osdep: add qemu_get_local_state_pathname()

This function returns ${prefix}/var/RELATIVE_PATHNAME on POSIX-y systems,
and <CSIDL_COMMON_APPDATA>/RELATIVE_PATHNAME on Win32.

http://msdn.microsoft.com/en-us/library/bb762494.aspx

  [...] This folder is used for application data that is not user
  specific. For example, an application can store a spell-check
  dictionary, a database of clip art, or a log file in the
  CSIDL_COMMON_APPDATA folder. [...]

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

include/qemu/osdep.h

@@ -204,4 +204,15 @@ const char *qemu_get_version(void);
 void fips_set_state(bool requested);
 bool fips_get_state(void);
 
+/* Return a dynamically allocated pathname denoting a file or directory that is
+ * appropriate for storing local state.
+ *
+ * @relative_pathname need not start with a directory separator; one will be
+ * added automatically.
+ *
+ * The caller is responsible for releasing the value returned with g_free()
+ * after use.
+ */
+char *qemu_get_local_state_pathname(const char *relative_pathname);
+
 #endif

util/oslib-posix.c

@@ -47,6 +47,8 @@ extern int daemon(int, int);
 #  define QEMU_VMALLOC_ALIGN getpagesize()
 #endif
 
+#include <glib/gprintf.h>
+
 #include "config-host.h"
 #include "sysemu/sysemu.h"
 #include "trace.h"
@@ -232,3 +234,10 @@ int qemu_utimens(const char *path, const struct timespec *times)
 
     return utimes(path, &tv[0]);
 }
+
+char *
+qemu_get_local_state_pathname(const char *relative_pathname)
+{
+    return g_strdup_printf("%s/%s", CONFIG_QEMU_LOCALSTATEDIR,
+                           relative_pathname);
+}

util/oslib-win32.c

@@ -26,12 +26,17 @@
  * THE SOFTWARE.
  */
 #include <windows.h>
+#include <glib.h>
+#include <stdlib.h>
 #include "config-host.h"
 #include "sysemu/sysemu.h"
 #include "qemu/main-loop.h"
 #include "trace.h"
 #include "qemu/sockets.h"
 
+/* this must come after including "trace.h" */
+#include <shlobj.h>
+
 void *qemu_oom_check(void *ptr)
 {
     if (ptr == NULL) {
@@ -160,3 +165,20 @@ int qemu_get_thread_id(void)
 {
     return GetCurrentThreadId();
 }
+
+char *
+qemu_get_local_state_pathname(const char *relative_pathname)
+{
+    HRESULT result;
+    char base_path[MAX_PATH+1] = "";
+
+    result = SHGetFolderPath(NULL, CSIDL_COMMON_APPDATA, NULL,
+                             /* SHGFP_TYPE_CURRENT */ 0, base_path);
+    if (result != S_OK) {
+        /* misconfigured environment */
+        g_critical("CSIDL_COMMON_APPDATA unavailable: %ld", (long)result);
+        abort();
+    }
+    return g_strdup_printf("%s" G_DIR_SEPARATOR_S "%s", base_path,
+                           relative_pathname);
+}