Interface Source

Supplies a stream of bytes. Use this interface to read data from wherever it's located: from the network, storage, or a buffer in memory. Sources may be layered to transform supplied data, such as to decompress, decrypt, or remove protocol framing.

Most applications shouldn't operate on a source directly, but rather on a BufferedSource which is both more efficient and more convenient. Use Okio.buffer(Source) to wrap any source with a buffer.

Sources are easy to test: just use a Buffer in your tests, and fill it with the data your application is to read.

Comparison with InputStream

This interface is functionally equivalent to InputStream.

InputStream requires multiple layers when consumed data is heterogeneous: a DataInputStream for primitive values, a BufferedInputStream for buffering, and InputStreamReader for strings. This class uses BufferedSource for all of the above.

Source avoids the impossible-to-implement available() method. Instead callers specify how many bytes they require.

Source omits the unsafe-to-compose mark and reset state that's tracked by InputStream; instead, callers just buffer what they need.

When implementing a source, you don't need to worry about the single-byte read method that is awkward to implement efficiently and returns one of 257 possible values.

And source has a stronger skip method: BufferedSource.skip(long) won't return prematurely.

Interop with InputStream

Use Okio.source(java.io.InputStream) to adapt an InputStream to a source. Use BufferedSource.inputStream() to adapt a source to an InputStream.