alsapid/lib.c

   1 /* -*- Mode: C ; c-basic-offset: 2 -*- */
   2 /*
   3  * LADI Session Handler (ladish)
   4  *
   5  * Copyright (C) 2010 Nedko Arnaudov <nedko@arnaudov.name>
   6  *
   7  **************************************************************************
   8  * This file contains implementation of the libasound LD_PRELOAD-ed alsapid library
   9  **************************************************************************
  10  *
  11  * LADI Session Handler is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * LADI Session Handler is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with LADI Session Handler. If not, see <http://www.gnu.org/licenses/>
  23  * or write to the Free Software Foundation, Inc.,
  24  * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  25  */
  26
  27 #define _GNU_SOURCE
  28
  29 #include <alsa/asoundlib.h>
  30 #include <dlfcn.h>
  31 #include <linux/limits.h>
  32 #include <stdio.h>
  33
  34 #include "alsapid.h"
  35
  36 #define API_VERSION "ALSA_0.9"
  37
  38 // gcc -g -shared -Wl,--version-script=asound.versions -o libasound.so -fPIC -ldl -Wall -Werror lib.c helper.c
  39 // LD_LIBRARY_PATH=alsapid LD_PRELOAD=libasound.so seq24
  40
  41 static void create_symlink(int alsa_client_id)
  42 {
  43   char src[PATH_MAX];
  44   char dst[PATH_MAX];
  45
  46   alsapid_compose_src_link(alsa_client_id, src);
  47   alsapid_compose_dst_link(dst);
  48
  49   //printf("'%s' -> '%s'\n", src, dst);
  50   if (unlink(src) != 0 && errno != ENOENT)
  51   {
  52     fprintf(stderr, "unlink(\"%s\") failed with %d (%s)", src, errno, strerror(errno));
  53   }
  54   if (symlink(dst, src) != 0)
  55   {
  56     fprintf(stderr, "symlink(\"%s\", \"%s\") failed with %d (%s)", dst, src, errno, strerror(errno));
  57   }
  58 }
  59
  60 static void destroy_symlink(int alsa_client_id)
  61 {
  62   char src[PATH_MAX];
  63
  64   alsapid_compose_src_link(alsa_client_id, src);
  65
  66   //printf("'%s'\n", src);
  67   if (unlink(src) != 0 && errno != ENOENT)
  68   {
  69     fprintf(stderr, "unlink(\"%s\") failed with %d (%s)", src, errno, strerror(errno));
  70   }
  71 }
  72
  73 //static int (* real_snd_seq_open)(snd_seq_t ** handle, const char * name, int streams, int mode);
  74 static int (* real_snd_seq_set_client_name)(snd_seq_t * seq, const char * name);
  75 static int (* real_snd_seq_close)(snd_seq_t * handle);
  76 //static int (* real_snd_seq_create_port)(snd_seq_t * handle, snd_seq_port_info_t * info);
  77 //static int (* real_snd_seq_create_simple_port)(snd_seq_t * seq, const char * name, unsigned int caps, unsigned int type);
  78
  79 void __attribute__ ((constructor)) init(void);
  80
  81 /* Library constructor */
  82 void init(void)
  83 {
  84 //  real_snd_seq_open               = dlvsym(RTLD_NEXT, "snd_seq_open",               API_VERSION);
  85   real_snd_seq_set_client_name    = dlvsym(RTLD_NEXT, "snd_seq_set_client_name",    API_VERSION);
  86   real_snd_seq_close              = dlvsym(RTLD_NEXT, "snd_seq_close",              API_VERSION);
  87 //  real_snd_seq_create_port        = dlvsym(RTLD_NEXT, "snd_seq_create_port",        API_VERSION);
  88 //  real_snd_seq_create_simple_port = dlvsym(RTLD_NEXT, "snd_seq_create_simple_port", API_VERSION);
  89 }
  90
  91 #define CHECK_FUNC(func)                                                \
  92   if (real_ ## func == NULL)                                            \
  93   {                                                                     \
  94     fprintf(stderr, "dlvsym(\"" #func "\", \""API_VERSION"\") failed.\n"); \
  95     return -1;                                                          \
  96   }
  97
  98 #if 0
  99 int snd_seq_open(snd_seq_t ** handle, const char * name, int streams, int mode)
 100 {
 101   int ret;
 102
 103   //printf("Attempt to create alsa client '%s', %d streams and mode %d\n", name, streams, mode);
 104
 105   CHECK_FUNC(snd_seq_open);
 106
 107   //printf("real_snd_seq_open = %p\n", real_snd_seq_open);
 108   ret = real_snd_seq_open(handle, name, streams, mode);
 109   if (ret == 0)
 110   {
 111     //printf("alsa client %p (%d) created\n", *handle, snd_seq_client_id(*handle));
 112   }
 113   return ret;
 114 }
 115 #endif
 116
 117 int snd_seq_set_client_name(snd_seq_t * seq, const char * name)
 118 {
 119   int ret;
 120
 121   //printf("Attempt to set alsa client name to '%s' of %p\n", name, seq); getchar();
 122
 123   CHECK_FUNC(snd_seq_set_client_name);
 124
 125   ret = real_snd_seq_set_client_name(seq, name);
 126
 127   //printf("name set?\n"); getchar();
 128
 129   if (ret == 0)
 130   {
 131     //printf("ALSAPID: pid = %lld SETNAME %d '%s'\n", (long long)getpid(), snd_seq_client_id(seq), name);
 132     create_symlink(snd_seq_client_id(seq));
 133   }
 134
 135   return ret;
 136 }
 137
 138 int snd_seq_close(snd_seq_t * handle)
 139 {
 140   CHECK_FUNC(snd_seq_close);
 141
 142   //printf("ALSAPID: pid = %lld CLOSE %d\n", (long long)getpid(), snd_seq_client_id(handle));
 143   destroy_symlink(snd_seq_client_id(handle));
 144
 145   return real_snd_seq_close(handle);
 146 }
 147
 148 #if 0
 149 int snd_seq_create_port(snd_seq_t * handle, snd_seq_port_info_t * info)
 150 {
 151   int ret;
 152
 153   CHECK_FUNC(snd_seq_create_port);
 154
 155   ret = real_snd_seq_create_port(handle, info);
 156
 157   //printf("port created?\n"); getchar();
 158
 159   return ret;
 160 }
 161
 162 int snd_seq_create_simple_port(snd_seq_t * seq, const char * name, unsigned int caps, unsigned int type)
 163 {
 164   int ret;
 165
 166   CHECK_FUNC(snd_seq_create_simple_port);
 167
 168   ret = real_snd_seq_create_simple_port(seq, name, caps, type);
 169
 170   //printf("simple port created?\n"); getchar();
 171
 172   return ret;
 173 }
 174 #endif