February 2013
Intermediate to advanced
380 pages
7h 45m
Japanese
Content preview from Nodeクックブック
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20
1 章 Web サーバを立てる
readStream
の 2 つ目のパラメータに
bufferSize
プロパティを持ったオブジェクトを渡して宣言す
ることで、バッファサイズを変更することができます。例えば、バッファサイズを 128KB にした
い場合は、
fs.createReadStream(f, {bufferSize: 128*1024});
と記述します。
data
イベントで渡される
chunk
は、
cache[f].content
に格納されるときにただ文字列のように
連結すればよいわけではありません。
chunk
はバイナリデータですが、
+
演算子を使って連結して
しまうとデータが文字列に変換されてしまうため、後でバイナリデータとして取り扱うことができ
なくなります。代わりに、
chunk
で渡されるバイナリデータを
cache[f].buffer
の
Buffer
インス
タンスに
copy
でコピーする必要があります。
ここでは、バイナリデータのコピーを補助するために
bufferOffset
変数を宣言しています。
chunk
を
cache[f].content
に足すたびに、
bufferOffset
に
chunk
の長さを足していきます。
chunk
から
Buffer.copy
メソッドを呼ぶ際に、コピー領域の先頭を表す
bufferOffset
を
2
番目の
パラメータに渡します。
Buffer
クラスは、大きなファイルを扱う際にパフォーマンスを向上させる効果を持っています。 ...
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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.