Function getExtensionFromBytes

utils/getMediaUrl.ts:62–92

(blob: Blob)

}

export async function getExtensionFromBytes(blob: Blob): Promise<string | undefined> {
    const buffer = await blob.slice(0, 12).arrayBuffer();
    const bytes = new Uint8Array(buffer);

    if (bytes[0] === 0x47 && bytes[1] === 0x49 && bytes[2] === 0x46 && bytes[3] === 0x38) {
        return "gif";
    }

    if (bytes[0] === 0x89 && bytes[1] === 0x50 && bytes[2] === 0x4E && bytes[3] === 0x47) {
        const fullBuffer = await blob.slice(0, 4096).arrayBuffer();
        const fullBytes = new Uint8Array(fullBuffer);
        for (let i = 0; i < fullBytes.length - 4; i++) {
            if (fullBytes[i] === 0x61 && fullBytes[i + 1] === 0x63 &&
                fullBytes[i + 2] === 0x54 && fullBytes[i + 3] === 0x4C) {
                return "apng";
            }
        }
        return "png";
    }

    if (bytes[0] === 0x52 && bytes[1] === 0x49 && bytes[2] === 0x46 && bytes[3] === 0x46 &&
        bytes[8] === 0x57 && bytes[9] === 0x45 && bytes[10] === 0x42 && bytes[11] === 0x50) {
        return "webp";
    }

    if (bytes[0] === 0xFF && bytes[1] === 0xD8 && bytes[2] === 0xFF) {
        return "jpg";
    }

    return undefined;
}

export function getUrlExtension(url: string): string | undefined {
    if (!url.startsWith("https:") && !url.startsWith("http:")) {