@mapbox/shp-write/src/points.js

write shapefiles from pure javascript

var ext = require('./extent');

module.exports.write = function writePoints(coordinates, extent, shpView, shxView) {

    var contentLength = 28, // 8 header, 20 content
        fileLength = 100,
        shpI = 0,
        shxI = 0;

    coordinates.forEach(function writePoint(coords, i) {
        // HEADER
        // 4 record number
        // 4 content length in 16-bit words (20/2)
        shpView.setInt32(shpI, i + 1);
        shpView.setInt32(shpI + 4, 10);

        // record
        // (8 + 8) + 4 = 20 content length
        shpView.setInt32(shpI + 8, 1, true); // POINT=1
        shpView.setFloat64(shpI + 12, coords[0], true); // X
        shpView.setFloat64(shpI + 20, coords[1], true); // Y

        // index
        shxView.setInt32(shxI, fileLength / 2); // length in 16-bit words
        shxView.setInt32(shxI + 4, 10);

        shxI += 8;
        shpI += contentLength;
        fileLength += contentLength;
    });
};

module.exports.extent = function(coordinates) {
    return coordinates.reduce(function(extent, coords) {
        return ext.enlarge(extent, coords);
    }, ext.blank());
};

module.exports.parts = function parts(geometries, TYPE) {
    return geometries.length;
};

module.exports.shxLength = function(coordinates) {
    return coordinates.length * 8;
};

module.exports.shpLength = function(coordinates) {
    return coordinates.length * 28;
};