text: /* $Id: alsa_stubs.c $ */
  /** @file
   * Stubs for libasound.
   */
  
  /*
   * Copyright (C) 2006-2015 Oracle Corporation
   *
   * This file is part of VirtualBox Open Source Edition (OSE), as
   * available from http://www.virtualbox.org. This file is free software;
   * you can redistribute it and/or modify it under the terms of the GNU
   * General Public License (GPL) as published by the Free Software
   * Foundation, in version 2 as it comes in the "COPYING" file of the
   * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
   * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
   */
  #define LOG_GROUP LOG_GROUP_DRV_HOST_AUDIO
  #include <iprt/assert.h>
  #include <iprt/ldr.h>
  #include <VBox/log.h>
  #include <VBox/err.h>
  
  #include <alsa/asoundlib.h>
  
  #include "alsa_stubs.h"
  
  #define VBOX_ALSA_LIB "libasound.so.2"
  
  #define PROXY_STUB(function, rettype, signature, shortsig) \
      static rettype (*pfn_ ## function) signature; \
      \
      rettype VBox_##function signature; \
      rettype VBox_##function signature \
      { \
          return pfn_ ## function shortsig; \
      }
  
  PROXY_STUB(snd_pcm_hw_params_any, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params),
             (pcm, params))
  PROXY_STUB(snd_pcm_close, int, (snd_pcm_t *pcm), (pcm))
  PROXY_STUB(snd_pcm_avail_update, snd_pcm_sframes_t, (snd_pcm_t *pcm),
             (pcm))
  PROXY_STUB(snd_pcm_hw_params_set_channels_near, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val),
             (pcm, params, val))
  PROXY_STUB(snd_pcm_hw_params_set_period_time_near, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir),
             (pcm, params, val, dir))
  PROXY_STUB(snd_pcm_prepare, int, (snd_pcm_t *pcm), (pcm))
  PROXY_STUB(snd_pcm_sw_params_sizeof, size_t, (void), ())
  PROXY_STUB(snd_pcm_hw_params_set_period_size_near, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir),
             (pcm, params, val, dir))
  PROXY_STUB(snd_pcm_hw_params_get_period_size, int,
             (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *frames, int *dir),
             (params, frames, dir))
  PROXY_STUB(snd_pcm_hw_params, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params),
             (pcm, params))
  PROXY_STUB(snd_pcm_hw_params_sizeof, size_t, (void), ())
  PROXY_STUB(snd_pcm_state, snd_pcm_state_t, (snd_pcm_t *pcm), (pcm))
  PROXY_STUB(snd_pcm_open, int,
             (snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode),
             (pcm, name, stream, mode))
  PROXY_STUB(snd_lib_error_set_handler, int, (snd_lib_error_handler_t handler),
             (handler))
  PROXY_STUB(snd_pcm_sw_params, int,
             (snd_pcm_t *pcm, snd_pcm_sw_params_t *params),
             (pcm, params))
  PROXY_STUB(snd_pcm_hw_params_get_period_size_min, int,
             (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *frames, int *dir),
             (params, frames, dir))
  PROXY_STUB(snd_pcm_writei, snd_pcm_sframes_t,
             (snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size),
             (pcm, buffer, size))
  PROXY_STUB(snd_pcm_readi, snd_pcm_sframes_t,
             (snd_pcm_t *pcm, void *buffer, snd_pcm_uframes_t size),
             (pcm, buffer, size))
  PROXY_STUB(snd_strerror, const char *, (int errnum), (errnum))
  PROXY_STUB(snd_pcm_drop, int, (snd_pcm_t *pcm), (pcm))
  PROXY_STUB(snd_pcm_resume, int, (snd_pcm_t *pcm), (pcm))
  PROXY_STUB(snd_pcm_hw_params_get_buffer_size, int,
             (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val),
             (params, val))
  PROXY_STUB(snd_pcm_hw_params_set_rate_near, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir),
             (pcm, params, val, dir))
  PROXY_STUB(snd_pcm_hw_params_set_access, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_access_t _access),
             (pcm, params, _access))
  PROXY_STUB(snd_pcm_hw_params_set_buffer_time_near, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val, int *dir),
             (pcm, params, val, dir))
  PROXY_STUB(snd_pcm_hw_params_set_buffer_size_near, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val),
             (pcm, params, val))
  PROXY_STUB(snd_pcm_hw_params_get_buffer_size_min, int,
             (const snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val),
             (params, val))
  PROXY_STUB(snd_pcm_hw_params_set_format, int,
             (snd_pcm_t *pcm, snd_pcm_hw_params_t *params, snd_pcm_format_t val),
             (pcm, params, val))
  PROXY_STUB(snd_pcm_sw_params_current, int,
             (snd_pcm_t *pcm, snd_pcm_sw_params_t *params),
             (pcm, params))
  PROXY_STUB(snd_pcm_sw_params_set_start_threshold, int,
             (snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val),
             (pcm, params, val))
  
  typedef struct
  {
      const char *name;
      void (**fn)(void);
  } SHARED_FUNC;
  
  #define ELEMENT(function) { #function , (void (**)(void)) & pfn_ ## function }
  static SHARED_FUNC SharedFuncs[] =
  {
      ELEMENT(snd_pcm_hw_params_any),
      ELEMENT(snd_pcm_close),
      ELEMENT(snd_pcm_avail_update),
      ELEMENT(snd_pcm_hw_params_set_channels_near),
      ELEMENT(snd_pcm_hw_params_set_period_time_near),
      ELEMENT(snd_pcm_prepare),
      ELEMENT(snd_pcm_sw_params_sizeof),
      ELEMENT(snd_pcm_hw_params_set_period_size_near),
      ELEMENT(snd_pcm_hw_params_get_period_size),
      ELEMENT(snd_pcm_hw_params),
      ELEMENT(snd_pcm_hw_params_sizeof),
      ELEMENT(snd_pcm_state),
      ELEMENT(snd_pcm_open),
      ELEMENT(snd_lib_error_set_handler),
      ELEMENT(snd_pcm_sw_params),
      ELEMENT(snd_pcm_hw_params_get_period_size_min),
      ELEMENT(snd_pcm_writei),
      ELEMENT(snd_pcm_readi),
      ELEMENT(snd_strerror),
      ELEMENT(snd_pcm_drop),
      ELEMENT(snd_pcm_resume),
      ELEMENT(snd_pcm_hw_params_get_buffer_size),
      ELEMENT(snd_pcm_hw_params_set_rate_near),
      ELEMENT(snd_pcm_hw_params_set_access),
      ELEMENT(snd_pcm_hw_params_set_buffer_time_near),
      ELEMENT(snd_pcm_hw_params_set_buffer_size_near),
      ELEMENT(snd_pcm_hw_params_get_buffer_size_min),
      ELEMENT(snd_pcm_hw_params_set_format),
      ELEMENT(snd_pcm_sw_params_current),
      ELEMENT(snd_pcm_sw_params_set_start_threshold),
  };
  #undef ELEMENT
  
  /**
   * Try to dynamically load the ALSA libraries.  This function is not
   * thread-safe, and should be called before attempting to use any of the
   * ALSA functions.
   *
   * @returns iprt status code
   */
  int audioLoadAlsaLib(void)
  {
      int rc = VINF_SUCCESS;
      unsigned i;
      static enum { NO = 0, YES, FAIL } isLibLoaded = NO;
      RTLDRMOD hLib;
  
      LogFlowFunc(("\n"));
      /* If this is not NO then the function has obviously been called twice,
         which is likely to be a bug. */
      if (NO != isLibLoaded)
      {
          AssertMsgFailed(("isLibLoaded == %s\n", YES == isLibLoaded ? "YES" : "NO"));
          return YES == isLibLoaded ? VINF_SUCCESS : VERR_NOT_SUPPORTED;
      }
      isLibLoaded = FAIL;
      rc = RTLdrLoad(VBOX_ALSA_LIB, &hLib);
      if (RT_FAILURE(rc))
      {
          LogRelFunc(("Failed to load library %s\n", VBOX_ALSA_LIB));
          return rc;
      }
      for (i=0; i<RT_ELEMENTS(SharedFuncs); i++)
      {
          rc = RTLdrGetSymbol(hLib, SharedFuncs[i].name, (void**)SharedFuncs[i].fn);
          if (RT_FAILURE(rc))
              return rc;
      }
      isLibLoaded = YES;
      return rc;
  }
  