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[meta] Add hb_conditional<> and hb_is_convertible()

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This commit is contained in:
Behdad Esfahbod 2019-05-09 14:35:15 -07:00
parent 5e3cbed048
commit 70a49f2e4a
3 changed files with 121 additions and 11 deletions
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6
src/Makefile.am
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@ -384,7 +384,7 @@ dump_use_data_SOURCES = dump-use-data.cc hb-ot-shape-complex-use-table.cc
dump_use_data_CPPFLAGS = $(HBCFLAGS)
dump_use_data_LDADD = libharfbuzz.la $(HBLIBS)
COMPILED_TESTS = test-algs test-iter test-ot-tag test-unicode-ranges
COMPILED_TESTS = test-algs test-iter test-meta test-ot-tag test-unicode-ranges
COMPILED_TESTS_CPPFLAGS = $(HBCFLAGS) -DMAIN -UNDEBUG
COMPILED_TESTS_LDADD = libharfbuzz.la $(HBLIBS)
check_PROGRAMS += $(COMPILED_TESTS)
@ -398,6 +398,10 @@ test_iter_SOURCES = test-iter.cc hb-static.cc
test_iter_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
test_iter_LDADD = $(COMPILED_TESTS_LDADD)
test_meta_SOURCES = test-meta.cc hb-static.cc
test_meta_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
test_meta_LDADD = $(COMPILED_TESTS_LDADD)
test_ot_tag_SOURCES = hb-ot-tag.cc
test_ot_tag_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
test_ot_tag_LDADD = $(COMPILED_TESTS_LDADD)

56
src/hb-meta.hh
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@ -52,6 +52,18 @@ typedef hb_bool_tt<true> hb_true_t;
typedef hb_bool_tt<false> hb_false_t;
/* Basic type SFINAE. */
template <bool B, typename T = void> struct hb_enable_if {};
template <typename T> struct hb_enable_if<true, T> { typedef T type; };
#define hb_enable_if(Cond) typename hb_enable_if<(Cond)>::type* = nullptr
/* Concepts/Requires alias: */
#define hb_requires(Cond) hb_enable_if((Cond))
template <typename T, typename T2> struct hb_is_same : hb_false_t {};
template <typename T> struct hb_is_same<T, T> : hb_true_t {};
#define hb_is_same(T, T2) hb_is_same<T, T2>::value
/* Function overloading SFINAE and priority. */
#define HB_RETURN(Ret, E) -> hb_head_tt<Ret, decltype ((E))> { return (E); }
@ -110,6 +122,40 @@ template <typename T> using hb_decay = hb_remove_const<hb_remove_reference<T>>;
hb_is_reference (A) >= hb_is_reference (B))
template<bool B, class T, class F>
struct _hb_conditional { typedef T type; };
template<class T, class F>
struct _hb_conditional<false, T, F> { typedef F type; };
template<bool B, class T, class F>
using hb_conditional = typename _hb_conditional<B, T, F>::type;
template <typename From, typename To>
struct hb_is_convertible
{
private:
static constexpr bool from_void = hb_is_same (void, hb_decay<From>);
static constexpr bool to_void = hb_is_same (void, hb_decay<To> );
static constexpr bool either_void = from_void || to_void;
static constexpr bool both_void = from_void && to_void;
static hb_true_t impl2 (hb_conditional<to_void, int, To>);
template <typename T>
static auto impl (hb_priority<1>) HB_AUTO_RETURN ( impl2 (hb_declval (T)) )
template <typename T>
static hb_false_t impl (hb_priority<0>);
public:
static constexpr bool value = both_void ||
(!either_void &&
decltype (impl<hb_conditional<from_void, int, From>> (hb_prioritize))::value);
};
#define hb_is_convertible(From,To) hb_is_convertible<From, To>::value
/* std::move and std::forward */
template <typename T>
@ -162,16 +208,6 @@ struct hb_reference_wrapper<T&>
};
template <bool B, typename T = void> struct hb_enable_if {};
template <typename T> struct hb_enable_if<true, T> { typedef T type; };
#define hb_enable_if(Cond) typename hb_enable_if<(Cond)>::type* = nullptr
/* Concepts/Requires alias: */
#define hb_requires(Cond) hb_enable_if((Cond))
template <typename T, typename T2> struct hb_is_same : hb_false_t {};
template <typename T> struct hb_is_same<T, T> : hb_true_t {};
#define hb_is_same(T, T2) hb_is_same<T, T2>::value
template <typename T> struct hb_is_signed;
template <> struct hb_is_signed<char> { static constexpr bool value = CHAR_MIN < 0; };
template <> struct hb_is_signed<signed char> { static constexpr bool value = true; };

70
src/test-meta.cc Normal file
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@ -0,0 +1,70 @@
/*
* Copyright © 2019 Facebook, Inc.
*
* This is part of HarfBuzz, a text shaping library.
*
* Permission is hereby granted, without written agreement and without
* license or royalty fees, to use, copy, modify, and distribute this
* software and its documentation for any purpose, provided that the
* above copyright notice and the following two paragraphs appear in
* all copies of this software.
*
* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*
* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
* Facebook Author(s): Behdad Esfahbod
*/
#include "hb.hh"
#include "hb-meta.hh"
int
main (int argc, char **argv)
{
static_assert (hb_is_convertible (void, void));
static_assert (hb_is_convertible (void, const void));
static_assert (hb_is_convertible (const void, void));
static_assert (hb_is_convertible (int, int));
static_assert (hb_is_convertible (char, int));
static_assert (hb_is_convertible (long, int));
static_assert (hb_is_convertible (int, int));
static_assert (hb_is_convertible (const int, int));
static_assert (hb_is_convertible (int, const int));
static_assert (hb_is_convertible (const int, const int));
static_assert (hb_is_convertible (int&, int));
static_assert (!hb_is_convertible (int, int&));
static_assert (hb_is_convertible (int, const int&));
static_assert (!hb_is_convertible (const int, int&));
static_assert (hb_is_convertible (const int, const int&));
static_assert (hb_is_convertible (int&, const int));
static_assert (hb_is_convertible (const int&, int));
static_assert (hb_is_convertible (const int&, const int));
static_assert (hb_is_convertible (int&, long));
static_assert (!hb_is_convertible (int&, long&));
static_assert (hb_is_convertible (int *, int *));
static_assert (hb_is_convertible (int *, const int *));
static_assert (!hb_is_convertible (const int *, int *));
static_assert (!hb_is_convertible (int *, long *));
static_assert (hb_is_convertible (int *, void *));
static_assert (!hb_is_convertible (void *, int *));
return 0;
}