From 534bd7d868b589ed1c70c181e1fa996611b15aea Mon Sep 17 00:00:00 2001
From: makoto kuwata <kwa@kuwata-lab.com>
Date: Mon, 27 Sep 2010 06:27:48 +0900
Subject: [PATCH 1/2] add Kernel#called_from() which is similar to caller()

* See comment of rb_f_called_from() on vm_eval.c for details.
---
 vm.c      |   23 +++++++++++++++++++++++
 vm_eval.c |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 0 deletions(-)

diff --git a/vm.c b/vm.c
index cfc9312..b854f76 100644
--- a/vm.c
+++ b/vm.c
@@ -748,6 +748,29 @@ vm_backtrace_each(rb_thread_t *th, int lev, void (*init)(void *), rb_backtrace_i
     return TRUE;
 }
 
+static VALUE
+vm_backtrace_get_location(rb_thread_t *th, int lev)
+{
+    const rb_control_frame_t *limit_cfp = th->cfp;
+    const rb_control_frame_t *cfp = (void *)(th->stack + th->stack_size);
+    int line_no;
+    VALUE filename, name;
+
+    cfp -= 2;
+    while (lev-- >= 0) {
+	if (++limit_cfp > cfp) {
+	    return Qnil;
+	}
+    }
+    if (limit_cfp->iseq == NULL) {
+	return Qnil;
+    }
+    line_no  = rb_vm_get_sourceline(limit_cfp);
+    filename = limit_cfp->iseq->filename;
+    name     = limit_cfp->iseq->name;
+    return rb_ary_new3(3, filename, line_no ? INT2NUM(line_no) : Qnil, name);
+}
+
 static void
 vm_backtrace_alloc(void *arg)
 {
diff --git a/vm_eval.c b/vm_eval.c
index 4137189..90b6195 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -18,6 +18,7 @@ static inline VALUE vm_yield(rb_thread_t *th, int argc, const VALUE *argv);
 static inline VALUE vm_backtrace(rb_thread_t *th, int lev);
 static int vm_backtrace_each(rb_thread_t *th, int lev, void (*init)(void *), rb_backtrace_iter_func *iter, void *arg);
 static NODE *vm_cref_push(rb_thread_t *th, VALUE klass, int noex, rb_block_t *blockptr);
+static VALUE vm_backtrace_get_location(rb_thread_t *th, int lev);
 static VALUE vm_exec(rb_thread_t *th);
 static void vm_set_eval_stack(rb_thread_t * th, VALUE iseqval, const NODE *cref);
 static int vm_collect_local_variables_in_heap(rb_thread_t *th, VALUE *dfp, VALUE ary);
@@ -1583,6 +1584,50 @@ rb_f_caller(int argc, VALUE *argv)
     return vm_backtrace(GET_THREAD(), lev);
 }
 
+/*
+ *  call-seq:
+ *     called_from(start=1)    -> array or nil
+ *
+ *  Returns file name, line number, and method name of the stack.
+ *  The optional _start_ parameter represents the number of stack
+ *  entries to skip.
+ *
+ *  Returns +nil+ if _start_ is greater than the size of
+ *  current execution stack.
+ *
+ *  Raises ArgumentError if _start_ is negative value.
+ *
+ *     # example.rb
+ *      1:  def f1()
+ *      2:    f2()
+ *      3:  end
+ *      4:  def f2()
+ *      5:    f3()
+ *      6:  end
+ *      7:  def f3()
+ *      8:    p called_from()    #=> ["example.rb", 5, "f2"]
+ *      9:    p called_from(0)   #=> ["example.rb", 9, "f3"]
+ *     10:    p called_from(1)   #=> ["example.rb", 5, "f2"]
+ *     11:    p called_from(2)   #=> ["example.rb", 2, "f1"]
+ *     12:    p called_from(3)   #=> ["example.rb", 15, "<main>"]
+ *     13:    p called_from(4)   #=> nil
+ *     14:  end
+ *     15:  f1()
+ */
+static VALUE
+rb_f_called_from(int argc, VALUE *argv)
+{
+    VALUE level;
+    int lev;
+    VALUE ary = Qnil;
+
+    rb_scan_args(argc, argv, "01", &level);
+    lev = NIL_P(level) ? 1 : NUM2INT(level);
+    if (lev < 0) rb_raise(rb_eArgError, "negative level (%d)", lev);
+
+    return vm_backtrace_get_location(GET_THREAD(), lev);
+}
+
 static int
 print_backtrace(void *arg, VALUE file, int line, VALUE method)
 {
@@ -1774,5 +1819,6 @@ Init_vm_eval(void)
     rb_define_method(rb_cModule, "class_eval", rb_mod_module_eval, -1);
 
     rb_define_global_function("caller", rb_f_caller, -1);
+    rb_define_global_function("called_from", rb_f_called_from, -1);
 }
 
-- 
1.7.2.3