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[ADT] Teach StringRef to derive from std::string_view #113752

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Oct 26, 2024
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[ADT] Teach StringRef to derive from std::string_view #113752

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41 changes: 10 additions & 31 deletions llvm/include/llvm/ADT/StringRef.h
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,9 @@ namespace llvm {
/// situations where the character data resides in some other buffer, whose
/// lifetime extends past that of the StringRef. For this reason, it is not in
/// general safe to store a StringRef.
class LLVM_GSL_POINTER StringRef {
class LLVM_GSL_POINTER StringRef : public std::string_view {
using Base = std::string_view;

public:
static constexpr size_t npos = ~size_t(0);

Expand All @@ -60,12 +62,6 @@ namespace llvm {
using const_reverse_iterator = std::reverse_iterator<const_iterator>;

private:
/// The start of the string, in an external buffer.
const char *Data = nullptr;

/// The length of the string.
size_t Length = 0;

// Workaround memcmp issue with null pointers (undefined behavior)
// by providing a specialized version
static int compareMemory(const char *Lhs, const char *Rhs, size_t Length) {
Expand All @@ -86,27 +82,25 @@ namespace llvm {

/// Construct a string ref from a cstring.
/*implicit*/ constexpr StringRef(const char *Str)
: Data(Str), Length(Str ?
: Base(Str, Str ?
// GCC 7 doesn't have constexpr char_traits. Fall back to __builtin_strlen.
#if defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE < 8
__builtin_strlen(Str)
__builtin_strlen(Str)
#else
std::char_traits<char>::length(Str)
std::char_traits<char>::length(Str)
#endif
: 0) {
: 0) {
}

/// Construct a string ref from a pointer and length.
/*implicit*/ constexpr StringRef(const char *data, size_t length)
: Data(data), Length(length) {}
: Base(data, length) {}

/// Construct a string ref from an std::string.
/*implicit*/ StringRef(const std::string &Str)
: Data(Str.data()), Length(Str.length()) {}
/*implicit*/ StringRef(const std::string &Str) : Base(Str) {}

/// Construct a string ref from an std::string_view.
/*implicit*/ constexpr StringRef(std::string_view Str)
: Data(Str.data()), Length(Str.size()) {}
/*implicit*/ constexpr StringRef(std::string_view Str) : Base(Str) {}

/// @}
/// @name Iterators
Expand Down Expand Up @@ -138,16 +132,9 @@ namespace llvm {
/// @name String Operations
/// @{

/// data - Get a pointer to the start of the string (which may not be null
/// terminated).
[[nodiscard]] constexpr const char *data() const { return Data; }

/// empty - Check if the string is empty.
[[nodiscard]] constexpr bool empty() const { return size() == 0; }

/// size - Get the string size.
[[nodiscard]] constexpr size_t size() const { return Length; }

/// front - Get the first character in the string.
[[nodiscard]] char front() const {
assert(!empty());
Expand Down Expand Up @@ -248,14 +235,6 @@ namespace llvm {
std::enable_if_t<std::is_same<T, std::string>::value, StringRef> &
operator=(T &&Str) = delete;

/// @}
/// @name Type Conversions
/// @{

constexpr operator std::string_view() const {
return std::string_view(data(), size());
}

/// @}
/// @name String Predicates
/// @{
Expand Down
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