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__)

// gcc 4.4 is using the same calling conventions as Microsoft on Win64
#if !defined(__WIN64__)

// 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 /* !defined(__WIN64__) */
#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	// gcc 4.4 is using the same calling conventions as Microsoft on Win64
162	#if !defined(__WIN64__)
163
164	// If microsoft compiler we can call IASIO directly so IASIOThiscallResolver
165	// is not used.
166	#if !defined(_MSC_VER)
167
168	#include <new>
169	#include <assert.h>
170
171	// We have a mechanism in iasiothiscallresolver.h to ensure that asio.h is
172	// #include'd before it in client code, we do NOT want to do this test here.
173	#define iasiothiscallresolver_sourcefile 1
174	#include "iasiothiscallresolver.h"
175	#undef iasiothiscallresolver_sourcefile
176
177	// iasiothiscallresolver.h redefines ASIOInit for clients, but we don't want
178	// this macro defined in this translation unit.
179	#undef ASIOInit
180
181	// theAsioDriver is a global pointer to the current IASIO instance which the
182	// ASIO SDK uses to perform all actions on the IASIO interface. We substitute
183	// our own forwarding interface into this pointer.
184	extern IASIO* theAsioDriver;
185
186	// The following macros define the inline assembler for BORLAND first then gcc
187
188	#if defined(__BCPLUSPLUS__) \|\| defined(__BORLANDC__)
189
190	#define CALL_THISCALL_0( resultName, thisPtr, funcOffset )\
191	void *this_ = (thisPtr); \
192	__asm { \
193	mov ecx, this_ ; \
194	mov eax, [ecx] ; \
195	call [eax+funcOffset] ; \
196	mov resultName, eax ; \
197	}
198
199	#define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 )\
200	void *this_ = (thisPtr); \
201	__asm { \
202	mov eax, param1 ; \
203	push eax ; \
204	mov ecx, this_ ; \
205	mov eax, [ecx] ; \
206	call [eax+funcOffset] ; \
207	}
208
209	#define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 )\
210	void *this_ = (thisPtr); \
211	__asm { \
212	mov eax, param1 ; \
213	push eax ; \
214	mov ecx, this_ ; \
215	mov eax, [ecx] ; \
216	call [eax+funcOffset] ; \
217	mov resultName, eax ; \
218	}
219
220	#define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 )\
221	void *this_ = (thisPtr); \
222	void *doubleParamPtr_ (&param1); \
223	__asm { \
224	mov eax, doubleParamPtr_ ; \
225	push [eax+4] ; \
226	push [eax] ; \
227	mov ecx, this_ ; \
228	mov eax, [ecx] ; \
229	call [eax+funcOffset] ; \
230	mov resultName, eax ; \
231	}
232
233	#define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 )\
234	void *this_ = (thisPtr); \
235	__asm { \
236	mov eax, param2 ; \
237	push eax ; \
238	mov eax, param1 ; \
239	push eax ; \
240	mov ecx, this_ ; \
241	mov eax, [ecx] ; \
242	call [eax+funcOffset] ; \
243	mov resultName, eax ; \
244	}
245
246	#define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
247	void *this_ = (thisPtr); \
248	__asm { \
249	mov eax, param4 ; \
250	push eax ; \
251	mov eax, param3 ; \
252	push eax ; \
253	mov eax, param2 ; \
254	push eax ; \
255	mov eax, param1 ; \
256	push eax ; \
257	mov ecx, this_ ; \
258	mov eax, [ecx] ; \
259	call [eax+funcOffset] ; \
260	mov resultName, eax ; \
261	}
262
263	#elif defined(__GNUC__)
264
265	#define CALL_THISCALL_0( resultName, thisPtr, funcOffset ) \
266	__asm__ __volatile__ ("movl (%1), %%edx\n\t" \
267	"call *"#funcOffset"(%%edx)\n\t" \
268	:"=a"(resultName) /* Output Operands */ \
269	:"c"(thisPtr) /* Input Operands */ \
270	); \
271
272	#define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 ) \
273	__asm__ __volatile__ ("pushl %0\n\t" \
274	"movl (%1), %%edx\n\t" \
275	"call *"#funcOffset"(%%edx)\n\t" \
276	: /* Output Operands */ \
277	:"r"(param1), /* Input Operands */ \
278	"c"(thisPtr) \
279	); \
280
281	#define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 ) \
282	__asm__ __volatile__ ("pushl %1\n\t" \
283	"movl (%2), %%edx\n\t" \
284	"call *"#funcOffset"(%%edx)\n\t" \
285	:"=a"(resultName) /* Output Operands */ \
286	:"r"(param1), /* Input Operands */ \
287	"c"(thisPtr) \
288	); \
289
290	#define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 ) \
291	__asm__ __volatile__ ("pushl 4(%1)\n\t" \
292	"pushl (%1)\n\t" \
293	"movl (%2), %%edx\n\t" \
294	"call *"#funcOffset"(%%edx);\n\t" \
295	:"=a"(resultName) /* Output Operands */ \
296	:"a"(&param1), /* Input Operands */ \
297	/* Note: Using "r" above instead of "a" fails */ \
298	/* when using GCC 3.3.3, and maybe later versions*/\
299	"c"(thisPtr) \
300	); \
301
302	#define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 ) \
303	__asm__ __volatile__ ("pushl %1\n\t" \
304	"pushl %2\n\t" \
305	"movl (%3), %%edx\n\t" \
306	"call *"#funcOffset"(%%edx)\n\t" \
307	:"=a"(resultName) /* Output Operands */ \
308	:"r"(param2), /* Input Operands */ \
309	"r"(param1), \
310	"c"(thisPtr) \
311	); \
312
313	#define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
314	__asm__ __volatile__ ("pushl %1\n\t" \
315	"pushl %2\n\t" \
316	"pushl %3\n\t" \
317	"pushl %4\n\t" \
318	"movl (%5), %%edx\n\t" \
319	"call *"#funcOffset"(%%edx)\n\t" \
320	:"=a"(resultName) /* Output Operands */ \
321	:"r"(param4), /* Input Operands */ \
322	"r"(param3), \
323	"r"(param2), \
324	"r"(param1), \
325	"c"(thisPtr) \
326	); \
327
328	#endif
329
330	// Our static singleton instance.
331	IASIOThiscallResolver IASIOThiscallResolver::instance;
332
333	// Constructor called to initialize static Singleton instance above. Note that
334	// it is important not to clear that_ incase it has already been set by the call
335	// to placement new in ASIOInit().
336	IASIOThiscallResolver::IASIOThiscallResolver()
337	{
338	}
339
340	// Constructor called from ASIOInit() below
341	IASIOThiscallResolver::IASIOThiscallResolver(IASIO* that)
342	: that_( that )
343	{
344	}
345
346	// Implement IUnknown methods as assert(false). IASIOThiscallResolver is not
347	// really a COM object, just a wrapper which will work with the ASIO SDK.
348	// If you wanted to use ASIO without the SDK you might want to implement COM
349	// aggregation in these methods.
350	HRESULT STDMETHODCALLTYPE IASIOThiscallResolver::QueryInterface(REFIID riid, void **ppv)
351	{
352	(void)riid; // suppress unused variable warning
353
354	assert( false ); // this function should never be called by the ASIO SDK.
355
356	*ppv = NULL;
357	return E_NOINTERFACE;
358	}
359
360	ULONG STDMETHODCALLTYPE IASIOThiscallResolver::AddRef()
361	{
362	assert( false ); // this function should never be called by the ASIO SDK.
363
364	return 1;
365	}
366
367	ULONG STDMETHODCALLTYPE IASIOThiscallResolver::Release()
368	{
369	assert( false ); // this function should never be called by the ASIO SDK.
370
371	return 1;
372	}
373
374	// Implement the IASIO interface methods by performing the vptr manipulation
375	// described above then delegating to the real implementation.
376	ASIOBool IASIOThiscallResolver::init(void *sysHandle)
377	{
378	ASIOBool result;
379	CALL_THISCALL_1( result, that_, 12, sysHandle );
380	return result;
381	}
382
383	void IASIOThiscallResolver::getDriverName(char *name)
384	{
385	CALL_VOID_THISCALL_1( that_, 16, name );
386	}
387
388	long IASIOThiscallResolver::getDriverVersion()
389	{
390	ASIOBool result;
391	CALL_THISCALL_0( result, that_, 20 );
392	return result;
393	}
394
395	void IASIOThiscallResolver::getErrorMessage(char *string)
396	{
397	CALL_VOID_THISCALL_1( that_, 24, string );
398	}
399
400	ASIOError IASIOThiscallResolver::start()
401	{
402	ASIOBool result;
403	CALL_THISCALL_0( result, that_, 28 );
404	return result;
405	}
406
407	ASIOError IASIOThiscallResolver::stop()
408	{
409	ASIOBool result;
410	CALL_THISCALL_0( result, that_, 32 );
411	return result;
412	}
413
414	ASIOError IASIOThiscallResolver::getChannels(long numInputChannels, long numOutputChannels)
415	{
416	ASIOBool result;
417	CALL_THISCALL_2( result, that_, 36, numInputChannels, numOutputChannels );
418	return result;
419	}
420
421	ASIOError IASIOThiscallResolver::getLatencies(long inputLatency, long outputLatency)
422	{
423	ASIOBool result;
424	CALL_THISCALL_2( result, that_, 40, inputLatency, outputLatency );
425	return result;
426	}
427
428	ASIOError IASIOThiscallResolver::getBufferSize(long minSize, long maxSize,
429	long preferredSize, long granularity)
430	{
431	ASIOBool result;
432	CALL_THISCALL_4( result, that_, 44, minSize, maxSize, preferredSize, granularity );
433	return result;
434	}
435
436	ASIOError IASIOThiscallResolver::canSampleRate(ASIOSampleRate sampleRate)
437	{
438	ASIOBool result;
439	CALL_THISCALL_1_DOUBLE( result, that_, 48, sampleRate );
440	return result;
441	}
442
443	ASIOError IASIOThiscallResolver::getSampleRate(ASIOSampleRate *sampleRate)
444	{
445	ASIOBool result;
446	CALL_THISCALL_1( result, that_, 52, sampleRate );
447	return result;
448	}
449
450	ASIOError IASIOThiscallResolver::setSampleRate(ASIOSampleRate sampleRate)
451	{
452	ASIOBool result;
453	CALL_THISCALL_1_DOUBLE( result, that_, 56, sampleRate );
454	return result;
455	}
456
457	ASIOError IASIOThiscallResolver::getClockSources(ASIOClockSource clocks, long numSources)
458	{
459	ASIOBool result;
460	CALL_THISCALL_2( result, that_, 60, clocks, numSources );
461	return result;
462	}
463
464	ASIOError IASIOThiscallResolver::setClockSource(long reference)
465	{
466	ASIOBool result;
467	CALL_THISCALL_1( result, that_, 64, reference );
468	return result;
469	}
470
471	ASIOError IASIOThiscallResolver::getSamplePosition(ASIOSamples sPos, ASIOTimeStamp tStamp)
472	{
473	ASIOBool result;
474	CALL_THISCALL_2( result, that_, 68, sPos, tStamp );
475	return result;
476	}
477
478	ASIOError IASIOThiscallResolver::getChannelInfo(ASIOChannelInfo *info)
479	{
480	ASIOBool result;
481	CALL_THISCALL_1( result, that_, 72, info );
482	return result;
483	}
484
485	ASIOError IASIOThiscallResolver::createBuffers(ASIOBufferInfo *bufferInfos,
486	long numChannels, long bufferSize, ASIOCallbacks *callbacks)
487	{
488	ASIOBool result;
489	CALL_THISCALL_4( result, that_, 76, bufferInfos, numChannels, bufferSize, callbacks );
490	return result;
491	}
492
493	ASIOError IASIOThiscallResolver::disposeBuffers()
494	{
495	ASIOBool result;
496	CALL_THISCALL_0( result, that_, 80 );
497	return result;
498	}
499
500	ASIOError IASIOThiscallResolver::controlPanel()
501	{
502	ASIOBool result;
503	CALL_THISCALL_0( result, that_, 84 );
504	return result;
505	}
506
507	ASIOError IASIOThiscallResolver::future(long selector,void *opt)
508	{
509	ASIOBool result;
510	CALL_THISCALL_2( result, that_, 88, selector, opt );
511	return result;
512	}
513
514	ASIOError IASIOThiscallResolver::outputReady()
515	{
516	ASIOBool result;
517	CALL_THISCALL_0( result, that_, 92 );
518	return result;
519	}
520
521	// Implement our substitute ASIOInit() method
522	ASIOError IASIOThiscallResolver::ASIOInit(ASIODriverInfo *info)
523	{
524	// To ensure that our instance's vptr is correctly constructed, even if
525	// ASIOInit is called prior to main(), we explicitly call its constructor
526	// (potentially over the top of an existing instance). Note that this is
527	// pretty ugly, and is only safe because IASIOThiscallResolver has no
528	// destructor and contains no objects with destructors.
529	new((void*)&instance) IASIOThiscallResolver( theAsioDriver );
530
531	// Interpose between ASIO client code and the real driver.
532	theAsioDriver = &instance;
533
534	// Note that we never need to switch theAsioDriver back to point to the
535	// real driver because theAsioDriver is reset to zero in ASIOExit().
536
537	// Delegate to the real ASIOInit
538	return ::ASIOInit(info);
539	}
540
541	#endif /* !defined(_MSC_VER) */
542	#endif /* !defined(__WIN64__) */
543	#endif /* Win32 */