// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#define _ALL_SOURCE 1
#include <threads.h>
#include <zircon/process.h>
#include <zircon/types.h>

#include "libc.h"

static mtx_t startup_handles_lock = MTX_INIT;
static uint32_t startup_handles_num;
static zx_handle_t* startup_handles;
static uint32_t* startup_handles_info;

static void shave_front(void) {
  while (startup_handles_num > 0 && startup_handles[0] == ZX_HANDLE_INVALID) {
    --startup_handles_num;
    ++startup_handles;
    ++startup_handles_info;
  }
}

static void shave_back(void) {
  while (startup_handles_num > 0 && startup_handles[startup_handles_num - 1] == ZX_HANDLE_INVALID)
    --startup_handles_num;
}

// This is called only once at startup, so it doesn't need locking.
ATTR_LIBC_VISIBILITY
void __libc_startup_handles_init(uint32_t nhandles, zx_handle_t handles[], uint32_t handle_info[]) {
  startup_handles_num = nhandles;
  startup_handles = handles;
  startup_handles_info = handle_info;
  shave_front();
  shave_back();
}

__EXPORT
zx_handle_t zx_take_startup_handle(uint32_t hnd_info) {
  zx_handle_t result = ZX_HANDLE_INVALID;
  mtx_lock(&startup_handles_lock);
  for (uint32_t i = 0; i < startup_handles_num; ++i) {
    if (startup_handles_info[i] == hnd_info) {
      result = startup_handles[i];
      startup_handles[i] = ZX_HANDLE_INVALID;
      startup_handles_info[i] = 0;
      if (i == 0)
        shave_front();
      else if (i == startup_handles_num - 1)
        shave_back();
      break;
    }
  }
  mtx_unlock(&startup_handles_lock);
  return result;
}