use anyhow::{anyhow, Context, Result};
use mime::Mime;
use std::io::prelude::*;
use std::io::ErrorKind;
use std::process::*;
pub fn is_svg(mime: &Mime) -> bool {
mime.type_() == mime::IMAGE && mime.subtype().as_str() == "svg"
}
pub fn is_png(mime: &Mime) -> bool {
*mime == mime::IMAGE_PNG
}
pub fn detect_mime_type(buffer: &[u8]) -> Result<Mime> {
let mut process = Command::new("file")
.arg("--brief")
.arg("--mime-type")
.arg("-")
.stdin(Stdio::piped())
.stdout(Stdio::piped())
.stderr(Stdio::piped())
.spawn()
.with_context(|| "Failed to spawn mime --brief --mime-type")?;
process
.stdin
.as_mut()
.expect("Forgot to pipe stdin?")
.write_all(buffer)
.or_else(|error| match error.kind() {
ErrorKind::BrokenPipe => Ok(()),
_ => Err(error),
})?;
let output = process
.wait_with_output()
.with_context(|| "Failed to read output from mime --brief --mime-type")?;
if output.status.success() {
let stdout = std::str::from_utf8(&output.stdout)
.with_context(|| {
format!(
"mime --brief --mime-type returned non-utf8: {:?}",
output.stdout
)
})?
.trim();
stdout
.parse()
.with_context(|| format!("Failed to parse mime type from output: {}", stdout))
} else {
Err(anyhow!(
"file --brief --mime-type failed with status {}: {}",
output.status,
String::from_utf8_lossy(&output.stderr)
))
}
}
#[cfg(test)]
mod tests {
use super::*;
use pretty_assertions::assert_eq;
#[test]
fn detect_mimetype_of_png_image() {
let data = include_bytes!("../sample/rust-logo-128x128.png");
let result = detect_mime_type(data);
assert!(result.is_ok(), "Unexpected error: {:?}", result);
assert_eq!(result.unwrap(), mime::IMAGE_PNG);
}
#[test]
fn detect_mimetype_of_svg_image() {
let data = include_bytes!("../sample/rust-logo.svg");
let result = detect_mime_type(data);
assert!(result.is_ok(), "Unexpected error: {:?}", result);
let mime = result.unwrap();
assert_eq!(mime.type_(), mime::IMAGE);
assert_eq!(mime.subtype().as_str(), "svg");
}
#[test]
fn detect_mimetype_of_magic_param_bytes_max_length() {
let data = std::iter::repeat(b'\0')
.take(1_048_576)
.collect::<Vec<u8>>();
let result = detect_mime_type(&data);
assert!(result.is_ok(), "Unexpected error: {:?}", result);
}
#[test]
fn detect_mimetype_of_larger_than_magic_param_bytes_max_length() {
let data = std::iter::repeat(b'\0')
.take(1_048_576 * 2)
.collect::<Vec<u8>>();
let result = detect_mime_type(&data);
assert!(result.is_ok(), "Unexpected error: {:?}", result);
}
}