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make OString(OStringLiteral) constructor constexpr

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i.e. a copy of
   commit 21584b304b
   make OUString(OUStringLiteral) constructor constexpr

Change-Id: If5b0c2b896f8a730d01a076d3eb9161ad628979b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/114480
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
This commit is contained in:
Noel Grandin
2021-04-22 18:38:34 +02:00
committed by Noel Grandin
parent ad8edac43e
commit bca539e889
1 changed files with 28 additions and 19 deletions
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include/rtl/string.hxx
+28 -19
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@@ -86,6 +86,7 @@ This class is not part of public API and is meant to be used only in LibreOffice
template<std::size_t N> class SAL_WARN_UNUSED OStringLiteral {
static_assert(N != 0);
static_assert(N - 1 <= std::numeric_limits<sal_Int32>::max(), "literal too long");
friend class OString;
public:
#if HAVE_CPP_CONSTEVAL
@@ -98,7 +99,7 @@ public:
assert(literal[N - 1] == '\0');
//TODO: Use C++20 constexpr std::copy_n (P0202R3):
for (std::size_t i = 0; i != N; ++i) {
buffer[i] = literal[i];
more.buffer[i] = literal[i];
}
}
@@ -118,32 +119,40 @@ public:
}
#endif
constexpr sal_Int32 getLength() const { return length; }
constexpr sal_Int32 getLength() const { return more.length; }
constexpr char const * getStr() const SAL_RETURNS_NONNULL { return buffer; }
constexpr char const * getStr() const SAL_RETURNS_NONNULL { return more.buffer; }
constexpr operator std::string_view() const { return {buffer, sal_uInt32(length)}; }
constexpr operator std::string_view() const { return {more.buffer, sal_uInt32(more.length)}; }
private:
static constexpr void assertLayout() {
// These static_asserts verifying the layout compatibility with rtl_String cannot be class
// member declarations, as offsetof requires a complete type, so defer them to here:
static_assert(offsetof(OStringLiteral, refCount) == offsetof(rtl_String, refCount));
static_assert(
std::is_same_v<decltype(refCount), decltype(rtl_String::refCount)>);
static_assert(offsetof(OStringLiteral, length) == offsetof(rtl_String, length));
static_assert(std::is_same_v<decltype(length), decltype(rtl_String::length)>);
static_assert(offsetof(OStringLiteral, buffer) == offsetof(rtl_String, buffer));
static_assert(
std::is_same_v<
std::remove_extent_t<decltype(buffer)>,
std::remove_extent_t<decltype(rtl_String::buffer)>>);
static_assert(offsetof(OStringLiteral, str.refCount) == offsetof(OStringLiteral, more.refCount));
static_assert(offsetof(OStringLiteral, str.length) == offsetof(OStringLiteral, more.length));
static_assert(offsetof(OStringLiteral, str.buffer) == offsetof(OStringLiteral, more.buffer));
}
// Same layout as rtl_String (include/rtl/string.h):
oslInterlockedCount refCount = 0x40000000; // SAL_STRING_STATIC_FLAG (sal/rtl/strimp.hxx)
sal_Int32 length = N - 1;
char buffer[N] = {}; //TODO: drop initialization for C++20 (P1331R2)
#if defined(_WIN32)
#pragma pack(push, 8)
#endif
union {
rtl_String str;
struct {
oslInterlockedCount refCount;
sal_Int32 length;
char buffer[N];
} more =
{
0x40000000, // SAL_STRING_STATIC_FLAG (sal/rtl/strimp.hxx)
N - 1,
{} //TODO: drop initialization for C++20 (P1331R2)
};
};
#if defined(_WIN32)
#pragma pack(pop)
#endif
};
#endif
@@ -329,7 +338,7 @@ public:
@since LibreOffice 7.1
*/
template<std::size_t N> OString(OStringLiteral<N> const & literal):
pData(const_cast<rtl_String *>(reinterpret_cast<rtl_String const *>(&literal))) {}
pData(const_cast<rtl_String *>(&literal.str)) {}
template<std::size_t N> OString(OStringLiteral<N> &&) = delete;
/// @endcond
#endif