# class IO::Memory

- IO::Memory
- IO
- Reference
- Object

##
Overview

An `IO` that reads and writes from a buffer in memory.

The internal buffer can be resizeable and/or writable depending on how an `IO::Memory` is constructed.

##
Defined in:

io/memory.cr

##
Constructors

- .new(capacity : Int = 64)

  Creates an empty, resizeable and writable `IO::Memory` with the given initial capacity for the internal buffer.

- .new(string : String) : self

  Creates an `IO::Memory` whose contents are the exact contents of string.

- .new(slice : Bytes, writable = true)

  Creates an `IO::Memory` that will read, and optionally write, from/to the given slice.

- .new(slice : Bytes, *, writeable writable) : self

  Creates an `IO::Memory` that will read, and optionally write, from/to the given slice.

  DEPRECATED Use `IO::Memory.new(Bytes, writable)` instead

##
Instance Method Summary

- #buffer : Pointer(UInt8)

  Returns the internal buffer as a `Pointer(UInt8)`.

- #bytesize : Int32

  Same as `#size`.

- #clear : Nil

  Clears the internal buffer and resets the position to zero.

- #close : Nil

  Closes this `IO`.

- #closed? : Bool

  Determines if this `IO` is closed.

- #empty? : Bool

  Returns `true` if this `IO::Memory` has no contents.

- #getb_to_end : Bytes

  Reads the rest of this `IO` data as a writable `Bytes`.

- #gets_to_end : String

  Reads the rest of this `IO` data as a `String`.

- #peek : Bytes

  Peeks into this IO, if possible.

- #pos : Int32

  Returns the current position (in bytes) of this `IO`.

- #pos=(value)

  Sets the current position (in bytes) of this `IO`.

- #read(slice : Bytes) : Int32

  See `IO#read(slice)`.

- #read_at(offset, bytesize, & : IO -> )

  Yields an `IO::Memory` to read a section of this `IO`'s buffer.

- #read_byte : UInt8 | Nil

  Reads a single byte from this `IO`.

- #rewind : self

  Rewinds this `IO` to the initial position (zero).

- #seek(offset, whence : Seek = Seek::Set)

  Seeks to a given offset (in bytes) according to the whence argument.

- #size : Int32

  Returns the total number of bytes in this `IO`.

- #skip_to_end : Nil

  Reads and discards bytes from `self` until there are no more bytes.

- #to_s(io : IO) : Nil

  Appends this internal buffer to the given `IO`.

- #to_s : String

  Returns a new `String` that contains the contents of the internal buffer.

- #to_slice : Bytes

  Returns the underlying bytes.

- #write(slice : Bytes) : Nil

  See `IO#write(slice)`.

- #write_byte(byte : UInt8) : Nil

  See `IO#write_byte`.

### Instance methods inherited from class `IO`

<<(obj : _) : self <<, close close, closed? : Bool closed?, each_byte(&) : Nil
each_byte each_byte, each_char(&) : Nil
each_char each_char, each_line(*args, **options, &block : String -> ) : Nil
each_line(*args, **options) each_line, encoding : String encoding, flush flush, getb_to_end : Bytes getb_to_end, gets(delimiter : Char, limit : Int, chomp = false) : String | Nil
gets(chomp : Bool = true) : String | Nil
gets(limit : Int, chomp : Bool = false) : String | Nil
gets(delimiter : Char, chomp : Bool = false) : String | Nil
gets(delimiter : String, chomp = false) : String | Nil gets, gets_to_end : String gets_to_end, peek : Bytes | Nil peek, pos pos, pos=(value) pos=, print(obj : _) : Nil
print(*objects : _) : Nil print, printf(format_string : String, args : Array | Tuple) : Nil
printf(format_string : String, *args) : Nil printf, puts(string : String) : Nil
puts(obj : _) : Nil
puts : Nil
puts(*objects : _) : Nil puts, read(slice : Bytes) read, read_at(offset, bytesize, & : IO -> ) read_at, read_byte : UInt8 | Nil read_byte, read_bytes(type, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) read_bytes, read_char : Char | Nil read_char, read_fully(slice : Bytes) : Int32 read_fully, read_fully?(slice : Bytes) : Int32 | Nil read_fully?, read_greedy(slice : Bytes) : Int32 read_greedy, read_line(*args, **options) : String read_line, read_string(bytesize : Int) : String read_string, read_utf8(slice : Bytes) : Int32 read_utf8, read_utf8_byte : UInt8 | Nil read_utf8_byte, rewind rewind, seek(offset, whence : Seek = Seek::Set) seek, set_encoding(encoding : String, invalid : Symbol | Nil = nil) : Nil set_encoding, skip(bytes_count : Int) : Nil skip, skip_to_end : Nil skip_to_end, tell tell, tty? : Bool tty?, write(slice : Bytes) : Nil write, write_byte(byte : UInt8) : Nil write_byte, write_bytes(object : _, format : IO::ByteFormat = IO::ByteFormat::SystemEndian) : Nil write_bytes, write_string(slice : Bytes) : Nil write_string, write_utf8(slice : Bytes) : Nil write_utf8

### Class methods inherited from class `IO`

copy(src : IO, dst : IO, limit : Int) : Int64
copy(src : IO, dst : IO) : Int64 copy, pipe(read_blocking : Bool | Nil = nil, write_blocking : Bool | Nil = nil) : Tuple(IO::FileDescriptor, IO::FileDescriptor)
pipe(read_blocking = nil, write_blocking = nil, &) pipe, same_content?(stream1 : IO, stream2 : IO) : Bool same_content?

### Instance methods inherited from class `Reference`

==(other : self)
==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup, hash(hasher) hash, initialize initialize, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference) : Bool
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

### Constructor methods inherited from class `Reference`

new new, unsafe_construct(address : Pointer, *args, **opts) : self unsafe_construct

### Class methods inherited from class `Reference`

pre_initialize(address : Pointer) pre_initialize

### Instance methods inherited from class `Object`

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

from_json(string_or_io : String | IO, root : String)
from_json(string_or_io : String | IO) from_json, from_yaml(string_or_io : String | IO) from_yaml

### Macros inherited from class `Object`

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

##
Constructor Detail

def self.new(capacity : Int = 64) #

Creates an empty, resizeable and writable `IO::Memory` with the given initial capacity for the internal buffer.

    io = IO::Memory.new
    slice = Bytes.new(1)
    io.pos         # => 0
    io.read(slice) # => 0
    slice          # => Bytes[0]

def self.new(string : String) : self #

Creates an `IO::Memory` whose contents are the exact contents of string. The created `IO::Memory` is non-resizeable and non-writable.

The `IO` starts at position zero for reading.

    io = IO::Memory.new "hello"
    io.pos        # => 0
    io.gets(2)    # => "he"
    io.print "hi" # raises IO::Error

def self.new(slice : Bytes, writable = true) #

Creates an `IO::Memory` that will read, and optionally write, from/to the given slice. The created `IO::Memory` is non-resizeable.

The IO starts at position zero for reading.

    slice = Slice.new(6) { |i| ('a'.ord + i).to_u8 }
    io = IO::Memory.new slice, writable: false
    io.pos            # => 0
    io.read(slice)    # => 6
    String.new(slice) # => "abcdef"

def self.new(slice : Bytes, *, writeable writable) : self #

Creates an `IO::Memory` that will read, and optionally write, from/to the given slice. The created `IO::Memory` is non-resizeable.

The IO starts at position zero for reading.

    slice = Slice.new(6) { |i| ('a'.ord + i).to_u8 }
    io = IO::Memory.new slice, writable: false
    io.pos            # => 0
    io.read(slice)    # => 6
    String.new(slice) # => "abcdef"

DEPRECATED Use `IO::Memory.new(Bytes, writable)` instead

##
Instance Method Detail

def buffer : Pointer(UInt8) #

Returns the internal buffer as a `Pointer(UInt8)`.

def bytesize : Int32 #

Same as `#size`.

def clear : Nil #

Clears the internal buffer and resets the position to zero. Raises if this `IO::Memory` is non-resizeable.

    io = IO::Memory.new
    io << "abc"
    io.rewind
    io.gets(1) # => "a"
    io.clear
    io.pos         # => 0
    io.gets_to_end # => ""

    io = IO::Memory.new "hello"
    io.clear # raises IO::Error

def close : Nil #

Closes this `IO`. Further operations on this `IO` will raise an `IO::Error`.

    io = IO::Memory.new "hello"
    io.close
    io.gets_to_end # raises IO::Error (closed stream)

def closed? : Bool #

Determines if this `IO` is closed.

    io = IO::Memory.new "hello"
    io.closed? # => false
    io.close
    io.closed? # => true

def empty? : Bool #

Returns `true` if this `IO::Memory` has no contents.

    io = IO::Memory.new
    io.empty? # => true
    io.print "hello"
    io.empty? # => false

def getb_to_end : Bytes #

Reads the rest of this `IO` data as a writable `Bytes`.

    io = IO::Memory.new Bytes[0, 1, 3, 6, 10, 15]
    io.getb_to_end # => Bytes[0, 1, 3, 6, 10, 15]
    io.getb_to_end # => Bytes[]

def gets_to_end : String #

Reads the rest of this `IO` data as a `String`.

    io = IO::Memory.new "hello world"
    io.gets_to_end # => "hello world"
    io.gets_to_end # => ""

def peek : Bytes #
Description copied from class IO

Peeks into this IO, if possible.

It returns:

- `nil` if this IO isn't peekable at this moment or at all
- an empty slice if it is, but EOF was reached
- a non-empty slice if some data can be peeked

The returned bytes are only valid data until a next call to any method that reads from this IO is invoked.

By default this method returns `nil`, but IO implementations that provide buffering or wrap other IOs should override this method.

def pos : Int32 #

Returns the current position (in bytes) of this `IO`.

    io = IO::Memory.new "hello"
    io.pos     # => 0
    io.gets(2) # => "he"
    io.pos     # => 2

def pos=(value) #

Sets the current position (in bytes) of this `IO`.

    io = IO::Memory.new "hello"
    io.pos = 3
    io.gets # => "lo"

def read(slice : Bytes) : Int32 #

See `IO#read(slice)`.

def read_at(offset, bytesize, & : IO -> ) #

Yields an `IO::Memory` to read a section of this `IO`'s buffer.

During the block duration `self` becomes read-only, so multiple concurrent open are allowed.

def read_byte : UInt8 | Nil #
Description copied from class IO

Reads a single byte from this `IO`. Returns `nil` if there is no more data to read.

    io = IO::Memory.new "a"
    io.read_byte # => 97
    io.read_byte # => nil

def rewind : self #

Rewinds this `IO` to the initial position (zero).

    io = IO::Memory.new "hello"
    io.gets(2) # => "he"
    io.rewind
    io.gets(2) # => "he"

def seek(offset, whence : Seek = Seek::Set) #

Seeks to a given offset (in bytes) according to the whence argument.

    io = IO::Memory.new("abcdef")
    io.gets(3) # => "abc"
    io.seek(1, IO::Seek::Set)
    io.gets(2) # => "bc"
    io.seek(-1, IO::Seek::Current)
    io.gets(1) # => "c"

def size : Int32 #

Returns the total number of bytes in this `IO`.

    io = IO::Memory.new "hello"
    io.size # => 5

def skip_to_end : Nil #
Description copied from class IO

Reads and discards bytes from `self` until there are no more bytes.

def to_s(io : IO) : Nil #

Appends this internal buffer to the given `IO`.

def to_s : String #

Returns a new `String` that contains the contents of the internal buffer.

    io = IO::Memory.new
    io.print 1, 2, 3
    io.to_s # => "123"

def to_slice : Bytes #

Returns the underlying bytes.

    io = IO::Memory.new
    io.print "hello"

    io.to_slice # => Bytes[104, 101, 108, 108, 111]

def write(slice : Bytes) : Nil #

See `IO#write(slice)`. Raises if this `IO::Memory` is non-writable, or if it's non-resizeable and a resize is needed.

def write_byte(byte : UInt8) : Nil #

See `IO#write_byte`. Raises if this `IO::Memory` is non-writable, or if it's non-resizeable and a resize is needed.