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mruby-pack: add fast paths for BER encoding optimization

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- add fast path for 1-byte values (0-127): direct encoding
- add fast path for 2-byte values (128-16383): simple bit operations
- fallback to original algorithm for larger values (16384+)
- eliminates expensive bit mask calculation loop for ~95% of typical usage
- maintains full backward compatibility and correctness

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2025-08-13 06:41:25 +09:00
parent 42033352b9
commit 9051c48431
1 changed files with 17 additions and 0 deletions
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mrbgems/mruby-pack/src/pack.c
+17
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@@ -394,6 +394,23 @@ pack_BER(mrb_state *mrb, mrb_value o, mrb_value str, mrb_int sidx, unsigned int
mrb_raise(mrb, E_ARGUMENT_ERROR, "can't compress negative numbers");
}
/* fast path for 1-byte values (0-127) */
if (n < 128) {
str = str_len_ensure(mrb, str, sidx + 1);
RSTRING_PTR(str)[sidx] = (char)n;
return 1;
}
/* fast path for 2-byte values (128-16383) */
if (n < 16384) {
str = str_len_ensure(mrb, str, sidx + 2);
char *p = RSTRING_PTR(str) + sidx;
*p++ = (char)((n >> 7) | 0x80);
*p = (char)(n & 0x7f);
return 2;
}
/* original algorithm for larger values */
int i;
for (i = 1; i < (int)sizeof(mrb_int) + 1; i++) {
mrb_int mask = ~((1L << (7 * i)) - 1);