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Rework StringRef interface and internals

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Now it no longer tries to be this weird hybrid between an owning
and non-owning reference, and is only ever non-owning. This is also
reflected in its interface, for example `StringRef::isNullTerminated`
is now public, and `StringRef::c_str()` has the precondition that it
is true.

Overview of the changes:
* The `StringRef::m_data` member has been completely removed, as it
had no more uses.
* `StringRef::isSubstring()` has been made public and renamed to
`StringRef::isNullTerminated()`, so that the name reflects what the
method actually does.
* `StringRef::currentData()` has been renamed to `StringRef::data()`,
to be in line with common C++ containers and container-alikes.
* `StringRef::c_str()` will no longer silently make copies. It instead
has a precondition that `isNullTerminated()` is true.
* If the user needs a null-terminated string, they should use the
`std::string` conversion operator and call `c_str()` on the resulting
`std::string`.
* Some small optimizations in various places.
* Basic functionality is now `constexpr`.
This commit is contained in:
Martin Hořeňovský
2019-10-21 17:44:11 +02:00
parent 87b745da66
commit 50cc14c94c
8 changed files with 317 additions and 417 deletions
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62
include/internal/catch_stringref.cpp
View File

@@ -5,14 +5,10 @@
* file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
*/
#if defined(__clang__)
# pragma clang diagnostic push
# pragma clang diagnostic ignored "-Wexit-time-destructors"
#endif
#include "catch_enforce.h"
#include "catch_stringref.h"
#include <algorithm>
#include <ostream>
#include <cstring>
#include <cstdint>
@@ -22,63 +18,33 @@ namespace Catch {
: StringRef( rawChars, static_cast<StringRef::size_type>(std::strlen(rawChars) ) )
{}
void StringRef::swap( StringRef& other ) noexcept {
std::swap( m_start, other.m_start );
std::swap( m_size, other.m_size );
std::swap( m_data, other.m_data );
}
auto StringRef::c_str() const -> char const* {
if( !isSubstring() )
return m_start;
const_cast<StringRef *>( this )->takeOwnership();
return m_data;
CATCH_ENFORCE(isNullTerminated(), "Called StringRef::c_str() on a non-null-terminated instance");
return m_start;
}
auto StringRef::currentData() const noexcept -> char const* {
auto StringRef::data() const noexcept -> char const* {
return m_start;
}
auto StringRef::isOwned() const noexcept -> bool {
return m_data != nullptr;
}
auto StringRef::isSubstring() const noexcept -> bool {
return m_start[m_size] != '\0';
}
void StringRef::takeOwnership() {
if( !isOwned() ) {
m_data = new char[m_size+1];
memcpy( m_data, m_start, m_size );
m_data[m_size] = '\0';
auto StringRef::substr( size_type start, size_type size ) const noexcept -> StringRef {
if (start < m_size) {
return StringRef(m_start + start, (std::min)(m_size - start, size));
} else {
return StringRef();
}
}
auto StringRef::substr( size_type start, size_type size ) const noexcept -> StringRef {
if( start < m_size )
return StringRef( m_start+start, size );
else
return StringRef();
}
auto StringRef::operator == ( StringRef const& other ) const noexcept -> bool {
return
size() == other.size() &&
(std::strncmp( m_start, other.m_start, size() ) == 0);
}
auto StringRef::operator != ( StringRef const& other ) const noexcept -> bool {
return !operator==( other );
return m_size == other.m_size
&& (std::memcmp( m_start, other.m_start, m_size ) == 0);
}
auto operator << ( std::ostream& os, StringRef const& str ) -> std::ostream& {
return os.write(str.currentData(), str.size());
return os.write(str.data(), str.size());
}
auto operator+=( std::string& lhs, StringRef const& rhs ) -> std::string& {
lhs.append(rhs.currentData(), rhs.size());
lhs.append(rhs.data(), rhs.size());
return lhs;
}
} // namespace Catch
#if defined(__clang__)
# pragma clang diagnostic pop
#endif

88
include/internal/catch_stringref.h
View File

@@ -16,49 +16,24 @@ namespace Catch {
/// A non-owning string class (similar to the forthcoming std::string_view)
/// Note that, because a StringRef may be a substring of another string,
/// it may not be null terminated. c_str() must return a null terminated
/// string, however, and so the StringRef will internally take ownership
/// (taking a copy), if necessary. In theory this ownership is not externally
/// visible - but it does mean (substring) StringRefs should not be shared between
/// threads.
/// it may not be null terminated.
class StringRef {
public:
using size_type = std::size_t;
using const_iterator = const char*;
private:
friend struct StringRefTestAccess;
char const* m_start;
size_type m_size;
char* m_data = nullptr;
void takeOwnership();
static constexpr char const* const s_empty = "";
public: // construction/ assignment
StringRef() noexcept
: StringRef( s_empty, 0 )
{}
char const* m_start = s_empty;
size_type m_size = 0;
StringRef( StringRef const& other ) noexcept
: m_start( other.m_start ),
m_size( other.m_size )
{}
StringRef( StringRef&& other ) noexcept
: m_start( other.m_start ),
m_size( other.m_size ),
m_data( other.m_data )
{
other.m_data = nullptr;
}
public: // construction
constexpr StringRef() noexcept = default;
StringRef( char const* rawChars ) noexcept;
StringRef( char const* rawChars, size_type size ) noexcept
constexpr StringRef( char const* rawChars, size_type size ) noexcept
: m_start( rawChars ),
m_size( size )
{}
@@ -68,27 +43,15 @@ namespace Catch {
m_size( stdString.size() )
{}
~StringRef() noexcept {
delete[] m_data;
}
auto operator = ( StringRef const &other ) noexcept -> StringRef& {
delete[] m_data;
m_data = nullptr;
m_start = other.m_start;
m_size = other.m_size;
return *this;
}
explicit operator std::string() const {
return std::string(m_start, m_size);
}
void swap( StringRef& other ) noexcept;
public: // operators
auto operator == ( StringRef const& other ) const noexcept -> bool;
auto operator != ( StringRef const& other ) const noexcept -> bool;
auto operator != (StringRef const& other) const noexcept -> bool {
return !(*this == other);
}
auto operator[] ( size_type index ) const noexcept -> char {
assert(index < m_size);
@@ -96,42 +59,45 @@ namespace Catch {
}
public: // named queries
auto empty() const noexcept -> bool {
constexpr auto empty() const noexcept -> bool {
return m_size == 0;
}
auto size() const noexcept -> size_type {
constexpr auto size() const noexcept -> size_type {
return m_size;
}
// Returns the current start pointer. If the StringRef is not
// null-terminated, throws std::domain_exception
auto c_str() const -> char const*;
public: // substrings and searches
auto substr( size_type start, size_type size ) const noexcept -> StringRef;
// Returns a substring of [start, start + length).
// If start + length > size(), then the substring is [start, size()).
// If start > size(), then the substring is empty.
auto substr( size_type start, size_type length ) const noexcept -> StringRef;
// Returns the current start pointer.
// Note that the pointer can change when if the StringRef is a substring
auto currentData() const noexcept -> char const*;
// Returns the current start pointer. May not be null-terminated.
auto data() const noexcept -> char const*;
constexpr auto isNullTerminated() const noexcept -> bool {
return m_start[m_size] == '\0';
}
public: // iterators
const_iterator begin() const { return m_start; }
const_iterator end() const { return m_start + m_size; }
private: // ownership queries - may not be consistent between calls
auto isOwned() const noexcept -> bool;
auto isSubstring() const noexcept -> bool;
constexpr const_iterator begin() const { return m_start; }
constexpr const_iterator end() const { return m_start + m_size; }
};
auto operator += ( std::string& lhs, StringRef const& sr ) -> std::string&;
auto operator << ( std::ostream& os, StringRef const& sr ) -> std::ostream&;
inline auto operator "" _sr( char const* rawChars, std::size_t size ) noexcept -> StringRef {
constexpr auto operator "" _sr( char const* rawChars, std::size_t size ) noexcept -> StringRef {
return StringRef( rawChars, size );
}
} // namespace Catch
inline auto operator "" _catch_sr( char const* rawChars, std::size_t size ) noexcept -> Catch::StringRef {
constexpr auto operator "" _catch_sr( char const* rawChars, std::size_t size ) noexcept -> Catch::StringRef {
return Catch::StringRef( rawChars, size );
}