2 IASIOThiscallResolver.cpp see the comments in iasiothiscallresolver.h for
\r
3 the top level description - this comment describes the technical details of
\r
6 The latest version of this file is available from:
\r
7 http://www.audiomulch.com/~rossb/code/calliasio
\r
9 please email comments to Ross Bencina <rossb@audiomulch.com>
\r
13 The IASIO interface declared in the Steinberg ASIO 2 SDK declares
\r
14 functions with no explicit calling convention. This causes MSVC++ to default
\r
15 to using the thiscall convention, which is a proprietary convention not
\r
16 implemented by some non-microsoft compilers - notably borland BCC,
\r
17 C++Builder, and gcc. MSVC++ is the defacto standard compiler used by
\r
18 Steinberg. As a result of this situation, the ASIO sdk will compile with
\r
19 any compiler, however attempting to execute the compiled code will cause a
\r
20 crash due to different default calling conventions on non-Microsoft
\r
23 IASIOThiscallResolver solves the problem by providing an adapter class that
\r
24 delegates to the IASIO interface using the correct calling convention
\r
25 (thiscall). Due to the lack of support for thiscall in the Borland and GCC
\r
26 compilers, the calls have been implemented in assembly language.
\r
28 A number of macros are defined for thiscall function calls with different
\r
29 numbers of parameters, with and without return values - it may be possible
\r
30 to modify the format of these macros to make them work with other inline
\r
36 A number of definitions of the thiscall calling convention are floating
\r
37 around the internet. The following definition has been validated against
\r
38 output from the MSVC++ compiler:
\r
40 For non-vararg functions, thiscall works as follows: the object (this)
\r
41 pointer is passed in ECX. All arguments are passed on the stack in
\r
42 right to left order. The return value is placed in EAX. The callee
\r
43 clears the passed arguments from the stack.
\r
46 FINDING FUNCTION POINTERS FROM AN IASIO POINTER
\r
48 The first field of a COM object is a pointer to its vtble. Thus a pointer
\r
49 to an object implementing the IASIO interface also points to a pointer to
\r
50 that object's vtbl. The vtble is a table of function pointers for all of
\r
51 the virtual functions exposed by the implemented interfaces.
\r
53 If we consider a variable declared as a pointer to IASO:
\r
55 IASIO *theAsioDriver
\r
57 theAsioDriver points to:
\r
59 object implementing IASIO
\r
65 in other words, theAsioDriver points to a pointer to an IASIOvtbl
\r
67 vtbl points to a table of function pointers:
\r
69 IASIOvtbl ( interface IASIO : public IUnknown )
\r
71 (IUnknown functions)
\r
72 0 virtual HRESULT STDMETHODCALLTYPE (*QueryInterface)(REFIID riid, void **ppv) = 0;
\r
73 4 virtual ULONG STDMETHODCALLTYPE (*AddRef)() = 0;
\r
74 8 virtual ULONG STDMETHODCALLTYPE (*Release)() = 0;
\r
77 12 virtual ASIOBool (*init)(void *sysHandle) = 0;
\r
78 16 virtual void (*getDriverName)(char *name) = 0;
\r
79 20 virtual long (*getDriverVersion)() = 0;
\r
80 24 virtual void (*getErrorMessage)(char *string) = 0;
\r
81 28 virtual ASIOError (*start)() = 0;
\r
82 32 virtual ASIOError (*stop)() = 0;
\r
83 36 virtual ASIOError (*getChannels)(long *numInputChannels, long *numOutputChannels) = 0;
\r
84 40 virtual ASIOError (*getLatencies)(long *inputLatency, long *outputLatency) = 0;
\r
85 44 virtual ASIOError (*getBufferSize)(long *minSize, long *maxSize,
\r
86 long *preferredSize, long *granularity) = 0;
\r
87 48 virtual ASIOError (*canSampleRate)(ASIOSampleRate sampleRate) = 0;
\r
88 52 virtual ASIOError (*getSampleRate)(ASIOSampleRate *sampleRate) = 0;
\r
89 56 virtual ASIOError (*setSampleRate)(ASIOSampleRate sampleRate) = 0;
\r
90 60 virtual ASIOError (*getClockSources)(ASIOClockSource *clocks, long *numSources) = 0;
\r
91 64 virtual ASIOError (*setClockSource)(long reference) = 0;
\r
92 68 virtual ASIOError (*getSamplePosition)(ASIOSamples *sPos, ASIOTimeStamp *tStamp) = 0;
\r
93 72 virtual ASIOError (*getChannelInfo)(ASIOChannelInfo *info) = 0;
\r
94 76 virtual ASIOError (*createBuffers)(ASIOBufferInfo *bufferInfos, long numChannels,
\r
95 long bufferSize, ASIOCallbacks *callbacks) = 0;
\r
96 80 virtual ASIOError (*disposeBuffers)() = 0;
\r
97 84 virtual ASIOError (*controlPanel)() = 0;
\r
98 88 virtual ASIOError (*future)(long selector,void *opt) = 0;
\r
99 92 virtual ASIOError (*outputReady)() = 0;
\r
102 The numbers in the left column show the byte offset of each function ptr
\r
103 from the beginning of the vtbl. These numbers are used in the code below
\r
104 to select different functions.
\r
106 In order to find the address of a particular function, theAsioDriver
\r
107 must first be dereferenced to find the value of the vtbl pointer:
\r
109 mov eax, theAsioDriver
\r
110 mov edx, [theAsioDriver] // edx now points to vtbl[0]
\r
112 Then an offset must be added to the vtbl pointer to select a
\r
113 particular function, for example vtbl+44 points to the slot containing
\r
114 a pointer to the getBufferSize function.
\r
116 Finally vtbl+x must be dereferenced to obtain the value of the function
\r
117 pointer stored in that address:
\r
119 call [edx+44] // call the function pointed to by
\r
120 // the value in the getBufferSize field of the vtbl
\r
125 Martin Fay's OpenASIO DLL at http://www.martinfay.com solves the same
\r
126 problem by providing a new COM interface which wraps IASIO with an
\r
127 interface that uses portable calling conventions. OpenASIO must be compiled
\r
128 with MSVC, and requires that you ship the OpenASIO DLL with your
\r
134 Ross Bencina: worked out the thiscall details above, wrote the original
\r
135 Borland asm macros, and a patch for asio.cpp (which is no longer needed).
\r
136 Thanks to Martin Fay for introducing me to the issues discussed here,
\r
137 and to Rene G. Ceballos for assisting with asm dumps from MSVC++.
\r
139 Antti Silvast: converted the original calliasio to work with gcc and NASM
\r
140 by implementing the asm code in a separate file.
\r
142 Fraser Adams: modified the original calliasio containing the Borland inline
\r
143 asm to add inline asm for gcc i.e. Intel syntax for Borland and AT&T syntax
\r
144 for gcc. This seems a neater approach for gcc than to have a separate .asm
\r
145 file and it means that we only need one version of the thiscall patch.
\r
147 Fraser Adams: rewrote the original calliasio patch in the form of the
\r
148 IASIOThiscallResolver class in order to avoid modifications to files from
\r
149 the Steinberg SDK, which may have had potential licence issues.
\r
151 Andrew Baldwin: contributed fixes for compatibility problems with more
\r
152 recent versions of the gcc assembler.
\r
156 // We only need IASIOThiscallResolver at all if we are on Win32. For other
\r
157 // platforms we simply bypass the IASIOThiscallResolver definition to allow us
\r
158 // to be safely #include'd whatever the platform to keep client code portable
\r
159 #if defined(WIN32) || defined(_WIN32) || defined(__WIN32__)
\r
162 // If microsoft compiler we can call IASIO directly so IASIOThiscallResolver
\r
164 #if !defined(_MSC_VER)
\r
168 #include <assert.h>
\r
170 // We have a mechanism in iasiothiscallresolver.h to ensure that asio.h is
\r
171 // #include'd before it in client code, we do NOT want to do this test here.
\r
172 #define iasiothiscallresolver_sourcefile 1
\r
173 #include "iasiothiscallresolver.h"
\r
174 #undef iasiothiscallresolver_sourcefile
\r
176 // iasiothiscallresolver.h redefines ASIOInit for clients, but we don't want
\r
177 // this macro defined in this translation unit.
\r
181 // theAsioDriver is a global pointer to the current IASIO instance which the
\r
182 // ASIO SDK uses to perform all actions on the IASIO interface. We substitute
\r
183 // our own forwarding interface into this pointer.
\r
184 extern IASIO* theAsioDriver;
\r
187 // The following macros define the inline assembler for BORLAND first then gcc
\r
189 #if defined(__BCPLUSPLUS__) || defined(__BORLANDC__)
\r
192 #define CALL_THISCALL_0( resultName, thisPtr, funcOffset )\
\r
193 void *this_ = (thisPtr); \
\r
197 call [eax+funcOffset] ; \
\r
198 mov resultName, eax ; \
\r
202 #define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 )\
\r
203 void *this_ = (thisPtr); \
\r
205 mov eax, param1 ; \
\r
209 call [eax+funcOffset] ; \
\r
213 #define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 )\
\r
214 void *this_ = (thisPtr); \
\r
216 mov eax, param1 ; \
\r
220 call [eax+funcOffset] ; \
\r
221 mov resultName, eax ; \
\r
225 #define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 )\
\r
226 void *this_ = (thisPtr); \
\r
227 void *doubleParamPtr_ (¶m1); \
\r
229 mov eax, doubleParamPtr_ ; \
\r
234 call [eax+funcOffset] ; \
\r
235 mov resultName, eax ; \
\r
239 #define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 )\
\r
240 void *this_ = (thisPtr); \
\r
242 mov eax, param2 ; \
\r
244 mov eax, param1 ; \
\r
248 call [eax+funcOffset] ; \
\r
249 mov resultName, eax ; \
\r
253 #define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
\r
254 void *this_ = (thisPtr); \
\r
256 mov eax, param4 ; \
\r
258 mov eax, param3 ; \
\r
260 mov eax, param2 ; \
\r
262 mov eax, param1 ; \
\r
266 call [eax+funcOffset] ; \
\r
267 mov resultName, eax ; \
\r
271 #elif defined(__GNUC__)
\r
274 #define CALL_THISCALL_0( resultName, thisPtr, funcOffset ) \
\r
275 __asm__ __volatile__ ("movl (%1), %%edx\n\t" \
\r
276 "call *"#funcOffset"(%%edx)\n\t" \
\r
277 :"=a"(resultName) /* Output Operands */ \
\r
278 :"c"(thisPtr) /* Input Operands */ \
\r
282 #define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 ) \
\r
283 __asm__ __volatile__ ("pushl %0\n\t" \
\r
284 "movl (%1), %%edx\n\t" \
\r
285 "call *"#funcOffset"(%%edx)\n\t" \
\r
286 : /* Output Operands */ \
\r
287 :"r"(param1), /* Input Operands */ \
\r
292 #define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 ) \
\r
293 __asm__ __volatile__ ("pushl %1\n\t" \
\r
294 "movl (%2), %%edx\n\t" \
\r
295 "call *"#funcOffset"(%%edx)\n\t" \
\r
296 :"=a"(resultName) /* Output Operands */ \
\r
297 :"r"(param1), /* Input Operands */ \
\r
302 #define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 ) \
\r
303 __asm__ __volatile__ ("pushl 4(%1)\n\t" \
\r
305 "movl (%2), %%edx\n\t" \
\r
306 "call *"#funcOffset"(%%edx);\n\t" \
\r
307 :"=a"(resultName) /* Output Operands */ \
\r
308 :"a"(¶m1), /* Input Operands */ \
\r
309 /* Note: Using "r" above instead of "a" fails */ \
\r
310 /* when using GCC 3.3.3, and maybe later versions*/\
\r
315 #define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 ) \
\r
316 __asm__ __volatile__ ("pushl %1\n\t" \
\r
318 "movl (%3), %%edx\n\t" \
\r
319 "call *"#funcOffset"(%%edx)\n\t" \
\r
320 :"=a"(resultName) /* Output Operands */ \
\r
321 :"r"(param2), /* Input Operands */ \
\r
327 #define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\
\r
328 __asm__ __volatile__ ("pushl %1\n\t" \
\r
332 "movl (%5), %%edx\n\t" \
\r
333 "call *"#funcOffset"(%%edx)\n\t" \
\r
334 :"=a"(resultName) /* Output Operands */ \
\r
335 :"r"(param4), /* Input Operands */ \
\r
346 // Our static singleton instance.
\r
347 IASIOThiscallResolver IASIOThiscallResolver::instance;
\r
349 // Constructor called to initialize static Singleton instance above. Note that
\r
350 // it is important not to clear that_ incase it has already been set by the call
\r
351 // to placement new in ASIOInit().
\r
352 IASIOThiscallResolver::IASIOThiscallResolver()
\r
356 // Constructor called from ASIOInit() below
\r
357 IASIOThiscallResolver::IASIOThiscallResolver(IASIO* that)
\r
362 // Implement IUnknown methods as assert(false). IASIOThiscallResolver is not
\r
363 // really a COM object, just a wrapper which will work with the ASIO SDK.
\r
364 // If you wanted to use ASIO without the SDK you might want to implement COM
\r
365 // aggregation in these methods.
\r
366 HRESULT STDMETHODCALLTYPE IASIOThiscallResolver::QueryInterface(REFIID riid, void **ppv)
\r
368 (void)riid; // suppress unused variable warning
\r
370 assert( false ); // this function should never be called by the ASIO SDK.
\r
373 return E_NOINTERFACE;
\r
376 ULONG STDMETHODCALLTYPE IASIOThiscallResolver::AddRef()
\r
378 assert( false ); // this function should never be called by the ASIO SDK.
\r
383 ULONG STDMETHODCALLTYPE IASIOThiscallResolver::Release()
\r
385 assert( false ); // this function should never be called by the ASIO SDK.
\r
391 // Implement the IASIO interface methods by performing the vptr manipulation
\r
392 // described above then delegating to the real implementation.
\r
393 ASIOBool IASIOThiscallResolver::init(void *sysHandle)
\r
396 CALL_THISCALL_1( result, that_, 12, sysHandle );
\r
400 void IASIOThiscallResolver::getDriverName(char *name)
\r
402 CALL_VOID_THISCALL_1( that_, 16, name );
\r
405 long IASIOThiscallResolver::getDriverVersion()
\r
408 CALL_THISCALL_0( result, that_, 20 );
\r
412 void IASIOThiscallResolver::getErrorMessage(char *string)
\r
414 CALL_VOID_THISCALL_1( that_, 24, string );
\r
417 ASIOError IASIOThiscallResolver::start()
\r
420 CALL_THISCALL_0( result, that_, 28 );
\r
424 ASIOError IASIOThiscallResolver::stop()
\r
427 CALL_THISCALL_0( result, that_, 32 );
\r
431 ASIOError IASIOThiscallResolver::getChannels(long *numInputChannels, long *numOutputChannels)
\r
434 CALL_THISCALL_2( result, that_, 36, numInputChannels, numOutputChannels );
\r
438 ASIOError IASIOThiscallResolver::getLatencies(long *inputLatency, long *outputLatency)
\r
441 CALL_THISCALL_2( result, that_, 40, inputLatency, outputLatency );
\r
445 ASIOError IASIOThiscallResolver::getBufferSize(long *minSize, long *maxSize,
\r
446 long *preferredSize, long *granularity)
\r
449 CALL_THISCALL_4( result, that_, 44, minSize, maxSize, preferredSize, granularity );
\r
453 ASIOError IASIOThiscallResolver::canSampleRate(ASIOSampleRate sampleRate)
\r
456 CALL_THISCALL_1_DOUBLE( result, that_, 48, sampleRate );
\r
460 ASIOError IASIOThiscallResolver::getSampleRate(ASIOSampleRate *sampleRate)
\r
463 CALL_THISCALL_1( result, that_, 52, sampleRate );
\r
467 ASIOError IASIOThiscallResolver::setSampleRate(ASIOSampleRate sampleRate)
\r
470 CALL_THISCALL_1_DOUBLE( result, that_, 56, sampleRate );
\r
474 ASIOError IASIOThiscallResolver::getClockSources(ASIOClockSource *clocks, long *numSources)
\r
477 CALL_THISCALL_2( result, that_, 60, clocks, numSources );
\r
481 ASIOError IASIOThiscallResolver::setClockSource(long reference)
\r
484 CALL_THISCALL_1( result, that_, 64, reference );
\r
488 ASIOError IASIOThiscallResolver::getSamplePosition(ASIOSamples *sPos, ASIOTimeStamp *tStamp)
\r
491 CALL_THISCALL_2( result, that_, 68, sPos, tStamp );
\r
495 ASIOError IASIOThiscallResolver::getChannelInfo(ASIOChannelInfo *info)
\r
498 CALL_THISCALL_1( result, that_, 72, info );
\r
502 ASIOError IASIOThiscallResolver::createBuffers(ASIOBufferInfo *bufferInfos,
\r
503 long numChannels, long bufferSize, ASIOCallbacks *callbacks)
\r
506 CALL_THISCALL_4( result, that_, 76, bufferInfos, numChannels, bufferSize, callbacks );
\r
510 ASIOError IASIOThiscallResolver::disposeBuffers()
\r
513 CALL_THISCALL_0( result, that_, 80 );
\r
517 ASIOError IASIOThiscallResolver::controlPanel()
\r
520 CALL_THISCALL_0( result, that_, 84 );
\r
524 ASIOError IASIOThiscallResolver::future(long selector,void *opt)
\r
527 CALL_THISCALL_2( result, that_, 88, selector, opt );
\r
531 ASIOError IASIOThiscallResolver::outputReady()
\r
534 CALL_THISCALL_0( result, that_, 92 );
\r
539 // Implement our substitute ASIOInit() method
\r
540 ASIOError IASIOThiscallResolver::ASIOInit(ASIODriverInfo *info)
\r
542 // To ensure that our instance's vptr is correctly constructed, even if
\r
543 // ASIOInit is called prior to main(), we explicitly call its constructor
\r
544 // (potentially over the top of an existing instance). Note that this is
\r
545 // pretty ugly, and is only safe because IASIOThiscallResolver has no
\r
546 // destructor and contains no objects with destructors.
\r
547 new((void*)&instance) IASIOThiscallResolver( theAsioDriver );
\r
549 // Interpose between ASIO client code and the real driver.
\r
550 theAsioDriver = &instance;
\r
552 // Note that we never need to switch theAsioDriver back to point to the
\r
553 // real driver because theAsioDriver is reset to zero in ASIOExit().
\r
555 // Delegate to the real ASIOInit
\r
556 return ::ASIOInit(info);
\r
560 #endif /* !defined(_MSC_VER) */
\r