从本地文件读取混合类型

发布于 2024-12-10 08:12:20 字数 1077 浏览 0 评论 0原文

我正在尝试使用 Javascript 读取混合有整数、浮点数和字符串的文件类型。

然后使用 File API 拖放该文件，将其作为数组缓冲区读取并用 DataView 包装。这可以处理数字类型，但我必须制定自己的方法来获取文本。

DataView.prototype.getAscii = function(byteOffset, byteLength)
{
    var bytes = new Array(byteLength);
    for (var i = 0; i < byteLength; i++) {
        bytes[i] = this.getUint8(byteOffset + i);
    }
    return String.fromCharCode.apply(null, bytes);
}

它工作得很好，但我担心读取大文件的单个字节的速度。类型化数组据说可以与普通数组互换使用，所以我尝试了这个：

DataView.prototype.getAscii = function(byteOffset, byteLength)
{
    var bytes = new Uint8Array(this.buffer, byteOffset, byteLength);
    return String.fromCharCode.apply(null, bytes);
}

我收到一条“TypeError: Function.prototype.apply: Arguments list has bad type”消息，所以它不像我的 Uint8Array 那样一个参数。

有没有更好的方法一次读取多个字符？ FileReader#readAsText() 读取整个文件，但不允许访问任何二进制方法。

原文

I am trying to read a file type that has a mixture of integers, floats and strings using Javascript.

The file is drag-dropped then, with the File API, read as array buffer and wrapped with a DataView. That takes care of the number types but I had to make my own method for getting text.

DataView.prototype.getAscii = function(byteOffset, byteLength)
{
    var bytes = new Array(byteLength);
    for (var i = 0; i < byteLength; i++) {
        bytes[i] = this.getUint8(byteOffset + i);
    }
    return String.fromCharCode.apply(null, bytes);
}

It works well enough but I worry about the speed of reading individual bytes for large files. Typed arrays can supposedly be used interchangeably with normal arrays so I tried this:

DataView.prototype.getAscii = function(byteOffset, byteLength)
{
    var bytes = new Uint8Array(this.buffer, byteOffset, byteLength);
    return String.fromCharCode.apply(null, bytes);
}

I get a "TypeError: Function.prototype.apply: Arguments list has wrong type" message so it doesn't like my Uint8Array as a parameter.

Is there a better way of reading many characters at once? FileReader#readAsText() reads the whole file but doesn't give access to any of the binary methods.

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