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//===- RewriteRope.h - Rope specialized for rewriter ------------*- 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
//
//===----------------------------------------------------------------------===//
//
// This file defines the RewriteRope class, which is a powerful string class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_REWRITE_CORE_REWRITEROPE_H
#define LLVM_CLANG_REWRITE_CORE_REWRITEROPE_H
#include "llvm/ADT/IntrusiveRefCntPtr.h"
#include "llvm/ADT/StringRef.h"
#include <cassert>
#include <cstddef>
#include <iterator>
#include <utility>
namespace clang {
//===--------------------------------------------------------------------===//
// RopeRefCountString Class
//===--------------------------------------------------------------------===//
/// RopeRefCountString - This struct is allocated with 'new char[]' from the
/// heap, and represents a reference counted chunk of string data. When its
/// ref count drops to zero, it is delete[]'d. This is primarily managed
/// through the RopePiece class below.
struct RopeRefCountString {
unsigned RefCount;
char Data[1]; // Variable sized.
void Retain() { ++RefCount; }
void Release() {
assert(RefCount > 0 && "Reference count is already zero.");
if (--RefCount == 0)
delete [] (char*)this;
}
};
//===--------------------------------------------------------------------===//
// RopePiece Class
//===--------------------------------------------------------------------===//
/// RopePiece - This class represents a view into a RopeRefCountString object.
/// This allows references to string data to be efficiently chopped up and
/// moved around without having to push around the string data itself.
///
/// For example, we could have a 1M RopePiece and want to insert something
/// into the middle of it. To do this, we split it into two RopePiece objects
/// that both refer to the same underlying RopeRefCountString (just with
/// different offsets) which is a nice constant time operation.
struct RopePiece {
llvm::IntrusiveRefCntPtr<RopeRefCountString> StrData;
unsigned StartOffs = 0;
unsigned EndOffs = 0;
RopePiece() = default;
RopePiece(llvm::IntrusiveRefCntPtr<RopeRefCountString> Str, unsigned Start,
unsigned End)
: StrData(std::move(Str)), StartOffs(Start), EndOffs(End) {}
const char &operator[](unsigned Offset) const {
return StrData->Data[Offset+StartOffs];
}
char &operator[](unsigned Offset) {
return StrData->Data[Offset+StartOffs];
}
unsigned size() const { return EndOffs-StartOffs; }
};
//===--------------------------------------------------------------------===//
// RopePieceBTreeIterator Class
//===--------------------------------------------------------------------===//
/// RopePieceBTreeIterator - This class provides read-only forward iteration
/// over bytes that are in a RopePieceBTree. This first iterates over bytes
/// in a RopePiece, then iterates over RopePiece's in a RopePieceBTreeLeaf,
/// then iterates over RopePieceBTreeLeaf's in a RopePieceBTree.
class RopePieceBTreeIterator {
/// CurNode - The current B+Tree node that we are inspecting.
const void /*RopePieceBTreeLeaf*/ *CurNode = nullptr;
/// CurPiece - The current RopePiece in the B+Tree node that we're
/// inspecting.
const RopePiece *CurPiece = nullptr;
/// CurChar - The current byte in the RopePiece we are pointing to.
unsigned CurChar = 0;
public:
using iterator_category = std::forward_iterator_tag;
using value_type = const char;
using difference_type = std::ptrdiff_t;
using pointer = value_type *;
using reference = value_type &;
RopePieceBTreeIterator() = default;
RopePieceBTreeIterator(const void /*RopePieceBTreeNode*/ *N);
char operator*() const {
return (*CurPiece)[CurChar];
}
bool operator==(const RopePieceBTreeIterator &RHS) const {
return CurPiece == RHS.CurPiece && CurChar == RHS.CurChar;
}
bool operator!=(const RopePieceBTreeIterator &RHS) const {
return !operator==(RHS);
}
RopePieceBTreeIterator& operator++() { // Preincrement
if (CurChar+1 < CurPiece->size())
++CurChar;
else
MoveToNextPiece();
return *this;
}
RopePieceBTreeIterator operator++(int) { // Postincrement
RopePieceBTreeIterator tmp = *this; ++*this; return tmp;
}
llvm::StringRef piece() const {
return llvm::StringRef(&(*CurPiece)[0], CurPiece->size());
}
void MoveToNextPiece();
};
//===--------------------------------------------------------------------===//
// RopePieceBTree Class
//===--------------------------------------------------------------------===//
class RopePieceBTree {
void /*RopePieceBTreeNode*/ *Root;
public:
RopePieceBTree();
RopePieceBTree(const RopePieceBTree &RHS);
RopePieceBTree &operator=(const RopePieceBTree &) = delete;
~RopePieceBTree();
using iterator = RopePieceBTreeIterator;
iterator begin() const { return iterator(Root); }
iterator end() const { return iterator(); }
unsigned size() const;
unsigned empty() const { return size() == 0; }
void clear();
void insert(unsigned Offset, const RopePiece &R);
void erase(unsigned Offset, unsigned NumBytes);
};
//===--------------------------------------------------------------------===//
// RewriteRope Class
//===--------------------------------------------------------------------===//
/// RewriteRope - A powerful string class. This class supports extremely
/// efficient insertions and deletions into the middle of it, even for
/// ridiculously long strings.
class RewriteRope {
RopePieceBTree Chunks;
/// We allocate space for string data out of a buffer of size AllocChunkSize.
/// This keeps track of how much space is left.
llvm::IntrusiveRefCntPtr<RopeRefCountString> AllocBuffer;
enum { AllocChunkSize = 4080 };
unsigned AllocOffs = AllocChunkSize;
public:
RewriteRope() = default;
RewriteRope(const RewriteRope &RHS) : Chunks(RHS.Chunks) {}
// The copy assignment operator is defined as deleted pending further
// motivation.
RewriteRope &operator=(const RewriteRope &) = delete;
using iterator = RopePieceBTree::iterator;
using const_iterator = RopePieceBTree::iterator;
iterator begin() const { return Chunks.begin(); }
iterator end() const { return Chunks.end(); }
unsigned size() const { return Chunks.size(); }
void clear() {
Chunks.clear();
}
void assign(const char *Start, const char *End) {
clear();
if (Start != End)
Chunks.insert(0, MakeRopeString(Start, End));
}
void insert(unsigned Offset, const char *Start, const char *End) {
assert(Offset <= size() && "Invalid position to insert!");
if (Start == End) return;
Chunks.insert(Offset, MakeRopeString(Start, End));
}
void erase(unsigned Offset, unsigned NumBytes) {
assert(Offset+NumBytes <= size() && "Invalid region to erase!");
if (NumBytes == 0) return;
Chunks.erase(Offset, NumBytes);
}
private:
RopePiece MakeRopeString(const char *Start, const char *End);
};
} // namespace clang
#endif // LLVM_CLANG_REWRITE_CORE_REWRITEROPE_H
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