Streams in memory

ByteReader and ByteWriter: a Reader over bytes already in memory, and a Writer that collects what is written into memory, for code that takes a stream when the data is in an array.

Source: runtime/io/memory.pep

ByteReader

struct ByteReader

A Reader over an array of bytes: each read takes the next bytes of the array, and the stream ends after its last byte.

The reader keeps a reference to the array and does not copy it; changing the array while reading changes what is read.

Example

import io;

var data = "one\ntwo\n".bytes();
var count = 0;
for (var line in io.ByteReader(data).lines()) {
    count += 1;
}
assert(count == 2, "two lines");

Properties

remaining

var remaining: ulong { get; }

The number of bytes not read yet.

Constructor

ByteReader()

construct(data: u8[])

Makes a reader positioned at the first byte of data.

Parameters

• data — the bytes to read

Methods

read

read(buffer: u8[], max: ulong): IoResult<ulong>

Appends up to max of the next bytes to buffer.

Parameters

• buffer — the array the bytes are appended to
• max — the most bytes to read

Returns

• the number of bytes appended, 0 once every byte has been read

ByteWriter

struct ByteWriter

A Writer that appends everything written to an array in memory, bytes.

Example

import io;

var out = io.ByteWriter();
out.print("n = ");
out.print_line(3);
assert(out.bytes == "n = 3\n".bytes(), "collected");

Fields

bytes

var bytes: u8[]

The bytes written so far, in order.

Constructor

ByteWriter()

construct()

Makes a writer with nothing written yet.

Methods

write

write(data: u8[]): IoResult<ulong>

Appends all of data to bytes.

Parameters

• data — the bytes to write

Returns

• the number of bytes written: always data.count

write_all

write_all(data: u8[]): IoResult<void>

Appends all of data to bytes.

Parameters

• data — the bytes to write

Returns

• an Ok result; writing to memory does not fail