May 2019
Intermediate to advanced
464 pages
9h 22m
Japanese
Content preview from Node.jsデザインパターン 第2版
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5.1
ストリームの重要性
105
t1
0x48 0x65 0x6c 0x6c 0x6f 0x20 0x4e
t2
コール
バック
通知
コール
バック
通知
Hello Node.js
Hello Node.js
コンシューマ
コンシューマ
0x6f 0x64 0x65 0x2e 0x6a 0x73
データ
読み込み
データ
読み込み
図5-2 ストリームを使った処理
ストリームを使う場合は新しいデータが読み込まれるたびにアプリケーションに通知されます。これ
により、アプリケーションはすべてのデータが揃うのを待つことなく、データの処理を開始できます。
この
2
つのアプローチにはどのような違いがあるのでしょうか。領域的な効率（
spatial efficiency
）と時
間的な効率（
time efficiency
）の
2
つの観点から違いを見ていきましょう。
5.1.2
領域的な効率
そもそも、すべてのデータをいったんバッファに読み込んでから処理する方式ではどうしても対応で
きないケースがあります。たとえば数百
M
バイトから数
G
バイトもあるような大きなファイルを読み込
むケースです。こうした場合、バッファにすべてのデータを読み込むのは避けるべきです。そうした処
理を並行で実行したりすると、メモリをすぐに使い切ってしまいます。もっ
とも、環境によってはメモ
リを使い切るよりも先に、処理系のバッファの最大サイズに達してしまうでしょう。
5.1.2.1
バッファを利用した
Gzip
の実装
これを実際に試すために、簡単なコマンドラインのアプリケーションを作
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.