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Diffstat (limited to 'include/ruby/internal/arithmetic/st_data_t.h')
| -rw-r--r-- | include/ruby/internal/arithmetic/st_data_t.h | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/include/ruby/internal/arithmetic/st_data_t.h b/include/ruby/internal/arithmetic/st_data_t.h new file mode 100644 index 0000000000..91776b3fce --- /dev/null +++ b/include/ruby/internal/arithmetic/st_data_t.h @@ -0,0 +1,75 @@ +#ifndef RBIMPL_ARITHMERIC_ST_DATA_T_H /*-*-C++-*-vi:se ft=cpp:*/ +#define RBIMPL_ARITHMERIC_ST_DATA_T_H +/** + * @file + * @author Ruby developers <ruby-core@ruby-lang.org> + * @copyright This file is a part of the programming language Ruby. + * Permission is hereby granted, to either redistribute and/or + * modify this file, provided that the conditions mentioned in the + * file COPYING are met. Consult the file for details. + * @warning Symbols prefixed with either `RBIMPL` or `rbimpl` are + * implementation details. Don't take them as canon. They could + * rapidly appear then vanish. The name (path) of this header file + * is also an implementation detail. Do not expect it to persist + * at the place it is now. Developers are free to move it anywhere + * anytime at will. + * @note To ruby-core: remember that this header can be possibly + * 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. + * @brief Arithmetic conversion between C's `st_data_t` and Ruby's. + */ +#include "ruby/internal/arithmetic/fixnum.h" +#include "ruby/internal/arithmetic/long.h" +#include "ruby/internal/attr/artificial.h" +#include "ruby/internal/attr/const.h" +#include "ruby/internal/attr/constexpr.h" +#include "ruby/internal/cast.h" +#include "ruby/internal/value.h" +#include "ruby/assert.h" +#include "ruby/st.h" + +#define ST2FIX RB_ST2FIX /**< @old{RB_ST2FIX} */ +/** @cond INTERNAL_MACRO */ +#define RB_ST2FIX RB_ST2FIX +/** @endcond */ + +RBIMPL_ATTR_CONST_UNLESS_DEBUG() +RBIMPL_ATTR_CONSTEXPR_UNLESS_DEBUG(CXX14) +RBIMPL_ATTR_ARTIFICIAL() +/** + * 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) +{ + SIGNED_VALUE x = RBIMPL_CAST((SIGNED_VALUE)i); + + if (x >= 0) { + x &= RUBY_FIXNUM_MAX; + } + else { + x |= RUBY_FIXNUM_MIN; + } + + RBIMPL_ASSERT_OR_ASSUME(RB_FIXABLE(x)); + unsigned long y = RBIMPL_CAST((unsigned long)x); + return RB_LONG2FIX(RBIMPL_CAST((long)y)); +} + +#endif /* RBIMPL_ARITHMETIC_ST_DATA_T_H */ |