Create buffer space
To create buffer space we can use the alloc() method in the global Buffer class in Node.js.
- The method takes the number of bytes (
integer) to allocate as the first argument. - The method returns a buffer object.
Let's allocate a buffer space of 10 bytes.
// allocate 10 bytes of buffer space
const buff = Buffer.alloc(10);
// display buff contents
console.log(buff); // <Buffer 00 00 00 00 00 00 00 00 00 00>
To initialize the bytes with other than 0, you can pass that integer or string as the second argument like this,
// allocate 10 bytes of buffer space
// allocate with integer 1
const buff = Buffer.alloc(10, 1);
// display buff contents
console.log(buff); // <Buffer 01 01 01 01 01 01 01 01 01 01>
Write to Buffer
To write to a buffer space we can use the write() method in the Buffer object.
- The method accepts a string as the first argument to write.
// allocate 10 bytes of buffer space
const buff = Buffer.alloc(10);
// write to buffer
const bytesWrote = buff.write("John Doe");
console.log(bytesWrote); // 8
console.log(buff); // Raw Buffer: <Buffer 4a 6f 68 6e 20 44 6f 65 00 00>
console.log(buff.toString()); // String: John Doe
We can use the toString() method in the buff object to convert a raw buffer to string.
We can also define the starting point where it needs to write to the buffer.
For example, if we want to write to buffer after 2 bytes we can pass that as the second argument to the write() method.
// allocate 10 bytes of buffer space
const buff = Buffer.alloc(10);
// write to buffer
// after 2 bytes
const bytesWrote = buff.write("John Doe", 2);
console.log(bytesWrote); // 8
console.log(buff); // Raw Buffer: <Buffer 00 00 4a 6f 68 6e 20 44 6f 65>
console.log(buff.toString()); // String: John Doe
If you look closely into the contents inside the buff variable you can see that the first 2 bytes are 00 00 which means we started writing into the buffer after 2 bytes.
See this example live in repl.it.