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// Copyright (c) Ankit Chaubey <ankitchaubey.dev@gmail.com>
//
// ferogram: async Telegram MTProto client in Rust
// https://github.com/ankit-chaubey/ferogram
//
// Licensed under either the MIT License or the Apache License 2.0.
// See the LICENSE-MIT or LICENSE-APACHE file in this repository:
// https://github.com/ankit-chaubey/ferogram
//
// Feel free to use, modify, and share this code.
// Please keep this notice when redistributing.
//! File type detection and metadata extraction.
//!
//! `detect_mime` sniffs the first bytes of a file for its true MIME type,
//! regardless of file extension. `FileMetadata` carries optional width,
//! height, and duration extracted from common formats.
/// Detected MIME type and optional media metadata.
#[derive(Debug, Clone)]
pub struct FileInfo {
/// True MIME type detected from file bytes (e.g. `"video/mp4"`).
/// Falls back to extension-based guess, then `"application/octet-stream"`.
pub mime_type: String,
/// Pixel width for images and videos (if detectable).
pub width: Option<u32>,
/// Pixel height for images and videos (if detectable).
pub height: Option<u32>,
/// Duration in seconds for video and audio (if detectable).
pub duration: Option<f64>,
}
/// Detect MIME type from file bytes using magic-byte signatures.
///
/// Requires at most the first 16 bytes. Extension is used only as a fallback.
pub fn detect_mime(bytes: &[u8], name: &str) -> String {
if let Some(kind) = infer::get(bytes) {
return kind.mime_type().to_string();
}
// infer fallback: extension-based via mime_guess
mime_guess::from_path(name)
.first_or_octet_stream()
.to_string()
}
/// Extract all available metadata from file bytes.
///
/// Reads only as much of `bytes` as needed for each format.
/// For video duration, pass the full file bytes (or use `file_info_from_path`
/// which reads the file itself).
pub fn file_info(bytes: &[u8], name: &str) -> FileInfo {
let mime_type = detect_mime(bytes, name);
let (width, height) = image_dimensions(bytes, &mime_type);
let duration = video_duration(bytes, &mime_type);
FileInfo {
mime_type,
width,
height,
duration,
}
}
/// Extract metadata from a file on disk without loading it fully into memory.
///
/// Uses async file I/O: reads only the header bytes needed for MIME/dimension
/// detection, then seeks for duration if needed.
pub async fn file_info_from_path(path: impl AsRef<std::path::Path>) -> std::io::Result<FileInfo> {
use tokio::io::AsyncReadExt;
let path = path.as_ref();
let name = path.file_name().and_then(|n| n.to_str()).unwrap_or("");
let mut f = tokio::fs::File::open(path).await?;
// Read first 64 KB; enough for MIME, image dimensions, and short video headers.
let mut header = vec![0u8; 65536];
let n = f.read(&mut header).await?;
header.truncate(n);
let mime_type = detect_mime(&header, name);
let (width, height) = image_dimensions(&header, &mime_type);
// For video duration we need the full file; use the path directly.
let duration = video_duration_from_path(path, &mime_type).await;
Ok(FileInfo {
mime_type,
width,
height,
duration,
})
}
// Extract pixel dimensions from common image/video headers.
fn image_dimensions(bytes: &[u8], mime: &str) -> (Option<u32>, Option<u32>) {
match mime {
"image/png" => png_dimensions(bytes),
"image/jpeg" => jpeg_dimensions(bytes),
"image/gif" => gif_dimensions(bytes),
"image/webp" => webp_dimensions(bytes),
_ => (None, None),
}
}
fn png_dimensions(b: &[u8]) -> (Option<u32>, Option<u32>) {
// PNG: 8-byte sig + 4-byte len + "IHDR" + 4-byte width + 4-byte height
if b.len() < 24 {
return (None, None);
}
if &b[0..8] != b"\x89PNG\r\n\x1a\n" {
return (None, None);
}
let Ok(wb): Result<[u8; 4], _> = b[16..20].try_into() else {
return (None, None);
};
let Ok(hb): Result<[u8; 4], _> = b[20..24].try_into() else {
return (None, None);
};
let w = u32::from_be_bytes(wb);
let h = u32::from_be_bytes(hb);
(Some(w), Some(h))
}
fn jpeg_dimensions(b: &[u8]) -> (Option<u32>, Option<u32>) {
if b.len() < 4 || b[0] != 0xFF || b[1] != 0xD8 {
return (None, None);
}
let mut i = 2;
while i + 9 < b.len() {
if b[i] != 0xFF {
break;
}
let marker = b[i + 1];
// SOF markers: C0, C1, C2
if matches!(marker, 0xC0..=0xC2) && i + 9 < b.len() {
let h = u16::from_be_bytes([b[i + 5], b[i + 6]]) as u32;
let w = u16::from_be_bytes([b[i + 7], b[i + 8]]) as u32;
return (Some(w), Some(h));
}
if i + 4 > b.len() {
break;
}
let len = u16::from_be_bytes([b[i + 2], b[i + 3]]) as usize;
i += 2 + len;
}
(None, None)
}
fn gif_dimensions(b: &[u8]) -> (Option<u32>, Option<u32>) {
// GIF: 6-byte header + 2-byte width (LE) + 2-byte height (LE)
if b.len() < 10 {
return (None, None);
}
if &b[0..6] != b"GIF87a" && &b[0..6] != b"GIF89a" {
return (None, None);
}
let w = u16::from_le_bytes([b[6], b[7]]) as u32;
let h = u16::from_le_bytes([b[8], b[9]]) as u32;
(Some(w), Some(h))
}
fn webp_dimensions(b: &[u8]) -> (Option<u32>, Option<u32>) {
// RIFF....WEBPVP8 or WEBPVP8L or WEBPVP8X
if b.len() < 30 || &b[0..4] != b"RIFF" || &b[8..12] != b"WEBP" {
return (None, None);
}
match &b[12..16] {
b"VP8 " if b.len() >= 30 => {
// VP8 bitstream: skip 10 bytes of chunk header, then 3 bytes tag, then w/h
let w = (u16::from_le_bytes([b[26], b[27]]) & 0x3FFF) as u32;
let h = (u16::from_le_bytes([b[28], b[29]]) & 0x3FFF) as u32;
(Some(w), Some(h))
}
b"VP8L" if b.len() >= 21 => {
let Ok(arr): Result<[u8; 4], _> = b[17..21].try_into() else {
return (None, None);
};
let bits = u32::from_le_bytes(arr);
let w = (bits & 0x3FFF) + 1;
let h = ((bits >> 14) & 0x3FFF) + 1;
(Some(w), Some(h))
}
b"VP8X" if b.len() >= 30 => {
// VP8X: canvas width-1 at bytes 24-26 (24-bit LE), height-1 at 27-29
let w = u32::from_le_bytes([b[24], b[25], b[26], 0]) + 1;
let h = u32::from_le_bytes([b[27], b[28], b[29], 0]) + 1;
(Some(w), Some(h))
}
_ => (None, None),
}
}
fn video_duration(_bytes: &[u8], mime: &str) -> Option<f64> {
// For in-memory bytes, only attempt if we have enough data and it's mp4/mov.
if !matches!(
mime,
"video/mp4" | "video/quicktime" | "audio/mp4" | "audio/x-m4a"
) {
return None;
}
// mp4 crate needs a Reader; wrap bytes in Cursor.
// Only available under `experimental` feature.
#[cfg(feature = "experimental")]
{
use std::io::Cursor;
let cursor = Cursor::new(_bytes);
if let Ok(mp4) = mp4::Mp4Reader::read_header(cursor, _bytes.len() as u64) {
return Some(mp4.duration().as_secs_f64());
}
}
None
}
async fn video_duration_from_path(_path: &std::path::Path, mime: &str) -> Option<f64> {
if !matches!(
mime,
"video/mp4" | "video/quicktime" | "audio/mp4" | "audio/x-m4a"
) {
return None;
}
#[cfg(feature = "experimental")]
{
// mp4 crate is sync; run in blocking thread.
let path = _path.to_path_buf();
return tokio::task::spawn_blocking(move || {
let f = std::fs::File::open(&path).ok()?;
let size = f.metadata().ok()?.len();
let reader = std::io::BufReader::new(f);
mp4::Mp4Reader::read_header(reader, size)
.ok()
.map(|m| m.duration().as_secs_f64())
})
.await
.ok()
.flatten();
}
#[allow(unreachable_code)]
None
}