尝试循环缓冲区 - Javascript

Question

对！这是我对循环缓冲区的尝试（用于图形程序，使用 canvas 元素）。还没有开始测试它。

问题是 - 谁能看出我的逻辑有任何缺陷？还是瓶颈？

/**
*   A circular buffer class.
*   @To add value -> bufferObject.addValue(xValue, yValue);
*   @To get the First-in value use -> bufferObject.getValue(0);
*   @To get the Last-in value use -> bufferObject.getValue(bufferObject.length);
**/

var circularBuffer = function (bufferSize) {

    this.bufferSize = bufferSize;
    this.buffer = new Array(this.bufferSize); // After testing on jPerf -> 2 x 1D array seems fastest solution.

    this.end = 0;
    this.start = 0;

    // Adds values to array in circular.
    this.addValue = function(xValue, yValue) {
        this.buffer[this.end] = {x : xValue, y: yValue};
        if (this.end != this.bufferSize) this.end++;
        else this.end = 0;
        if(this.end == this.start) this.start ++;
    };

    // Returns a value from the buffer
    this.getValue = function(index) {

        var i = index+this.start;

        if(i >= this.bufferSize) i -= this.bufferSize; //Check here.

        return this.buffer[i]
    };

    // Returns the length of the buffer
    this.getLength = function() {
        if(this.start > this.end || this.start == this.bufferSize) {
            return this.xBuffer.length;
        } else {
            return this.end - this.start;
        }
    };

    // Returns true if the buffer has been initialized.
    this.isInitialized = function() {
        if(this.end != this.start) return true;
        else return false;
    };
}

请随意重用此代码。

更新了两次（并经过测试！）。

Answer 1

更新：找到另一个实现Circular buffer in JavaScript

将类变量设为私有，更正了旧的 xBuffer 引用。今晚将进行更多编辑。

/**
*   A circular buffer class.
*   @To add value -> bufferObject.addValue(xValue, yValue);
*   @To get the First-in value use -> bufferObject.getValue(0);
*   @To get the Last-in value use -> bufferObject.getValue(bufferObject.length);
**/

var circularBuffer = function (buffer_size) {

    var bufferSize = buffer_size;
    var buffer = new Array(bufferSize); // After testing on jPerf -> 2 x 1D array seems fastest solution.

    var end = 0;
    var start = 0;

    // Adds values to array in circular.
    this.addValue = function(xValue, yValue) {
        buffer[end] = {x : xValue, y: yValue};
        if (end != bufferSize) end++;
        else end = 0;
        if(end == start) start++;
    };

    // Returns a value from the buffer
    this.getValue = function(index) {

        var i = index+start;

        if(i >= bufferSize) i -= bufferSize; //Check here.

        return buffer[i];
    };

    // Returns the length of the buffer
    this.getLength = function() {
        if(start > end || start == bufferSize) {
            return buffer.length;
        } else {
            return end - start;
        }
    };

    // Returns true if the buffer has been initialized.
    this.isInitialized = function() {
        return (end != start) ? true : false;
    };
}

Answer 2

我在上面实现了 Vogomatix 的代码，但遇到了一些错误。代码会注销缓冲区的末尾，自动扩展缓冲区大小，并将 addValue 函数绑定到特定类型。我已经调整了代码以适用于任何对象类型，添加了一些私有子例程来简化，并添加了一个函数来将内容转储到字符串中，并带有一个可选的分隔符。还使用了命名空间。

缺少的是 removeValue()，但它只是检查计数是否大于零，然后调用 _pop()。

这样做是因为我需要一个滚动的、滚动的入站消息文本缓冲区，它不会无限增长。我将对象与 textarea 一起使用，因此我得到了类似控制台窗口的行为，即不会无限期地占用内存的滚动文本框。

为了方便起见，这已经过测试，因为我正在快速编码，因此在此处发布，希望 OverFlow 的同胞使用并退火代码。

///////////////////////////////////////////////////////////////////////////////
// STYLE DECLARATION
// Use double quotes in JavaScript


///////////////////////////////////////////////////////////////////////////////
// Global Namespace for this application
//

var nz = nz || {};
nz.cbuffer = new Object();


///////////////////////////////////////////////////////////////////////////////
// CIRCULAR BUFFER
//

// CREDIT: 
// Based on...
// Vogomatix http://stackoverflow.com/questions/20119513/attempt-at-circular-buffer-javascript
// But re-written after finding some undocumented features...
/**
*   A circular buffer class, storing any type of Javascript object.
*   To add value -> bufferObject.addValue(obj);
*   To get the First-in value use -> bufferObject.getValue(0);
*   To get the Last-in value use -> bufferObject.getValue(bufferObject.length);
*   To dump to string use -> bufferObject.streamToString(sOptionalDelimiter); // Defaults to "\r\n"
**/

nz.cbuffer.circularBuffer = function (buffer_size) {

    var bufferSize = buffer_size > 0 ? buffer_size : 1; // At worst, make an array of size 1
    var buffer = new Array(bufferSize);

    var end = 0; // Index of last element.
    var start = 0; // Index of first element.
    var count = 0; // Count of elements

    // 'Private' function to push object onto buffer.
    this._push = function (obj) {
        buffer[end] = obj; // Write
        end++; // Advance        
        if (end == bufferSize) {
            end = 0; // Wrap if illegal
        }
        count++;
    }

    // 'Private' function to pop object from buffer. 
    this._pop = function () {
        var obj = buffer[start];
        start++;
        if (start == bufferSize) {
            start = 0; // Wrap
        }
        count--;
        return obj;
    }

    // Adds values to buffer.
    this.addValue = function (obj) {
        if (count < bufferSize) {
            // Just push
            this._push(obj);
        }
        else {
            // Pop, then push
            this._pop();
            this._push(obj);
        }
    }

    // Returns a value from the buffer.  Index is relative to current notional start.
    this.getValue = function (index) {

        if (index >= count || index < 0) return; // Catch attempt to access illegal index

        var i = index + start;

        if (i >= bufferSize) {
            i -= bufferSize;
        }

        return buffer[i];
    }

    // Returns the length of the buffer.
    this.getLength = function () {
        return count;
    }

    // Returns all items as strings, separated by optional delimiter.
    this.streamToString = function (delim) {

        delim = (typeof delim === "undefined") ? "\r\n" : delim; // Default syntax; Default to CRLF

        var strReturn = "";

        var once = 0;
        var index = 0;
        var read = index + start;
        for (; index < count; ++index) {
            if (once == 1) strReturn += delim.toString();
            strReturn += buffer[read].toString();
            read++;
            if (read >= bufferSize) read = 0;
            once = 1;
        }

        return strReturn;
    }
}