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Diffstat (limited to 'libbase/include/core/adt/Twine.h')
| -rw-r--r-- | libbase/include/core/adt/Twine.h | 679 |
1 files changed, 679 insertions, 0 deletions
diff --git a/libbase/include/core/adt/Twine.h b/libbase/include/core/adt/Twine.h new file mode 100644 index 0000000..66d8264 --- /dev/null +++ b/libbase/include/core/adt/Twine.h @@ -0,0 +1,679 @@ +/* + RCC-Project + + Copyright (C) 2026 Richard Qin + + This file is part of RCC-Project. + + RCC-Project is free software; you can redistribute it and/or modify it under + the terms of the GNU General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your option) any + later version. + + RCC-Project is distributed in the hope that it will be useful, but WITHOUT ANY + WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A + PARTICULAR PURPOSE. See the GNU General Public License for more details. + + You should have received a copy of the GNU General Public License along with + RCC-Project; see the file COPYING. If not see + <http://www.gnu.org/licenses/>. + */ + +//===- core/adt/Twine.h - Fast Temporary String Concatenation -*- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +#ifndef LIBBASE_ADT_TWINE_H +#define LIBBASE_ADT_TWINE_H + +#include "core/adt/SmallVector.h" +#include "core/compiler/Compiler.h" +#include "core/error/ErrorHandling.h" +#include <cassert> +#include <cstddef> +#include <cstdint> +#include <string> +#include <string_view> + +namespace libbase +{ + +class formatv_object_base; +class raw_ostream; + +/// Twine - A lightweight data structure for efficiently representing the +/// concatenation of temporary values as strings. +/// +/// A Twine is a kind of rope, it represents a concatenated string using a +/// binary-tree, where the string is the preorder of the nodes. Since the +/// Twine can be efficiently rendered into a buffer when its result is used, +/// it avoids the cost of generating temporary values for intermediate string +/// results -- particularly in cases when the Twine result is never +/// required. By explicitly tracking the type of leaf nodes, we can also avoid +/// the creation of temporary strings for conversions operations (such as +/// appending an integer to a string). +/// +/// A Twine is not intended for use directly and should not be stored, its +/// implementation relies on the ability to store pointers to temporary stack +/// objects which may be deallocated at the end of a statement. Twines should +/// only be used as const references in arguments, when an API wishes +/// to accept possibly-concatenated strings. +/// +/// Twines support a special 'null' value, which always concatenates to form +/// itself, and renders as an empty string. This can be returned from APIs to +/// effectively nullify any concatenations performed on the result. +/// +/// \b Implementation +/// +/// Given the nature of a Twine, it is not possible for the Twine's +/// concatenation method to construct interior nodes; the result must be +/// represented inside the returned value. For this reason a Twine object +/// actually holds two values, the left- and right-hand sides of a +/// concatenation. We also have nullary Twine objects, which are effectively +/// sentinel values that represent empty strings. +/// +/// Thus, a Twine can effectively have zero, one, or two children. The \see +/// isNullary(), \see isUnary(), and \see isBinary() predicates exist for +/// testing the number of children. +/// +/// We maintain a number of invariants on Twine objects (FIXME: Why): +/// - Nullary twines are always represented with their Kind on the left-hand +/// side, and the Empty kind on the right-hand side. +/// - Unary twines are always represented with the value on the left-hand +/// side, and the Empty kind on the right-hand side. +/// - If a Twine has another Twine as a child, that child should always be +/// binary (otherwise it could have been folded into the parent). +/// +/// These invariants are check by \see isValid(). +/// +/// \b Efficiency Considerations +/// +/// The Twine is designed to yield efficient and small code for common +/// situations. For this reason, the concat() method is inlined so that +/// concatenations of leaf nodes can be optimized into stores directly into a +/// single stack allocated object. +/// +/// In practice, not all compilers can be trusted to optimize concat() fully, +/// so we provide two additional methods (and accompanying operator+ +/// overloads) to guarantee that particularly important cases (cstring plus +/// string view) codegen as desired. +class Twine +{ + /// NodeKind - Represent the type of an argument. + enum NodeKind : unsigned char + { + /// An empty string; the result of concatenating anything with it is also + /// empty. + NullKind, + + /// The empty string. + EmptyKind, + + /// A pointer to a Twine instance. + TwineKind, + + /// A pointer to a C string instance. + CStringKind, + + /// A pointer to an std::string instance. + StdStringKind, + + /// A pointer and length representation. Used for std::string_view and + /// SmallVector. It stores the pointer and length directly. + PtrAndLengthKind, + + /// A pointer to a formatv_object_base instance. + FormatvObjectKind, + + /// A char value, to render as a character. + CharKind, + + /// An unsigned int value, to render as an unsigned decimal integer. + DecUIKind, + + /// An int value, to render as a signed decimal integer. + DecIKind, + + /// An unsigned long value, to render as an unsigned decimal integer. + DecULKind, + + /// A long value, to render as a signed decimal integer. + DecLKind, + + /// An unsigned long long value, to render as an unsigned decimal integer. + DecULLKind, + + /// A long long value, to render as a signed decimal integer. + DecLLKind, + + /// A uint64_t value, to render as an unsigned hexadecimal integer. + UHexKind + }; + + union Child + { + const Twine *twine; + const char *cString; + const std::string *stdString; + struct + { + const char *ptr; + size_t length; + } ptrAndLength; + const formatv_object_base *formatvObject; + char character; + unsigned int decUI; + int decI; + unsigned long decUL; + long decL; + unsigned long long decULL; + long long decLL; + uint64_t uHex; + }; + + /// LHS - The prefix in the concatenation, which may be uninitialized for + /// Null or Empty kinds. + Child LHS; + + /// RHS - The suffix in the concatenation, which may be uninitialized for + /// Null or Empty kinds. + Child RHS; + + /// LHSKind - The NodeKind of the left hand side, \see getLHSKind(). + NodeKind LHSKind = EmptyKind; + + /// RHSKind - The NodeKind of the right hand side, \see getRHSKind(). + NodeKind RHSKind = EmptyKind; + + /// Construct a nullary twine; the kind must be NullKind or EmptyKind. + explicit Twine (NodeKind Kind) : LHSKind (Kind) + { + assert (isNullary () && "Invalid kind!"); + } + + /// Construct a binary twine. + explicit Twine (const Twine &LHS, const Twine &RHS) + : LHSKind (TwineKind), RHSKind (TwineKind) + { + this->LHS.twine = &LHS; + this->RHS.twine = &RHS; + assert (isValid () && "Invalid twine!"); + } + + /// Construct a twine from explicit values. + explicit Twine (Child LHS, NodeKind LHSKind, Child RHS, NodeKind RHSKind) + : LHS (LHS), RHS (RHS), LHSKind (LHSKind), RHSKind (RHSKind) + { + assert (isValid () && "Invalid twine!"); + } + + /// Check for the null twine. + bool + isNull () const + { + return getLHSKind () == NullKind; + } + + /// Check for the empty twine. + bool + isEmpty () const + { + return getLHSKind () == EmptyKind; + } + + /// Check if this is a nullary twine (null or empty). + bool + isNullary () const + { + return isNull () || isEmpty (); + } + + /// Check if this is a unary twine. + bool + isUnary () const + { + return getRHSKind () == EmptyKind && !isNullary (); + } + + /// Check if this is a binary twine. + bool + isBinary () const + { + return getLHSKind () != NullKind && getRHSKind () != EmptyKind; + } + + /// Check if this is a valid twine (satisfying the invariants on + /// order and number of arguments). + bool + isValid () const + { + // Nullary twines always have Empty on the RHS. + if (isNullary () && getRHSKind () != EmptyKind) + { + return false; + } + + // Null should never appear on the RHS. + if (getRHSKind () == NullKind) + { + return false; + } + + // The RHS cannot be non-empty if the LHS is empty. + if (getRHSKind () != EmptyKind && getLHSKind () == EmptyKind) + { + return false; + } + + // A twine child should always be binary. + if (getLHSKind () == TwineKind && !LHS.twine->isBinary ()) + { + return false; + } + if (getRHSKind () == TwineKind && !RHS.twine->isBinary ()) + { + return false; + } + + return true; + } + + /// Get the NodeKind of the left-hand side. + NodeKind + getLHSKind () const + { + return LHSKind; + } + + /// Get the NodeKind of the right-hand side. + NodeKind + getRHSKind () const + { + return RHSKind; + } + + /// Print one child from a twine. + void + printOneChild (raw_ostream &OS, Child Ptr, NodeKind Kind) const; + + /// Print the representation of one child from a twine. + void + printOneChildRepr (raw_ostream &OS, Child Ptr, NodeKind Kind) const; + +public: + /// @name Constructors + /// @{ + + /// Construct from an empty string. + /*implicit*/ Twine () + { + assert (isValid () && "Invalid twine!"); + } + + Twine (const Twine &) = default; + + /// Construct from a C string. + /// + /// We take care here to optimize "" into the empty twine -- this will be + /// optimized out for string constants. This allows Twine arguments have + /// default "" values, without introducing unnecessary string constants. + /*implicit*/ Twine (const char *Str) + { + if (Str[0] != '\0') + { + LHS.cString = Str; + LHSKind = CStringKind; + } + else + { + LHSKind = EmptyKind; + } + + assert (isValid () && "Invalid twine!"); + } + /// Delete the implicit conversion from nullptr as Twine(const char *) + /// cannot take nullptr. + /*implicit*/ Twine (std::nullptr_t) = delete; + + /// Construct from an std::string. + /*implicit*/ Twine (const std::string &Str) : LHSKind (StdStringKind) + { + LHS.stdString = &Str; + assert (isValid () && "Invalid twine!"); + } + + /// Construct from an std::string_view by converting it to a pointer and + /// length. This handles string_views on a pure API basis, and avoids + /// storing one (or a pointer to one) inside a Twine, which avoids problems + /// when mixing code compiled under various C++ standards. + /*implicit*/ Twine (std::string_view Str) : LHSKind (PtrAndLengthKind) + { + LHS.ptrAndLength.ptr = Str.data (); + LHS.ptrAndLength.length = Str.length (); + assert (isValid () && "Invalid twine!"); + } + + /// Construct from a SmallString. + /*implicit*/ Twine (const SmallVectorImpl<char> &Str) + : LHSKind (PtrAndLengthKind) + { + LHS.ptrAndLength.ptr = Str.data (); + LHS.ptrAndLength.length = Str.size (); + assert (isValid () && "Invalid twine!"); + } + + /// Construct from a formatv_object_base. + /*implicit*/ Twine (const formatv_object_base &Fmt) + : LHSKind (FormatvObjectKind) + { + LHS.formatvObject = &Fmt; + assert (isValid () && "Invalid twine!"); + } + + /// Construct from a char. + explicit Twine (char Val) : LHSKind (CharKind) + { + LHS.character = Val; + } + + /// Construct from a signed char. + explicit Twine (signed char Val) : LHSKind (CharKind) + { + LHS.character = static_cast<char> (Val); + } + + /// Construct from an unsigned char. + explicit Twine (unsigned char Val) : LHSKind (CharKind) + { + LHS.character = static_cast<char> (Val); + } + + /// Construct a twine to print \p Val as an unsigned decimal integer. + explicit Twine (unsigned Val) : LHSKind (DecUIKind) + { + LHS.decUI = Val; + } + + /// Construct a twine to print \p Val as a signed decimal integer. + explicit Twine (int Val) : LHSKind (DecIKind) + { + LHS.decI = Val; + } + + /// Construct a twine to print \p Val as an unsigned decimal integer. + explicit Twine (unsigned long Val) : LHSKind (DecULKind) + { + LHS.decUL = Val; + } + + /// Construct a twine to print \p Val as a signed decimal integer. + explicit Twine (long Val) : LHSKind (DecLKind) + { + LHS.decL = Val; + } + + /// Construct a twine to print \p Val as an unsigned decimal integer. + explicit Twine (unsigned long long Val) : LHSKind (DecULLKind) + { + LHS.decULL = Val; + } + + /// Construct a twine to print \p Val as a signed decimal integer. + explicit Twine (long long Val) : LHSKind (DecLLKind) + { + LHS.decLL = Val; + } + + // FIXME: Unfortunately, to make sure this is as efficient as possible we + // need extra binary constructors from particular types. We can't rely on + // the compiler to be smart enough to fold operator+()/concat() down to the + // right thing. Yet. + + /// Construct as the concatenation of a C string and a string view. + /*implicit*/ Twine (const char *LHS, std::string_view RHS) + : LHSKind (CStringKind), RHSKind (PtrAndLengthKind) + { + this->LHS.cString = LHS; + this->RHS.ptrAndLength.ptr = RHS.data (); + this->RHS.ptrAndLength.length = RHS.size (); + assert (isValid () && "Invalid twine!"); + } + + /// Construct as the concatenation of a string view and a C string. + /*implicit*/ Twine (std::string_view LHS, const char *RHS) + : LHSKind (PtrAndLengthKind), RHSKind (CStringKind) + { + this->LHS.ptrAndLength.ptr = LHS.data (); + this->LHS.ptrAndLength.length = LHS.size (); + this->RHS.cString = RHS; + assert (isValid () && "Invalid twine!"); + } + + /// Since the intended use of twines is as temporary objects, assignments + /// when concatenating might cause undefined behavior or stack corruptions + Twine & + operator= (const Twine &) = delete; + + /// Create a 'null' string, which is an empty string that always + /// concatenates to form another empty string. + static Twine + createNull () + { + return Twine (NullKind); + } + + /// @} + /// @name Numeric Conversions + /// @{ + + // Construct a twine to print \p Val as an unsigned hexadecimal integer. + static Twine + utohexstr (uint64_t Val) + { + Child LHS, RHS; + LHS.uHex = Val; + RHS.twine = nullptr; + return Twine (LHS, UHexKind, RHS, EmptyKind); + } + + /// @} + /// @name Predicate Operations + /// @{ + + /// Check if this twine is trivially empty; a false return value does not + /// necessarily mean the twine is empty. + bool + isTriviallyEmpty () const + { + return isNullary (); + } + + /// Return true if this twine can be dynamically accessed as a single + /// string view with getSingleStringView(). + bool + isSingleStringView () const + { + if (getRHSKind () != EmptyKind) + { + return false; + } + + switch (getLHSKind ()) + { + case EmptyKind: + case CStringKind: + case StdStringKind: + case PtrAndLengthKind: + return true; + default: + return false; + } + } + + /// @} + /// @name String Operations + /// @{ + + Twine + concat (const Twine &Suffix) const; + + /// @} + /// @name Output & Conversion. + /// @{ + + /// Return the twine contents as a std::string. + LIBBASE_ABI std::string + str () const; + + /// Append the concatenated string into the given SmallString or SmallVector. + LIBBASE_ABI void + toVector (SmallVectorImpl<char> &Out) const; + + /// This returns the twine as a single string view. This method is only valid + /// if isSingleStringView() is true. + std::string_view + getSingleStringView () const + { + assert (isSingleStringView () && + "This cannot be had as a single string view!"); + switch (getLHSKind ()) + { + default: + libbase_unreachable ("Out of sync with isSingleStringView"); + case EmptyKind: + return std::string_view (); + case CStringKind: + return std::string_view (LHS.cString); + case StdStringKind: + return std::string_view (*LHS.stdString); + case PtrAndLengthKind: + return std::string_view (LHS.ptrAndLength.ptr, LHS.ptrAndLength.length); + } + } + + /// This returns the twine as a single string view if it can be + /// represented as such. Otherwise the twine is written into the given + /// SmallVector and a string view to the SmallVector's data is returned. + std::string_view + toStringView (SmallVectorImpl<char> &Out) const + { + if (isSingleStringView ()) + { + return getSingleStringView (); + } + toVector (Out); + return std::string_view (Out.data (), Out.size ()); + } + + /// This returns the twine as a single null terminated string view if it + /// can be represented as such. Otherwise the twine is written into the + /// given SmallVector and a string view to the SmallVector's data is returned. + /// + /// The returned string view's size does not include the null terminator. + LIBBASE_ABI std::string_view + toNullTerminatedStringView (SmallVectorImpl<char> &Out) const; + + /// Write the concatenated string represented by this twine to the + /// stream \p OS. + LIBBASE_ABI void + print (raw_ostream &OS) const; + + /// Write the representation of this twine to the stream \p OS. + LIBBASE_ABI void + printRepr (raw_ostream &OS) const; + +#if !defined(NDEBUG) || defined(LIBBASE_ENABLE_DUMP) + /// Dump the concatenated string represented by this twine to stderr. + LIBBASE_DUMP_METHOD void + dump () const; + + /// Dump the representation of this twine to stderr. + LIBBASE_DUMP_METHOD void + dumpRepr () const; +#endif + + /// @} +}; + +/// @name Twine Inline Implementations +/// @{ + +inline Twine +Twine::concat (const Twine &Suffix) const +{ + // Concatenation with null is null. + if (isNull () || Suffix.isNull ()) + { + return Twine (NullKind); + } + + // Concatenation with empty yields the other side. + if (isEmpty ()) + { + return Suffix; + } + if (Suffix.isEmpty ()) + { + return *this; + } + + // Otherwise we need to create a new node, taking care to fold in unary + // twines. + Child NewLHS, NewRHS; + NewLHS.twine = this; + NewRHS.twine = &Suffix; + NodeKind NewLHSKind = TwineKind, NewRHSKind = TwineKind; + if (isUnary ()) + { + NewLHS = LHS; + NewLHSKind = getLHSKind (); + } + if (Suffix.isUnary ()) + { + NewRHS = Suffix.LHS; + NewRHSKind = Suffix.getLHSKind (); + } + + return Twine (NewLHS, NewLHSKind, NewRHS, NewRHSKind); +} + +inline Twine +operator+ (const Twine &LHS, const Twine &RHS) +{ + return LHS.concat (RHS); +} + +/// Additional overload to guarantee simplified codegen; this is equivalent to +/// concat(). + +inline Twine +operator+ (const char *LHS, std::string_view RHS) +{ + return Twine (LHS, RHS); +} + +/// Additional overload to guarantee simplified codegen; this is equivalent to +/// concat(). + +inline Twine +operator+ (std::string_view LHS, const char *RHS) +{ + return Twine (LHS, RHS); +} + +inline raw_ostream & +operator<< (raw_ostream &OS, const Twine &RHS) +{ + RHS.print (OS); + return OS; +} + +/// @} + +} // end namespace libbase + +#endif // LIBBASE_ADT_TWINE_H |