javascript 调整数组缓冲区的大小
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Resize ArrayBuffer
提问by don kaka
If I want to create an arraybuffer, I write: var buff = new ArrayBuffer(size)
如果我想创建一个数组缓冲区，我写： var buff = new ArrayBuffer(size)
But how is it possible to resize an existing buffer? I mean, adding some more bytes at the end of the buffer.
但是如何调整现有缓冲区的大小呢？我的意思是，在缓冲区的末尾添加更多字节。
采纳答案by progrenhard
var buff = new ArrayBuffer(32);
buff[31] = 43;
var newBuff = new ArrayBuffer(buff.byteLength*2);
for (var i=0;i<buff.byteLength;i++){
newBuff[i] = buff[i];
}
buff = newBuff;
I've done it in C++ like this. Just made a bigger array and copy the contents over and then return the larger array and set it as the original.
我已经像这样用 C++ 完成了。只是做了一个更大的数组并复制内容，然后返回更大的数组并将其设置为原始数组。
回答by user7090288
回答by Artyer
The way to do that would be ArrayBuffer.transfer(oldBuffer, newByteLength), like so:
这样做的方法是ArrayBuffer.transfer(oldBuffer, newByteLength)，像这样：
var buffA = new ArrayBuffer(30);
var buffB = ArrayBuffer.transfer(buffA, 40);
// buffA is now an empty array buffer (`buffA.byteLength === 0`)
// whereas buffB is a new buffer that starts with a's contents
// and ends with 10 bytes that are 0s.
// Much faster than manually copying. You could even just do:
var buffA = new ArrayBuffer(30);
buffA = ArrayBuffer.transfer(buffA, 40);
// Or as a prototype method
ArrayBuffer.prototype.resize = function(newByteLength) {
return ArrayBuffer.transfer(this, newByteLength);
}
var buffA = new ArrayBuffer(30);
buffA = buffA.resize(40);
However (as of October 2017) there is 0% browser support (not even Node.js support) and is not even drafted yet.
但是（截至 2017 年 10 月）浏览器支持率为 0%（甚至不支持 Node.js），甚至还没有起草。
Until this is available, you can use the polyfill given on the page, which copies 8 bytes at a time, so is relatively quick for large arrays (Though it does not empty the given array, which is impossible to do).
在此可用之前，您可以使用页面上给出的 polyfill，它一次复制 8 个字节，因此对于大型数组来说相对较快（尽管它不会清空给定数组，这是不可能的）。
Here is a modified version using TypeArray.prototype.setinstead of for loops:
这是使用TypeArray.prototype.set代替 for 循环的修改版本：
if (!ArrayBuffer.transfer) {
ArrayBuffer.transfer = function(oldBuffer, newByteLength) {
var srcBuffer = Object(oldBuffer);
var destBuffer = new ArrayBuffer(newByteLength);
if (!(srcBuffer instanceof ArrayBuffer) || !(destBuffer instanceof ArrayBuffer)) {
throw new TypeError('Source and destination must be ArrayBuffer instances');
}
var copylen = Math.min(srcBuffer.byteLength, destBuffer.byteLength);
/* Copy 8 bytes at a time */
var length = Math.trunc(copylen / 64);
(new Float64Array(destBuffer, 0, length))
.set(new Float64Array(srcBuffer, 0, length));
/* Copy the remaining 0 to 7 bytes, 1 byte at a time */
var offset = length * 64;
length = copylen - offset;
(new Uint8Array(srcBuffer, offset, length))
.set(new Uint8Array(destBuffer, offset, length));
return destBuffer;
};
}
回答by Denys Séguret
You can't.
你不能。
The ArrayBuffer is a data type that is used to represent a generic, fixed-lengthbinary data buffer.
ArrayBuffer 是一种数据类型，用于表示通用的、 固定长度的二进制数据缓冲区。
I don't know what you try to do but obviously you don't use them how they're meant to be used.
我不知道你想做什么，但显然你没有按照它们的意图使用它们。
This pageis a good starting point to learn how to use typed arrays in JavaScript.
此页面是学习如何在 JavaScript 中使用类型化数组的良好起点。
回答by Jon Lennart Aasenden
What you are looking for is the "set" method. After creating a new, larger array, simply call the set function and copy over the older content.
您正在寻找的是“设置”方法。创建新的更大的数组后，只需调用 set 函数并复制旧内容。
