gis-tools-ts/dist/readers/shapefile/mmap.js

A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.

import { DataBaseFile } from './dbf';
import { MMapReader } from '../mmap';
import { ShapeFileReader } from './shp';
import { Transformer } from '../../proj4';
import { shapefileFromGzip } from '.';
import { exists, readFile } from 'fs/promises';
export * from './dbf';
export * from './shp';
/**
 * # Build a Shapefile from an input path
 *
 * ## Description
 * Given a path to where all the shapefile relevant files exist, build a Shapefile
 *
 * Assumes the input is pointing to a shapefile or name without the extension.
 * The algorithm will find the rest of the paths if they exist. May also be a gzipped folder.
 *
 * ## Usage
 * ```ts
 * import { LambertConformalConic, EPSG_9974 } from 'gis-tools-ts';
 * import { shapefileFromPath } from 'gis-tools-ts/mmap';
 *
 * const reader = await shapefileFromPath('path/to/files', [LambertConformalConic], { EPSG_9974 });
 *
 * for await (const feature of reader) {
 *   console.log(feature);
 * }
 * ```
 * @param input - the path to the .shp file or name without the extension
 * @returns - a Shapefile
 */
export async function shapefileFromPath(input) {
    if (input.endsWith('.zip')) {
        const gzipData = await readFile(input);
        return shapefileFromGzip(gzipData.buffer);
    }
    const path = input.replace('.shp', '');
    const shp = `${path}.shp`;
    const dbf = `${path}.dbf`;
    const prj = `${path}.prj`;
    const cpg = `${path}.cpg`;
    if (!(await exists(shp)))
        throw new Error('Shapefile does not exist');
    const definition = {
        shp,
        dbf: (await exists(dbf)) ? dbf : undefined,
        prj: (await exists(prj)) ? prj : undefined,
        cpg: (await exists(cpg)) ? cpg : undefined,
    };
    return shapefileFromDefinition(definition);
}
/**
 * # Build a Shapefile from a Definition
 *
 * ## Description
 * Given a collection of files, build a Shapefile
 *
 * ## Usage
 * ```ts
 * import { LambertConformalConic, EPSG_9974 } from 'gis-tools-ts';
 * import { shapefileFromDefinition } from 'gis-tools-ts/mmap';
 * import type { Definition } from 'gis-tools-ts';
 *
 * const def: Definition = {
 *   shp: 'path/to/file.shp',
 *   dbf: 'path/to/file.dbf',
 *   prj: 'path/to/file.prj',
 *   cpg: 'path/to/file.cpg'
 * };
 *
 * const reader = await shapefileFromDefinition(def, [LambertConformalConic], { EPSG_9974 });
 *
 * for await (const feature of reader) {
 *   console.log(feature);
 * }
 * ```
 * @param def - a description of the data to parse
 * @returns - a Shapefile
 */
export async function shapefileFromDefinition(def) {
    const { shp, dbf, prj, cpg } = def;
    const encoding = cpg !== undefined ? await readFile(cpg, { encoding: 'utf8' }) : 'utf8';
    const transform = prj !== undefined ? new Transformer(await readFile(prj, { encoding: 'utf8' })) : undefined;
    const dbfReader = dbf !== undefined ? new MMapReader(dbf) : undefined;
    const databaseFile = dbfReader !== undefined ? new DataBaseFile(dbfReader, encoding) : undefined;
    return new ShapeFileReader(new MMapReader(shp), databaseFile, transform);
}
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