_ ; \
238	mov eax, [ecx] ; \
239	call [eax+funcOffset] ; \
240	mov resultName, eax ; \
241	}
242
243	#define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
244	void *this_ = (thisPtr); \
245	__asm { \
246	mov eax, param4 ; \
247	push eax ; \
248	mov eax, param3 ; \
249	push eax ; \
250	mov eax, param2 ; \
251	push eax ; \
252	mov eax, param1 ; \
253	push eax ; \
254	mov ecx, this_ ; \
255	mov eax, [ecx] ; \
256	call [eax+funcOffset] ; \
257	mov resultName, eax ; \
258	}
259
260	#elif defined(__GNUC__)
261
262	#define CALL_THISCALL_0( resultName, thisPtr, funcOffset ) \
263	__asm__ __volatile__ ("movl (%1), %%edx\n\t" \
264	"call *"#funcOffset"(%%edx)\n\t" \
265	:"=a"(resultName) /* Output Operands */ \
266	:"c"(thisPtr) /* Input Operands */ \
267	); \
268
269	#define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 ) \
270	__asm__ __volatile__ ("pushl %0\n\t" \
271	"movl (%1), %%edx\n\t" \
272	"call *"#funcOffset"(%%edx)\n\t" \
273	: /* Output Operands */ \
274	:"r"(param1), /* Input Operands */ \
275	"c"(thisPtr) \
276	); \
277
278	#define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 ) \
279	__asm__ __volatile__ ("pushl %1\n\t" \
280	"movl (%2), %%edx\n\t" \
281	"call *"#funcOffset"(%%edx)\n\t" \
282	:"=a"(resultName) /* Output Operands */ \
283	:"r"(param1), /* Input Operands */ \
284	"c"(thisPtr) \
285	); \
286
287	#define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 ) \
288	__asm__ __volatile__ ("pushl 4(%1)\n\t" \
289	"pushl (%1)\n\t" \
290	"movl (%2), %%edx\n\t" \
291	"call *"#funcOffset"(%%edx);\n\t" \
292	:"=a"(resultName) /* Output Operands */ \
293	:"a"(&param1), /* Input Operands */ \
294	/* Note: Using "r" above instead of "a" fails */ \
295	/* when using GCC 3.3.3, and maybe later versions*/\
296	"c"(thisPtr) \
297	); \
298
299	#define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 ) \
300	__asm__ __volatile__ ("pushl %1\n\t" \
301	"pushl %2\n\t" \
302	"movl (%3), %%edx\n\t" \
303	"call *"#funcOffset"(%%edx)\n\t" \
304	:"=a"(resultName) /* Output Operands */ \
305	:"r"(param2), /* Input Operands */ \
306	"r"(param1), \
307	"c"(thisPtr) \
308	); \
309
310	#define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
311	__asm__ __volatile__ ("pushl %1\n\t" \
312	"pushl %2\n\t" \
313	"pushl %3\n\t" \
314	"pushl %4\n\t" \
315	"movl (%5), %%edx\n\t" \
316	"call *"#funcOffset"(%%edx)\n\t" \
317	:"=a"(resultName) /* Output Operands */ \
318	:"r"(param4), /* Input Operands */ \
319	"r"(param3), \
320	"r"(param2), \
321	"r"(param1), \
322	"c"(thisPtr) \
323	); \
324
325	#endif
326
327	// Our static singleton instance.
328	IASIOThiscallResolver IASIOThiscallResolver::instance;
329
330	// Constructor called to initialize static Singleton instance above. Note that
331	// it is important not to clear that_ incase it has already been set by the call
332	// to placement new in ASIOInit().
333	IASIOThiscallResolver::IASIOThiscallResolver()
334	{
335	}
336
337	// Constructor called from ASIOInit() below
338	IASIOThiscallResolver::IASIOThiscallResolver(IASIO* that)
339	: that_( that )
340	{
341	}
342
343	// Implement IUnknown methods as assert(false). IASIOThiscallResolver is not
344	// really a COM object, just a wrapper which will work with the ASIO SDK.
345	// If you wanted to use ASIO without the SDK you might want to implement COM
346	// aggregation in these methods.
347	HRESULT STDMETHODCALLTYPE IASIOThiscallResolver::QueryInterface(REFIID riid, void **ppv)
348	{
349	(void)riid; // suppress unused variable warning
350
351	assert( false ); // this function should never be called by the ASIO SDK.
352
353	*ppv = NULL;
354	return E_NOINTERFACE;
355	}
356
357	ULONG STDMETHODCALLTYPE IASIOThiscallResolver::AddRef()
358	{
359	assert( false ); // this function should never be called by the ASIO SDK.
360
361	return 1;
362	}
363
364	ULONG STDMETHODCALLTYPE IASIOThiscallResolver::Release()
365	{
366	assert( false ); // this function should never be called by the ASIO SDK.
367
368	return 1;
369	}
370
371	// Implement the IASIO interface methods by performing the vptr manipulation
372	// described above then delegating to the real implementation.
373	ASIOBool IASIOThiscallResolver::init(void *sysHandle)
374	{
375	ASIOBool result;
376	CALL_THISCALL_1( result, that_, 12, sysHandle );
377	return result;
378	}
379
380	void IASIOThiscallResolver::getDriverName(char *name)
381	{
382	CALL_VOID_THISCALL_1( that_, 16, name );
383	}
384
385	long IASIOThiscallResolver::getDriverVersion()
386	{
387	ASIOBool result;
388	CALL_THISCALL_0( result, that_, 20 );
389	return result;
390	}
391
392	void IASIOThiscallResolver::getErrorMessage(char *string)
393	{
394	CALL_VOID_THISCALL_1( that_, 24, string );
395	}
396
397	ASIOError IASIOThiscallResolver::start()
398	{
399	ASIOBool result;
400	CALL_THISCALL_0( result, that_, 28 );
401	return result;
402	}
403
404	ASIOError IASIOThiscallResolver::stop()
405	{
406	ASIOBool result;
407	CALL_THISCALL_0( result, that_, 32 );
408	return result;
409	}
410
411	ASIOError IASIOThiscallResolver::getChannels(long numInputChannels, long numOutputChannels)
412	{
413	ASIOBool result;
414	CALL_THISCALL_2( result, that_, 36, numInputChannels, numOutputChannels );
415	return result;
416	}
417
418	ASIOError IASIOThiscallResolver::getLatencies(long inputLatency, long outputLatency)
419	{
420	ASIOBool result;
421	CALL_THISCALL_2( result, that_, 40, inputLatency, outputLatency );
422	return result;
423	}
424
425	ASIOError IASIOThiscallResolver::getBufferSize(long minSize, long maxSize,
426	long preferredSize, long granularity)
427	{
428	ASIOBool result;
429	CALL_THISCALL_4( result, that_, 44, minSize, maxSize, preferredSize, granularity );
430	return result;
431	}
432
433	ASIOError IASIOThiscallResolver::canSampleRate(ASIOSampleRate sampleRate)
434	{
435	ASIOBool result;
436	CALL_THISCALL_1_DOUBLE( result, that_, 48, sampleRate );
437	return result;
438	}
439
440	ASIOError IASIOThiscallResolver::getSampleRate(ASIOSampleRate *sampleRate)
441	{
442	ASIOBool result;
443	CALL_THISCALL_1( result, that_, 52, sampleRate );
444	return result;
445	}
446
447	ASIOError IASIOThiscallResolver::setSampleRate(ASIOSampleRate sampleRate)
448	{
449	ASIOBool result;
450	CALL_THISCALL_1_DOUBLE( result, that_, 56, sampleRate );
451	return result;
452	}
453
454	ASIOError IASIOThiscallResolver::getClockSources(ASIOClockSource clocks, long numSources)
455	{
456	ASIOBool result;
457	CALL_THISCALL_2( result, that_, 60, clocks, numSources );
458	return result;
459	}
460
461	ASIOError IASIOThiscallResolver::setClockSource(long reference)
462	{
463	ASIOBool result;
464	CALL_THISCALL_1( result, that_, 64, reference );
465	return result;
466	}
467
468	ASIOError IASIOThiscallResolver::getSamplePosition(ASIOSamples sPos, ASIOTimeStamp tStamp)
469	{
470	ASIOBool result;
471	CALL_THISCALL_2( result, that_, 68, sPos, tStamp );
472	return result;
473	}
474
475	ASIOError IASIOThiscallResolver::getChannelInfo(ASIOChannelInfo *info)
476	{
477	ASIOBool result;
478	CALL_THISCALL_1( result, that_, 72, info );
479	return result;
480	}
481
482	ASIOError IASIOThiscallResolver::createBuffers(ASIOBufferInfo *bufferInfos,
483	long numChannels, long bufferSize, ASIOCallbacks *callbacks)
484	{
485	ASIOBool result;
486	CALL_THISCALL_4( result, that_, 76, bufferInfos, numChannels, bufferSize, callbacks );
487	return result;
488	}
489
490	ASIOError IASIOThiscallResolver::disposeBuffers()
491	{
492	ASIOBool result;
493	CALL_THISCALL_0( result, that_, 80 );
494	return result;
495	}
496
497	ASIOError IASIOThiscallResolver::controlPanel()
498	{
499	ASIOBool result;
500	CALL_THISCALL_0( result, that_, 84 );
501	return result;
502	}
503
504	ASIOError IASIOThiscallResolver::future(long selector,void *opt)
505	{
506	ASIOBool result;
507	CALL_THISCALL_2( result, that_, 88, selector, opt );
508	return result;
509	}
510
511	ASIOError IASIOThiscallResolver::outputReady()
512	{
513	ASIOBool result;
514	CALL_THISCALL_0( result, that_, 92 );
515	return result;
516	}
517
518	// Implement our substitute ASIOInit() method
519	ASIOError IASIOThiscallResolver::ASIOInit(ASIODriverInfo *info)
520	{
521	// To ensure that our instance's vptr is correctly constructed, even if
522	// ASIOInit is called prior to main(), we explicitly call its constructor
523	// (potentially over the top of an existing instance). Note that this is
524	// pretty ugly, and is only safe because IASIOThiscallResolver has no
525	// destructor and contains no objects with destructors.
526	new((void*)&instance) IASIOThiscallResolver( theAsioDriver );
527
528	// Interpose between ASIO client code and the real driver.
529	theAsioDriver = &instance;
530
531	// Note that we never need to switch theAsioDriver back to point to the
532	// real driver because theAsioDriver is reset to zero in ASIOExit().
533
534	// Delegate to the real ASIOInit
535	return ::ASIOInit(info);
536	}
537
538	#endif /* !defined(_MSC_VER) */
539
540	#endif /* Win32 */