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	senoner	1500	/*
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 */