aspnetcore/src/Microsoft.AspNetCore.Routing/Matching/DfaMatcherBuilder.cs

687 lines
27 KiB
C#

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing.Patterns;
using Microsoft.Extensions.Logging;
namespace Microsoft.AspNetCore.Routing.Matching
{
internal class DfaMatcherBuilder : MatcherBuilder
{
private readonly List<RouteEndpoint> _endpoints = new List<RouteEndpoint>();
private readonly ILoggerFactory _loggerFactory;
private readonly ParameterPolicyFactory _parameterPolicyFactory;
private readonly EndpointSelector _selector;
private readonly MatcherPolicy[] _policies;
private readonly INodeBuilderPolicy[] _nodeBuilders;
private readonly EndpointComparer _comparer;
// These collections are reused when building candidates
private readonly Dictionary<string, int> _assignments;
private readonly List<KeyValuePair<string, object>> _slots;
private readonly List<(string parameterName, int segmentIndex, int slotIndex)> _captures;
private readonly List<(RoutePatternPathSegment pathSegment, int segmentIndex)> _complexSegments;
private readonly List<KeyValuePair<string, IRouteConstraint>> _constraints;
private int _stateIndex;
public DfaMatcherBuilder(
ILoggerFactory loggerFactory,
ParameterPolicyFactory parameterPolicyFactory,
EndpointSelector selector,
IEnumerable<MatcherPolicy> policies)
{
_loggerFactory = loggerFactory;
_parameterPolicyFactory = parameterPolicyFactory;
_selector = selector;
_policies = policies.OrderBy(p => p.Order).ToArray();
// Taking care to use _policies, which has been sorted.
_nodeBuilders = _policies.OfType<INodeBuilderPolicy>().ToArray();
_comparer = new EndpointComparer(_policies.OfType<IEndpointComparerPolicy>().ToArray());
_assignments = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
_slots = new List<KeyValuePair<string, object>>();
_captures = new List<(string parameterName, int segmentIndex, int slotIndex)>();
_complexSegments = new List<(RoutePatternPathSegment pathSegment, int segmentIndex)>();
_constraints = new List<KeyValuePair<string, IRouteConstraint>>();
}
public override void AddEndpoint(RouteEndpoint endpoint)
{
_endpoints.Add(endpoint);
}
public DfaNode BuildDfaTree(bool includeLabel = false)
{
// We build the tree by doing a BFS over the list of entries. This is important
// because a 'parameter' node can also traverse the same paths that literal nodes
// traverse. This means that we need to order the entries first, or else we will
// miss possible edges in the DFA.
_endpoints.Sort(_comparer);
// Since we're doing a BFS we will process each 'level' of the tree in stages
// this list will hold the set of items we need to process at the current
// stage.
var work = new List<(RouteEndpoint endpoint, List<DfaNode> parents)>(_endpoints.Count);
List<(RouteEndpoint endpoint, List<DfaNode> parents)> previousWork = null;
var root = new DfaNode() { PathDepth = 0, Label = includeLabel ? "/" : null };
// To prepare for this we need to compute the max depth, as well as
// a seed list of items to process (entry, root).
var maxDepth = 0;
for (var i = 0; i < _endpoints.Count; i++)
{
var endpoint = _endpoints[i];
maxDepth = Math.Max(maxDepth, endpoint.RoutePattern.PathSegments.Count);
work.Add((endpoint, new List<DfaNode>() { root, }));
}
var workCount = work.Count;
// Now we process the entries a level at a time.
for (var depth = 0; depth <= maxDepth; depth++)
{
// As we process items, collect the next set of items.
List<(RouteEndpoint endpoint, List<DfaNode> parents)> nextWork;
var nextWorkCount = 0;
if (previousWork == null)
{
nextWork = new List<(RouteEndpoint endpoint, List<DfaNode> parents)>();
}
else
{
// Reuse previous collection for the next collection
// Don't clear the list so nested lists can be reused
nextWork = previousWork;
}
for (var i = 0; i < workCount; i++)
{
var (endpoint, parents) = work[i];
if (!HasAdditionalRequiredSegments(endpoint, depth))
{
for (var j = 0; j < parents.Count; j++)
{
var parent = parents[j];
parent.AddMatch(endpoint);
}
}
// Find the parents of this edge at the current depth
List<DfaNode> nextParents;
if (nextWorkCount < nextWork.Count)
{
nextParents = nextWork[nextWorkCount].parents;
nextParents.Clear();
nextWork[nextWorkCount] = (endpoint, nextParents);
}
else
{
nextParents = new List<DfaNode>();
// Add to the next set of work now so the list will be reused
// even if there are no parents
nextWork.Add((endpoint, nextParents));
}
var segment = GetCurrentSegment(endpoint, depth);
if (segment == null)
{
continue;
}
for (var j = 0; j < parents.Count; j++)
{
var parent = parents[j];
var part = segment.Parts[0];
if (segment.IsSimple && part is RoutePatternLiteralPart literalPart)
{
DfaNode next = null;
var literal = literalPart.Content;
if (parent.Literals == null ||
!parent.Literals.TryGetValue(literal, out next))
{
next = new DfaNode()
{
PathDepth = parent.PathDepth + 1,
Label = includeLabel ? parent.Label + literal + "/" : null,
};
parent.AddLiteral(literal, next);
}
nextParents.Add(next);
}
else if (segment.IsSimple && part is RoutePatternParameterPart parameterPart && parameterPart.IsCatchAll)
{
// A catch all should traverse all literal nodes as well as parameter nodes
// we don't need to create the parameter node here because of ordering
// all catchalls will be processed after all parameters.
if (parent.Literals != null)
{
nextParents.AddRange(parent.Literals.Values);
}
if (parent.Parameters != null)
{
nextParents.Add(parent.Parameters);
}
// We also create a 'catchall' here. We don't do further traversals
// on the catchall node because only catchalls can end up here. The
// catchall node allows us to capture an unlimited amount of segments
// and also to match a zero-length segment, which a parameter node
// doesn't allow.
if (parent.CatchAll == null)
{
parent.CatchAll = new DfaNode()
{
PathDepth = parent.PathDepth + 1,
Label = includeLabel ? parent.Label + "{*...}/" : null,
};
// The catchall node just loops.
parent.CatchAll.Parameters = parent.CatchAll;
parent.CatchAll.CatchAll = parent.CatchAll;
}
parent.CatchAll.AddMatch(endpoint);
}
else if (segment.IsSimple && part.IsParameter)
{
if (parent.Parameters == null)
{
parent.Parameters = new DfaNode()
{
PathDepth = parent.PathDepth + 1,
Label = includeLabel ? parent.Label + "{...}/" : null,
};
}
// A parameter should traverse all literal nodes as well as the parameter node
if (parent.Literals != null)
{
nextParents.AddRange(parent.Literals.Values);
}
nextParents.Add(parent.Parameters);
}
else
{
// Complex segment - we treat these are parameters here and do the
// expensive processing later. We don't want to spend time processing
// complex segments unless they are the best match, and treating them
// like parameters in the DFA allows us to do just that.
if (parent.Parameters == null)
{
parent.Parameters = new DfaNode()
{
PathDepth = parent.PathDepth + 1,
Label = includeLabel ? parent.Label + "{...}/" : null,
};
}
if (parent.Literals != null)
{
nextParents.AddRange(parent.Literals.Values);
}
nextParents.Add(parent.Parameters);
}
}
if (nextParents.Count > 0)
{
nextWorkCount++;
}
}
// Prepare the process the next stage.
previousWork = work;
work = nextWork;
workCount = nextWorkCount;
}
// Build the trees of policy nodes (like HTTP methods). Post-order traversal
// means that we won't have infinite recursion.
root.Visit(ApplyPolicies);
return root;
}
private RoutePatternPathSegment GetCurrentSegment(RouteEndpoint endpoint, int depth)
{
if (depth < endpoint.RoutePattern.PathSegments.Count)
{
return endpoint.RoutePattern.PathSegments[depth];
}
if (endpoint.RoutePattern.PathSegments.Count == 0)
{
return null;
}
var lastSegment = endpoint.RoutePattern.PathSegments[endpoint.RoutePattern.PathSegments.Count - 1];
if (lastSegment.IsSimple && lastSegment.Parts[0] is RoutePatternParameterPart parameterPart && parameterPart.IsCatchAll)
{
return lastSegment;
}
return null;
}
public override Matcher Build()
{
#if DEBUG
var includeLabel = true;
#else
var includeLabel = false;
#endif
var root = BuildDfaTree(includeLabel);
// State count is the number of nodes plus an exit state
var stateCount = 1;
var maxSegmentCount = 0;
root.Visit((node) =>
{
stateCount++;
maxSegmentCount = Math.Max(maxSegmentCount, node.PathDepth);
});
_stateIndex = 0;
// The max segment count is the maximum path-node-depth +1. We need
// the +1 to capture any additional content after the 'last' segment.
maxSegmentCount++;
var states = new DfaState[stateCount];
var exitDestination = stateCount - 1;
AddNode(root, states, exitDestination);
// The root state only has a jump table.
states[exitDestination] = new DfaState(
Array.Empty<Candidate>(),
Array.Empty<IEndpointSelectorPolicy>(),
JumpTableBuilder.Build(exitDestination, exitDestination, null),
null);
return new DfaMatcher(_loggerFactory.CreateLogger<DfaMatcher>(), _selector, states, maxSegmentCount);
}
private int AddNode(
DfaNode node,
DfaState[] states,
int exitDestination)
{
node.Matches?.Sort(_comparer);
var currentStateIndex = _stateIndex;
var currentDefaultDestination = exitDestination;
var currentExitDestination = exitDestination;
(string text, int destination)[] pathEntries = null;
PolicyJumpTableEdge[] policyEntries = null;
if (node.Literals != null)
{
pathEntries = new (string text, int destination)[node.Literals.Count];
var index = 0;
foreach (var kvp in node.Literals)
{
var transition = Transition(kvp.Value);
pathEntries[index++] = (kvp.Key, transition);
}
}
if (node.Parameters != null &&
node.CatchAll != null &&
ReferenceEquals(node.Parameters, node.CatchAll))
{
// This node has a single transition to but it should accept zero-width segments
// this can happen when a node only has catchall parameters.
currentExitDestination = currentDefaultDestination = Transition(node.Parameters);
}
else if (node.Parameters != null && node.CatchAll != null)
{
// This node has a separate transition for zero-width segments
// this can happen when a node has both parameters and catchall parameters.
currentDefaultDestination = Transition(node.Parameters);
currentExitDestination = Transition(node.CatchAll);
}
else if (node.Parameters != null)
{
// This node has paramters but no catchall.
currentDefaultDestination = Transition(node.Parameters);
}
else if (node.CatchAll != null)
{
// This node has a catchall but no parameters
currentExitDestination = currentDefaultDestination = Transition(node.CatchAll);
}
if (node.PolicyEdges != null && node.PolicyEdges.Count > 0)
{
policyEntries = new PolicyJumpTableEdge[node.PolicyEdges.Count];
var index = 0;
foreach (var kvp in node.PolicyEdges)
{
policyEntries[index++] = new PolicyJumpTableEdge(kvp.Key, Transition(kvp.Value));
}
}
var candidates = CreateCandidates(node.Matches);
// Perf: most of the time there aren't any endpoint selector policies, create
// this lazily.
List<IEndpointSelectorPolicy> endpointSelectorPolicies = null;
if (node.Matches?.Count > 0)
{
for (var i = 0; i < _policies.Length; i++)
{
if (_policies[i] is IEndpointSelectorPolicy endpointSelectorPolicy &&
endpointSelectorPolicy.AppliesToEndpoints(node.Matches))
{
if (endpointSelectorPolicies == null)
{
endpointSelectorPolicies = new List<IEndpointSelectorPolicy>();
}
endpointSelectorPolicies.Add(endpointSelectorPolicy);
}
}
}
states[currentStateIndex] = new DfaState(
candidates,
endpointSelectorPolicies?.ToArray() ?? Array.Empty<IEndpointSelectorPolicy>(),
JumpTableBuilder.Build(currentDefaultDestination, currentExitDestination, pathEntries),
BuildPolicy(currentExitDestination, node.NodeBuilder, policyEntries));
return currentStateIndex;
int Transition(DfaNode next)
{
// Break cycles
if (ReferenceEquals(node, next))
{
return _stateIndex;
}
else
{
_stateIndex++;
return AddNode(next, states, exitDestination);
}
}
}
private static PolicyJumpTable BuildPolicy(int exitDestination, INodeBuilderPolicy nodeBuilder, PolicyJumpTableEdge[] policyEntries)
{
if (policyEntries == null)
{
return null;
}
return nodeBuilder.BuildJumpTable(exitDestination, policyEntries);
}
// Builds an array of candidates for a node, assigns a 'score' for each
// endpoint.
internal Candidate[] CreateCandidates(IReadOnlyList<Endpoint> endpoints)
{
if (endpoints == null || endpoints.Count == 0)
{
return Array.Empty<Candidate>();
}
var candiates = new Candidate[endpoints.Count];
var score = 0;
var examplar = endpoints[0];
candiates[0] = CreateCandidate(examplar, score);
for (var i = 1; i < endpoints.Count; i++)
{
var endpoint = endpoints[i];
if (!_comparer.Equals(examplar, endpoint))
{
// This endpoint doesn't have the same priority.
examplar = endpoint;
score++;
}
candiates[i] = CreateCandidate(endpoint, score);
}
return candiates;
}
// internal for tests
internal Candidate CreateCandidate(Endpoint endpoint, int score)
{
_assignments.Clear();
_slots.Clear();
_captures.Clear();
_complexSegments.Clear();
_constraints.Clear();
(string parameterName, int segmentIndex, int slotIndex) catchAll = default;
if (endpoint is RouteEndpoint routeEndpoint)
{
foreach (var kvp in routeEndpoint.RoutePattern.Defaults)
{
_assignments.Add(kvp.Key, _assignments.Count);
_slots.Add(kvp);
}
for (var i = 0; i < routeEndpoint.RoutePattern.PathSegments.Count; i++)
{
var segment = routeEndpoint.RoutePattern.PathSegments[i];
if (!segment.IsSimple)
{
continue;
}
var parameterPart = segment.Parts[0] as RoutePatternParameterPart;
if (parameterPart == null)
{
continue;
}
if (!_assignments.TryGetValue(parameterPart.Name, out var slotIndex))
{
slotIndex = _assignments.Count;
_assignments.Add(parameterPart.Name, slotIndex);
var hasDefaultValue = parameterPart.Default != null || parameterPart.IsCatchAll;
_slots.Add(hasDefaultValue ? new KeyValuePair<string, object>(parameterPart.Name, parameterPart.Default) : default);
}
if (parameterPart.IsCatchAll)
{
catchAll = (parameterPart.Name, i, slotIndex);
}
else
{
_captures.Add((parameterPart.Name, i, slotIndex));
}
}
for (var i = 0; i < routeEndpoint.RoutePattern.PathSegments.Count; i++)
{
var segment = routeEndpoint.RoutePattern.PathSegments[i];
if (segment.IsSimple)
{
continue;
}
_complexSegments.Add((segment, i));
}
foreach (var kvp in routeEndpoint.RoutePattern.ParameterPolicies)
{
var parameter = routeEndpoint.RoutePattern.GetParameter(kvp.Key); // may be null, that's ok
var parameterPolicyReferences = kvp.Value;
for (var i = 0; i < parameterPolicyReferences.Count; i++)
{
var reference = parameterPolicyReferences[i];
var parameterPolicy = _parameterPolicyFactory.Create(parameter, reference);
if (parameterPolicy is IRouteConstraint routeConstraint)
{
_constraints.Add(new KeyValuePair<string, IRouteConstraint>(kvp.Key, routeConstraint));
}
}
}
}
return new Candidate(
endpoint,
score,
_slots.ToArray(),
_captures.ToArray(),
catchAll,
_complexSegments.ToArray(),
_constraints.ToArray());
}
private int[] GetGroupLengths(DfaNode node)
{
var nodeMatches = node.Matches;
if (nodeMatches == null || nodeMatches.Count == 0)
{
return Array.Empty<int>();
}
var groups = new List<int>();
var length = 1;
var exemplar = nodeMatches[0];
for (var i = 1; i < nodeMatches.Count; i++)
{
if (!_comparer.Equals(exemplar, nodeMatches[i]))
{
groups.Add(length);
length = 0;
exemplar = nodeMatches[i];
}
length++;
}
groups.Add(length);
return groups.ToArray();
}
private static bool HasAdditionalRequiredSegments(RouteEndpoint endpoint, int depth)
{
for (var i = depth; i < endpoint.RoutePattern.PathSegments.Count; i++)
{
var segment = endpoint.RoutePattern.PathSegments[i];
if (!segment.IsSimple)
{
// Complex segments always require more processing
return true;
}
var parameterPart = segment.Parts[0] as RoutePatternParameterPart;
if (parameterPart == null)
{
// It's a literal
return true;
}
if (!parameterPart.IsOptional &&
!parameterPart.IsCatchAll &&
parameterPart.Default == null)
{
return true;
}
}
return false;
}
private void ApplyPolicies(DfaNode node)
{
if (node.Matches == null || node.Matches.Count == 0)
{
return;
}
// Start with the current node as the root.
var work = new List<DfaNode>() { node, };
List<DfaNode> previousWork = null;
for (var i = 0; i < _nodeBuilders.Length; i++)
{
var nodeBuilder = _nodeBuilders[i];
// Build a list of each
List<DfaNode> nextWork;
if (previousWork == null)
{
nextWork = new List<DfaNode>();
}
else
{
// Reuse previous collection for the next collection
previousWork.Clear();
nextWork = previousWork;
}
for (var j = 0; j < work.Count; j++)
{
var parent = work[j];
if (!nodeBuilder.AppliesToEndpoints(parent.Matches ?? (IReadOnlyList<Endpoint>)Array.Empty<Endpoint>()))
{
// This node-builder doesn't care about this node, so add it to the list
// to be processed by the next node-builder.
nextWork.Add(parent);
continue;
}
// This node-builder does apply to this node, so we need to create new nodes for each edge,
// and then attach them to the parent.
var edges = nodeBuilder.GetEdges(parent.Matches ?? (IReadOnlyList<Endpoint>)Array.Empty<Endpoint>());
for (var k = 0; k < edges.Count; k++)
{
var edge = edges[k];
var next = new DfaNode()
{
// If parent label is null then labels are not being included
Label = (parent.Label != null) ? parent.Label + " " + edge.State.ToString() : null,
};
if (edge.Endpoints.Count > 0)
{
next.AddMatches(edge.Endpoints);
}
nextWork.Add(next);
parent.AddPolicyEdge(edge.State, next);
}
// Associate the node-builder so we can build a jump table later.
parent.NodeBuilder = nodeBuilder;
// The parent no longer has matches, it's not considered a terminal node.
parent.Matches?.Clear();
}
previousWork = work;
work = nextWork;
}
}
}
}