module: Create pa_module_exists()

This new function checks if a certain module name is available in the
system.

configure.ac

@@ -1217,6 +1217,7 @@ PACTL_BINARY=${bindir}/pactl${EXEEXT}
 AX_DEFINE_DIR(PACTL_BINARY, PACTL_BINARY, [Location of pactl binary])
 
 AC_SUBST(PA_SOEXT, [.so])
+AC_DEFINE(PA_SOEXT, [".so"], [Shared object extension])
 
 AC_SUBST(pulseconfdir, ["${sysconfdir}/pulse"])
 AX_DEFINE_DIR(PA_DEFAULT_CONFIG_DIR, pulseconfdir, [Location of configuration files])

src/pulsecore/module.c

@@ -28,6 +28,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
+#include <ltdl.h>
 
 #include <pulse/xmalloc.h>
 #include <pulse/proplist.h>
@@ -47,6 +48,60 @@
 #define PA_SYMBOL_GET_N_USED "pa__get_n_used"
 #define PA_SYMBOL_GET_DEPRECATE "pa__get_deprecated"
 
+bool pa_module_exists(const char *name) {
+    const char *paths, *state = NULL;
+    char *n, *p, *pathname;
+    bool result;
+
+    pa_assert(name);
+
+    if (name[0] == PA_PATH_SEP_CHAR) {
+        result = access(name, F_OK) == 0 ? true : false;
+        pa_log_debug("Checking for existence of '%s': %s", name, result ? "success" : "failure");
+        if (result)
+            return true;
+    }
+
+    if (!(paths = lt_dlgetsearchpath()))
+        return false;
+
+    /* strip .so from the end of name, if present */
+    n = pa_xstrdup(name);
+    p = rindex(n, '.');
+    if (p && pa_streq(p, PA_SOEXT))
+        p[0] = 0;
+
+    while ((p = pa_split(paths, ":", &state))) {
+        pathname = pa_sprintf_malloc("%s" PA_PATH_SEP "%s" PA_SOEXT, p, n);
+        result = access(pathname, F_OK) == 0 ? true : false;
+        pa_log_debug("Checking for existence of '%s': %s", pathname, result ? "success" : "failure");
+        pa_xfree(pathname);
+        pa_xfree(p);
+        if (result) {
+            pa_xfree(n);
+            return true;
+        }
+    }
+
+    state = NULL;
+    if (PA_UNLIKELY(pa_run_from_build_tree())) {
+        while ((p = pa_split(paths, ":", &state))) {
+            pathname = pa_sprintf_malloc("%s" PA_PATH_SEP ".libs" PA_PATH_SEP "%s" PA_SOEXT, p, n);
+            result = access(pathname, F_OK) == 0 ? true : false;
+            pa_log_debug("Checking for existence of '%s': %s", pathname, result ? "success" : "failure");
+            pa_xfree(pathname);
+            pa_xfree(p);
+            if (result) {
+                pa_xfree(n);
+                return true;
+            }
+        }
+    }
+
+    pa_xfree(n);
+    return false;
+}
+
 pa_module* pa_module_load(pa_core *c, const char *name, const char *argument) {
     pa_module *m = NULL;
     bool (*load_once)(void);

src/pulsecore/module.h

@@ -50,6 +50,8 @@ struct pa_module {
     pa_proplist *proplist;
 };
 
+bool pa_module_exists(const char *name);
+
 pa_module* pa_module_load(pa_core *c, const char *name, const char *argument);
 
 void pa_module_unload(pa_core *c, pa_module *m, bool force);