Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 | 1x 1x 1x 1x 7x 7x 1x 6x 1x 5x 1x 4x 4x 4x 4x 4x 4x 904x 4x 4x 4x 4x 4x 4x 900x 852x 852x 852x 852x 48x 44x 44x 44x 44x 44x 44x 4x 1x 60x 1x 1x | /** ****************************************************************************************************
* File: GeohashStream.js
* Project: geohash
* @author Nick Soggin <iSkore@users.noreply.github.com> on 11-Feb-2019
*******************************************************************************************************/
'use strict';
const
{ Readable } = require( 'stream' );
const
getBBoxStartingPoint = require( './getBBoxStartingPoint' ),
neighbor = require( './neighbor' ),
{
isNumber
} = require( './utils' );
class GeohashStream extends Readable
{
/**
* GeohashStream
*
* extends Readable stream
*
* @param {object} opts - configuration object
* @param {number} opts.minLng - bbox min longitude
* @param {number} opts.minLat - bbox min latitude
* @param {number} opts.maxLng - bbox max longitude
* @param {number} opts.maxLat - bbox max latitude
* @param {number} opts.precision - geohash precision
*/
constructor( opts )
{
super();
if ( !opts ) {
throw new Error(
'[GeohashStream] requires options defining bbox (minLng, minLat, maxLng, maxLat) and precision'
);
}
else if (
!isNumber( opts.minLng ) || !isNumber( opts.minLat ) ||
!isNumber( opts.maxLng ) || !isNumber( opts.maxLat )
) {
throw new Error( '[GeohashStream] minLng, minLat, maxLng, and maxLat must be numbers' );
}
else if ( !isNumber( opts.precision ) ) {
throw new Error( '[GeohashStream] precision must be a number' );
}
this.startingBBox = getBBoxStartingPoint(
opts.minLng,
opts.minLat,
opts.maxLng,
opts.maxLat,
opts.precision
);
this._x = -1;
this._y = -1;
this.x = this.startingBBox.lngStep;
this.y = this.startingBBox.latStep;
this._nextChunk = null;
}
nextChunk()
{
if ( this._x === -1 && this._y === -1 ) {
this._nextChunk = this.startingBBox.hashSouthWest;
this.lastNorth = this._nextChunk;
this.lastEast = this._nextChunk;
this._x++;
this._y++;
return this._nextChunk;
}
else if ( this._x < this.x ) {
this._nextChunk = neighbor( this.lastEast, 'e' );
this.lastEast = this._nextChunk;
this._x++;
return this._nextChunk;
}
else if ( this._y < this.y ) {
this._x = 0;
this._nextChunk = neighbor( this.lastNorth, 'n' );
this.lastNorth = this._nextChunk;
this.lastEast = this._nextChunk;
this._y++;
return this._nextChunk;
}
return null;
}
_read()
{
let chunk;
while ( ( chunk = this.nextChunk() ) !== null ) {
this.push( chunk );
}
this.push( null );
}
}
module.exports = GeohashStream;
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