如何获得一个UInt64的价值，只有toString的方法？ [英] How to get value of a UInt64, toString only way?

问题描述

我有这个：
ctypes.UInt64（7）

返回这个：

$ p $ var chars = SendMessage（hToolbar，TB_GETBUTTONTEXTW，local_tbb.idCommand，ctypes.voidptr_t（0））;


所以

  console.log（'chars ='，chars，chars.toString（），uneval（chars））; 
  

给出

所以我可以通过去 chars.toString（）来获取值，但是我必须运行一个 parseInt chars.UInt64 ？

解决方案

64位整数在js-ctypes中是Javascript缺乏兼容的类型。所有的Javascript编号都是IEEE双精度浮点数（ double ），这些可以表示 53位整数。所以你甚至不应该试图自己解析int，除非你知道结果符合 double 。例如。你不能知道这个指针。

例如，考虑以下几点：$ b​​
$ b

  // 6 * 8-bit = 48 bit; 48℃ 53，所以这是OK 
（（parseInt（0xffffffffffff，16）+ 2）== parseInt（0xffffffffffff，16））== false 
 //然而，7 * 8位= 56位; 56 < 53，所以这是不正确
（（parseInt（0xffffffffffffff，16）+ 2）== parseInt（0xffffffffffffff，16））== true 
 //糟糕，比较相等，因为双精度浮点数
 //不能实际保存parseInt结果，这仍然远低于64位！ 
  

让我们正确处理JS中的64位整数...

如果您只是想进行比较，请使用 UInt64.compare（） / Int64.compare（）

  //数字==另一个数字
 ctypes.UInt64.compare（ctypes.UInt64（ 7），ctypes.UInt64（7））== 0 
 // number！=另一个数字
 ctypes.UInt64.compare（ctypes.UInt64（7），ctypes.UInt64 6））！= 0 
 // number>另一个数字
 ctypes.UInt64.compare（ctypes.UInt64（7），ctypes.UInt64（6））> 0 
 //数字<另一个数字
 ctypes.UInt64.compare（ctypes.UInt64（7），ctypes.UInt64（8））< 0 
  

如果您需要结果，但不确定它是否为32位无符号整数，可以检测你是否处理32位无符号整数，这些整数只是打包到 Uint64 中：



  ctypes.UInt64.compare（ctypes.UInt64（7），ctypes.UInt64（0xffffffff））< 0 
  

以及 Int64 ，但你需要比较最小值和最大值：



  ctypes.Int64.compare（ctypes.Int64（7 ），ctypes.Int64（2147483647））< 0&& 
 ctypes.Int64.compare（ctypes.Int64（7），ctypes.Int64（ -  2147483648））> 0 
  

因此，一旦您知道或检测到JS 双，可以很安全地调用 parseInt 。
$ b

  var number = ...; 
 if（ctypes.UInt64.compare（number，ctypes.UInt64（0xffffffff））> 0）{
 throw错误（哎呀，我们的代码无法正确处理的意外的大数值） ; 
} 
 chars = parseInt（chars.toString（），10）; 
  

（为了完整起见，还有 UInt64.hi（） / Int64.hi（）和 UInt64.lo（） / Int64.lo（）得到真正的64位整数的高低32位，并自己做64位整数数学（问题/ 1652654 /添加-64-bit-numbers-using-32-bit-arithmetic>例如），但要小心头号。 PS： SendMessage 的返回值是 intptr_t 不是 uintptr_t ，因为 SendMessage（hwnd，TB_GETBUTTONTEXT，...）可能在失败时返回 -1 ！ / b>



所以把所有这些放在一起（未经测试）：

$ p $ var $ SendMessage = user32.declare（
'SendMessageW'，
ctypes.winapi_abi，
ctypes.intptr_t，
ctypes.voidptr_t，// HWND
ctypes.uint32_t，// MSG
ctypes.uintptr_t，// WPARAM
ctypes.intptr_t // LPARAM
）;
// ...

var chars = SendMessage（hToolbar，TB_GETBUTTONTEXTW，local_tbb.idCommand，ctypes.voidptr_t（0））;
if（ctypes.Int64.compare（chars，ctypes.Int64（0））<0）{
throw new Error（TB_GETBUTTONTEXT returned a failure（negative value））;

if（ctypes.Int64.comare（chars，ctypes.Int64（32768））> 0）{
throw new错误（TB_GETBUTTONTEXT返回不合理的大数目> 32KiB ）;
}
chars = parseInt（chars.toString（））;





I have this: "ctypes.UInt64("7")"

It is returned by this:

var chars = SendMessage(hToolbar, TB_GETBUTTONTEXTW, local_tbb.idCommand, ctypes.voidptr_t(0));

so

console.log('chars=', chars, chars.toString(), uneval(chars));

gives

'chars=' 'UInt64 {  }' "7" 'ctypes.UInt64("7")'

So I can get the value by going chars.toString(), but I have to run a parseInt on that, is there anyway to read it like a property? Like chars.UInt64?

解决方案

The problem with 64-bit integers in js-ctypes is that Javascript lacks a compatible type. All Javascript numbers are IEEE double precision floating point numbers (double), and those can represent 53-bit integers at most. So you shouldn't even be trying to parse the int yourself, unless you know for a fact that the result would fit into a double. E.g. You cannot know this for pointers.

E.g. consider the following:

// 6 * 8-bit = 48 bit; 48 < 53, so this is OK
((parseInt("0xffffffffffff", 16) + 2) == parseInt("0xffffffffffff", 16)) == false
// However, 7 * 8-bit = 56 bit; 56 < 53, so this is not OK
((parseInt("0xffffffffffffff", 16) + 2) == parseInt("0xffffffffffffff", 16)) == true
// Oops, that compared equal, because a double precision floating point
// cannot actual hold the parseInt result, which is still well below 64-bit!

Lets deal with 64-bit integers in JS properly...

If you just want to comparisons, use UInt64.compare()/Int64.compare(), e.g.

// number == another number
ctypes.UInt64.compare(ctypes.UInt64("7"), ctypes.UInt64("7")) == 0
// number != another number
ctypes.UInt64.compare(ctypes.UInt64("7"), ctypes.UInt64("6")) != 0
// number > another number
ctypes.UInt64.compare(ctypes.UInt64("7"), ctypes.UInt64("6")) > 0
// number < another number
ctypes.UInt64.compare(ctypes.UInt64("7"), ctypes.UInt64("8")) < 0

If you need the result, but are not sure it is a 32-bit unsigned integer, you can detect if you're dealing with 32 bit unsigned integers that are just packed into Uint64:

ctypes.UInt64.compare(ctypes.UInt64("7"), ctypes.UInt64("0xffffffff")) < 0

And the analog for 32-bit signed integers in Int64, but you need to compare minimum and maximum:

ctypes.Int64.compare(ctypes.Int64("7"), ctypes.Int64("2147483647")) < 0 &&
ctypes.Int64.compare(ctypes.Int64("7"), ctypes.Int64("-2147483648")) > 0

So, once you know or detected that something will fit into a JS double, it is safe to call parseInt on it.

var number = ...;
if (ctypes.UInt64.compare(number, ctypes.UInt64("0xffffffff")) > 0) {
  throw Error("Whoops, unexpectedly large value that our code would not handle correctly");
}
chars = parseInt(chars.toString(), 10); 

(For the sake of completeness, there is also UInt64.hi()/Int64.hi() and UInt64.lo()/Int64.lo() to get the high and low 32-bits for real 64-bit integers and do 64-bit integer math yourself (e.g.), but beware of endianess).

PS: The return value of SendMessage is intptr_t not uintptr_t, which is important here because SendMessage(hwnd, TB_GETBUTTONTEXT, ...) may return -1 on failure!

So putting all this together (untested):

var SendMessage = user32.declare(
    'SendMessageW',
    ctypes.winapi_abi,
    ctypes.intptr_t,
    ctypes.voidptr_t, // HWND
    ctypes.uint32_t, // MSG
    ctypes.uintptr_t, // WPARAM
    ctypes.intptr_t // LPARAM
);
// ...

var chars = SendMessage(hToolbar, TB_GETBUTTONTEXTW, local_tbb.idCommand, ctypes.voidptr_t(0));
if (ctypes.Int64.compare(chars, ctypes.Int64("0")) < 0) {
  throw new Error("TB_GETBUTTONTEXT returned a failure (negative value)");
}
if (ctypes.Int64.comare(chars, ctypes.Int64("32768")) > 0) {
  throw new Error("TB_GETBUTTONTEXT returned unreasonably large number > 32KiB");
}
chars = parseInt(chars.toString());

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