string_view: implement access API and port libcxx tests

[KFilipek]

• string_view: add string_view access API libcxx tests
• string_view: implement access API
• string_view: port LIBCXX access tests to use pmem::obj::string_view

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This change is 

[igchor]

Reviewed 7 of 7 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[codecov]

Codecov Report

Merging #938 into master will decrease coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #938      +/-   ##
==========================================
- Coverage   96.07%   95.98%   -0.10%     
==========================================
  Files          48       48              
  Lines        6122     6134      +12     
==========================================
+ Hits         5882     5888       +6     
- Misses        240      246       +6     

Flag	Coverage Δ
#tests_clang_debug_cpp17	95.94% <ø> (-0.09%)	⬇️
#tests_gcc_debug	92.37% <100.00%> (-0.19%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
include/libpmemobj++/string_view.hpp	100.00% <100.00%> (ø)
include/libpmemobj++/condition_variable.hpp	73.80% <0.00%> (-4.77%)	⬇️
...j++/container/detail/concurrent_skip_list_impl.hpp	97.99% <0.00%> (-0.27%)	⬇️
...ude/libpmemobj++/container/concurrent_hash_map.hpp	93.76% <0.00%> (-0.21%)	⬇️

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[lukaszstolarczuk]

Reviewed 6 of 7 files at r1, 1 of 1 files at r2.
Reviewable status: all files reviewed, 9 unresolved discussions (waiting on @KFilipek)

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include/libpmemobj++/string_view.hpp, line 166 at r2 (raw file):

 * Returns count of characters stored in this pmem::obj::string_view data.
 *
 * @return pointer to C-like string (char *), it may not end with null

returns pointer to c-like string? (here and above)

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include/libpmemobj++/string_view.hpp, line 206 at r2 (raw file):

/**
 * Returns reference to a last character in the view.

to the last char

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include/libpmemobj++/string_view.hpp, line 219 at r2 (raw file):

/**
 * Returns reference to a first character in the view.

.

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include/libpmemobj++/string_view.hpp, line 220 at r2 (raw file):

/**
 * Returns reference to a first character in the view.
 *

perhaps also worth mention what if empty() == true

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tests/external/libcxx/string.view/string.view.access/at.pass.cpp, line 37 at r2 (raw file):

	}

#ifndef TEST_HAS_NO_EXCEPTIONS

I know it's ported from libcxx, but I'd remove this if. We throw exceptions in at and if we ever change it, this test will just fail... which is good, I guess

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tests/external/libcxx/string.view/string.view.access/back.pass.cpp, line 55 at r2 (raw file):

	{
		constexpr pmem::obj::basic_string_view<char> sv("ABC", 2);
		static_assert(sv.length() == 2, "");

why not UT_ASSERT?

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tests/external/libcxx/string.view/string.view.access/data.pass.cpp, line 49 at r2 (raw file):

		constexpr const char *s = "ABC";
		constexpr pmem::obj::basic_string_view<char> sv(s, 2);
		static_assert(sv.length() == 2, "");

.

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tests/external/libcxx/string.view/string.view.access/front.pass.cpp, line 54 at r2 (raw file):

	{
		constexpr pmem::obj::basic_string_view<char> sv("ABC", 2);
		static_assert(sv.length() == 2, "");

.

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tests/external/libcxx/string.view/string.view.access/index.pass.cpp, line 59 at r2 (raw file):

		constexpr pmem::obj::basic_string_view<char> sv("ABC", 2);
		static_assert(sv.length() == 2, "");
		static_assert(sv[0] == 'A', "");

.

[KFilipek]

Reviewable status: all files reviewed, 9 unresolved discussions (waiting on @lukaszstolarczuk)

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include/libpmemobj++/string_view.hpp, line 166 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

returns pointer to c-like string? (here and above)

No, I don't see any reason to duplicate "return" word:
https://pmem.io/libpmemobj-cpp/master/doxygen/classpmem_1_1obj_1_1basic__string.html#afec7256ef676461b095a0e2f662893e0
The same here in return section:
https://en.cppreference.com/w/cpp/string/basic_string_view/front

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include/libpmemobj++/string_view.hpp, line 206 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

to the last char

Done.

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include/libpmemobj++/string_view.hpp, line 219 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

.

Done.

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include/libpmemobj++/string_view.hpp, line 220 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

perhaps also worth mention what if empty() == true

Done.

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tests/external/libcxx/string.view/string.view.access/at.pass.cpp, line 37 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

I know it's ported from libcxx, but I'd remove this if. We throw exceptions in at and if we ever change it, this test will just fail... which is good, I guess

Done.

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tests/external/libcxx/string.view/string.view.access/back.pass.cpp, line 55 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

why not UT_ASSERT?

because static_assert is evaluated in compile-time in opposite to assert which is underlying.

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tests/external/libcxx/string.view/string.view.access/data.pass.cpp, line 49 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

.

The same here, above is the constexpr

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tests/external/libcxx/string.view/string.view.access/front.pass.cpp, line 54 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

.

.

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tests/external/libcxx/string.view/string.view.access/index.pass.cpp, line 59 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

.

.

[igchor]

Reviewed 1 of 2 files at r3.
Reviewable status: 6 of 7 files reviewed, 10 unresolved discussions (waiting on @KFilipek and @lukaszstolarczuk)

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include/libpmemobj++/string_view.hpp, line 13 at r1 (raw file):

#include <algorithm>
#include <stdexcept>

You should leave stdexcept here - for out_of_range

[lukaszstolarczuk]

Reviewed 2 of 2 files at r3.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @KFilipek)

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include/libpmemobj++/string_view.hpp, line 166 at r2 (raw file):

Previously, KFilipek (Krzysztof Filipek) wrote…

No, I don't see any reason to duplicate "return" word:
https://pmem.io/libpmemobj-cpp/master/doxygen/classpmem_1_1obj_1_1basic__string.html#afec7256ef676461b095a0e2f662893e0
The same here in return section:
https://en.cppreference.com/w/cpp/string/basic_string_view/front

no, no. You didn't understand me ;) this are length and size - do they return a pointer to a string? I don't thinks so... ;)

[KFilipek]

Reviewable status: 6 of 7 files reviewed, 2 unresolved discussions (waiting on @igchor and @lukaszstolarczuk)

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include/libpmemobj++/string_view.hpp, line 13 at r1 (raw file):

Previously, igchor (Igor Chorążewicz) wrote…

You should leave stdexcept here - for out_of_range

Done.

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include/libpmemobj++/string_view.hpp, line 166 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

no, no. You didn't understand me ;) this are length and size - do they return a pointer to a string? I don't thinks so... ;)

Done. Sorry xD

[lukaszstolarczuk]

Reviewed 1 of 1 files at r4.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @igchor)

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include/libpmemobj++/string_view.hpp, line 166 at r2 (raw file):

Previously, KFilipek (Krzysztof Filipek) wrote…

Done. Sorry xD

no problem, thx

[igchor]

Reviewable status: complete! all files reviewed, all discussions resolved