divyadesai | 81bb7ba | 2020-03-11 11:45:23 +0000 | [diff] [blame] | 1 | package iradix |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "sort" |
| 6 | ) |
| 7 | |
| 8 | // WalkFn is used when walking the tree. Takes a |
| 9 | // key and value, returning if iteration should |
| 10 | // be terminated. |
| 11 | type WalkFn func(k []byte, v interface{}) bool |
| 12 | |
| 13 | // leafNode is used to represent a value |
| 14 | type leafNode struct { |
| 15 | mutateCh chan struct{} |
| 16 | key []byte |
| 17 | val interface{} |
| 18 | } |
| 19 | |
| 20 | // edge is used to represent an edge node |
| 21 | type edge struct { |
| 22 | label byte |
| 23 | node *Node |
| 24 | } |
| 25 | |
| 26 | // Node is an immutable node in the radix tree |
| 27 | type Node struct { |
| 28 | // mutateCh is closed if this node is modified |
| 29 | mutateCh chan struct{} |
| 30 | |
| 31 | // leaf is used to store possible leaf |
| 32 | leaf *leafNode |
| 33 | |
| 34 | // prefix is the common prefix we ignore |
| 35 | prefix []byte |
| 36 | |
| 37 | // Edges should be stored in-order for iteration. |
| 38 | // We avoid a fully materialized slice to save memory, |
| 39 | // since in most cases we expect to be sparse |
| 40 | edges edges |
| 41 | } |
| 42 | |
| 43 | func (n *Node) isLeaf() bool { |
| 44 | return n.leaf != nil |
| 45 | } |
| 46 | |
| 47 | func (n *Node) addEdge(e edge) { |
| 48 | num := len(n.edges) |
| 49 | idx := sort.Search(num, func(i int) bool { |
| 50 | return n.edges[i].label >= e.label |
| 51 | }) |
| 52 | n.edges = append(n.edges, e) |
| 53 | if idx != num { |
| 54 | copy(n.edges[idx+1:], n.edges[idx:num]) |
| 55 | n.edges[idx] = e |
| 56 | } |
| 57 | } |
| 58 | |
| 59 | func (n *Node) replaceEdge(e edge) { |
| 60 | num := len(n.edges) |
| 61 | idx := sort.Search(num, func(i int) bool { |
| 62 | return n.edges[i].label >= e.label |
| 63 | }) |
| 64 | if idx < num && n.edges[idx].label == e.label { |
| 65 | n.edges[idx].node = e.node |
| 66 | return |
| 67 | } |
| 68 | panic("replacing missing edge") |
| 69 | } |
| 70 | |
| 71 | func (n *Node) getEdge(label byte) (int, *Node) { |
| 72 | num := len(n.edges) |
| 73 | idx := sort.Search(num, func(i int) bool { |
| 74 | return n.edges[i].label >= label |
| 75 | }) |
| 76 | if idx < num && n.edges[idx].label == label { |
| 77 | return idx, n.edges[idx].node |
| 78 | } |
| 79 | return -1, nil |
| 80 | } |
| 81 | |
| 82 | func (n *Node) getLowerBoundEdge(label byte) (int, *Node) { |
| 83 | num := len(n.edges) |
| 84 | idx := sort.Search(num, func(i int) bool { |
| 85 | return n.edges[i].label >= label |
| 86 | }) |
| 87 | // we want lower bound behavior so return even if it's not an exact match |
| 88 | if idx < num { |
| 89 | return idx, n.edges[idx].node |
| 90 | } |
| 91 | return -1, nil |
| 92 | } |
| 93 | |
| 94 | func (n *Node) delEdge(label byte) { |
| 95 | num := len(n.edges) |
| 96 | idx := sort.Search(num, func(i int) bool { |
| 97 | return n.edges[i].label >= label |
| 98 | }) |
| 99 | if idx < num && n.edges[idx].label == label { |
| 100 | copy(n.edges[idx:], n.edges[idx+1:]) |
| 101 | n.edges[len(n.edges)-1] = edge{} |
| 102 | n.edges = n.edges[:len(n.edges)-1] |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | func (n *Node) GetWatch(k []byte) (<-chan struct{}, interface{}, bool) { |
| 107 | search := k |
| 108 | watch := n.mutateCh |
| 109 | for { |
| 110 | // Check for key exhaustion |
| 111 | if len(search) == 0 { |
| 112 | if n.isLeaf() { |
| 113 | return n.leaf.mutateCh, n.leaf.val, true |
| 114 | } |
| 115 | break |
| 116 | } |
| 117 | |
| 118 | // Look for an edge |
| 119 | _, n = n.getEdge(search[0]) |
| 120 | if n == nil { |
| 121 | break |
| 122 | } |
| 123 | |
| 124 | // Update to the finest granularity as the search makes progress |
| 125 | watch = n.mutateCh |
| 126 | |
| 127 | // Consume the search prefix |
| 128 | if bytes.HasPrefix(search, n.prefix) { |
| 129 | search = search[len(n.prefix):] |
| 130 | } else { |
| 131 | break |
| 132 | } |
| 133 | } |
| 134 | return watch, nil, false |
| 135 | } |
| 136 | |
| 137 | func (n *Node) Get(k []byte) (interface{}, bool) { |
| 138 | _, val, ok := n.GetWatch(k) |
| 139 | return val, ok |
| 140 | } |
| 141 | |
| 142 | // LongestPrefix is like Get, but instead of an |
| 143 | // exact match, it will return the longest prefix match. |
| 144 | func (n *Node) LongestPrefix(k []byte) ([]byte, interface{}, bool) { |
| 145 | var last *leafNode |
| 146 | search := k |
| 147 | for { |
| 148 | // Look for a leaf node |
| 149 | if n.isLeaf() { |
| 150 | last = n.leaf |
| 151 | } |
| 152 | |
| 153 | // Check for key exhaution |
| 154 | if len(search) == 0 { |
| 155 | break |
| 156 | } |
| 157 | |
| 158 | // Look for an edge |
| 159 | _, n = n.getEdge(search[0]) |
| 160 | if n == nil { |
| 161 | break |
| 162 | } |
| 163 | |
| 164 | // Consume the search prefix |
| 165 | if bytes.HasPrefix(search, n.prefix) { |
| 166 | search = search[len(n.prefix):] |
| 167 | } else { |
| 168 | break |
| 169 | } |
| 170 | } |
| 171 | if last != nil { |
| 172 | return last.key, last.val, true |
| 173 | } |
| 174 | return nil, nil, false |
| 175 | } |
| 176 | |
| 177 | // Minimum is used to return the minimum value in the tree |
| 178 | func (n *Node) Minimum() ([]byte, interface{}, bool) { |
| 179 | for { |
| 180 | if n.isLeaf() { |
| 181 | return n.leaf.key, n.leaf.val, true |
| 182 | } |
| 183 | if len(n.edges) > 0 { |
| 184 | n = n.edges[0].node |
| 185 | } else { |
| 186 | break |
| 187 | } |
| 188 | } |
| 189 | return nil, nil, false |
| 190 | } |
| 191 | |
| 192 | // Maximum is used to return the maximum value in the tree |
| 193 | func (n *Node) Maximum() ([]byte, interface{}, bool) { |
| 194 | for { |
| 195 | if num := len(n.edges); num > 0 { |
| 196 | n = n.edges[num-1].node |
| 197 | continue |
| 198 | } |
| 199 | if n.isLeaf() { |
| 200 | return n.leaf.key, n.leaf.val, true |
| 201 | } else { |
| 202 | break |
| 203 | } |
| 204 | } |
| 205 | return nil, nil, false |
| 206 | } |
| 207 | |
| 208 | // Iterator is used to return an iterator at |
| 209 | // the given node to walk the tree |
| 210 | func (n *Node) Iterator() *Iterator { |
| 211 | return &Iterator{node: n} |
| 212 | } |
| 213 | |
| 214 | // rawIterator is used to return a raw iterator at the given node to walk the |
| 215 | // tree. |
| 216 | func (n *Node) rawIterator() *rawIterator { |
| 217 | iter := &rawIterator{node: n} |
| 218 | iter.Next() |
| 219 | return iter |
| 220 | } |
| 221 | |
| 222 | // Walk is used to walk the tree |
| 223 | func (n *Node) Walk(fn WalkFn) { |
| 224 | recursiveWalk(n, fn) |
| 225 | } |
| 226 | |
| 227 | // WalkPrefix is used to walk the tree under a prefix |
| 228 | func (n *Node) WalkPrefix(prefix []byte, fn WalkFn) { |
| 229 | search := prefix |
| 230 | for { |
| 231 | // Check for key exhaution |
| 232 | if len(search) == 0 { |
| 233 | recursiveWalk(n, fn) |
| 234 | return |
| 235 | } |
| 236 | |
| 237 | // Look for an edge |
| 238 | _, n = n.getEdge(search[0]) |
| 239 | if n == nil { |
| 240 | break |
| 241 | } |
| 242 | |
| 243 | // Consume the search prefix |
| 244 | if bytes.HasPrefix(search, n.prefix) { |
| 245 | search = search[len(n.prefix):] |
| 246 | |
| 247 | } else if bytes.HasPrefix(n.prefix, search) { |
| 248 | // Child may be under our search prefix |
| 249 | recursiveWalk(n, fn) |
| 250 | return |
| 251 | } else { |
| 252 | break |
| 253 | } |
| 254 | } |
| 255 | } |
| 256 | |
| 257 | // WalkPath is used to walk the tree, but only visiting nodes |
| 258 | // from the root down to a given leaf. Where WalkPrefix walks |
| 259 | // all the entries *under* the given prefix, this walks the |
| 260 | // entries *above* the given prefix. |
| 261 | func (n *Node) WalkPath(path []byte, fn WalkFn) { |
| 262 | search := path |
| 263 | for { |
| 264 | // Visit the leaf values if any |
| 265 | if n.leaf != nil && fn(n.leaf.key, n.leaf.val) { |
| 266 | return |
| 267 | } |
| 268 | |
| 269 | // Check for key exhaution |
| 270 | if len(search) == 0 { |
| 271 | return |
| 272 | } |
| 273 | |
| 274 | // Look for an edge |
| 275 | _, n = n.getEdge(search[0]) |
| 276 | if n == nil { |
| 277 | return |
| 278 | } |
| 279 | |
| 280 | // Consume the search prefix |
| 281 | if bytes.HasPrefix(search, n.prefix) { |
| 282 | search = search[len(n.prefix):] |
| 283 | } else { |
| 284 | break |
| 285 | } |
| 286 | } |
| 287 | } |
| 288 | |
| 289 | // recursiveWalk is used to do a pre-order walk of a node |
| 290 | // recursively. Returns true if the walk should be aborted |
| 291 | func recursiveWalk(n *Node, fn WalkFn) bool { |
| 292 | // Visit the leaf values if any |
| 293 | if n.leaf != nil && fn(n.leaf.key, n.leaf.val) { |
| 294 | return true |
| 295 | } |
| 296 | |
| 297 | // Recurse on the children |
| 298 | for _, e := range n.edges { |
| 299 | if recursiveWalk(e.node, fn) { |
| 300 | return true |
| 301 | } |
| 302 | } |
| 303 | return false |
| 304 | } |