Class: Store::Digest::ReadWrapper

Inherits:
Object
  • Object
show all
Defined in:
lib/store/digest/readwrapper.rb

Overview

This class is an attempt to normalize input so that it can be #read like an IO handle. Use the class method ReadWrapper.coerce to determine if it's even necessary.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(obj) ⇒ ReadWrapper

Initialize a wrapper.

Parameters:

  • obj (#call, #each) —

    a suitable object

Raises:

  • (ArgumentError) —

    said object is unsuitable



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# File 'lib/store/digest/readwrapper.rb', line 101

def initialize obj
  test = obj.respond_to?(:arity) ? obj :
    obj.respond_to?(:call) ? obj.method(:call) : nil

  if test
    raise ArgumentError,
      'Callable object is expected to take a write handle as an argument' if
      test.arity == 0
  elsif obj.respond_to?(:each)
    nil
  elsif obj.respond_to? :to_s
    obj = [obj.to_s]
  else
    raise ArgumentError,
      'Argument must respond to #call(write_fh) or #each or #to_s'
  end

  @done  = false
  @mutex = Mutex.new

  @read, @write = IO.pipe

  @thread = Thread.new do
    if obj.respond_to? :call
      obj.call @write
    else
      obj.each { |x| @write << x.to_s.b }
    end
  rescue Errno::EPIPE # => e
    nil # not sure if we do anything here
  ensure
    @write.close unless @write.closed?
  end
end

Class Method Details

.coerce(obj, thunk: false) ⇒ ReadWrapper, Object Also known as: []

Attempt to coerce a suitable object or no-op.

Parameters:

  • obj (Object) —

    an object to be coerced

  • thunk (false, true) (defaults to: false) —

    let a thunk (a zero-arity callable that in this case returns a read handle) pass through; if falsy, it will execute the thunk and expect it to return something that quacks like a read handle, and throw an error if it isn't.

Returns:

  • (ReadWrapper, Object) —

    a new proxy object around whatever the input is, or the original input if file-handle-ey enough

Raises:

  • (ArgumentError) —

    if the input is not sufficiently coercible



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# File 'lib/store/digest/readwrapper.rb', line 65

def self.coerce obj, thunk: false
  return obj if [self, Store::Digest::Entry].any? { |c| obj.is_a? c }

  return obj.open('rb') if obj.is_a? Pathname

  return obj if quacks? obj # no need for this if it can read

  return StringIO.new(obj) if obj.is_a? String

  # response bodies /don't do this but other stuff does
  if obj.respond_to?(:arity) && obj.arity == 0 ||
      obj.respond_to?(:call) && obj.method(:call).arity == 0
    # let the thunk through
    return obj if thunk

    out = obj.call
    raise ArgumentError,
      'a `call` with no arguments must return an IO-like object' unless
      quacks? out

    return out
  end

  new obj
end

.quacks?(obj) ⇒ false, true

Test if the object quacks like an IO.

Parameters:

  • obj (Object) —

    said object

Returns:

  • (false, true) 


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# File 'lib/store/digest/readwrapper.rb', line 20

def self.quacks? obj
  obj.is_a?(IO) or %i[gets read close].all? do |m|
    obj.respond_to? m
  end
end

Instance Method Details

#close ⇒ Object

close for parity with IO



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# File 'lib/store/digest/readwrapper.rb', line 167

def close
  cleanup
  nil # close returns nil
end

#gets(sep = $/, chomp = false) ⇒ String?

gets for parity with IO

Returns:

  • (String, nil) 


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# File 'lib/store/digest/readwrapper.rb', line 140

def gets sep = $/, chomp = false
  unless @read.closed?
    out = @read.gets sep, chomp
    cleanup if out.nil?

    out
  end
end

#read(maxlen = nil, string = nil) ⇒ String?

read for parity with IO

Parameters:

  • maxlen (Integer) (defaults to: nil) —

    the length to read

  • string (String) (defaults to: nil) —

    an optional string

Returns:

  • (String, nil) 


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# File 'lib/store/digest/readwrapper.rb', line 156

def read maxlen = nil, string = nil
  unless @read.closed?
    out = @read.read maxlen, string
    cleanup if out.nil?

    out
  end
end