/*
 * Copyright (c) 2012-2018 Zeex
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <stddef.h>
#include <windows.h>

typedef __int64 QWORD;

#define SUBHOOK_CODE_PROTECT_FLAGS PAGE_EXECUTE_READWRITE

int subhook_unprotect(void *address, size_t size) {
  DWORD old_flags;
  BOOL result = VirtualProtect(address,
                               size,
                               SUBHOOK_CODE_PROTECT_FLAGS,
                               &old_flags);
  return !result;
}

void *subhook_alloc_code(void *target_address, size_t size) {
#if defined _M_AMD64 || defined __amd64__
  if (target_address != NULL) {
    SYSTEM_INFO sys_info;
    DWORD page_size;
    QWORD offset;

    GetSystemInfo(&sys_info);
    page_size = sys_info.dwPageSize;

    QWORD pivot = (QWORD)target_address & ~((QWORD)page_size - 1);
    void *result;

    for (offset = page_size; offset <= ((QWORD)1 << 31); offset += page_size) {
      result = VirtualAlloc((void *)(pivot - offset),
                            size,
                            MEM_COMMIT | MEM_RESERVE,
                            SUBHOOK_CODE_PROTECT_FLAGS);
      if (result != NULL) {
        return result;
      }
      result = VirtualAlloc((void *)(pivot + offset),
                            size,
                            MEM_COMMIT | MEM_RESERVE,
                            SUBHOOK_CODE_PROTECT_FLAGS);
      if (result != NULL) {
        return result;
      }
    }
  }
#endif

  return VirtualAlloc(NULL,
                      size,
                      MEM_COMMIT | MEM_RESERVE,
                      SUBHOOK_CODE_PROTECT_FLAGS);
}

int subhook_free_code(void *address, size_t size) {
  (void)size;

  if (address == NULL) {
    return 0;
  }
  return !VirtualFree(address, 0, MEM_RELEASE);
}