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| 1 | +// Copyright 2023 CUE Authors |
| 2 | +// |
| 3 | +// Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | +// you may not use this file except in compliance with the License. |
| 5 | +// You may obtain a copy of the License at |
| 6 | +// |
| 7 | +// http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | +// |
| 9 | +// Unless required by applicable law or agreed to in writing, software |
| 10 | +// distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | +// See the License for the specific language governing permissions and |
| 13 | +// limitations under the License. |
| 14 | + |
| 15 | +package adt |
| 16 | + |
| 17 | +// This file contains functionality for pattern constraints. |
| 18 | + |
| 19 | +// Constraints keeps track of pattern constraints and the set of allowed |
| 20 | +// fields. |
| 21 | +type Constraints struct { |
| 22 | + // Pairs lists Pattern-Constraint pairs. |
| 23 | + Pairs []PatternConstraint // TODO(perf): move to Arcs? |
| 24 | + |
| 25 | + // Allowed is a Value that defines the set of all allowed fields. |
| 26 | + // To check if a field is allowed, its correpsonding CUE value can be |
| 27 | + // unified with this value. |
| 28 | + Allowed Value |
| 29 | +} |
| 30 | + |
| 31 | +// A PatternConstraint represents a single |
| 32 | +// |
| 33 | +// [pattern]: T. |
| 34 | +// |
| 35 | +// The Vertex holds a list of conjuncts to represent the constraints. We use |
| 36 | +// a Vertex so that these can be evaluated and compared for equality. |
| 37 | +// Unlike for regular Vertex values, CloseInfo.closeContext is set for |
| 38 | +// constraints: it is needed when matching subfields to ensure that conjuncts |
| 39 | +// get inserted into the proper groups. |
| 40 | +type PatternConstraint struct { |
| 41 | + Pattern Value |
| 42 | + Constraint *Vertex |
| 43 | +} |
| 44 | + |
| 45 | +// insertListEllipsis inserts the given list ellipsis as a pattern constraint on |
| 46 | +// n, applying it to all elements at indexes >= offset. |
| 47 | +func (n *nodeContext) insertListEllipsis(offset int, ellipsis Conjunct) { |
| 48 | + ctx := n.ctx |
| 49 | + |
| 50 | + var p Value |
| 51 | + if offset == 0 { |
| 52 | + p = &BasicType{ |
| 53 | + Src: ellipsis.Field().Source(), |
| 54 | + K: IntKind, |
| 55 | + } |
| 56 | + } else { |
| 57 | + p = &BoundValue{ |
| 58 | + Src: nil, // TODO: field source. |
| 59 | + Op: GreaterEqualOp, |
| 60 | + Value: ctx.NewInt64(int64(offset)), |
| 61 | + } |
| 62 | + } |
| 63 | + n.insertConstraint(p, ellipsis) |
| 64 | +} |
| 65 | + |
| 66 | +// insertConstraint ensures a given pattern constraint is present in the |
| 67 | +// constraints of n and reports whether the pair was added newly. |
| 68 | +// |
| 69 | +// The given conjunct must have a closeContext associated with it. This ensures |
| 70 | +// that different pattern constraints pairs originating from the same |
| 71 | +// closeContext will be collated properly in fields to which these constraints |
| 72 | +// are applied. |
| 73 | +func (n *nodeContext) insertConstraint(pattern Value, c Conjunct) bool { |
| 74 | + if c.CloseInfo.cc == nil { |
| 75 | + panic("constraint conjunct must have closeContext associated with it") |
| 76 | + } |
| 77 | + |
| 78 | + ctx := n.ctx |
| 79 | + v := n.node |
| 80 | + |
| 81 | + pcs := v.PatternConstraints |
| 82 | + if pcs == nil { |
| 83 | + pcs = &Constraints{} |
| 84 | + v.PatternConstraints = pcs |
| 85 | + } |
| 86 | + |
| 87 | + var constraint *Vertex |
| 88 | + for _, pc := range pcs.Pairs { |
| 89 | + if Equal(ctx, pc.Pattern, pattern, 0) { |
| 90 | + constraint = pc.Constraint |
| 91 | + break |
| 92 | + } |
| 93 | + } |
| 94 | + |
| 95 | + if constraint == nil { |
| 96 | + constraint = &Vertex{} |
| 97 | + pcs.Pairs = append(pcs.Pairs, PatternConstraint{ |
| 98 | + Pattern: pattern, |
| 99 | + Constraint: constraint, |
| 100 | + }) |
| 101 | + } else if constraint.hasConjunct(c) { |
| 102 | + // The constraint already existed and the conjunct was already added. |
| 103 | + return false |
| 104 | + } |
| 105 | + |
| 106 | + constraint.addConjunctUnchecked(c) |
| 107 | + return true |
| 108 | +} |
| 109 | + |
| 110 | +// matchPattern reports whether f matches pattern. The result reflects |
| 111 | +// whether unification of pattern with f converted to a CUE value succeeds. |
| 112 | +func matchPattern(n *nodeContext, pattern Value, f Feature) bool { |
| 113 | + if pattern == nil { |
| 114 | + return false |
| 115 | + } |
| 116 | + |
| 117 | + // TODO(perf): this assumes that comparing an int64 against apd.Decimal |
| 118 | + // is faster than converting this to a Num and using that for comparison. |
| 119 | + // This may very well not be the case. But it definitely will be if we |
| 120 | + // special-case integers that can fit in an int64 (or int32 if we want to |
| 121 | + // avoid many bound checks), which we probably should. Especially when we |
| 122 | + // allow list constraints, like [<10]: T. |
| 123 | + var label Value |
| 124 | + if int64(f.Index()) == MaxIndex { |
| 125 | + f = 0 |
| 126 | + } else if f.IsString() { |
| 127 | + label = f.ToValue(n.ctx) |
| 128 | + } |
| 129 | + |
| 130 | + return matchPatternValue(n.ctx, pattern, f, label) |
| 131 | +} |
| 132 | + |
| 133 | +// matchPatternValue matches a concrete value against f. label must be the |
| 134 | +// CUE value that is obtained from converting f. |
| 135 | +// |
| 136 | +// This is an optimization an intended to be faster than regular CUE evaluation |
| 137 | +// for the majority of cases where pattern constraints are used. |
| 138 | +func matchPatternValue(ctx *OpContext, pattern Value, f Feature, label Value) (result bool) { |
| 139 | + pattern = Unwrap(pattern) |
| 140 | + label = Unwrap(label) |
| 141 | + |
| 142 | + if pattern == label { |
| 143 | + return true |
| 144 | + } |
| 145 | + |
| 146 | + // Fast track for the majority of cases. |
| 147 | + switch x := pattern.(type) { |
| 148 | + case *Bottom: |
| 149 | + // TODO: hoist and reuse with the identical code in optional.go. |
| 150 | + if x == cycle { |
| 151 | + err := ctx.NewPosf(pos(pattern), "cyclic pattern constraint") |
| 152 | + for _, c := range ctx.vertex.Conjuncts { |
| 153 | + err.AddPosition(c.Elem()) |
| 154 | + } |
| 155 | + ctx.AddBottom(&Bottom{ |
| 156 | + Err: err, |
| 157 | + }) |
| 158 | + } |
| 159 | + if ctx.errs == nil { |
| 160 | + ctx.AddBottom(x) |
| 161 | + } |
| 162 | + return false |
| 163 | + |
| 164 | + case *Top: |
| 165 | + return true |
| 166 | + |
| 167 | + case *BasicType: |
| 168 | + k := label.Kind() |
| 169 | + return x.K&k == k |
| 170 | + |
| 171 | + case *BoundValue: |
| 172 | + switch x.Kind() { |
| 173 | + case StringKind: |
| 174 | + if label == nil { |
| 175 | + return false |
| 176 | + } |
| 177 | + str := label.(*String).Str |
| 178 | + return x.validateStr(ctx, str) |
| 179 | + |
| 180 | + case NumKind: |
| 181 | + return x.validateInt(ctx, int64(f.Index())) |
| 182 | + } |
| 183 | + |
| 184 | + case *Num: |
| 185 | + if !f.IsInt() { |
| 186 | + return false |
| 187 | + } |
| 188 | + yi := int64(f.Index()) |
| 189 | + xi, err := x.X.Int64() |
| 190 | + return err == nil && xi == yi |
| 191 | + |
| 192 | + case *String: |
| 193 | + y, ok := label.(*String) |
| 194 | + return ok && x.Str == y.Str |
| 195 | + |
| 196 | + case *Conjunction: |
| 197 | + for _, a := range x.Values { |
| 198 | + if !matchPatternValue(ctx, a, f, label) { |
| 199 | + return false |
| 200 | + } |
| 201 | + } |
| 202 | + return true |
| 203 | + |
| 204 | + case *Disjunction: |
| 205 | + for _, a := range x.Values { |
| 206 | + if matchPatternValue(ctx, a, f, label) { |
| 207 | + return true |
| 208 | + } |
| 209 | + } |
| 210 | + return false |
| 211 | + } |
| 212 | + |
| 213 | + // Slow track. |
| 214 | + // |
| 215 | + // TODO(perf): if a pattern tree has many values that are not handled in the |
| 216 | + // fast track, it is probably more efficient to handle everything in the |
| 217 | + // slow track. One way to signal this would be to have a "value thunk" at |
| 218 | + // the root that causes the fast track to be bypassed altogether. |
| 219 | + |
| 220 | + if label == nil { |
| 221 | + label = f.ToValue(ctx) |
| 222 | + } |
| 223 | + |
| 224 | + n := ctx.newInlineVertex(nil, nil, |
| 225 | + MakeConjunct(ctx.e, pattern, ctx.ci), |
| 226 | + MakeConjunct(ctx.e, label, ctx.ci)) |
| 227 | + n.Finalize(ctx) |
| 228 | + return n.Err(ctx) == nil |
| 229 | +} |
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