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Reader

[Source]

Store network data and provide a parsing interface.

Reader provides a way to extract typed data from a sequence of bytes. The Reader manages the underlying data structures to provide a read cursor over a contiguous sequence of bytes. It is useful for decoding data that is received over a network or stored in a file. Chunk of bytes are added to the Reader using the append method, and typed data is extracted using the getter methods.

For example, suppose we have a UDP-based network data protocol where messages consist of the following:

  • list_size - the number of items in the following list of items as a big-endian 32-bit integer
  • zero or more items of the following data:
  • a big-endian 64-bit floating point number
  • a string that starts with a big-endian 32-bit integer that specifies the length of the string, followed by a number of bytes that represent the string

A message would be something like this:

[message_length][list_size][float1][string1][float2][string2]...

The following program uses a Reader to decode a message of this type and print them:

use "buffered"
use "collections"

class Notify is InputNotify
  let _env: Env
  new create(env: Env) =>
    _env = env
  fun ref apply(data: Array[U8] iso) =>
    let rb = Reader
    rb.append(consume data)
    try
      while true do
        let len = rb.i32_be()?
        let items = rb.i32_be()?.usize()
        for range in Range(0, items) do
          let f = rb.f32_be()?
          let str_len = rb.i32_be()?.usize()
          let str = String.from_array(rb.block(str_len)?)
          _env.out.print("[(" + f.string() + "), (" + str + ")]")
        end
      end
    end

actor Main
  new create(env: Env) =>
    env.input(recover Notify(env) end, 1024)

class ref Reader

Constructors

create

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new iso create()
: Reader iso^

Returns

Public Functions

size

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Return the number of available bytes.

fun box size()
: USize val

Returns

clear

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Discard all pending data.

fun ref clear()
: None val

Returns

append

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Add a chunk of data.

fun ref append(
  data: (String val | Array[U8 val] val))
: None val

Parameters

Returns

skip

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Skip n bytes.

fun ref skip(
  n: USize val)
: None val ?

Parameters

Returns

block

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Return a block as a contiguous chunk of memory. Will throw an error if you request a block larger than what is currently stored in the Reader.

fun ref block(
  len: USize val)
: Array[U8 val] iso^ ?

Parameters

Returns

read_until

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Find the first occurrence of the separator and return the block of bytes before its position. The separator is not included in the returned array, but it is removed from the buffer. To read a line of text, prefer line() that handles \n and \r\n.

fun ref read_until(
  separator: U8 val)
: Array[U8 val] iso^ ?

Parameters

  • separator: U8 val

Returns

line

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Return a \n or \r\n terminated line as a string. By default the newline is not included in the returned string, but it is removed from the buffer. Set keep_line_breaks to true to keep the line breaks in the returned line.

fun ref line(
  keep_line_breaks: Bool val = false)
: String iso^ ?

Parameters

  • keep_line_breaks: Bool val = false

Returns

u8

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Get a U8. Raise an error if there isn't enough data.

fun ref u8()
: U8 val ?

Returns

  • U8 val ?

i8

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Get an I8.

fun ref i8()
: I8 val ?

Returns

  • I8 val ?

u16_be

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Get a big-endian U16.

fun ref u16_be()
: U16 val ?

Returns

u16_le

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Get a little-endian U16.

fun ref u16_le()
: U16 val ?

Returns

i16_be

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Get a big-endian I16.

fun ref i16_be()
: I16 val ?

Returns

i16_le

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Get a little-endian I16.

fun ref i16_le()
: I16 val ?

Returns

u32_be

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Get a big-endian U32.

fun ref u32_be()
: U32 val ?

Returns

u32_le

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Get a little-endian U32.

fun ref u32_le()
: U32 val ?

Returns

i32_be

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Get a big-endian I32.

fun ref i32_be()
: I32 val ?

Returns

i32_le

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Get a little-endian I32.

fun ref i32_le()
: I32 val ?

Returns

u64_be

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Get a big-endian U64.

fun ref u64_be()
: U64 val ?

Returns

u64_le

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Get a little-endian U64.

fun ref u64_le()
: U64 val ?

Returns

i64_be

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Get a big-endian I64.

fun ref i64_be()
: I64 val ?

Returns

i64_le

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Get a little-endian I64.

fun ref i64_le()
: I64 val ?

Returns

u128_be

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Get a big-endian U128.

fun ref u128_be()
: U128 val ?

Returns

u128_le

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Get a little-endian U128.

fun ref u128_le()
: U128 val ?

Returns

i128_be

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Get a big-endian I129.

fun ref i128_be()
: I128 val ?

Returns

i128_le

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Get a little-endian I128.

fun ref i128_le()
: I128 val ?

Returns

f32_be

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Get a big-endian F32.

fun ref f32_be()
: F32 val ?

Returns

f32_le

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Get a little-endian F32.

fun ref f32_le()
: F32 val ?

Returns

f64_be

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Get a big-endian F64.

fun ref f64_be()
: F64 val ?

Returns

f64_le

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Get a little-endian F64.

fun ref f64_le()
: F64 val ?

Returns

peek_u8

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Peek at a U8 at the given offset. Raise an error if there isn't enough data.

fun box peek_u8(
  offset: USize val = 0)
: U8 val ?

Parameters

Returns

  • U8 val ?

peek_i8

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Peek at an I8.

fun box peek_i8(
  offset: USize val = 0)
: I8 val ?

Parameters

Returns

  • I8 val ?

peek_u16_be

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Peek at a big-endian U16.

fun box peek_u16_be(
  offset: USize val = 0)
: U16 val ?

Parameters

Returns

peek_u16_le

[Source]

Peek at a little-endian U16.

fun box peek_u16_le(
  offset: USize val = 0)
: U16 val ?

Parameters

Returns

peek_i16_be

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Peek at a big-endian I16.

fun box peek_i16_be(
  offset: USize val = 0)
: I16 val ?

Parameters

Returns

peek_i16_le

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Peek at a little-endian I16.

fun box peek_i16_le(
  offset: USize val = 0)
: I16 val ?

Parameters

Returns

peek_u32_be

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Peek at a big-endian U32.

fun box peek_u32_be(
  offset: USize val = 0)
: U32 val ?

Parameters

Returns

peek_u32_le

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Peek at a little-endian U32.

fun box peek_u32_le(
  offset: USize val = 0)
: U32 val ?

Parameters

Returns

peek_i32_be

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Peek at a big-endian I32.

fun box peek_i32_be(
  offset: USize val = 0)
: I32 val ?

Parameters

Returns

peek_i32_le

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Peek at a little-endian I32.

fun box peek_i32_le(
  offset: USize val = 0)
: I32 val ?

Parameters

Returns

peek_u64_be

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Peek at a big-endian U64.

fun box peek_u64_be(
  offset: USize val = 0)
: U64 val ?

Parameters

Returns

peek_u64_le

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Peek at a little-endian U64.

fun box peek_u64_le(
  offset: USize val = 0)
: U64 val ?

Parameters

Returns

peek_i64_be

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Peek at a big-endian I64.

fun box peek_i64_be(
  offset: USize val = 0)
: I64 val ?

Parameters

Returns

peek_i64_le

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Peek at a little-endian I64.

fun box peek_i64_le(
  offset: USize val = 0)
: I64 val ?

Parameters

Returns

peek_u128_be

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Peek at a big-endian U128.

fun box peek_u128_be(
  offset: USize val = 0)
: U128 val ?

Parameters

Returns

peek_u128_le

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Peek at a little-endian U128.

fun box peek_u128_le(
  offset: USize val = 0)
: U128 val ?

Parameters

Returns

peek_i128_be

[Source]

Peek at a big-endian I129.

fun box peek_i128_be(
  offset: USize val = 0)
: I128 val ?

Parameters

Returns

peek_i128_le

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Peek at a little-endian I128.

fun box peek_i128_le(
  offset: USize val = 0)
: I128 val ?

Parameters

Returns

peek_f32_be

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Peek at a big-endian F32.

fun box peek_f32_be(
  offset: USize val = 0)
: F32 val ?

Parameters

Returns

peek_f32_le

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Peek at a little-endian F32.

fun box peek_f32_le(
  offset: USize val = 0)
: F32 val ?

Parameters

Returns

peek_f64_be

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Peek at a big-endian F64.

fun box peek_f64_be(
  offset: USize val = 0)
: F64 val ?

Parameters

Returns

peek_f64_le

[Source]

Peek at a little-endian F64.

fun box peek_f64_le(
  offset: USize val = 0)
: F64 val ?

Parameters

Returns