Class: SyntaxTree::YARV::Once

Inherits:
Instruction show all
Defined in:
lib/syntax_tree/yarv/instructions.rb

Overview

### Summary

‘once` is an instruction that wraps an instruction sequence and ensures that is it only ever executed once for the lifetime of the program. It uses a cache to ensure that it is only executed once. It pushes the result of running the instruction sequence onto the stack.

### Usage

~~~ruby END { puts “END” } ~~~

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Instruction

#branch_targets, #canonical, #falls_through?, #leaves?, #pops, #side_effects?

Constructor Details

#initialize(iseq, cache) ⇒ Once

Returns a new instance of Once.



2618
2619
2620
2621
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2618

def initialize(iseq, cache)
  @iseq = iseq
  @cache = cache
end

Instance Attribute Details

#cache ⇒ Object (readonly)

Returns the value of attribute cache.



2616
2617
2618
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2616

def cache
  @cache
end

#iseq ⇒ Object (readonly)

Returns the value of attribute iseq.



2616
2617
2618
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2616

def iseq
  @iseq
end

Instance Method Details

#==(other) ⇒ Object 



2636
2637
2638
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2636

def ==(other)
  other.is_a?(Once) && other.iseq == iseq && other.cache == cache
end

#call(vm) ⇒ Object 



2648
2649
2650
2651
2652
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2648

def call(vm)
  return if @executed
  vm.push(vm.run_block_frame(iseq, vm.frame))
  @executed = true
end

#deconstruct_keys(_keys) ⇒ Object 



2632
2633
2634
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2632

def deconstruct_keys(_keys)
  { iseq: iseq, cache: cache }
end

#disasm(fmt) ⇒ Object 



2623
2624
2625
2626
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2623

def disasm(fmt)
  fmt.enqueue(iseq)
  fmt.instruction("once", [iseq.name, fmt.inline_storage(cache)])
end

#length ⇒ Object 



2640
2641
2642
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2640

def length
  3
end

#pushes ⇒ Object 



2644
2645
2646
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2644

def pushes
  1
end

#to_a(_iseq) ⇒ Object 



2628
2629
2630
 
# File 'lib/syntax_tree/yarv/instructions.rb', line 2628

def to_a(_iseq)
  [:once, iseq.to_a, cache]
end