大数组压缩 [英] Large number array compression

问题描述

我有一个javascript应用程序，发送大量的数字数据下来。然后将该数据存储在数据库中。我有大小问题（太多带宽，数据库变得太大）。我现在准备牺牲一些压缩性能。

I've got a javascript application that sends a large amount of numerical data down the wire. This data is then stored in a database. I am having size issues (too much bandwidth, database getting too big). I am now ready to sacrifice some performance for compression.

我正在考虑实现一个基数62 number.toString（62）和parseInt（压缩，62）。这肯定会减少数据的大小，但在我去之前，我做这个我认为我会把它给在这里的人，因为我知道必须有一些外箱解决方案，我没有考虑。

I was thinking of implementing a base 62 number.toString(62) and parseInt(compressed, 62). This would certainly reduce the size of the data but before I go ahead and do this I thought I would put it to the folks here as I know there must be some outside the box solution I have not considered.

基本规范是：
- 将大数字数组压缩成JSONP传输的字符串（所以我认为UTF是外出的）
- 相对较快，看起来我不期望相同的性能，我现在，但我也不想gzip压缩。

The basic specs are: - Compress large number arrays into strings for JSONP transfer (So I think UTF is out) - Be relatively fast, look I'm not expecting same performance as I have now but I also don't want gzip compression either.

任何想法将非常感激。

感谢

Guido Tapia

Guido Tapia

推荐答案

这样做可能是编码为二进制类型，如signed / unsigned ints，并手动解码，如 http ：//snippets.dzone.com/posts/show/685 ，这将需要服务器端代码来创建二进制数据。

Another way of doing this might be to encode to binary types such as signed/unsigned ints, and manually decode as at http://snippets.dzone.com/posts/show/685 which would require server side code to create the binary data.

然后你可以huffman压缩或类似于RLE的内容（请参阅 http://rosettacode.org/wiki/Run-length_encoding#JavaScript ，但在IE中可能会有一些问题，无需修改）进一步压缩数据。

You could then huffman compression or something similar like RLE (see http://rosettacode.org/wiki/Run-length_encoding#JavaScript for an implementation, though it may have some issues in IE without modifying) to compress the data further.

EDIT ：
或者，您可以将数字本身转换为未编码的URI字符范围内的基数（radix）（参见 http://en.wikipedia.org/wiki/Percent-encoding ），如果许多数字大于2位数，它应该工作得很好。我在 http：//转换了代码code.activestate.com/recipes/111286-numeric-base-converter-that-accepts-arbitrary-digi/ from python to do this。

EDIT: Alternatively, you could convert the numbers themselves to a base (radix) in the unencoded URI character range (see http://en.wikipedia.org/wiki/Percent-encoding) which should work well if many of the numbers are larger than 2 digits. I converted the code at http://code.activestate.com/recipes/111286-numeric-base-converter-that-accepts-arbitrary-digi/ from python to do this.

它目前不处理浮动，但它可以很容易做到：

It currently doesn't handle floats, but it could be done fairly easily:

function get_map(s) {
    d = {}
    for (var i=0; i<s.length; i++) {
        d[s.charAt(i)] = i}
    d.length = s.length
    d._s = s
    return d}

var separate_with = '~';
var encodable = get_map('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_.'); // - is reserved for negatives obviously :-P
var base10 = get_map('0123456789')

// UNCOMMENT ME for length/speed testing in a wider base!
// You may wish to experiment with the ranges for a happy medium between bandwidth and DB space :-P
/*var encodable = ''
for (var i=1; i<128; i++) {
    encodable += String.fromCharCode(i)
}
encodable = get_map(encodable)*/

function baseconvert(number, fromdigits, todigits) {
    var number = String(number)

    if (number.charAt(0) == '-') {
        number = number.slice(1, number.length)
        neg=1}
    else {
        neg=0}

    // make an integer out of the number
    var x = 0
    for (var i=0; i<number.length; i++) {
        var digit = number.charAt(i)
        x = x*fromdigits.length + fromdigits[digit]
    }

    // create the result in base 'todigits.length'
    res = ""
    while (x>0) {
        remainder = x % todigits.length
        res = todigits._s.charAt(remainder) + res
        x = parseInt(x/todigits.length)
    }

    if (neg) res = "-"+res
    return res
}

function encodeNums(L) {
    var r = []
    for (var i=0; i<L.length; i++) {
         r.push(baseconvert(L[i], base10, encodable))
    }
    return r.join(separate_with)
}

function decodeNums(s) {
    var r = []
    var s = s.split(separate_with)
    for (var i=0; i<s.length; i++) {
         r.push(parseInt(baseconvert(s[i], encodable, base10)))
    }
    return r
}

var test = [5, 654645, 24324, 652124, 65, 65289543, 65278432, 643175874158, 652754327543]
alert(encodeNums(test))
alert(decodeNums(encodeNums(test)))

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