ipip-datx/lib/district.js

IPIP.net官方支持的IP数据库datx格式查询代码

var fs = require("fs");
var net = require("net");

module.exports = class District {
    constructor(name){
        this.data = fs.readFileSync(name);
        this.indexSize = this.bytes2Uint32(
            this.data[0],
            this.data[1],
            this.data[2],
            this.data[3]
        );
    }

    findSync(ip) {

        if (!net.isIPv4(ip)){
            return false;
        }

        let ips = ip.split(".")
        let val = this.bytes2Uint32(ips[0], ips[1], ips[2], ips[3])

        let low = 0;
        let mid = 0;
        let pos = 0;
        let high = parseInt((this.indexSize - 262148 - 262144) / 13) - 1;
        let pos1 = 0;
        let start = 0;
        let end = 0;

        while (low <= high) {
            mid = Math.ceil((low + high) / 2);
            pos = mid * 13 + 262148;

            start = this.bytes2Uint32(
                this.data[pos],
                this.data[pos + 1],
                this.data[pos + 2],
                this.data[pos + 3]                
            )
            end = this.bytes2Uint32(
                this.data[pos + 4],
                this.data[pos + 5],
                this.data[pos + 6],
                this.data[pos + 7]
            )

            if (val > end) {
                low = mid + 1;
            } else if (val < start) {
                high = mid - 1;
            } else {
                let off = this.bytes2Uint32(
                    this.data[pos + 11],
                    this.data[pos + 10],
                    this.data[pos + 9],
                    this.data[pos + 8]
                )
                let len = this.data[pos + 12];

                pos = off - 262144 + this.indexSize;
                let buf = Buffer.alloc(len);
                this.data.copy(buf, 0, pos, pos+len);
                
                return String(buf).split("\t");
            }
        }

        return null;
    }

    bytes2Uint32(a, b, c, d) {
        let v = (a << 24 | b << 16 | c << 8 | d)
        if (v < 0) {
            return v + 4294967296;
        } else {
            return v;
        }
    }
}