HTML HyperText Markup Language

SIGNATURE = bytes.fromhex("3c21646f6374797065")
OFFSET = 0

def is_html(path: str) -> bool:
    with open(path, "rb") as f:
        f.seek(OFFSET)
        head = f.read(len(SIGNATURE))
    return head == SIGNATURE

const SIGNATURE = [0x3c, 0x21, 0x64, 0x6f, 0x63, 0x74, 0x79, 0x70, 0x65];
const OFFSET = 0;

// bytes: a Uint8Array / Buffer holding the start of the file
export function isHtml(bytes) {
  return SIGNATURE.every((byte, i) => bytes[OFFSET + i] === byte);
}

package fileid

import "bytes"

var ishtmlSignature = []byte{0x3c, 0x21, 0x64, 0x6f, 0x63, 0x74, 0x79, 0x70, 0x65}

const ishtmlOffset = 0

func IsHtml(b []byte) bool {
	end := ishtmlOffset + len(ishtmlSignature)
	if len(b) < end {
		return false
	}
	return bytes.Equal(b[ishtmlOffset:end], ishtmlSignature)
}

const SIGNATURE: &[u8] = &[0x3c, 0x21, 0x64, 0x6f, 0x63, 0x74, 0x79, 0x70, 0x65];
const OFFSET: usize = 0;

fn is_html(bytes: &[u8]) -> bool {
    bytes.get(OFFSET..OFFSET + SIGNATURE.len()) == Some(SIGNATURE)
}

<?php
$signature = "\x3c\x21\x64\x6f\x63\x74\x79\x70\x65";
$offset = 0;

function is_html(string $bytes): bool {
    global $signature, $offset;
    return substr($bytes, $offset, strlen($signature)) === $signature;
}