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Updated events and buffers, mostly grammar and formatting. These sect…

…ions still need to be expanded a little more.
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commit cc13650daa33ba3f5d58022fa13fd75ad5c1fe6f 1 parent 9c1ebd5
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Showing with 66 additions and 37 deletions.
  1. +65 −36 chapters/buffers.md
  2. +1 −1  chapters/events.md
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101 chapters/buffers.md
@@ -5,61 +5,90 @@
The simplest way to construct a `Buffer` from a string is to simply pass a string as the first argument. As you can see by the log output, we now have a buffer object containing 5 bytes of data represented in hexadecimal.
- var hello = new Buffer('Hello');
-
- console.log(hello);
- // => <Buffer 48 65 6c 6c 6f>
+ > var hello = new Buffer('Hello');
+
+ > console.log(hello);
+ <Buffer 48 65 6c 6c 6f>
- console.log(hello.toString());
- // => "Hello"
+ > console.log(hello.toString());
+ 'Hello'
By default the encoding is "utf8", however this can be specified by passing as string as the second argument. The ellipsis below for example will be printed to stdout as the '&' character when in "ascii" encoding.
- var buf = new Buffer('…');
- console.log(buf.toString());
- // => …
+ > var buf = new Buffer('…');
+ > console.log(buf.toString());
+ '…'
- var buf = new Buffer('…', 'ascii');
- console.log(buf.toString());
- // => &
+ > var buf = new Buffer('…', 'ascii');
+ > console.log(buf.toString());
+ '&'
-An alternative method is to pass an array of integers representing the octet stream, however in this case functionality equivalent.
+An alternative method is to pass an array of integers representing the octet stream.
- var hello = new Buffer([0x48, 0x65, 0x6c, 0x6c, 0x6f]);
+ > var h = [0x48, 0x65, 0x6c, 0x6c, 0x6f];
+ > h
+ [ 72, 101, 108, 108, 111 ]
-Buffers can also be created with an integer representing the number of bytes allocated, after which we may call the `write()` method, providing an optional offset and encoding. As shown below we provide the offset of 2 bytes to our second call to `write()`, buffering "Hel", and then we continue on to write another two bytes with an offset of 3, completing "Hello".
+ > h.toString();
+ '72,101,108,108,111'
- var buf = new Buffer(5);
- buf.write('He');
- buf.write('l', 2);
- buf.write('lo', 3);
- console.log(buf.toString());
- // => "Hello"
+ > var hello = new Buffer(h);
+ <Buffer 48 65 6c 6c 6f>
+
+ > hello.toString();
+ 'Hello'
+
+
+Buffers can also be created with an integer representing the number of bytes allocated, after which we may call the `write()` method, providing an optional offset and encoding. As shown below, we create a buffer large enough to hold the string "Hello World!" After writing 'Hello', we see the bytes 5 through 12 are unused bytes. We then write ' World' starting at byte 6 and examine the output. Whoops! We skipped a byte. We can overwrite this part of the buffer with ' World!' starting at byte 5. We then call `toString()` on the buffer and see that the buffer is now filled with the desired string.
+
+ > var hello = new Buffer(12);
+ > hello.write('Hello');
+ 5
+
+ > hello.toString();
+ 'Hello\u0000�̵\u0001\u0000\u0000'
+ > hello.write(' World', 6);
+ 6
+
+ > hello.toString();
+ 'Hello\u0000 World'
+
+ > hello.write(' World!', 5);
+ 7
+
+ > hello.toString();
+ 'Hello World!'
+
+ > hello.length
+ 12
The `.length` property of a buffer instance contains the byte length of the stream, opposed to JavaScript strings which will simply return the number of characters. For example the ellipsis character '…' consists of three bytes, however the buffer will respond with the byte length, and not the character length.
- var ellipsis = new Buffer('…', 'utf8');
+ > var ellipsis = new Buffer('…', 'utf8');
+ > console.log('… string length: %d', '…'.length);
+ … string length: 1
+
+ > console.log('… byte length: %d', ellipsis.length);
+ … byte length: 3
- console.log('… string length: %d', '…'.length);
- // => … string length: 1
+ > ellipsis
+ <Buffer e2 80 a6>
- console.log('… byte length: %d', ellipsis.length);
- // => … byte length: 3
-
- console.log(ellipsis);
- // => <Buffer e2 80 a6>
+When dealing with a JavaScript string, we may pass it to the `Buffer.byteLength()` method to determine it's byte length.
-When dealing with JavaScript strings, we may pass it to the `Buffer.byteLength()` method to determine it's byte length.
+ > Buffer.byteLength('…');
+ 3
The api is written in such a way that it is String-like, so for example we can work with "slices" of a `Buffer` by passing offsets to the `slice()` method:
- var chunk = buf.slice(4, 9);
- console.log(chunk.toString());
- // => "some"
+ > var chunk = buf.slice(4, 9);
+ > console.log(chunk.toString());
+ 'some'
Alternatively when expecting a string we can pass offsets to `Buffer#toString()`:
- var buf = new Buffer('just some data');
- console.log(buf.toString('ascii', 4, 9));
- // => "some"
+ > var buffer = new Buffer('The quick brown fox');
+ > buffer.toString('ascii', 4, 9);
+ 'quick'
+A Buffer object has a number of helper functions: `.utf8Write()`, `.utf8Slice()`, `.asciiWrite()`, `.asciiSlice()`, `.binaryWrite()`, `.binarySlice()`. These methods provide similar functionality while enforcing proper encoding.
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2  chapters/events.md
@@ -50,7 +50,7 @@ Bark twice a second:
## Removing Event Listeners
-As we have seen event listeners are simply functions which are called when we `emit()` an event. Although not seen often we can remove these listeners by calling the `removeListener(type, callback)` method. In the example below we emit the _message_ "foo bar" every `300` milliseconds, which has the callback of `console.log()`. After 1000 milliseconds we call `removeListener()` with the same arguments that we passed to `on()` originally. To compliment this method is `removeAllListeners(type)` which removes all listeners associated to the given _type_.
+As we have seen, event listeners are simply functions which are called when we `emit()` an event. Although not seen often we can remove these listeners by calling the `removeListener(type, callback)` method. In the example below we emit the _message_ "foo bar" every `300` milliseconds, which has the callback of `console.log()`. After 1000 milliseconds we call `removeListener()` with the same arguments that we passed to `on()` originally. To compliment this method is `removeAllListeners(type)` which removes all listeners associated to the given _type_.
var EventEmitter = require('events').EventEmitter;
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