From f61e9237e666f776414294e786df70f629fe5b73 Mon Sep 17 00:00:00 2001
From: yellows8 <yellows8@users.noreply.github.com>
Date: Sat, 15 Dec 2018 21:50:27 -0500
Subject: [PATCH] Added accountGetPreselectedUser.

---
 nx/include/switch/services/acc.h    |  4 ++++
 nx/include/switch/services/applet.h |  1 +
 nx/source/services/acc.c            | 36 +++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/nx/include/switch/services/acc.h b/nx/include/switch/services/acc.h
index e9067313..7a48003e 100644
--- a/nx/include/switch/services/acc.h
+++ b/nx/include/switch/services/acc.h
@@ -63,3 +63,7 @@ Result accountProfileGetImageSize(AccountProfile* profile, size_t* image_size);
 Result accountProfileLoadImage(AccountProfile* profile, void* buf, size_t len, size_t* image_size);
 
 void accountProfileClose(AccountProfile* profile);
+
+/// Gets the userID which was selected by the profile-selector applet (if any), prior to launching the currently running Application title. This can only be used once under the current process, under an Application title.
+Result accountGetPreselectedUser(u128 *userID);
+
diff --git a/nx/include/switch/services/applet.h b/nx/include/switch/services/applet.h
index 0973d684..d65396da 100644
--- a/nx/include/switch/services/applet.h
+++ b/nx/include/switch/services/applet.h
@@ -87,6 +87,7 @@ Result appletCreateManagedDisplayLayer(u64 *out);
  * @param s Output storage.
  * @param kind See \ref AppletLaunchParameterKind.
  * @note Can only be used in Applications.
+ * @note See also acc.h \ref accountGetPreselectedUser (wrapper for appletPopLaunchParameter etc).
  */
 Result appletPopLaunchParameter(AppletStorage *s, AppletLaunchParameterKind kind);
 
diff --git a/nx/source/services/acc.c b/nx/source/services/acc.c
index 93b8e2e8..68d136ef 100644
--- a/nx/source/services/acc.c
+++ b/nx/source/services/acc.c
@@ -4,6 +4,7 @@
 #include "arm/atomics.h"
 #include "services/acc.h"
 #include "services/sm.h"
+#include "services/applet.h"
 
 static Service g_accSrv;
 static u64 g_refCnt;
@@ -325,3 +326,38 @@ void accountProfileClose(AccountProfile* profile) {
     serviceClose(&profile->s);
 }
 
+Result accountGetPreselectedUser(u128 *userID) {
+    Result rc=0;
+    AppletStorage storage;
+    s64 tmpsize=0;
+
+    struct {
+        u32  magicnum;//These two fields must match fixed values.
+        u8   unk_x4;
+        u8   pad[3];
+        u128 userID;
+        u8   unk_x18[0x70];//unused
+    } PACKED storagedata;
+
+    memset(&storagedata, 0, sizeof(storagedata));
+
+    rc = appletPopLaunchParameter(&storage, AppletLaunchParameterKind_PreselectedUser);
+
+    if (R_SUCCEEDED(rc)) {
+        rc = appletStorageGetSize(&storage, &tmpsize);
+        if (R_SUCCEEDED(rc) && tmpsize < sizeof(storagedata))
+            rc = MAKERESULT(Module_Libnx, LibnxError_BadInput);
+
+        if (R_SUCCEEDED(rc)) rc = appletStorageRead(&storage, 0, &storagedata, sizeof(storagedata));
+
+        appletStorageClose(&storage);
+
+        if (R_SUCCEEDED(rc) && (storagedata.magicnum!=0xc79497ca || storagedata.unk_x4!=1))
+            rc = MAKERESULT(Module_Libnx, LibnxError_BadInput);
+
+        if (R_SUCCEEDED(rc) && userID) *userID = storagedata.userID;
+    }
+
+    return rc;
+}
+