diff options
Diffstat (limited to 'include/ruby/internal/arithmetic/st_data_t.h')
| -rw-r--r-- | include/ruby/internal/arithmetic/st_data_t.h | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/include/ruby/internal/arithmetic/st_data_t.h b/include/ruby/internal/arithmetic/st_data_t.h index 93a5ccb7a1..3bff4ffc0b 100644 --- a/include/ruby/internal/arithmetic/st_data_t.h +++ b/include/ruby/internal/arithmetic/st_data_t.h @@ -17,7 +17,7 @@ * recursively included from extension libraries written in C++. * Do not expect for instance `__VA_ARGS__` is always available. * We assume C99 for ruby itself but we don't assume languages of - * extension libraries. They could be written in C++98. + * extension libraries. They could be written in C++98. * @brief Arithmetic conversion between C's `st_data_t` and Ruby's. */ #include "ruby/internal/arithmetic/fixnum.h" @@ -30,7 +30,7 @@ #include "ruby/assert.h" #include "ruby/st.h" -#define ST2FIX RB_ST2FIX +#define ST2FIX RB_ST2FIX /**< @old{RB_ST2FIX} */ /** @cond INTERNAL_MACRO */ #define RB_ST2FIX RB_ST2FIX /** @endcond */ @@ -38,7 +38,23 @@ RBIMPL_ATTR_CONST_UNLESS_DEBUG() RBIMPL_ATTR_CONSTEXPR_UNLESS_DEBUG(CXX14) RBIMPL_ATTR_ARTIFICIAL() -/* See also [ruby-core:84395] [Bug #14218] [ruby-core:82687] [Bug #13877] */ +/** + * Converts a C's `st_data_t` into an instance of ::rb_cInteger. + * + * @param[in] i The data in question. + * @return A converted result + * @warning THIS CONVERSION LOSES DATA! Be warned. + * @see https://bugs.ruby-lang.org/issues/13877 + * @see https://bugs.ruby-lang.org/issues/14218 + * + * @internal + * + * This is needed because of hash functions. Hash functions return + * `st_data_t`, which could theoretically be bigger than Fixnums. However + * allocating Bignums for them every time we calculate hash values is just too + * heavy. To avoid penalty we need to ignore some upper bit(s) and stick to + * Fixnums. This function is used for that purpose. + */ static inline VALUE RB_ST2FIX(st_data_t i) { @@ -56,4 +72,4 @@ RB_ST2FIX(st_data_t i) return RB_LONG2FIX(y); } -#endif /* RBIMPL_ARITHMERIC_ST_DATA_T_H */ +#endif /* RBIMPL_ARITHMETIC_ST_DATA_T_H */ |