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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
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GPG key ID: DE48307B8B0D381A
8 changed files with 317 additions and 417 deletions
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115
projects/SelfTest/IntrospectiveTests/String.tests.cpp
View file

@ -4,39 +4,15 @@
#include <cstring>
namespace Catch {
// Implementation of test accessors
struct StringRefTestAccess {
static auto isOwned( StringRef const& stringRef ) -> bool {
return stringRef.isOwned();
}
static auto isSubstring( StringRef const& stringRef ) -> bool {
return stringRef.isSubstring();
}
};
namespace {
auto isOwned( StringRef const& stringRef ) -> bool {
return StringRefTestAccess::isOwned( stringRef );
}
auto isSubstring( StringRef const& stringRef ) -> bool {
return StringRefTestAccess::isSubstring( stringRef );
}
} // end anonymous namespace
} // namespace Catch
TEST_CASE( "StringRef", "[Strings][StringRef]" ) {
using Catch::StringRef;
using Catch::isOwned; using Catch::isSubstring;
SECTION( "Empty string" ) {
StringRef empty;
REQUIRE( empty.empty() );
REQUIRE( empty.size() == 0 );
REQUIRE( empty.isNullTerminated() );
REQUIRE( std::strcmp( empty.c_str(), "" ) == 0 );
}
@ -44,28 +20,22 @@ TEST_CASE( "StringRef", "[Strings][StringRef]" ) {
StringRef s = "hello";
REQUIRE( s.empty() == false );
REQUIRE( s.size() == 5 );
REQUIRE( isSubstring( s ) == false );
REQUIRE( s.isNullTerminated() );
auto rawChars = s.currentData();
auto rawChars = s.data();
REQUIRE( std::strcmp( rawChars, "hello" ) == 0 );
SECTION( "c_str() does not cause copy" ) {
REQUIRE( isOwned( s ) == false );
REQUIRE( s.c_str() == rawChars );
REQUIRE( isOwned( s ) == false );
}
REQUIRE_NOTHROW(s.c_str());
REQUIRE(s.c_str() == rawChars);
REQUIRE(s.data() == rawChars);
}
SECTION( "From sub-string" ) {
StringRef original = StringRef( "original string" ).substr(0, 8);
REQUIRE( original == "original" );
REQUIRE( isSubstring( original ) );
REQUIRE( isOwned( original ) == false );
original.c_str(); // Forces it to take ownership
REQUIRE( isOwned( original ) );
REQUIRE_FALSE(original.isNullTerminated());
REQUIRE_THROWS(original.c_str());
REQUIRE_NOTHROW(original.data());
}
@ -76,26 +46,9 @@ TEST_CASE( "StringRef", "[Strings][StringRef]" ) {
SECTION( "zero-based substring" ) {
REQUIRE( ss.empty() == false );
REQUIRE( ss.size() == 5 );
REQUIRE( std::strcmp( ss.c_str(), "hello" ) == 0 );
REQUIRE( std::strncmp( ss.data(), "hello", 5 ) == 0 );
REQUIRE( ss == "hello" );
}
SECTION( "c_str() causes copy" ) {
REQUIRE( isSubstring( ss ) );
REQUIRE( isOwned( ss ) == false );
auto rawChars = ss.currentData();
REQUIRE( rawChars == s.currentData() ); // same pointer value
REQUIRE( ss.c_str() != rawChars );
REQUIRE( isOwned( ss ) );
SECTION( "Self-assignment after substring" ) {
ss = *&ss; // the *& are there to suppress warnings (see: "Improvements to Clang's diagnostics" in https://rev.ng/gitlab/revng-bar-2019/clang/raw/master/docs/ReleaseNotes.rst)
REQUIRE( isOwned(ss) == false );
REQUIRE( ss == "hello" );
REQUIRE( rawChars == ss.currentData() ); // same pointer value
}
}
SECTION( "non-zero-based substring") {
ss = s.substr( 6, 6 );
@ -105,21 +58,32 @@ TEST_CASE( "StringRef", "[Strings][StringRef]" ) {
SECTION( "Pointer values of full refs should match" ) {
StringRef s2 = s;
REQUIRE( s.c_str() == s2.c_str() );
REQUIRE( s.data() == s2.data() );
}
SECTION( "Pointer values of substring refs should not match" ) {
REQUIRE( s.c_str() != ss.c_str() );
SECTION( "Pointer values of substring refs should also match" ) {
REQUIRE( s.data() == ss.data() );
}
SECTION("Past the end substring") {
REQUIRE(s.substr(s.size() + 1, 123).empty());
}
SECTION("Substring off the end are trimmed") {
ss = s.substr(6, 123);
REQUIRE(std::strcmp(ss.c_str(), "world!") == 0);
}
// TODO: substring into string + size is longer than end
}
SECTION( "Comparisons" ) {
REQUIRE( StringRef("hello") == StringRef("hello") );
REQUIRE( StringRef("hello") != StringRef("cello") );
SECTION( "Comparisons are deep" ) {
char buffer1[] = "Hello";
char buffer2[] = "Hello";
CHECK(buffer1 != buffer2);
StringRef left(buffer1), right(buffer2);
REQUIRE( left == right );
REQUIRE(left != left.substr(0, 3));
}
SECTION( "from std::string" ) {
@ -159,3 +123,28 @@ TEST_CASE( "StringRef", "[Strings][StringRef]" ) {
}
}
}
TEST_CASE("StringRef at compilation time", "[Strings][StringRef][constexpr]") {
using Catch::StringRef;
SECTION("Simple constructors") {
STATIC_REQUIRE(StringRef{}.size() == 0);
STATIC_REQUIRE(StringRef{ "abc", 3 }.size() == 3);
STATIC_REQUIRE(StringRef{ "abc", 3 }.isNullTerminated());
STATIC_REQUIRE(StringRef{ "abc", 2 }.size() == 2);
STATIC_REQUIRE_FALSE(StringRef{ "abc", 2 }.isNullTerminated());
}
SECTION("UDL construction") {
constexpr auto sr1 = "abc"_catch_sr;
STATIC_REQUIRE_FALSE(sr1.empty());
STATIC_REQUIRE(sr1.size() == 3);
STATIC_REQUIRE(sr1.isNullTerminated());
using Catch::operator"" _sr;
constexpr auto sr2 = ""_sr;
STATIC_REQUIRE(sr2.empty());
STATIC_REQUIRE(sr2.size() == 0);
STATIC_REQUIRE(sr2.isNullTerminated());
}
}