Add WebAudio backend

CMakeLists.txt

@@ -298,7 +298,9 @@ elseif(UNIX)
   )
   target_include_directories(PortAudio PRIVATE src/os/unix)
   target_link_libraries(PortAudio PRIVATE m)
-  set(PKGCONFIG_LDFLAGS_PRIVATE "${PKGCONFIG_LDFLAGS_PUBLIC} -lm -lpthread")
+  if (NOT WASM)
+    set(PKGCONFIG_LDFLAGS_PRIVATE "${PKGCONFIG_LDFLAGS_PUBLIC} -lm -lpthread")
+  endif()
   set(PKGCONFIG_CFLAGS "${PKGCONFIG_CFLAGS} -pthread")
 
   if(APPLE)
@@ -330,6 +332,17 @@ elseif(UNIX)
 
     set(PKGCONFIG_LDFLAGS_PRIVATE
       "${PKGCONFIG_LDFLAGS_PRIVATE} -framework CoreAudio -framework AudioToolbox -framework AudioUnit -framework CoreFoundation -framework CoreServices")
+  elseif(WASM)
+    option(PA_USE_WEBAUDIO "Enable support for WebAudio" ON)
+
+    if (PA_USE_WEBAUDIO)
+      target_compile_definitions(PortAudio PUBLIC PA_USE_WEBAUDIO=1)
+      set(PKGCONFIG_CFLAGS "${PKGCONFIG_CFLAGS} -DPA_USE_WEBAUDIO=1")
+
+      set(PORTAUDIO_PUBLIC_HEADERS ${PORTAUDIO_PUBLIC_HEADERS} include/pa_webaudio.h)
+      target_sources(PortAudio PRIVATE src/hostapi/webaudio/pa_webaudio.c)
+      set(PA_PRIVATE_COMPILE_DEFINITIONS ${PA_PRIVATE_COMPILE_DEFINITIOS} PA_USE_WEBAUDIO)
+    endif()
   else()
     # Some BSDs have a reimplementation of alsalib, so do not explicitly check for Linux.
     find_package(ALSA)

doc/src/tutorial/compiling_wasm.dox

@@ -0,0 +1,16 @@
+/** @page compile_wasm Building PortAudio for WebAssemblys
+@ingroup tutorial
+
+<b>NOTE:</b> These instructions best work under Linux. Other platforms haven't been tested and might not work.
+
+Building PortAudio for WebAssembly is support only through CMake. To build PortAudio for WebAssembly, you need to install Emscripten. Follow the instructions at https://emscripten.org/docs/getting_started/downloads.html to install and setup Emscripten. Make sure that you also install emcmake and emmake as well.
+
+Once you've installed Emscripten, run the following:
+
+@code
+mkdir build && cd build
+emcmake cmake -DWASM=1 <portaudio_root>
+emmake make
+@endcode
+
+*/

include/pa_webaudio.h

@@ -0,0 +1,12 @@
+#ifndef PA_WEBAUDIO_H
+#define PA_WEBAUDIO_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/common/pa_hostapi.h

@@ -111,6 +111,13 @@ are defaulted to 1.
 #error "Portaudio: PA_NO_<APINAME> is no longer supported, please remove definition and use PA_USE_<APINAME> instead"
 #endif
 
+#ifndef PA_USE_WEBAUDIO
+#define PA_USE_WEBAUDIO 0
+#elif (PA_USE_WEBAUDIO != 0) && (PA_USE_WEBAUDIO != 1)
+#undef PA_USE_WEBAUDIO
+#define PA_USE_WEBAUDIO 1
+#endif
+
 #ifndef PA_USE_OSS
 #define PA_USE_OSS 0
 #elif (PA_USE_OSS != 0) && (PA_USE_OSS != 1)