qubit-mime 0.5.2

MIME type detection utilities for Rust based on filename glob rules and content magic
Documentation 
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/*******************************************************************************
 *
 *    Copyright (c) 2026 Haixing Hu.
 *
 *    SPDX-License-Identifier: Apache-2.0
 *
 *    Licensed under the Apache License, Version 2.0.
 *
 ******************************************************************************/
//! Shared media stream classifier helpers.

use std::fs;
use std::io::Read;
use std::path::Path;
use std::path::PathBuf;
use std::sync::atomic::{
    AtomicU64,
    Ordering,
};

use crate::{
    MimeError,
    MimeResult,
};

/// Validates that a path is a readable local file.
///
/// # Parameters
/// - `path`: Path to validate.
///
/// # Errors
/// Returns [`MimeError::Io`](crate::MimeError::Io) when metadata cannot be read or the file cannot
/// be opened, and [`MimeError::InvalidClassifierInput`](crate::MimeError::InvalidClassifierInput)
/// when the path is not a regular file.
pub(crate) fn validate_readable_file(path: &Path) -> MimeResult<()> {
    let metadata = fs::metadata(path)?;
    if !metadata.is_file() {
        return Err(MimeError::invalid_classifier_input(format!(
            "path is not a regular file: {}",
            path.display()
        )));
    }
    fs::File::open(path)?;
    Ok(())
}

/// Stages a reader into a temporary file and calls `classify`.
///
/// # Parameters
/// - `reader`: Stream whose content should be staged.
/// - `classify`: Callback receiving the temporary local file path.
///
/// # Returns
/// The callback result.
///
/// # Errors
/// Returns [`MimeError::Io`](crate::MimeError::Io) when the stream cannot be read or the
/// temporary file cannot be written, or returns the callback error when classification fails.
pub(crate) fn with_temp_reader<T>(
    reader: &mut dyn Read,
    classify: impl FnOnce(&Path) -> MimeResult<T>,
) -> MimeResult<T> {
    let path = unique_temp_path("FileBasedMediaStreamClassifier", ".tmp");
    let mut content = Vec::new();
    reader.read_to_end(&mut content)?;
    fs::write(&path, content)?;
    let result = classify(&path);
    let _ = fs::remove_file(&path);
    result
}

/// Builds a best-effort unique temporary path.
///
/// # Parameters
/// - `prefix`: Filename prefix.
/// - `suffix`: Filename suffix.
///
/// # Returns
/// Path under the OS temporary directory.
fn unique_temp_path(prefix: &str, suffix: &str) -> PathBuf {
    static COUNTER: AtomicU64 = AtomicU64::new(0);
    let counter = COUNTER.fetch_add(1, Ordering::Relaxed);
    std::env::temp_dir().join(format!("{prefix}-{}-{counter}{suffix}", std::process::id()))
}