将位数组转换为字节和浮点数

Question

我试图从一个数组（只包含位）读取浮点数（每个浮点数32位）当我尝试使用ArrayBuffer和DataView时，我最后得到了奇怪的值。我期待有两个浮点数，但我看到所有数字都是0。

我在这里错过了什么？我希望2个浮点数（firsNum，secNum）分别来自4个byes

// Simple array contain 8 bytes
var myBitsArr = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0];

// Array buffer with size of 8 bytes
const buffer = new ArrayBuffer(8);

// Loop all the data to the array buffer add 8 bits at each time
for (var i = 0; i < myBitsArr.length / 8; i++) {
  var byteCounter = i * 8;
  var b_0 = myBitsArr[byteCounter + 0] << 0;
  var b_1 = myBitsArr[byteCounter + 1] << 1;
  var b_2 = myBitsArr[byteCounter + 2] << 2;
  var b_3 = myBitsArr[byteCounter + 3] << 3;
  var b_4 = myBitsArr[byteCounter + 4] << 4;
  var b_5 = myBitsArr[byteCounter + 5] << 5;
  var b_6 = myBitsArr[byteCounter + 6] << 6;
  var b_7 = myBitsArr[byteCounter + 7] << 7;

  buffer[i] = (b_0 + b_1 + b_2 + b_3 + b_4 + b_5 + b_6 + b_7);
}

console.log(buffer)

// View the floating numbers
var viewNumbers = new DataView(buffer);
var firsNum = viewNumbers.getFloat32(0); // get 0 back and not float number
var secNum = viewNumbers.getFloat32(1); // get 0 back and not float number
console.log(firsNum, secNum)

Answer 1

除了这些评论：ArrayBuffer不是一个数组，这就是为什么buffer[i]没有做任何有用的事情。你需要一个typedarray，很可能是Uint8Array，下面叫做uint8：

// Simple array contain 8 bytes
var myBitsArr = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0];

// Array buffer with size of 8 bytes
const buffer = new ArrayBuffer(8);
const uint8 = new Uint8Array(buffer);

// Loop all the data to the array buffer add 8 bits at each time
for (var i = 0; i < myBitsArr.length / 8; i++) {
  var byteCounter = i * 8;
  var b_0 = myBitsArr[byteCounter + 0] << 0;
  var b_1 = myBitsArr[byteCounter + 1] << 1;
  var b_2 = myBitsArr[byteCounter + 2] << 2;
  var b_3 = myBitsArr[byteCounter + 3] << 3;
  var b_4 = myBitsArr[byteCounter + 4] << 4;
  var b_5 = myBitsArr[byteCounter + 5] << 5;
  var b_6 = myBitsArr[byteCounter + 6] << 6;
  var b_7 = myBitsArr[byteCounter + 7] << 7;

  uint8[i] = (b_0 + b_1 + b_2 + b_3 + b_4 + b_5 + b_6 + b_7);
}

console.log(buffer)

// View the floating numbers
var viewNumbers = new DataView(buffer);
var firsNum = viewNumbers.getFloat32(0,true); // get 0 back and not float number
var secNum = viewNumbers.getFloat32(4,true); // get 0 back and not float number
console.log(firsNum, secNum);

然后它做了一些事情，显示“4.600743118071239e-41 4.027191656623092e-41”没有true-s（大端）和“4 240”此刻（小端，仍然可能是错误的）。通过翻转位顺序，它通常产生奇怪的数字，但是第二个星座得到-35.5。