Prioritize embedded string in the following functions:
- `str_new_static`
- `str_new`
- `mrb_str_new_capa`
- `mrb_str_pool`
The reasons are as follows:
- Consistency with `mrb_str_byte_subseq` and `str_replace`.
- Memory locality increases and may be slightly faster.
- No conversion cost to embedded string when modifying the string.
On 64-bit CPU, there is padding in `RBasic`, so reorder the fields and use
it as buffer of embedded string. This change allows 4 more bytes to be
embedded on 64-bit CPU.
However, an incompatibility will occur if `RString::as::ary` is accessed
directly because `RString` structure has changed.
- `mrb_str_index_m()` and `mrb_str_rindex()`
Make `mrb_get_args()` called only once from called twice.
- `mrb_str_byteslice()`
Replace `goto` with `if ~ else`.
Previously `String#rindex` returned the wrong index when given an
invalid UTF-8 string.
```terminal
% ruby26 -e 'str = "\xf0☀\xf1☁\xf2☂\xf3☃\xf0☀\xf1☁\xf2☂\xf3☃"; p str.rindex("☁")'
11
% ./mruby-head -e 'str = "\xf0☀\xf1☁\xf2☂\xf3☃\xf0☀\xf1☁\xf2☂\xf3☃"; p str.rindex("☁")'
nil
% ./mruby-patched -e 'str = "\xf0☀\xf1☁\xf2☂\xf3☃\xf0☀\xf1☁\xf2☂\xf3☃"; p str.rindex("☁")'
11
```
I think the string buffer of NOFREE string always exists and does not need
to be released, so it can be shared as another NOFREE string.
Also changed the `mrb_shared_string` field order so that eliminate padding if
`int` and `mrb_int` sizes are less than pointer size.
But this changes requires `OP_ARYCAT` and `OP_ARYPUSH` to accept `nil`
as their first operand. Alternative VMs (e.g. `mruby/c`) that understand
mruby bytecode need to be updated.
`mrb_string_value_cstr` and `mrb_string_value_len`: obsolete
`mrb_string_cstr`: new function to retrieve NULL terminated C string
`RSTRING_CSTR`: wrapper macro of `mrb_string_cstr`
The binary sizes (gems are only `mruby-bin-mruby`) are reduced slightly in
my environment than before the introduction of new specifiers/modifiers
(5116789a) with this change.
------------+-------------------+-------------------+--------
BINARY | BEFORE (5116789a) | AFTER (This PR) | RATIO
------------+-------------------+-------------------+--------
mruby | 593416 bytes | 593208 bytes | -0.04%
libmruby.a | 769048 bytes | 767264 bytes | -0.23%
------------+-------------------+-------------------+--------
BTW, I accidentally changed `tasks/toolchains/visualcpp.rake` at #4613,
so I put it back.
- `size_t` is more commonly used.
- `len` argument of `mrb_str_new()` is `size_t`.
NOTE:
The test for `%l` is temporarily disabled because adding a new type to
`mrbgems/mruby-test/vformat.c` causes an error (memory error?) on Visual
Studio 2017 in AppVeyor.
It potentially not work when `mrb_float` is `float` because `float` variable
in variable length arguments is promoted to `double`.
Also I fixed build with `MRB_WITHOUT_FLOAT`.
It potentially breaks, for example, in the case of `mrb_int` is 64-bit
and more smaller type is passed by `%d`. In fact, the problem could
become apparent when I used `%d` to `backtrace_location::lineno` in
`src/backtrace.c:mrb_unpack_backtrace()` on AppVeyor.
Therefore, change `%d` for `int` (not `mrb_int`) so that it can be
used mostly without casting.
Format sequence syntax:
%[modifier]specifier
Modifiers:
----------+------------------------------------------------------------
Modifier | Meaning
----------+------------------------------------------------------------
! | Convert to string by corresponding `inspect` instead of
| corresponding `to_s`.
----------+------------------------------------------------------------
Specifiers:
----------+----------------+--------------------------------------------
Specifier | Argument Type | Note
----------+----------------+--------------------------------------------
c | char |
d,i | mrb_int |
f | mrb_float |
l | char*, mrb_int | Arguments are string and length.
n | mrb_sym |
s | char* | Argument is NUL terminated string.
t | mrb_value | Convert to type (class) of object.
v,S | mrb_value |
C | struct RClass* |
T | mrb_value | Convert to real type (class) of object.
Y | mrb_value | Same as `!v` if argument is `true`, `false`
| | or `nil`, otherwise same as `T`.
% | - | Convert to percent sign itself (no argument
| | taken).
----------+----------------+--------------------------------------------
This change will increase the binary size, but replacing all format strings
with new specifiers/modifiers will decrease the size because it reduces
inline expansion of `mrb_obj_value()`, etc. at the caller.
David Siaw