util to get get symbol from a library

Added dlGetSymFromLib() to provide a utility that dlopen()'s
a library, and get the pointer to a symbol name.

Change-Id: I770eaef18a61aaa458833b3ca778f44b299585f5
CRs-Fixed: 2404939

4 files changed, 61 insertions, 1 deletions

diff --git a/utils/Android.mk b/utils/Android.mk
index ec6bf05..3887696 100644
--- a/utils/Android.mk
+++ b/utils/Android.mk
@@ -9,6 +9,7 @@ include $(CLEAR_VARS)
 
 ## Libs
 LOCAL_SHARED_LIBRARIES := \
+    libdl \
     libutils \
     libcutils \
     liblog \
diff --git a/utils/Makefile.am b/utils/Makefile.am
index 33afc1b..50e1e9a 100644
--- a/utils/Makefile.am
+++ b/utils/Makefile.am
@@ -61,7 +61,7 @@ libgps_utils_la_LDFLAGS = -Wl,-z,defs -lpthread -shared -version-info 1:0:0
 libgps_utils_la_CPPFLAGS = $(AM_CFLAGS) $(AM_CPPFLAGS)
 endif
 
-libgps_utils_la_LIBADD = $(CUTILS_LIBS)
+libgps_utils_la_LIBADD = $(CUTILS_LIBS) -ldl
 
 #Create and Install libraries
 lib_LTLIBRARIES = libgps_utils.la
diff --git a/utils/loc_misc_utils.cpp b/utils/loc_misc_utils.cpp
index b7c8406..70fdbc3 100644
--- a/utils/loc_misc_utils.cpp
+++ b/utils/loc_misc_utils.cpp
@@ -30,6 +30,7 @@
 #define LOG_TAG "LocSvc_misc_utils"
 #include <stdio.h>
 #include <string.h>
+#include <dlfcn.h>
 #include <log_util.h>
 #include <loc_misc_utils.h>
 #include <ctype.h>
@@ -112,3 +113,33 @@ void loc_util_trim_space(char *org_string)
 err:
     return;
 }
+
+inline void logDlError(const char* failedCall) {
+    const char * err = dlerror();
+    LOC_LOGe("%s error: %s", failedCall, (nullptr == err) ? "unknown" : err);
+}
+
+void* dlGetSymFromLib(void*& libHandle, const char* libName, const char* symName)
+{
+    void* sym = nullptr;
+    if ((nullptr != libHandle || nullptr != libName) && nullptr != symName) {
+        if (nullptr == libHandle) {
+            libHandle = dlopen(libName, RTLD_NOW);
+            if (nullptr == libHandle) {
+                logDlError("dlopen");
+            }
+        }
+        // NOT else, as libHandle gets assigned 5 line above
+        if (nullptr != libHandle) {
+            sym = dlsym(libHandle, symName);
+            if (nullptr == sym) {
+                logDlError("dlsym");
+            }
+        }
+    } else {
+        LOC_LOGe("Either libHandle (%p) or libName (%p) must not be null; "
+                 "symName (%p) can not be null.", libHandle, libName, symName);
+    }
+
+    return sym;
+}
diff --git a/utils/loc_misc_utils.h b/utils/loc_misc_utils.h
index 7d66d84..fad1b6d 100644
--- a/utils/loc_misc_utils.h
+++ b/utils/loc_misc_utils.h
@@ -92,6 +92,34 @@ SIDE EFFECTS
    N/A
 ===========================================================================*/
 void loc_util_trim_space(char *org_string);
+
+/*===========================================================================
+FUNCTION dlGetSymFromLib
+
+DESCRIPTION
+   Handy function to get a pointer to a symbol from a library.
+
+   If libHandle is not null, it will be used as the handle to the library. In
+   that case libName wll not be used;
+   libHandle is an in / out parameter.
+   If libHandle is null, libName will be used to dlopen.
+   Either libHandle or libName must not be nullptr.
+   symName must not be null.
+
+DEPENDENCIES
+   N/A
+
+RETURN VALUE
+   pointer to symName. Could be nullptr if
+       Parameters are incorrect; or
+       libName can not be opened; or
+       symName can not be found.
+
+SIDE EFFECTS
+   N/A
+===========================================================================*/
+void* dlGetSymFromLib(void*& libHandle, const char* libName, const char* symName);
+
 #ifdef __cplusplus
 }
 #endif