debug.c: new debug line information format `mrb_debug_line_packed_map`.

It uses BER number compression of delta of instruction positions and line
numbers. BER compression is a variable length number representation.

* `mrb_debug_line_ary`: array of line numbers represented in `uint16_t`.
  `[lineno, lineno, ...]`

* `mrb_debug_line_flat_map`: array of `mrb_irep_debug_info_line`, which
  is `struct {uint32_t pos; uint16_t lineno}`, for each line.

* `mrb_debug_line_packed_map` [new]: sequence of BER compressed 2
  numbers, `pos_delta, lineno_delta`. Deltas are differences from
  previous values (starting `0`). `line_entry_counts` represents total
  length of a packed map string for this type.

1 files changed, 4 insertions, 2 deletions

diff --git a/include/mruby/debug.h b/include/mruby/debug.h
index 2062a9308..2e6898e39 100644
--- a/include/mruby/debug.h
+++ b/include/mruby/debug.h
@@ -16,7 +16,8 @@ MRB_BEGIN_DECL
 
 typedef enum mrb_debug_line_type {
   mrb_debug_line_ary = 0,
-  mrb_debug_line_flat_map = 1
+  mrb_debug_line_flat_map,
+  mrb_debug_line_packed_map
 } mrb_debug_line_type;
 
 typedef struct mrb_irep_debug_info_line {
@@ -31,8 +32,9 @@ typedef struct mrb_irep_debug_info_file {
   mrb_debug_line_type line_type;
   union {
     void *ptr;
-    mrb_irep_debug_info_line *flat_map;
     uint16_t *ary;
+    mrb_irep_debug_info_line *flat_map;
+    char *packed_map;
   } lines;
 } mrb_irep_debug_info_file;