diginext-utils/esm/string/guessMimeType.js

README.md

import { createReadStream } from "fs";
export async function guessMimeType(filepath) {
    return new Promise((resolve, reject) => {
        const stream = createReadStream(filepath, {
            start: 0,
            end: 11, // Read only first 12 bytes
        });
        let buffer = new Uint8Array(0);
        stream.on("data", (chunk) => {
            const chunkArray = new Uint8Array(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
            // Manual concatenation
            const newBuffer = new Uint8Array(buffer.length + chunkArray.length);
            newBuffer.set(buffer);
            newBuffer.set(chunkArray, buffer.length);
            buffer = newBuffer;
        });
        stream.on("end", () => {
            // Convert to hex string
            const toHex = (arr, start, end) => {
                return Array.from(arr.slice(start, end))
                    .map((b) => b.toString(16).padStart(2, "0"))
                    .join("");
            };
            const signature = toHex(buffer, 0, 4);
            switch (signature) {
                case "89504e47":
                    resolve("image/png");
                    break;
                case "47494638":
                    resolve("image/gif");
                    break;
                case "52494646":
                    if (buffer.length >= 12) {
                        const webpSignature = toHex(buffer, 8, 12);
                        if (webpSignature === "57454250") {
                            resolve("image/webp");
                        }
                        else {
                            resolve("unknown");
                        }
                    }
                    else {
                        resolve("unknown");
                    }
                    break;
                case "00000018":
                case "0000001c":
                case "00000020":
                    resolve("video/mp4");
                    break;
                case "66747970":
                    resolve("video/quicktime");
                    break;
                case "1a45dfa3":
                    resolve("video/webm");
                    break;
                case "000001ba":
                case "000001b3":
                    resolve("video/mpeg");
                    break;
                default:
                    if (signature.startsWith("ffd8ff")) {
                        resolve("image/jpeg");
                    }
                    else {
                        resolve("application/octet-stream");
                    }
            }
        });
        stream.on("error", reject);
    });
}
export default guessMimeType;