Some time ago, [a **FastAPI** user asked](https://github.com/fastapi/fastapi/issues/3#issuecomment-454956920):

> What’s the history of this project? It seems to have come from nowhere to awesome in a few weeks [...]

Here's a little bit of that history.

## Alternatives { #alternatives }

)

// Max bzip2 concurrency across calls. 50% of GOMAXPROCS.
var bz2Limiter = pbzip2.CreateConcurrencyPool((runtime.GOMAXPROCS(0) + 1) / 2)

func detect(r *bufio.Reader) format {
	z, err := r.Peek(4)
	if err != nil {
		return formatUnknown
	}
	for _, f := range magicHeaders {
		if bytes.Equal(f.header, z[:len(f.header)]) {
			return f.f
		}
	}
	return formatUnknown
}

 *   <li>time-based expiration of entries, measured since last access or last write
 *   <li>keys automatically wrapped in {@linkplain WeakReference weak} references
 *   <li>values automatically wrapped in {@linkplain WeakReference weak} or {@linkplain
 *       SoftReference soft} references
 *   <li>notification of evicted (or otherwise removed) entries
 *   <li>accumulation of cache access statistics
 * </ul>

     * User property to configure separate reference types for cache keys.
     * This enables fine-grained analysis of cache misses caused by key vs value evictions.
     * Supported values are {@code HARD}, {@code SOFT} and {@code WEAK}.
     *
     * @since 4.1.0
     */
    public static final String MAVEN_CACHE_KEY_REFS = "maven.cache.keyValueRefs";

    /**
     * User property to configure separate reference types for cache values.

func (c *LRU[K, V]) Contains(key K) (ok bool) {
	c.mu.RLock()
	defer c.mu.RUnlock()
	_, ok = c.items[key]
	return ok
}

// Peek returns the key value (or undefined if not found) without updating
// the "recently used"-ness of the key.
func (c *LRU[K, V]) Peek(key K) (value V, ok bool) {
	c.mu.RLock()
	defer c.mu.RUnlock()
	var ent *Entry[K, V]
	if ent, ok = c.items[key]; ok {
		// Expired item check

    assertThat(sepStopwatchA.get()).isNotNull();
    // Clear all references to the Stopwatch and wait for it to be gc'd.
    sepStopwatchA.set(null);
    GcFinalization.awaitClear(sepStopwatchRef.get());
    // Return a weak reference to the parallel ClassLoader. This is the reference that should
    // eventually become clear if there are no other references to the ClassLoader.
    return new WeakReference<ClassLoader>(sepLoader);
  }

  /**

import com.google.common.collect.Lists;
import com.google.common.collect.MapMaker;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.j2objc.annotations.Weak;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

`UploadFile` には次の `async` メソッドがあります。いずれも内部で対応するファイルメソッド（内部の `SpooledTemporaryFile`）を呼び出します。

- `write(data)`: `data`（`str` または `bytes`）を書き込みます。
- `read(size)`: `size`（`int`）バイト/文字を読み込みます。
- `seek(offset)`: ファイル内のバイト位置 `offset`（`int`）に移動します。
    - 例: `await myfile.seek(0)` はファイルの先頭に移動します。
    - 一度 `await myfile.read()` を実行して、もう一度内容を読みたい場合に特に便利です。
- `close()`: ファイルを閉じます。

これらはすべて `async` メソッドなので、`await` する必要があります。

    assertThat(sepStopwatchA.get()).isNotNull();
    // Clear all references to the Stopwatch and wait for it to be gc'd.
    sepStopwatchA.set(null);
    GcFinalization.awaitClear(sepStopwatchRef.get());
    // Return a weak reference to the parallel ClassLoader. This is the reference that should
    // eventually become clear if there are no other references to the ClassLoader.
    return new WeakReference<ClassLoader>(sepLoader);
  }

  /**

    /**
     * Function code to retrieve DFS referrals
     */
    public static final int FSCTL_DFS_GET_REFERRALS = 0x0060194;
    /**
     * Function code to peek at named pipe data without removing it
     */
    public static final int FSCTL_PIPE_PEEK = 0x0011400C;
    /**
     * Function code to wait for a named pipe to become available
     */