Compressing and Decompressing Buffers

The Zlib module provides several helper functions that make it easy to compress/decompress data buffers. They all use the same basic format of function(buffer, callback), where function is the compression/decompression method, buffer is the buffer to be compressed/decompressed, and callback is the callback function that is executed after the compression/decompression occurs.

The simplest way to illustrate buffer compression/decompression is to show you some examples. The code in Listing 5.11 provides several compression/decompression examples and outputs the size results of each as shown in Figure 5.11.

Listing 5.11 zlib_buffers.js: Compressing/decompressing buffers using the Zlib module

Click here to view code image

01 var zlib = require("zlib");
02 var input = '...............text...............';
03 zlib.deflate(input, function(err, buffer) {
04   if (!err) {
05     console.log("deflate (%s): ", buffer.length, buffer.toString('base64'));
06     zlib.inflate(buffer, function(err, buffer) {
07       if (!err) {
08         console.log("inflate (%s): ", buffer.length, buffer.toString());
09       }
10     });
11     zlib.unzip(buffer, function(err, buffer) {
12       if (!err) {
13         console.log("unzip deflate (%s): ", buffer.length, buffer.toString());
14       }
15     });
16   }
17 });
18
19 zlib.deflateRaw(input, function(err, buffer) {
20   if (!err) {
21     console.log("deflateRaw (%s): ", buffer.length, buffer.toString('base64'));
22     zlib.inflateRaw(buffer, function(err, buffer) {
23       if (!err) {
24         console.log("inflateRaw (%s): ", buffer.length, buffer.toString());
25       }
26     });
27   }
28 });
29
30 zlib.gzip(input, function(err, buffer) {
31   if (!err) {
32     console.log("gzip (%s): ", buffer.length, buffer.toString('base64'));
33     zlib.gunzip(buffer, function(err, buffer) {
34       if (!err) {
35         console.log("gunzip (%s): ", buffer.length, buffer.toString());
36       }
37     });
38     zlib.unzip(buffer, function(err, buffer) {
39       if (!err) {
40         console.log("unzip gzip (%s): ", buffer.length, buffer.toString());
41       }
42     });
43   }
44 });

Figure 5.11 Output of zilb_buffers.js, compressing/decompressing buffers.