Module: Runar::SDK::ANFInterpreter

Defined in:
lib/runar/sdk/anf_interpreter.rb

Constant Summary collapse

IMPLICIT_PARAMS =

Implicit params injected by the compiler — never required from the caller.

%w[_changePKH _changeAmount _newAmount txPreimage].freeze
MAX_LOOP_ITERATIONS =

Maximum number of iterations allowed for a single loop node.

Bitcoin Script loops (unrolled at compile time) are bounded by script size limits. A count above this threshold in the ANF IR almost certainly indicates a malformed or adversarially crafted artifact rather than a legitimate contract. Capping here prevents the interpreter from hanging or consuming unbounded memory when simulating state transitions.

65_536

Class Method Summary collapse

Class Method Details

.bin2num_int(hex_str) ⇒ Integer

Convert a little-endian sign-magnitude hex string to an integer.

Parameters:

  • hex_str (String)

Returns:

  • (Integer) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 639

def bin2num_int(hex_str)
  return 0 if hex_str.nil? || hex_str.empty?

  result_bytes = hex_str.scan(/../).map { |h| h.to_i(16) }
  return 0 if result_bytes.empty?

  negative = (result_bytes.last & 0x80) != 0
  result_bytes[-1] &= 0x7f

  result = 0
  result_bytes.each_with_index { |b, i| result |= b << (8 * i) }

  negative ? -result : result
end

.compute_new_state(anf, method_name, current_state, args, max_loop_iterations: MAX_LOOP_ITERATIONS) ⇒ Hash

Compute the new state after executing a contract method.

Parameters:

  • anf (Hash) —

    the ANF IR from the compiled artifact (plain Hash from JSON)

  • method_name (String) —

    the method to execute (must be a public method)

  • current_state (Hash) —

    current contract state (property name → value)

  • args (Hash) —

    method arguments (param name → value)

  • max_loop_iterations (Integer) (defaults to: MAX_LOOP_ITERATIONS) —

    optional override for the loop iteration limit

Returns:

  • (Hash) —

    the updated state (merged with current_state)

Raises:

  • (ArgumentError) —

    when method_name is not found as a public method in the ANF IR



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# File 'lib/runar/sdk/anf_interpreter.rb', line 48

def compute_new_state(anf, method_name, current_state, args, max_loop_iterations: MAX_LOOP_ITERATIONS)
  method = find_public_method(anf, method_name)

  unless method
    raise ArgumentError,
          "computeNewState: method '#{method_name}' not found in ANF IR"
  end

  # Store the configurable loop limit for use in eval_value.
  Thread.current[:runar_max_loop_iterations] = max_loop_iterations

  # Initialize environment with property values.
  env = {}
  Array(anf['properties']).each do |prop|
    name = prop['name']
    env[name] = current_state.fetch(name, prop['initialValue'])
  end

  # Load method params, skipping implicit compiler-injected ones.
  Array(method['params']).each do |param|
    pname = param['name']
    next if IMPLICIT_PARAMS.include?(pname)
    next unless args.key?(pname) || args.key?(pname.to_sym)

    env[pname] = args.key?(pname) ? args[pname] : args[pname.to_sym]
  end

  state_delta = {}
  eval_bindings(Array(method['body']), env, state_delta, anf)

  current_state.merge(state_delta)
ensure
  Thread.current[:runar_max_loop_iterations] = nil
end

.eval_bin_op(op, left, right, result_type = nil) ⇒ Object

Evaluate a binary operation on two values.

When result_type is ‘bytes’, or both operands are strings, byte semantics are used. Otherwise numeric (bigint) semantics apply.

rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/MethodLength

Parameters:

  • op (String)
  • left (Object)
  • right (Object)
  • result_type (String, nil) (defaults to: nil)

Returns:

  • (Object) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 218

def eval_bin_op(op, left, right, result_type = nil)
  if result_type == 'bytes' || (left.is_a?(String) && right.is_a?(String))
    return eval_bytes_bin_op(op, (left || '').to_s, (right || '').to_s)
  end

  l = to_int(left)
  r = to_int(right)

  case op
  when '+'  then l + r
  when '-'  then l - r
  when '*'  then l * r
  when '/'  then r == 0 ? 0 : truncate_div(l, r)
  when '%'  then r == 0 ? 0 : truncate_mod(l, r)
  when '==', '===' then l == r
  when '!=', '!==' then l != r
  when '<'  then l < r
  when '<=' then l <= r
  when '>'  then l > r
  when '>=' then l >= r
  when '&&', 'and' then is_truthy(left) && is_truthy(right)
  when '||', 'or'  then is_truthy(left) || is_truthy(right)
  when '&'  then l & r
  when '|'  then l | r
  when '^'  then l ^ r
  when '<<' then l << r
  when '>>' then l >> r
  else 0
  end
end

.eval_bindings(bindings, env, state_delta, anf = nil) ⇒ Object

Walk a list of ANF bindings, updating env with each result.

Parameters:

  • bindings (Array<Hash>) —

    list of { name:, value: } binding nodes

  • env (Hash) —

    current name → value environment (mutated in place)

  • state_delta (Hash) —

    accumulated state mutations (mutated in place)

  • anf (Hash, nil) (defaults to: nil) —

    full ANF IR (for method lookup)



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# File 'lib/runar/sdk/anf_interpreter.rb', line 89

def eval_bindings(bindings, env, state_delta, anf = nil)
  bindings.each do |binding|
    val = eval_value(binding['value'], env, state_delta, anf)
    env[binding['name']] = val
  end
end

.eval_bytes_bin_op(op, left, right) ⇒ Object

Binary op for byte strings (hex-encoded).

Parameters:

  • op (String)
  • left (String)
  • right (String)

Returns:

  • (Object) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 281

def eval_bytes_bin_op(op, left, right)
  case op
  when '+'          then left + right   # concatenation
  when '==', '===' then left == right
  when '!=', '!==' then left != right
  else ''
  end
end

.eval_bytes_unary_op(op, operand) ⇒ Object

Unary op for byte strings.

Parameters:

  • op (String)
  • operand (Object)

Returns:

  • (Object) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 319

def eval_bytes_unary_op(op, operand)
  return operand unless op == '~'

  hex_str = (operand || '').to_s
  [hex_str].pack('H*').bytes.map { |b| (~b) & 0xff }.pack('C*').unpack1('H*')
end

.eval_call(func, args) ⇒ Object

Evaluate a call to a built-in function.

rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/MethodLength, Metrics/PerceivedComplexity

Parameters:

  • func (String)
  • args (Array)

Returns:

  • (Object) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 336

def eval_call(func, args)
  case func
  # Mock crypto — always return true in simulation.
  when 'checkSig', 'checkMultiSig', 'checkPreimage'
    true

  # Real hash functions.
  when 'sha256'   then hash_fn('sha256',   args[0])
  when 'hash256'  then hash_fn('hash256',  args[0])
  when 'hash160'  then hash_fn('hash160',  args[0])
  when 'ripemd160' then hash_fn('ripemd160', args[0])

  # Assert — no-op in simulation.
  when 'assert'
    nil

  # Byte operations.
  when 'num2bin'
    n      = to_int(args[0])
    length = to_int(args[1]).to_i
    num2bin_hex(n, length)

  when 'bin2num'
    bin2num_int((args[0] || '').to_s)

  when 'cat'
    (args[0] || '').to_s + (args[1] || '').to_s

  when 'substr'
    hex_str = (args[0] || '').to_s
    start   = to_int(args[1]).to_i
    length  = to_int(args[2]).to_i
    hex_str[start * 2, length * 2] || ''

  when 'reverseBytes'
    hex_str = (args[0] || '').to_s
    hex_str.scan(/../).reverse.join

  when 'len'
    hex_str = (args[0] || '').to_s
    hex_str.length / 2

  # Math built-ins.
  when 'abs'
    to_int(args[0]).abs

  when 'min'
    [to_int(args[0]), to_int(args[1])].min

  when 'max'
    [to_int(args[0]), to_int(args[1])].max

  when 'within'
    x = to_int(args[0])
    x >= to_int(args[1]) && x < to_int(args[2])

  when 'safediv'
    d = to_int(args[1])
    d == 0 ? 0 : truncate_div(to_int(args[0]), d)

  when 'safemod'
    d = to_int(args[1])
    d == 0 ? 0 : truncate_mod(to_int(args[0]), d)

  when 'clamp'
    v  = to_int(args[0])
    lo = to_int(args[1])
    hi = to_int(args[2])
    v < lo ? lo : v > hi ? hi : v

  when 'sign'
    v = to_int(args[0])
    v > 0 ? 1 : v < 0 ? -1 : 0

  when 'pow'
    base = to_int(args[0])
    exp  = to_int(args[1])
    exp < 0 ? 0 : base**exp

  when 'sqrt'
    v = to_int(args[0])
    integer_sqrt(v)

  when 'gcd'
    a = to_int(args[0]).abs
    b = to_int(args[1]).abs
    a, b = b, a % b while b != 0
    a

  when 'divmod'
    a = to_int(args[0])
    b = to_int(args[1])
    b == 0 ? 0 : truncate_div(a, b)

  when 'log2'
    v = to_int(args[0])
    integer_log2(v)

  when 'bool'
    is_truthy(args[0]) ? 1 : 0

  when 'mulDiv'
    truncate_div(to_int(args[0]) * to_int(args[1]), to_int(args[2]))

  when 'percentOf'
    truncate_div(to_int(args[0]) * to_int(args[1]), 10_000)

  # Preimage intrinsics — return dummy values in simulation.
  when 'extractOutputHash', 'extractAmount'
    '00' * 32

  else
    nil
  end
end

.eval_method_call(_obj, method_name, args, caller_env = nil, state_delta = nil, anf = nil) ⇒ Object

Evaluate a call to a private method defined in the ANF IR.

Creates a new child environment with property values from the caller, maps positional args to the method’s params, evaluates the body, propagates any state mutations back to the caller, and returns the value of the last binding.

Parameters:

  • _obj (Object) —

    receiver (unused — all calls are this-calls)

  • method_name (String, nil)
  • args (Array)
  • caller_env (Hash, nil) (defaults to: nil)
  • state_delta (Hash, nil) (defaults to: nil)
  • anf (Hash, nil) (defaults to: nil)

Returns:

  • (Object) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 471

def eval_method_call(_obj, method_name, args, caller_env = nil, state_delta = nil, anf = nil)
  return nil unless anf && method_name

  private_method = Array(anf['methods']).find do |m|
    m['name'] == method_name && !m['isPublic']
  end

  return nil unless private_method

  # Build a new env seeded with property values from the caller.
  new_env = {}
  if caller_env
    Array(anf['properties']).each do |prop|
      name = prop['name']
      new_env[name] = caller_env[name] if caller_env.key?(name)
    end
  end

  # Map positional args to the method's declared params.
  params = Array(private_method['params'])
  params.each_with_index do |param, i|
    new_env[param['name']] = args[i] if i < args.length
  end

  body = Array(private_method['body'])
  child_delta = {}
  eval_bindings(body, new_env, child_delta, anf)

  # Propagate state mutations back to the caller environment.
  state_delta&.merge!(child_delta)
  if caller_env
    child_delta.each { |k, v| caller_env[k] = v }
  end

  body.empty? ? nil : new_env[body.last['name']]
end

.eval_unary_op(op, operand, result_type = nil) ⇒ Object

Evaluate a unary operation on a value.

Parameters:

  • op (String)
  • operand (Object)
  • result_type (String, nil) (defaults to: nil)

Returns:

  • (Object) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 300

def eval_unary_op(op, operand, result_type = nil)
  if result_type == 'bytes'
    return eval_bytes_unary_op(op, operand)
  end

  val = to_int(operand)
  case op
  when '-'      then -val
  when '!', 'not' then !is_truthy(operand)
  when '~'      then ~val
  else val
  end
end

.eval_value(value, env, state_delta, anf = nil) ⇒ Object

Evaluate a single ANF value node, dispatching on its kind.

rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/MethodLength, Metrics/PerceivedComplexity

Parameters:

  • value (Hash)
  • env (Hash)
  • state_delta (Hash)
  • anf (Hash, nil) (defaults to: nil)

Returns:

  • (Object) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 104

def eval_value(value, env, state_delta, anf = nil)
  kind = value['kind'].to_s

  case kind
  when 'load_param', 'load_prop'
    env[value['name']]

  when 'load_const'
    v = value['value']
    # Handle @ref: aliases — resolve to the named env variable.
    v.is_a?(String) && v.start_with?('@ref:') ? env[v[5..]] : v

  when 'bin_op'
    eval_bin_op(
      value['op'],
      env[value['left']],
      env[value['right']],
      value['result_type']
    )

  when 'unary_op'
    eval_unary_op(
      value['op'],
      env[value['operand']],
      value['result_type']
    )

  when 'call'
    call_args = Array(value['args']).map { |a| env[a] }
    eval_call(value['func'], call_args)

  when 'method_call'
    call_args = Array(value['args']).map { |a| env[a] }
    eval_method_call(env[value['object']], value['method'], call_args, env, state_delta, anf)

  when 'if'
    cond   = env[value['cond']]
    branch = is_truthy(cond) ? value['then'] : value['else']
    child_env = env.dup
    eval_bindings(Array(branch), child_env, state_delta, anf)
    env.merge!(child_env)
    branch && !branch.empty? ? child_env[branch.last['name']] : nil

  when 'loop'
    count    = (value['count'] || 0).to_i
    limit = Thread.current[:runar_max_loop_iterations] || MAX_LOOP_ITERATIONS
    if count > limit
      raise "ANF interpreter: loop count #{count} exceeds maximum of #{limit}"
    end

    body     = Array(value['body'])
    iter_var = value['iterVar'].to_s
    last_val = nil
    count.times do |i|
      env[iter_var] = i
      loop_env = env.dup
      eval_bindings(body, loop_env, state_delta, anf)
      env.merge!(loop_env)
      last_val = body.empty? ? nil : loop_env[body.last['name']]
    end
    last_val

  when 'assert'
    nil

  when 'update_prop'
    new_val = env[value['value']]
    env[value['name']]         = new_val
    state_delta[value['name']] = new_val
    nil

  when 'add_output'
    # Map stateValues to mutable properties in declaration order.
    state_values = Array(value['stateValues'])
    if state_values.any? && anf
      mutable_props = Array(anf['properties'])
        .reject { |p| p['readonly'] }
        .map { |p| p['name'] }
      state_values.each_with_index do |sv, i|
        next if i >= mutable_props.length

        resolved  = env[sv]
        prop_name = mutable_props[i]
        env[prop_name]         = resolved
        state_delta[prop_name] = resolved
      end
    end
    nil

  when 'check_preimage', 'deserialize_state', 'get_state_script', 'add_raw_output'
    # On-chain-only operations — skip in simulation.
    nil

  else
    nil
  end
end

.find_public_method(anf, method_name) ⇒ Hash?

Find a public method by name in the ANF IR.

Parameters:

  • anf (Hash)
  • method_name (String)

Returns:

  • (Hash, nil) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 699

def find_public_method(anf, method_name)
  Array(anf['methods']).find do |m|
    m['name'] == method_name && m['isPublic']
  end
end

.hash_fn(name, input_val) ⇒ String

Compute a named hash function over hex-encoded input.

Parameters:

  • name (String) —

    ‘sha256’, ‘hash256’, ‘ripemd160’, or ‘hash160’

  • input_val (Object) —

    hex-encoded byte string

Returns:

  • (String) —

    hex-encoded digest



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# File 'lib/runar/sdk/anf_interpreter.rb', line 517

def hash_fn(name, input_val)
  hex_str = (input_val || '').to_s
  data    = [hex_str].pack('H*')

  case name
  when 'sha256'   then Digest::SHA256.hexdigest(data)
  when 'hash256'  then Digest::SHA256.hexdigest(Digest::SHA256.digest(data))
  when 'ripemd160' then Digest::RMD160.hexdigest(data)
  when 'hash160'  then Digest::RMD160.hexdigest(Digest::SHA256.digest(data))
  else ''
  end
end

.integer_log2(v) ⇒ Integer

Integer base-2 logarithm (floor).

Parameters:

  • v (Integer)

Returns:

  • (Integer) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 678

def integer_log2(v)
  return 0 if v <= 0

  bits = 0
  x    = v
  while x > 1
    x >>= 1
    bits += 1
  end
  bits
end

.integer_sqrt(v) ⇒ Integer

Integer square root using Newton’s method (matching the Python reference).

Parameters:

  • v (Integer)

Returns:

  • (Integer) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 662

def integer_sqrt(v)
  return 0 if v <= 0

  x = v
  y = (x + 1) / 2
  while y < x
    x = y
    y = (x + v / x) / 2
  end
  x
end

.is_truthy(v) ⇒ Boolean

Determine truthiness of a value using Runar/Bitcoin Script semantics.

Matches on-chain Bitcoin Script OP_IF semantics for truthiness. A value is falsy if it is empty, all-zero bytes, or negative zero (0x80).

Parameters:

  • v (Object)

Returns:



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# File 'lib/runar/sdk/anf_interpreter.rb', line 568

def is_truthy(v) # rubocop:disable Naming/PredicateName
  case v
  when TrueClass  then true
  when FalseClass then false
  when Integer    then v != 0
  when Float      then v != 0.0
  when String
    return false if v.empty?
    return false if v == '0' || v == 'false'
    # Hex-encoded byte string: apply Bitcoin Script semantics
    if v.length.even? && v.match?(/\A[0-9a-fA-F]*\z/)
      bytes = [v].pack('H*').bytes
      return false if bytes.empty?
      # All-zero bytes: falsy (e.g. "00", "0000")
      return false if bytes.all?(&:zero?)
      # Negative zero: all zeros except last byte is 0x80 (e.g. "80", "0080")
      return false if bytes[0...-1].all?(&:zero?) && bytes[-1] == 0x80
    end
    true
  else false
  end
end

.num2bin_hex(n, byte_len) ⇒ String

Convert an integer to a little-endian sign-magnitude hex string.

This matches Bitcoin Script’s num2bin semantics: the sign bit occupies the MSB of the last byte, and the value is padded (or truncated) to the requested byte length.

Parameters:

  • n (Integer)
  • byte_len (Integer)

Returns:

  • (String) —

    hex-encoded bytes (2 * byte_len characters)



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# File 'lib/runar/sdk/anf_interpreter.rb', line 604

def num2bin_hex(n, byte_len)
  return '00' * byte_len if n == 0

  negative = n < 0
  abs_n    = n.abs

  result_bytes = []
  tmp = abs_n
  while tmp > 0
    result_bytes << (tmp & 0xff)
    tmp >>= 8
  end

  # Encode sign bit into the last byte, adding an extra byte if needed.
  if negative
    if (result_bytes.last & 0x80) == 0
      result_bytes[-1] |= 0x80
    else
      result_bytes << 0x80
    end
  else
    result_bytes << 0x00 if (result_bytes.last & 0x80) != 0
  end

  # Pad to requested length, then truncate.
  result_bytes << 0x00 while result_bytes.length < byte_len
  result_bytes = result_bytes[0, byte_len]

  result_bytes.map { |b| format('%02x', b) }.join
end

.to_int(v) ⇒ Integer

Convert any value to an Integer.

Handles Ruby Integer, Float, Boolean, and String (including “42n” BigInt notation from JSON serialization).

Parameters:

  • v (Object)

Returns:

  • (Integer) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 541

def to_int(v)
  case v
  when Integer then v
  when TrueClass  then 1
  when FalseClass then 0
  when Float   then v.to_i
  when String
    # "42n" format from JSON serialized bigints.
    if v.match?(/\A-?\d+n\z/)
      v.chomp('n').to_i
    elsif v.match?(/\A-?\d+\z/)
      v.to_i
    else
      0
    end
  else
    0
  end
end

.truncate_div(a, b) ⇒ Integer

Integer division truncating toward zero (matching JS/Bitcoin semantics).

Ruby’s built-in ‘/` floors toward negative infinity; this matches truncation toward zero used by Bitcoin Script and JavaScript.

Parameters:

  • a (Integer)
  • b (Integer)

Returns:

  • (Integer) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 258

def truncate_div(a, b)
  if (a < 0) != (b < 0) && (a % b != 0)
    (a.to_f / b).truncate
  else
    a / b
  end
end

.truncate_mod(a, b) ⇒ Integer

Modulo matching truncation toward zero.

Parameters:

  • a (Integer)
  • b (Integer)

Returns:

  • (Integer) 


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# File 'lib/runar/sdk/anf_interpreter.rb', line 271

def truncate_mod(a, b)
  a - truncate_div(a, b) * b
end