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/// Checks if the specified bytes match the signature.
macro_rules! check_signature {
($bytes:expr, $offset:literal, $signature:literal) => {
$bytes.len() >= $offset + $signature.len() && &$bytes[$offset..$offset + $signature.len()] == $signature
};
($bytes:expr, $([$([$offset:literal, $signature:literal]),*]),*) => {
$($(check_signature!($bytes, $offset, $signature))&&*)||*
};
}
/// Generates `FileFormat` enum using a database described in YAML-like format.
macro_rules! file_format {
{
$(
- format: $format:ident
description: $description:literal
media_type: $media_type:literal
extensions: [$($extension:literal),+]
signatures:
$(
- parts:
$(
- offset: $offset:literal
value: $signature:literal
)+
)+
)+
} => {
use std::{fs, io::Error, path::Path, str};
/// Represents a file format.
#[derive(Clone, Debug, PartialEq)]
pub enum FileFormat {
$(
#[doc=$description]
$format,
)*
/// UTF-8 encoded text
Text,
/// Arbitrary binary data
Binary,
}
impl FileFormat {
/// Determines file format from bytes.
///
/// If the signature of the file is not recognized,
/// it will try to detect if the file is an UTF-8 encoded text and if so return [`FileFormat::Text`].
/// Otherwise, it will return [`FileFormat::Binary`] which corresponds to arbitrary binary data.
///
/// # Examples
///
/// Detects from the first bytes of a PNG file:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_bytes(b"\x89\x50\x4E\x47\x0D\x0A\x1A\x0A");
/// assert_eq!(format, FileFormat::Png);
/// assert_eq!(format.media_type(), "image/png");
/// assert_eq!(format.preferred_extension(), "png");
///```
///
/// Detects from an UTF-8 text:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_bytes("岁月不留人".as_bytes());
/// assert_eq!(format, FileFormat::Text);
/// assert_eq!(format.media_type(), "text/plain");
/// assert_eq!(format.preferred_extension(), "txt");
///```
///
/// Detects from a zeroed buffer:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_bytes(&[0; 1000]);
/// assert_eq!(format, FileFormat::Binary);
/// assert_eq!(format.media_type(), "application/octet-stream");
/// assert_eq!(format.preferred_extension(), "bin");
///```
pub fn from_bytes(bytes: &[u8]) -> FileFormat {
$(if check_signature!(bytes, $([$([$offset, $signature]),*]),*) {
return FileFormat::$format;
})*
if FileFormat::is_utf8_text(bytes) {
FileFormat::Text
} else {
FileFormat::Binary
}
}
/// Determines file format from an extension.
///
/// # Examples
///
/// Detects from an extension:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_extension("ttf");
/// assert_eq!(format, Some(FileFormat::TrueType));
///```
///
/// Detects from an unknown extension:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_extension("foobar");
/// assert_eq!(format, None);
///```
pub fn from_extension(extension: &str) -> Option<FileFormat> {
match extension {
$($($extension)|* => Some(FileFormat::$format),)*
"txt" => Some(FileFormat::Text),
"bin" => Some(FileFormat::Binary),
_ => None,
}
}
/// Determines file format from a media type.
///
/// # Examples
///
/// Detects from a media type:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_media_type("video/mp4");
/// assert_eq!(format, Some(FileFormat::Mp4));
///```
///
/// Detects from an unknown media type:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_media_type("foo/bar");
/// assert_eq!(format, None);
///```
pub fn from_media_type(media_type: &str) -> Option<FileFormat> {
match media_type {
$($media_type => Some(FileFormat::$format),)*
"text/plain" => Some(FileFormat::Text),
"application/octet-stream" => Some(FileFormat::Binary),
_ => None,
}
}
/// Determines file format from a file.
///
/// # Examples
///
/// Basic usage:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::from_file("Cargo.toml")?;
/// assert_eq!(format, FileFormat::Text);
/// # Ok::<(), std::io::Error>(())
///```
pub fn from_file<P: AsRef<Path>>(path: P) -> Result<FileFormat, Error> {
Ok(FileFormat::from_bytes(&fs::read(&path)?))
}
/// Returns the media type (formerly known as MIME type) of the file format.
///
/// # Examples
///
/// Basic usage:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::Zstandard;
/// assert_eq!(format.media_type(), "application/zstd");
///```
pub fn media_type(&self) -> &str {
match self {
$(FileFormat::$format => $media_type,)*
FileFormat::Text => "text/plain",
FileFormat::Binary => "application/octet-stream"
}
}
/// Returns the extensions list of the file format.
///
/// # Examples
///
/// Basic usage:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::Midi;
/// assert_eq!(format.extensions(), vec!["mid", "midi"]);
///```
pub fn extensions(&self) -> Vec<&str> {
match self {
$(FileFormat::$format => vec!($($extension),*),)*
FileFormat::Text => vec!("txt"),
FileFormat::Binary => vec!("bin")
}
}
/// Returns the preferred extension of the file format.
///
/// # Examples
///
/// Basic usage:
///
/// ```rust
/// use file_format::FileFormat;
///
/// let format = FileFormat::Wmv;
/// assert_eq!(format.preferred_extension(), "wmv");
///```
pub fn preferred_extension(&self) -> &str {
self.extensions().first().unwrap()
}
/// Returns `true` if the specified bytes can be considered as human readable UTF-8 text.
/// Except `\t`, `\n` and `\r`, we consider all control characters as non human readable.
fn is_utf8_text(bytes: &[u8]) -> bool {
str::from_utf8(bytes).map_or(false, |string| {
string
.chars()
.find(|character| {
character.is_control()
&& *character != '\t'
&& *character != '\n'
&& *character != '\r'
})
.is_none()
})
}
}
};
}