firefox/xpcom/reflect/xptcall/md/test/invoke_test.cpp

/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <stdio.h>

typedef unsigned nsresult;
typedef unsigned uint32_t;
typedef unsigned nsXPCVariant;

#if defined(WIN32)
#  define NS_IMETHOD virtual nsresult __stdcall
#  define NS_IMETHODIMP nsresult __stdcall
#else
#  define NS_IMETHOD virtual nsresult
#  define NS_IMETHODIMP nsresult
#endif

class base {
 public:
  NS_IMETHOD ignored() = 0;
};

class foo : public base {
 public:
  NS_IMETHOD callme1(int i, int j) = 0;
  NS_IMETHOD callme2(int i, int j) = 0;
  NS_IMETHOD callme3(int i, int j) = 0;
};

class bar : public foo {
 public:
  NS_IMETHOD ignored() override;
  NS_IMETHOD callme1(int i, int j) override;
  NS_IMETHOD callme2(int i, int j) override;
  NS_IMETHOD callme3(int i, int j) override;
};

/*
class baz : public base {
public:
  NS_IMETHOD ignored() override;
  NS_IMETHOD callme1() override;
  NS_IMETHOD callme2() override;
  NS_IMETHOD callme3() override;
  void setfoo(foo* f) {other = f;}

  foo* other;
};
NS_IMETHODIMP baz::ignored(){return 0;}
*/

NS_IMETHODIMP bar::ignored() { return 0; }

NS_IMETHODIMP bar::callme1(int i, int j) {
  printf("called bar::callme1 with: %d %d\n", i, j);
  return 5;
}

NS_IMETHODIMP bar::callme2(int i, int j) {
  printf("called bar::callme2 with: %d %d\n", i, j);
  return 5;
}

NS_IMETHODIMP bar::callme3(int i, int j) {
  printf("called bar::callme3 with: %d %d\n", i, j);
  return 5;
}

void docall(foo* f, int i, int j) { f->callme1(i, j); }

/***************************************************************************/
#if defined(WIN32)

static uint32_t __stdcall invoke_count_words(uint32_t paramCount,
                                             nsXPCVariant* s) {
  return paramCount;
}

static void __stdcall invoke_copy_to_stack(uint32_t* d, uint32_t paramCount,
                                           nsXPCVariant* s) {
  for (uint32_t i = 0; i < paramCount; i++, d++, s++) {
    *((uint32_t*)d) = *((uint32_t*)s);
  }
}

static nsresult __stdcall DoInvoke(void* that, uint32_t index,
                                   uint32_t paramCount, nsXPCVariant* params) {
  __asm {
        push    params
        push    paramCount
        call    invoke_count_words  // stdcall, result in eax
        shl     eax,2  // *= 4
        sub     esp,eax  // make space for params
        mov     edx,esp
        push    params
        push    paramCount
        push    edx
        call    invoke_copy_to_stack  // stdcall
        mov     ecx,that  // instance in ecx
        push    ecx  // push this
        mov     edx,[ecx]  // vtable in edx
        mov     eax,index
        shl     eax,2  // *= 4
        add     edx,eax
        call    [edx]  // stdcall, i.e. callee cleans up stack.
  }
}

#else
/***************************************************************************/
// just Linux_x86 now. Add other later...

static uint32_t invoke_count_words(uint32_t paramCount, nsXPCVariant* s) {
  return paramCount;
}

static void invoke_copy_to_stack(uint32_t* d, uint32_t paramCount,
                                 nsXPCVariant* s) {
  for (uint32_t i = 0; i < paramCount; i++, d++, s++) {
    *((uint32_t*)d) = *((uint32_t*)s);
  }
}

static nsresult DoInvoke(void* that, uint32_t index, uint32_t paramCount,
                         nsXPCVariant* params) {
  uint32_t result;
  void* fn_count = invoke_count_words;
  void* fn_copy = invoke_copy_to_stack;

  __asm__ __volatile__(
      "pushl %4\n\t"
      "pushl %3\n\t"
      "movl  %5, %%eax\n\t"
      "call  *%%eax\n\t" /* count words */
      "addl  $0x8, %%esp\n\t"
      "shl   $2, %%eax\n\t"    /* *= 4 */
      "subl  %%eax, %%esp\n\t" /* make room for params */
      "movl  %%esp, %%edx\n\t"
      "pushl %4\n\t"
      "pushl %3\n\t"
      "pushl %%edx\n\t"
      "movl  %6, %%eax\n\t"
      "call  *%%eax\n\t" /* copy params */
      "addl  $0xc, %%esp\n\t"
      "movl  %1, %%ecx\n\t"
      "pushl %%ecx\n\t"
      "movl  (%%ecx), %%edx\n\t"
      "movl  %2, %%eax\n\t" /* function index */
      "shl   $2, %%eax\n\t" /* *= 4 */
      "addl  $8, %%eax\n\t" /* += 8 */
      "addl  %%eax, %%edx\n\t"
      "call  *(%%edx)\n\t" /* safe to not cleanup esp */
      "movl  %%eax, %0"
      : "=g"(result)     /* %0 */
      : "g"(that),       /* %1 */
        "g"(index),      /* %2 */
        "g"(paramCount), /* %3 */
        "g"(params),     /* %4 */
        "g"(fn_count),   /* %5 */
        "g"(fn_copy)     /* %6 */
      : "ax", "cx", "dx", "memory");

  return result;
}

#endif
/***************************************************************************/

int main() {
  nsXPCVariant params1[2] = {1, 2};
  nsXPCVariant params2[2] = {2, 4};
  nsXPCVariant params3[2] = {3, 6};

  foo* a = new bar();

  //  printf("calling via C++...\n");
  //  docall(a, 12, 24);

  printf("calling via ASM...\n");
  DoInvoke(a, 1, 2, params1);
  DoInvoke(a, 2, 2, params2);
  DoInvoke(a, 3, 2, params3);

  return 0;
}