edit

Binding#remove_local_variable

drbrain | Fri, 24 Apr 2009 00:29:07 GMT

Posted in Misc, Ruby

require 'rubygems'
require 'inline'

class Binding
  inline do |builder|
    builder.include '"node.h"'
    builder.include '"env.h"'

    ##
    # struct BLOCK isn't in any header, so include it here.

    builder.prefix <<-C
struct BLOCK {
  NODE *var;
  NODE *body;
  VALUE self;
  struct FRAME frame;
  struct SCOPE *scope;
  VALUE klass;
  NODE *cref;
  int iter;
  int vmode;
  int flags;
  int uniq;
  struct RVarmap *dyna_vars;
  VALUE orig_thread;
  VALUE wrapper;
  VALUE block_obj;
  struct BLOCK *outer;
  struct BLOCK *prev;
};
    C

    ##
    # :method: remove_local_variable
    #
    # Removes the local variable +name+ and replaces it with nil.
    #
    # Ordinarily if a local variable didn't exist it would raise
    # NoMethodError, but currently after #remove_local_variable it doesn't, it
    # just returns nil.
    #
    # In order to make this behave correctly, block->body would need to be
    # walked, duping nodes (so as not to affect future invocations of this
    # method) and replacing the LVAR nodes with VCALL nodes.
    #
    # That's just too much work for 17:15, though.  Maybe tomorrow.

    builder.c <<-C
VALUE remove_local_variable(VALUE name) {
  struct BLOCK *block;
  struct SCOPE *scope;
  ID name_id;
  ID *local_table;
  int i, n;
  VALUE entry;

  name_id = SYM2ID(name);

  Data_Get_Struct(self, struct BLOCK, block);

  scope = block->scope;
  local_table = scope->local_tbl;

  if (local_table) {
    n = *local_table++;
    for (i = 2; i < n; i++) { /* skip $_ and $~ */
      if (!rb_is_local_id(local_table[i])) continue; /* skip flip states */
      if (local_table[i] == name_id) {
        entry = scope->local_vars[i];
        local_table[i] = (ID)NULL;
        scope->local_vars[i] = Qnil;
        return entry;
      }
    }
  }

  return Qnil;
}
    C
    
  end
end

a = :my_value

p :lvar_a => a

b = binding
p :remove_local_variable_says => b.remove_local_variable(:a)

p :lvar_a => a # TODO raise exception

comments

Comments