support "sideload over ADB" mode

Rather than depending on the existence of some place to store a file
that is accessible to users on an an unbootable device (eg, a physical
sdcard, external USB drive, etc.), add support for sideloading
packages sent to the device with adb.

This change adds a "minimal adbd" which supports nothing but receiving
a package over adb (with the "adb sideload" command) and storing it to
a fixed filename in the /tmp ramdisk, from where it can be verified
and sideloaded in the usual way.  This should be leave available even
on locked user-build devices.

The user can select "apply package from ADB" from the recovery menu,
which starts minimal-adb mode (shutting down any real adbd that may be
running).  Once minimal-adb has received a package it exits
(restarting real adbd if appropriate) and then verification and
installation of the received package proceeds.

Change-Id: I6fe13161ca064a98d06fa32104e1f432826582f5
diff --git a/minadbd/fdevent.h b/minadbd/fdevent.h
new file mode 100644
index 0000000..a0ebe2a
--- /dev/null
+++ b/minadbd/fdevent.h
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2006 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __FDEVENT_H
+#define __FDEVENT_H
+
+#include <stdint.h>  /* for int64_t */
+
+/* events that may be observed */
+#define FDE_READ              0x0001
+#define FDE_WRITE             0x0002
+#define FDE_ERROR             0x0004
+#define FDE_TIMEOUT           0x0008
+
+/* features that may be set (via the events set/add/del interface) */
+#define FDE_DONT_CLOSE        0x0080
+
+typedef struct fdevent fdevent;
+
+typedef void (*fd_func)(int fd, unsigned events, void *userdata);
+
+/* Allocate and initialize a new fdevent object
+ * Note: use FD_TIMER as 'fd' to create a fd-less object
+ * (used to implement timers).
+*/
+fdevent *fdevent_create(int fd, fd_func func, void *arg);
+
+/* Uninitialize and deallocate an fdevent object that was
+** created by fdevent_create()
+*/
+void fdevent_destroy(fdevent *fde);
+
+/* Initialize an fdevent object that was externally allocated
+*/
+void fdevent_install(fdevent *fde, int fd, fd_func func, void *arg);
+
+/* Uninitialize an fdevent object that was initialized by
+** fdevent_install()
+*/
+void fdevent_remove(fdevent *item);
+
+/* Change which events should cause notifications
+*/
+void fdevent_set(fdevent *fde, unsigned events);
+void fdevent_add(fdevent *fde, unsigned events);
+void fdevent_del(fdevent *fde, unsigned events);
+
+void fdevent_set_timeout(fdevent *fde, int64_t  timeout_ms);
+
+/* loop forever, handling events.
+*/
+void fdevent_loop();
+
+struct fdevent 
+{
+    fdevent *next;
+    fdevent *prev;
+
+    int fd;
+    int force_eof;
+
+    unsigned short state;
+    unsigned short events;
+
+    fd_func func;
+    void *arg;
+};
+
+
+#endif