whale example

Author: James Halliday

streams/whale.js

@@ -0,0 +1,43 @@
+// first do:
+// curl -s http://www.gutenberg.org/cache/epub/2701/pg2701.txt > mobydick.txt
+
+var fs = require('fs');
+var path = require('path');
+var through = require('through2');
+var combine = require('stream-combiner2')
+var split = require('split');
+
+read('mobydick.txt')
+    .pipe(replace(/\s+/g, '\n'))
+    .pipe(filter(/whale/i))
+    .pipe(linecount(function (count) {
+        console.log(count)
+    }))
+;
+
+function read (file) {
+    return fs.createReadStream(path.join(__dirname, file));
+}
+
+function replace (pattern, replacement) {
+    return combine(split(), through(function (buf, enc, next) {
+        var line = buf.toString('utf8');
+        this.push(line.replace(pattern, replacement) + '\n');
+        next();
+    }));
+}
+
+function filter (pattern) {
+    return combine(split(), through(function (buf, enc, next) {
+        var line = buf.toString('utf8');
+        if (pattern.test(line)) this.push(line + '\n');
+        next();
+    }));
+}
+
+function linecount (cb) {
+    var count = 0;
+    return combine(split(), through(write, end));
+    function write (buf, enc, next) { count ++; next() }
+    function end () { cb(count) }
+}