gis-tools-ts/dist/writers/file.js

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

import { createWriteStream } from 'fs';
import { finished } from 'stream/promises';
import { open } from 'fs/promises';
/** The File writer is to be used by bun/node/deno on the local filesystem. */
export class FileWriter {
    file;
    #stream;
    #textEncoder = new TextEncoder();
    /** @param file - the location of the PMTiles data in the FS */
    constructor(file) {
        this.file = file;
        this.#stream = createWriteStream(file, { flags: 'a+' }); // Open with append mode and create stream
    }
    /**
     * Write data to the buffer
     * @param data - the data to write
     * @param offset - where in the buffer to start
     */
    async write(data, offset) {
        const fd = await open(this.file, 'r+'); // Open file for reading and writing
        try {
            await fd.write(data, 0, data.length, offset); // Write at the specified offset
        }
        finally {
            await fd.close(); // Close the file after writing
        }
    }
    /**
     * Append data to the buffer
     * @param data - the data to append
     * @returns - a promise that resolves when the data is appended
     */
    async append(data) {
        return await new Promise((resolve, reject) => {
            this.#stream.write(data, (err) => {
                if (err instanceof Error)
                    reject(err);
                else
                    resolve();
            });
        });
    }
    /**
     * Append string to the buffer synchronously
     * @param string - the string to append
     */
    async appendString(string) {
        await this.append(this.#textEncoder.encode(string));
    }
    /**
     * Append data to the buffer synchronously
     * @param data - the data to append
     */
    appendSync(data) {
        this.#stream.write(data); // Write data synchronously
    }
    /**
     * Append string to the buffer synchronously
     * @param string - the string to append
     */
    appendStringSync(string) {
        this.appendSync(this.#textEncoder.encode(string));
    }
    /**
     * Slice the buffer
     * @param start - the start of the slice
     * @param end - the end of the slice
     * @returns - the sliced buffer
     */
    async slice(start, end) {
        const length = end - start;
        const buffer = Buffer.alloc(length);
        const fd = await open(this.file, 'r');
        try {
            await fd.read(buffer, 0, length, start);
            return new Uint8Array(buffer.buffer, buffer.byteOffset, buffer.byteLength);
        }
        finally {
            await fd.close();
        }
    }
    /** Close the file */
    async close() {
        this.#stream.end();
        await finished(this.#stream);
    }
}
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