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Use RBasic padding for embedded string on 64-bit CPU

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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.
This commit is contained in:
KOBAYASHI Shuji
2019-08-20 18:49:55 +09:00
parent b836fd05dd
commit 8157672a29
4 changed files with 15 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/mruby/string.h
+8 -3
View File
@@ -16,7 +16,8 @@ MRB_BEGIN_DECL
extern const char mrb_digitmap[];
#define RSTRING_EMBED_LEN_MAX ((mrb_int)(sizeof(void*) * 3 - 1))
#define RSTRING_EMBED_LEN_MAX \
((mrb_int)(sizeof(void*) * 3 + sizeof(void*) - 32 / CHAR_BIT - 1))
struct RString {
MRB_OBJECT_HEADER;
@@ -30,9 +31,12 @@ struct RString {
} aux;
char *ptr;
} heap;
char ary[RSTRING_EMBED_LEN_MAX + 1];
} as;
};
struct RStringEmbed {
MRB_OBJECT_HEADER;
char ary[];
};
#define RSTR_SET_TYPE_FLAG(s, type) (RSTR_UNSET_TYPE_FLAG(s), (s)->flags |= MRB_STR_##type)
#define RSTR_UNSET_TYPE_FLAG(s) ((s)->flags &= ~(MRB_STR_TYPE_MASK|MRB_STR_EMBED_LEN_MASK))
@@ -53,11 +57,12 @@ struct RString {
(s)->as.heap.len = (mrb_int)(n);\
}\
} while (0)
#define RSTR_EMBED_PTR(s) (((struct RStringEmbed*)(s))->ary)
#define RSTR_EMBED_LEN(s)\
(mrb_int)(((s)->flags & MRB_STR_EMBED_LEN_MASK) >> MRB_STR_EMBED_LEN_SHIFT)
#define RSTR_EMBEDDABLE_P(len) ((len) <= RSTRING_EMBED_LEN_MAX)
#define RSTR_PTR(s) ((RSTR_EMBED_P(s)) ? (s)->as.ary : (s)->as.heap.ptr)
#define RSTR_PTR(s) ((RSTR_EMBED_P(s)) ? RSTR_EMBED_PTR(s) : (s)->as.heap.ptr)
#define RSTR_LEN(s) ((RSTR_EMBED_P(s)) ? RSTR_EMBED_LEN(s) : (s)->as.heap.len)
#define RSTR_CAPA(s) (RSTR_EMBED_P(s) ? RSTRING_EMBED_LEN_MAX : (s)->as.heap.aux.capa)