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__)) && !defined(_WIN64) 160 161 162 // If microsoft compiler we can call IASIO directly so IASIOThiscallResolver 163 // is not used. 164 #if !defined(_MSC_VER) 165 166 167 #include <new> 168 #include <assert.h> 169 170 // We have a mechanism in iasiothiscallresolver.h to ensure that asio.h is 171 // #include'd before it in client code, we do NOT want to do this test here. 172 #define iasiothiscallresolver_sourcefile 1 173 #include "iasiothiscallresolver.h" 174 #undef iasiothiscallresolver_sourcefile 175 176 // iasiothiscallresolver.h redefines ASIOInit for clients, but we don't want 177 // this macro defined in this translation unit. 178 #undef ASIOInit 179 180 181 // 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; 185 186 187 // The following macros define the inline assembler for BORLAND first then gcc 188 189 #if defined(__BCPLUSPLUS__) || defined(__BORLANDC__) 190 191 192 #define CALL_THISCALL_0( resultName, thisPtr, funcOffset )\ 193 void *this_ = (thisPtr); \ 194 __asm { \ 195 mov ecx, this_ ; \ 196 mov eax, [ecx] ; \ 197 call [eax+funcOffset] ; \ 198 mov resultName, eax ; \ 199 } 200 201 202 #define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 )\ 203 void *this_ = (thisPtr); \ 204 __asm { \ 205 mov eax, param1 ; \ 206 push eax ; \ 207 mov ecx, this_ ; \ 208 mov eax, [ecx] ; \ 209 call [eax+funcOffset] ; \ 210 } 211 212 213 #define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 )\ 214 void *this_ = (thisPtr); \ 215 __asm { \ 216 mov eax, param1 ; \ 217 push eax ; \ 218 mov ecx, this_ ; \ 219 mov eax, [ecx] ; \ 220 call [eax+funcOffset] ; \ 221 mov resultName, eax ; \ 222 } 223 224 225 #define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 )\ 226 void *this_ = (thisPtr); \ 227 void *doubleParamPtr_ (¶m1); \ 228 __asm { \ 229 mov eax, doubleParamPtr_ ; \ 230 push [eax+4] ; \ 231 push [eax] ; \ 232 mov ecx, this_ ; \ 233 mov eax, [ecx] ; \ 234 call [eax+funcOffset] ; \ 235 mov resultName, eax ; \ 236 } 237 238 239 #define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 )\ 240 void *this_ = (thisPtr); \ 241 __asm { \ 242 mov eax, param2 ; \ 243 push eax ; \ 244 mov eax, param1 ; \ 245 push eax ; \ 246 mov ecx, this_ ; \ 247 mov eax, [ecx] ; \ 248 call [eax+funcOffset] ; \ 249 mov resultName, eax ; \ 250 } 251 252 253 #define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\ 254 void *this_ = (thisPtr); \ 255 __asm { \ 256 mov eax, param4 ; \ 257 push eax ; \ 258 mov eax, param3 ; \ 259 push eax ; \ 260 mov eax, param2 ; \ 261 push eax ; \ 262 mov eax, param1 ; \ 263 push eax ; \ 264 mov ecx, this_ ; \ 265 mov eax, [ecx] ; \ 266 call [eax+funcOffset] ; \ 267 mov resultName, eax ; \ 268 } 269 270 271 #elif defined(__GNUC__) 272 273 274 #define CALL_THISCALL_0( resultName, thisPtr, funcOffset ) \ 275 __asm__ __volatile__ ("movl (%1), %%edx\n\t" \ 276 "call *"#funcOffset"(%%edx)\n\t" \ 277 :"=a"(resultName) /* Output Operands */ \ 278 :"c"(thisPtr) /* Input Operands */ \ 279 : "%edx" /* Clobbered Registers */ \ 280 ); \ 281 282 283 #define CALL_VOID_THISCALL_1( thisPtr, funcOffset, param1 ) \ 284 __asm__ __volatile__ ("pushl %0\n\t" \ 285 "movl (%1), %%edx\n\t" \ 286 "call *"#funcOffset"(%%edx)\n\t" \ 287 : /* Output Operands */ \ 288 :"r"(param1), /* Input Operands */ \ 289 "c"(thisPtr) \ 290 : "%edx" /* Clobbered Registers */ \ 291 ); \ 292 293 294 #define CALL_THISCALL_1( resultName, thisPtr, funcOffset, param1 ) \ 295 __asm__ __volatile__ ("pushl %1\n\t" \ 296 "movl (%2), %%edx\n\t" \ 297 "call *"#funcOffset"(%%edx)\n\t" \ 298 :"=a"(resultName) /* Output Operands */ \ 299 :"r"(param1), /* Input Operands */ \ 300 "c"(thisPtr) \ 301 : "%edx" /* Clobbered Registers */ \ 302 ); \ 303 304 305 #define CALL_THISCALL_1_DOUBLE( resultName, thisPtr, funcOffset, param1 ) \ 306 do { \ 307 double param1f64 = param1; /* Cast explicitly to double */ \ 308 double *param1f64Ptr = ¶m1f64; /* Make pointer to address */ \ 309 __asm__ __volatile__ ("pushl 4(%1)\n\t" \ 310 "pushl (%1)\n\t" \ 311 "movl (%2), %%edx\n\t" \ 312 "call *"#funcOffset"(%%edx);\n\t" \ 313 : "=a"(resultName) /* Output Operands */ \ 314 : "r"(param1f64Ptr), /* Input Operands */ \ 315 "c"(thisPtr), \ 316 "m"(*param1f64Ptr) /* Using address */ \ 317 : "%edx" /* Clobbered Registers */ \ 318 ); \ 319 } while (0); \ 320 321 322 #define CALL_THISCALL_2( resultName, thisPtr, funcOffset, param1, param2 ) \ 323 __asm__ __volatile__ ("pushl %1\n\t" \ 324 "pushl %2\n\t" \ 325 "movl (%3), %%edx\n\t" \ 326 "call *"#funcOffset"(%%edx)\n\t" \ 327 :"=a"(resultName) /* Output Operands */ \ 328 :"r"(param2), /* Input Operands */ \ 329 "r"(param1), \ 330 "c"(thisPtr) \ 331 : "%edx" /* Clobbered Registers */ \ 332 ); \ 333 334 335 #define CALL_THISCALL_4( resultName, thisPtr, funcOffset, param1, param2, param3, param4 )\ 336 __asm__ __volatile__ ("pushl %1\n\t" \ 337 "pushl %2\n\t" \ 338 "pushl %3\n\t" \ 339 "pushl %4\n\t" \ 340 "movl (%5), %%edx\n\t" \ 341 "call *"#funcOffset"(%%edx)\n\t" \ 342 :"=a"(resultName) /* Output Operands */ \ 343 :"r"(param4), /* Input Operands */ \ 344 "r"(param3), \ 345 "r"(param2), \ 346 "r"(param1), \ 347 "c"(thisPtr) \ 348 : "%edx" /* Clobbered Registers */ \ 349 ); \ 350 351 #endif 352 353 354 355 // Our static singleton instance. 356 IASIOThiscallResolver IASIOThiscallResolver::instance; 357 358 // Constructor called to initialize static Singleton instance above. Note that 359 // it is important not to clear that_ incase it has already been set by the call 360 // to placement new in ASIOInit(). 361 IASIOThiscallResolver::IASIOThiscallResolver() 362 { 363 } 364 365 // Constructor called from ASIOInit() below 366 IASIOThiscallResolver::IASIOThiscallResolver(IASIO* that) 367 : that_( that ) 368 { 369 } 370 371 // Implement IUnknown methods as assert(false). IASIOThiscallResolver is not 372 // really a COM object, just a wrapper which will work with the ASIO SDK. 373 // If you wanted to use ASIO without the SDK you might want to implement COM 374 // aggregation in these methods. 375 HRESULT STDMETHODCALLTYPE IASIOThiscallResolver::QueryInterface(REFIID riid, void **ppv) 376 { 377 (void)riid; // suppress unused variable warning 378 379 assert( false ); // this function should never be called by the ASIO SDK. 380 381 *ppv = NULL; 382 return E_NOINTERFACE; 383 } 384 385 ULONG STDMETHODCALLTYPE IASIOThiscallResolver::AddRef() 386 { 387 assert( false ); // this function should never be called by the ASIO SDK. 388 389 return 1; 390 } 391 392 ULONG STDMETHODCALLTYPE IASIOThiscallResolver::Release() 393 { 394 assert( false ); // this function should never be called by the ASIO SDK. 395 396 return 1; 397 } 398 399 400 // Implement the IASIO interface methods by performing the vptr manipulation 401 // described above then delegating to the real implementation. 402 ASIOBool IASIOThiscallResolver::init(void *sysHandle) 403 { 404 ASIOBool result; 405 CALL_THISCALL_1( result, that_, 12, sysHandle ); 406 return result; 407 } 408 409 void IASIOThiscallResolver::getDriverName(char *name) 410 { 411 CALL_VOID_THISCALL_1( that_, 16, name ); 412 } 413 414 long IASIOThiscallResolver::getDriverVersion() 415 { 416 ASIOBool result; 417 CALL_THISCALL_0( result, that_, 20 ); 418 return result; 419 } 420 421 void IASIOThiscallResolver::getErrorMessage(char *string) 422 { 423 CALL_VOID_THISCALL_1( that_, 24, string ); 424 } 425 426 ASIOError IASIOThiscallResolver::start() 427 { 428 ASIOBool result; 429 CALL_THISCALL_0( result, that_, 28 ); 430 return result; 431 } 432 433 ASIOError IASIOThiscallResolver::stop() 434 { 435 ASIOBool result; 436 CALL_THISCALL_0( result, that_, 32 ); 437 return result; 438 } 439 440 ASIOError IASIOThiscallResolver::getChannels(long *numInputChannels, long *numOutputChannels) 441 { 442 ASIOBool result; 443 CALL_THISCALL_2( result, that_, 36, numInputChannels, numOutputChannels ); 444 return result; 445 } 446 447 ASIOError IASIOThiscallResolver::getLatencies(long *inputLatency, long *outputLatency) 448 { 449 ASIOBool result; 450 CALL_THISCALL_2( result, that_, 40, inputLatency, outputLatency ); 451 return result; 452 } 453 454 ASIOError IASIOThiscallResolver::getBufferSize(long *minSize, long *maxSize, 455 long *preferredSize, long *granularity) 456 { 457 ASIOBool result; 458 CALL_THISCALL_4( result, that_, 44, minSize, maxSize, preferredSize, granularity ); 459 return result; 460 } 461 462 ASIOError IASIOThiscallResolver::canSampleRate(ASIOSampleRate sampleRate) 463 { 464 ASIOBool result; 465 CALL_THISCALL_1_DOUBLE( result, that_, 48, sampleRate ); 466 return result; 467 } 468 469 ASIOError IASIOThiscallResolver::getSampleRate(ASIOSampleRate *sampleRate) 470 { 471 ASIOBool result; 472 CALL_THISCALL_1( result, that_, 52, sampleRate ); 473 return result; 474 } 475 476 ASIOError IASIOThiscallResolver::setSampleRate(ASIOSampleRate sampleRate) 477 { 478 ASIOBool result; 479 CALL_THISCALL_1_DOUBLE( result, that_, 56, sampleRate ); 480 return result; 481 } 482 483 ASIOError IASIOThiscallResolver::getClockSources(ASIOClockSource *clocks, long *numSources) 484 { 485 ASIOBool result; 486 CALL_THISCALL_2( result, that_, 60, clocks, numSources ); 487 return result; 488 } 489 490 ASIOError IASIOThiscallResolver::setClockSource(long reference) 491 { 492 ASIOBool result; 493 CALL_THISCALL_1( result, that_, 64, reference ); 494 return result; 495 } 496 497 ASIOError IASIOThiscallResolver::getSamplePosition(ASIOSamples *sPos, ASIOTimeStamp *tStamp) 498 { 499 ASIOBool result; 500 CALL_THISCALL_2( result, that_, 68, sPos, tStamp ); 501 return result; 502 } 503 504 ASIOError IASIOThiscallResolver::getChannelInfo(ASIOChannelInfo *info) 505 { 506 ASIOBool result; 507 CALL_THISCALL_1( result, that_, 72, info ); 508 return result; 509 } 510 511 ASIOError IASIOThiscallResolver::createBuffers(ASIOBufferInfo *bufferInfos, 512 long numChannels, long bufferSize, ASIOCallbacks *callbacks) 513 { 514 ASIOBool result; 515 CALL_THISCALL_4( result, that_, 76, bufferInfos, numChannels, bufferSize, callbacks ); 516 return result; 517 } 518 519 ASIOError IASIOThiscallResolver::disposeBuffers() 520 { 521 ASIOBool result; 522 CALL_THISCALL_0( result, that_, 80 ); 523 return result; 524 } 525 526 ASIOError IASIOThiscallResolver::controlPanel() 527 { 528 ASIOBool result; 529 CALL_THISCALL_0( result, that_, 84 ); 530 return result; 531 } 532 533 ASIOError IASIOThiscallResolver::future(long selector,void *opt) 534 { 535 ASIOBool result; 536 CALL_THISCALL_2( result, that_, 88, selector, opt ); 537 return result; 538 } 539 540 ASIOError IASIOThiscallResolver::outputReady() 541 { 542 ASIOBool result; 543 CALL_THISCALL_0( result, that_, 92 ); 544 return result; 545 } 546 547 548 // Implement our substitute ASIOInit() method 549 ASIOError IASIOThiscallResolver::ASIOInit(ASIODriverInfo *info) 550 { 551 // To ensure that our instance's vptr is correctly constructed, even if 552 // ASIOInit is called prior to main(), we explicitly call its constructor 553 // (potentially over the top of an existing instance). Note that this is 554 // pretty ugly, and is only safe because IASIOThiscallResolver has no 555 // destructor and contains no objects with destructors. 556 new((void*)&instance) IASIOThiscallResolver( theAsioDriver ); 557 558 // Interpose between ASIO client code and the real driver. 559 theAsioDriver = &instance; 560 561 // Note that we never need to switch theAsioDriver back to point to the 562 // real driver because theAsioDriver is reset to zero in ASIOExit(). 563 564 // Delegate to the real ASIOInit 565 return ::ASIOInit(info); 566 } 567 568 569 #endif /* !defined(_MSC_VER) */ 570 571 #endif /* Win32 */ 572 573