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//===- FileMatchTrie.cpp --------------------------------------------------===//
//
// 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 contains the implementation of a FileMatchTrie.
//
//===----------------------------------------------------------------------===//
#include "clang/Tooling/FileMatchTrie.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"
#include <string>
#include <vector>
using namespace clang;
using namespace tooling;
namespace {
/// Default \c PathComparator using \c llvm::sys::fs::equivalent().
struct DefaultPathComparator : public PathComparator {
bool equivalent(StringRef FileA, StringRef FileB) const override {
return FileA == FileB || llvm::sys::fs::equivalent(FileA, FileB);
}
};
} // namespace
namespace clang {
namespace tooling {
/// A node of the \c FileMatchTrie.
///
/// Each node has storage for up to one path and a map mapping a path segment to
/// child nodes. The trie starts with an empty root node.
class FileMatchTrieNode {
public:
/// Inserts 'NewPath' into this trie. \c ConsumedLength denotes
/// the number of \c NewPath's trailing characters already consumed during
/// recursion.
///
/// An insert of a path
/// 'p'starts at the root node and does the following:
/// - If the node is empty, insert 'p' into its storage and abort.
/// - If the node has a path 'p2' but no children, take the last path segment
/// 's' of 'p2', put a new child into the map at 's' an insert the rest of
/// 'p2' there.
/// - Insert a new child for the last segment of 'p' and insert the rest of
/// 'p' there.
///
/// An insert operation is linear in the number of a path's segments.
void insert(StringRef NewPath, unsigned ConsumedLength = 0) {
// We cannot put relative paths into the FileMatchTrie as then a path can be
// a postfix of another path, violating a core assumption of the trie.
if (llvm::sys::path::is_relative(NewPath))
return;
if (Path.empty()) {
// This is an empty leaf. Store NewPath and return.
Path = std::string(NewPath);
return;
}
if (Children.empty()) {
// This is a leaf, ignore duplicate entry if 'Path' equals 'NewPath'.
if (NewPath == Path)
return;
// Make this a node and create a child-leaf with 'Path'.
StringRef Element(llvm::sys::path::filename(
StringRef(Path).drop_back(ConsumedLength)));
Children[Element].Path = Path;
}
StringRef Element(llvm::sys::path::filename(
StringRef(NewPath).drop_back(ConsumedLength)));
Children[Element].insert(NewPath, ConsumedLength + Element.size() + 1);
}
/// Tries to find the node under this \c FileMatchTrieNode that best
/// matches 'FileName'.
///
/// If multiple paths fit 'FileName' equally well, \c IsAmbiguous is set to
/// \c true and an empty string is returned. If no path fits 'FileName', an
/// empty string is returned. \c ConsumedLength denotes the number of
/// \c Filename's trailing characters already consumed during recursion.
///
/// To find the best matching node for a given path 'p', the
/// \c findEquivalent() function is called recursively for each path segment
/// (back to front) of 'p' until a node 'n' is reached that does not ..
/// - .. have children. In this case it is checked
/// whether the stored path is equivalent to 'p'. If yes, the best match is
/// found. Otherwise continue with the parent node as if this node did not
/// exist.
/// - .. a child matching the next path segment. In this case, all children of
/// 'n' are an equally good match for 'p'. All children are of 'n' are found
/// recursively and their equivalence to 'p' is determined. If none are
/// equivalent, continue with the parent node as if 'n' didn't exist. If one
/// is equivalent, the best match is found. Otherwise, report and ambigiuity
/// error.
StringRef findEquivalent(const PathComparator& Comparator,
StringRef FileName,
bool &IsAmbiguous,
unsigned ConsumedLength = 0) const {
// Note: we support only directory symlinks for performance reasons.
if (Children.empty()) {
// As far as we do not support file symlinks, compare
// basenames here to avoid request to file system.
if (llvm::sys::path::filename(Path) ==
llvm::sys::path::filename(FileName) &&
Comparator.equivalent(StringRef(Path), FileName))
return StringRef(Path);
return {};
}
StringRef Element(llvm::sys::path::filename(FileName.drop_back(
ConsumedLength)));
llvm::StringMap<FileMatchTrieNode>::const_iterator MatchingChild =
Children.find(Element);
if (MatchingChild != Children.end()) {
StringRef Result = MatchingChild->getValue().findEquivalent(
Comparator, FileName, IsAmbiguous,
ConsumedLength + Element.size() + 1);
if (!Result.empty() || IsAmbiguous)
return Result;
}
// If `ConsumedLength` is zero, this is the root and we have no filename
// match. Give up in this case, we don't try to find symlinks with
// different names.
if (ConsumedLength == 0)
return {};
std::vector<StringRef> AllChildren;
getAll(AllChildren, MatchingChild);
StringRef Result;
for (const auto &Child : AllChildren) {
if (Comparator.equivalent(Child, FileName)) {
if (Result.empty()) {
Result = Child;
} else {
IsAmbiguous = true;
return {};
}
}
}
return Result;
}
private:
/// Gets all paths under this FileMatchTrieNode.
void getAll(std::vector<StringRef> &Results,
llvm::StringMap<FileMatchTrieNode>::const_iterator Except) const {
if (Path.empty())
return;
if (Children.empty()) {
Results.push_back(StringRef(Path));
return;
}
for (llvm::StringMap<FileMatchTrieNode>::const_iterator
It = Children.begin(), E = Children.end();
It != E; ++It) {
if (It == Except)
continue;
It->getValue().getAll(Results, Children.end());
}
}
// The stored absolute path in this node. Only valid for leaf nodes, i.e.
// nodes where Children.empty().
std::string Path;
// The children of this node stored in a map based on the next path segment.
llvm::StringMap<FileMatchTrieNode> Children;
};
} // namespace tooling
} // namespace clang
FileMatchTrie::FileMatchTrie()
: Root(new FileMatchTrieNode), Comparator(new DefaultPathComparator()) {}
FileMatchTrie::FileMatchTrie(PathComparator *Comparator)
: Root(new FileMatchTrieNode), Comparator(Comparator) {}
FileMatchTrie::~FileMatchTrie() {
delete Root;
}
void FileMatchTrie::insert(StringRef NewPath) {
Root->insert(NewPath);
}
StringRef FileMatchTrie::findEquivalent(StringRef FileName,
raw_ostream &Error) const {
if (llvm::sys::path::is_relative(FileName)) {
Error << "Cannot resolve relative paths";
return {};
}
bool IsAmbiguous = false;
StringRef Result = Root->findEquivalent(*Comparator, FileName, IsAmbiguous);
if (IsAmbiguous)
Error << "Path is ambiguous";
return Result;
}
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