Function sniffImageMimeType

apps/sim/providers/attachments.ts:212–248

(base64: string)

}

function sniffImageMimeType(base64: string): string {
  let bytes: Buffer
  try {
    bytes = Buffer.from(base64, 'base64')
  } catch {
    return ''
  }

  if (
    bytes.length >= 8 &&
    bytes.subarray(0, 8).equals(Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]))
  ) {
    return 'image/png'
  }

  if (bytes.length >= 3 && bytes[0] === 0xff && bytes[1] === 0xd8 && bytes[2] === 0xff) {
    return 'image/jpeg'
  }

  if (
    bytes.length >= 6 &&
    (bytes.subarray(0, 6).equals(Buffer.from('GIF87a')) ||
      bytes.subarray(0, 6).equals(Buffer.from('GIF89a')))
  ) {
    return 'image/gif'
  }

  if (
    bytes.length >= 12 &&
    bytes.subarray(0, 4).equals(Buffer.from('RIFF')) &&
    bytes.subarray(8, 12).equals(Buffer.from('WEBP'))
  ) {
    return 'image/webp'
  }

  return ''
}

function getAttachmentExtension(file: UserFile, mimeType: string): string {
  if (mimeType === 'text/markdown') return 'md'