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1//===--- FileDistance.h - File proximity scoring -----------------*- C++-*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This library measures the distance between file paths.10// It's used for ranking symbols, e.g. in code completion.11// |foo/bar.h -> foo/bar.h| = 0.12// |foo/bar.h -> foo/baz.h| < |foo/bar.h -> baz.h|.13// This is an edit-distance, where edits go up or down the directory tree.14// It's not symmetrical, the costs of going up and down may not match.15//16// Dealing with multiple sources:17// In practice we care about the distance from a source file, but files near18// its main-header and #included files are considered "close".19// So we start with a set of (anchor, cost) pairs, and call the distance to a20// path the minimum of `cost + |source -> path|`.21//22// We allow each source to limit the number of up-traversals paths may start23// with. Up-traversals may reach things that are not "semantically near".24//25// Symbol URI schemes:26// Symbol locations may be represented by URIs rather than file paths directly.27// In this case we want to perform distance computations in URI space rather28// than in file-space, without performing redundant conversions.29// Therefore we have a lookup structure that accepts URIs, so that intermediate30// calculations for the same scheme can be reused.31//32// Caveats:33// Assuming up and down traversals each have uniform costs is simplistic.34// Often there are "semantic roots" whose children are almost unrelated.35// (e.g. /usr/include/, or / in an umbrella repository). We ignore this.36//37//===----------------------------------------------------------------------===//38 39#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FILEDISTANCE_H40#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FILEDISTANCE_H41 42#include "llvm/ADT/ArrayRef.h"43#include "llvm/ADT/DenseMap.h"44#include "llvm/ADT/StringMap.h"45#include "llvm/ADT/StringRef.h"46#include <memory>47 48namespace clang {49namespace clangd {50 51struct FileDistanceOptions {52 unsigned UpCost = 2; // |foo/bar.h -> foo|53 unsigned DownCost = 1; // |foo -> foo/bar.h|54 unsigned IncludeCost = 2; // |foo.cc -> included_header.h|55 bool AllowDownTraversalFromRoot = true; // | / -> /a |56};57 58struct SourceParams {59 // Base cost for paths starting at this source.60 unsigned Cost = 0;61 // Limits the number of upwards traversals allowed from this source.62 unsigned MaxUpTraversals = std::numeric_limits<unsigned>::max();63};64 65// Supports lookups to find the minimum distance to a file from any source.66// This object should be reused, it memoizes intermediate computations.67class FileDistance {68public:69 static constexpr unsigned Unreachable = std::numeric_limits<unsigned>::max();70 static const llvm::hash_code RootHash;71 72 FileDistance(llvm::StringMap<SourceParams> Sources,73 const FileDistanceOptions &Opts = {});74 75 // Computes the minimum distance from any source to the file path.76 unsigned distance(llvm::StringRef Path);77 78private:79 // Costs computed so far. Always contains sources and their ancestors.80 // We store hash codes only. Collisions are rare and consequences aren't dire.81 llvm::DenseMap<llvm::hash_code, unsigned> Cache;82 FileDistanceOptions Opts;83};84 85// Supports lookups like FileDistance, but the lookup keys are URIs.86// We convert each of the sources to the scheme of the URI and do a FileDistance87// comparison on the bodies.88class URIDistance {89public:90 // \p Sources must contain absolute paths, not URIs.91 URIDistance(llvm::StringMap<SourceParams> Sources,92 const FileDistanceOptions &Opts = {})93 : Sources(Sources), Opts(Opts) {}94 95 // Computes the minimum distance from any source to the URI.96 // Only sources that can be mapped into the URI's scheme are considered.97 unsigned distance(llvm::StringRef URI);98 99private:100 // Returns the FileDistance for a URI scheme, creating it if needed.101 FileDistance &forScheme(llvm::StringRef Scheme);102 103 // We cache the results using the original strings so we can skip URI parsing.104 llvm::DenseMap<llvm::hash_code, unsigned> Cache;105 llvm::StringMap<SourceParams> Sources;106 llvm::StringMap<std::unique_ptr<FileDistance>> ByScheme;107 FileDistanceOptions Opts;108};109 110/// Support lookups like FileDistance, but the lookup keys are symbol scopes.111/// For example, a scope "na::nb::" is converted to "/na/nb".112class ScopeDistance {113public:114 /// QueryScopes[0] is the preferred scope.115 ScopeDistance(llvm::ArrayRef<std::string> QueryScopes);116 117 unsigned distance(llvm::StringRef SymbolScope);118 119private:120 FileDistance Distance;121};122 123} // namespace clangd124} // namespace clang125 126#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_FILEDISTANCE_H127