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Commit b843791b authored by Chia-I Wu's avatar Chia-I Wu
Browse files

Add native_handle_init 

HIDL requires file descriptors to be wrapped in native_handle_t.  We want
a low overhead way to do that when the number of file descriptors is known
at compile time.  Instead of

  // wrap an fd in native_handle_t
  native_handle_t* fd_handle = native_handle_create(1, 0);
  if (!fd_handle) {
    // clean up and return error
  }
  fd_handle->data[0] = fd;

  hidl_cb(..., fd_handle);

  native_handle_delete(fd_handle);

this change adds native_handle_init to allow for

  // wrap an fd in native_handle_t
  NATIVE_HANDLE_DECLARE_STORAGE(fd_storage, 1, 0);
  native_handle_t* fd_handle = native_handle_init(fd_storage, 1, 0);
  fd_handle->data[0] = fd;

  hidl_cb(..., fd_handle);

Test: make libcutils
Bug: 32021609
Change-Id: If1fd07482243d37492fdea57c602a1b13c8953cc
parent 5980fe4a

include/cutils/native_handle.h

+15 −0
Original line number Diff line number Diff line
@@ -17,10 +17,17 @@ 
#ifndef NATIVE_HANDLE_H_

#define NATIVE_HANDLE_H_



#include <stdalign.h>



#ifdef __cplusplus

extern "C" {

#endif



/* Declare a char array for use with native_handle_init */

#define NATIVE_HANDLE_DECLARE_STORAGE(name, maxFds, maxInts) \

    alignas(native_handle_t) char name[                            \

      sizeof(native_handle_t) + sizeof(int) * (maxFds + maxInts)]



typedef struct native_handle

{

    int version;        /* sizeof(native_handle_t) */
@@ -46,6 +53,14 @@ typedef struct native_handle 
 */

int native_handle_close(const native_handle_t* h);



/*

 * native_handle_init

 *

 * Initializes a native_handle_t from storage.  storage must be declared with

 * NATIVE_HANDLE_DECLARE_STORAGE.  numFds and numInts must not respectively

 * exceed maxFds and maxInts used to declare the storage.

 */

native_handle_t* native_handle_init(char* storage, int numFds, int numInts);



/*

 * native_handle_create

libcutils/native_handle.c

+14 −0
Original line number Diff line number Diff line
@@ -28,6 +28,20 @@ 
static const int kMaxNativeFds = 1024;

static const int kMaxNativeInts = 1024;



native_handle_t* native_handle_init(char* storage, int numFds, int numInts)

{

    if ((uintptr_t) storage % alignof(native_handle_t)) {

        return NULL;

    }



    native_handle_t* handle = (native_handle_t*) storage;

    handle->version = sizeof(native_handle_t);

    handle->numFds = numFds;

    handle->numInts = numInts;



    return handle;

}



native_handle_t* native_handle_create(int numFds, int numInts)

{

    if (numFds < 0 || numInts < 0 || numFds > kMaxNativeFds || numInts > kMaxNativeInts) {