string-buffer

string-buffer

This is the StringBuffer class that LEON uses internally. It provides all the methods of a Node.js Buffer object, but it stores its data in a string, meaning it is portable enough to be used in the browser as well as on the server.

Usage

var StringBuffer = require('string-buffer');

or

<script src="string-buffer.js" type="text/javascript"></script>

var buffer = StringBuffer();
var secondBuffer = StringBuffer();
buffer.writeUInt8(254, 0);
secondBuffer.writeDoubleBE(232.222, 0);
buffer = StringBuffer.concat([ buffer, secondBuffer ]);
buffer
// <StringBuffer fe 40 6d 07 1a 9f be 76 c9>

You can also pass negative indices to the methods to indicate you want to read or write that many characters from the end of the line. Passing -1 as an index anywhere where you are reading data (as opposed to writing it) means "the last byte in the buffer." Passing -1 as an index where you are writing data signifies "the end of the StringBuffer, no overwriting," so if you wanted to overwrite the last byte in the buffer with the value 0 you would use buffer.writeUInt8(0, -2) and if you wanted to read that byte you would use buffer.readUInt8(-1). The reason this was done is so you can do stuff like this:

buffer.clear();
buffer.writeUInt8(5, -1);
buffer.writeUInt8(4, -1);
buffer.readUInt8(-2);
// 5
buffer.readUInt8(-1);
// 4

StringBuffer will throw if you attempt to write a number that cannot be stored in that type, such as trying to store a floating point value that requires double precision in a float. To suppress this behavior, you can pass true as the third argument to StringBuffer#writeFloatLE or what have you. This is consistent with the Node.js API.

You can convert a StringBuffer to a typed array with StringBuffer#toTypedArray(type, bigEndian). You should pass true as the second argument if your data is in big endian format, otherwise the second argument can be omitted. If you don't supply a first argument it will default to Uint8Array, otherwise you can supply any one of the typed array constructors as the first argument to return a typed array of that variant. For example if you want a Int32Array and your data is little endian, you can do something like

var arr = buffer.toTypedArray(Int32Array);

You can convert back from a typed array using StringBuffer.fromTypedArray(array, bigEndian). If you want your data in big endian format, pass true as the second argument, otherwise the second argument can be omitted.

You can also convert your buffer directly to a Blob object by calling StringBuffer#toBlob(mimeType, bigEndian).

Also, you can create a StringBuffer directly from a Blob or File object using StringBuffer.fromBlob(blob, cb) or StringBuffer.fromFile(file, cb). Both these functions are asynchronous and receive an error object as the first argument to the callback, and the StringBuffer as the second argument.

If you are working in a Node.js environment and you need to convert a StringBuffer instance to a Buffer instance, you can use StringBuffer#toBuffer() to do so. If you want to get a StringBuffer from a buffer you can pass the buffer to StringBuffer.fromBuffer(buf).

You can a