rss-tools/vendor/go.etcd.io/bbolt/internal/common/page.go (view raw)
| 1 | package common |
| 2 | |
| 3 | import ( |
| 4 | "fmt" |
| 5 | "os" |
| 6 | "sort" |
| 7 | "unsafe" |
| 8 | ) |
| 9 | |
| 10 | const PageHeaderSize = unsafe.Sizeof(Page{}) |
| 11 | |
| 12 | const MinKeysPerPage = 2 |
| 13 | |
| 14 | const BranchPageElementSize = unsafe.Sizeof(branchPageElement{}) |
| 15 | const LeafPageElementSize = unsafe.Sizeof(leafPageElement{}) |
| 16 | const pgidSize = unsafe.Sizeof(Pgid(0)) |
| 17 | |
| 18 | const ( |
| 19 | BranchPageFlag = 0x01 |
| 20 | LeafPageFlag = 0x02 |
| 21 | MetaPageFlag = 0x04 |
| 22 | FreelistPageFlag = 0x10 |
| 23 | ) |
| 24 | |
| 25 | const ( |
| 26 | BucketLeafFlag = 0x01 |
| 27 | ) |
| 28 | |
| 29 | type Pgid uint64 |
| 30 | |
| 31 | type Page struct { |
| 32 | id Pgid |
| 33 | flags uint16 |
| 34 | count uint16 |
| 35 | overflow uint32 |
| 36 | } |
| 37 | |
| 38 | func NewPage(id Pgid, flags, count uint16, overflow uint32) *Page { |
| 39 | return &Page{ |
| 40 | id: id, |
| 41 | flags: flags, |
| 42 | count: count, |
| 43 | overflow: overflow, |
| 44 | } |
| 45 | } |
| 46 | |
| 47 | // Typ returns a human-readable page type string used for debugging. |
| 48 | func (p *Page) Typ() string { |
| 49 | if p.IsBranchPage() { |
| 50 | return "branch" |
| 51 | } else if p.IsLeafPage() { |
| 52 | return "leaf" |
| 53 | } else if p.IsMetaPage() { |
| 54 | return "meta" |
| 55 | } else if p.IsFreelistPage() { |
| 56 | return "freelist" |
| 57 | } |
| 58 | return fmt.Sprintf("unknown<%02x>", p.flags) |
| 59 | } |
| 60 | |
| 61 | func (p *Page) IsBranchPage() bool { |
| 62 | return p.flags == BranchPageFlag |
| 63 | } |
| 64 | |
| 65 | func (p *Page) IsLeafPage() bool { |
| 66 | return p.flags == LeafPageFlag |
| 67 | } |
| 68 | |
| 69 | func (p *Page) IsMetaPage() bool { |
| 70 | return p.flags == MetaPageFlag |
| 71 | } |
| 72 | |
| 73 | func (p *Page) IsFreelistPage() bool { |
| 74 | return p.flags == FreelistPageFlag |
| 75 | } |
| 76 | |
| 77 | // Meta returns a pointer to the metadata section of the page. |
| 78 | func (p *Page) Meta() *Meta { |
| 79 | return (*Meta)(UnsafeAdd(unsafe.Pointer(p), unsafe.Sizeof(*p))) |
| 80 | } |
| 81 | |
| 82 | func (p *Page) FastCheck(id Pgid) { |
| 83 | Assert(p.id == id, "Page expected to be: %v, but self identifies as %v", id, p.id) |
| 84 | // Only one flag of page-type can be set. |
| 85 | Assert(p.IsBranchPage() || |
| 86 | p.IsLeafPage() || |
| 87 | p.IsMetaPage() || |
| 88 | p.IsFreelistPage(), |
| 89 | "page %v: has unexpected type/flags: %x", p.id, p.flags) |
| 90 | } |
| 91 | |
| 92 | // LeafPageElement retrieves the leaf node by index |
| 93 | func (p *Page) LeafPageElement(index uint16) *leafPageElement { |
| 94 | return (*leafPageElement)(UnsafeIndex(unsafe.Pointer(p), unsafe.Sizeof(*p), |
| 95 | LeafPageElementSize, int(index))) |
| 96 | } |
| 97 | |
| 98 | // LeafPageElements retrieves a list of leaf nodes. |
| 99 | func (p *Page) LeafPageElements() []leafPageElement { |
| 100 | if p.count == 0 { |
| 101 | return nil |
| 102 | } |
| 103 | data := UnsafeAdd(unsafe.Pointer(p), unsafe.Sizeof(*p)) |
| 104 | elems := unsafe.Slice((*leafPageElement)(data), int(p.count)) |
| 105 | return elems |
| 106 | } |
| 107 | |
| 108 | // BranchPageElement retrieves the branch node by index |
| 109 | func (p *Page) BranchPageElement(index uint16) *branchPageElement { |
| 110 | return (*branchPageElement)(UnsafeIndex(unsafe.Pointer(p), unsafe.Sizeof(*p), |
| 111 | unsafe.Sizeof(branchPageElement{}), int(index))) |
| 112 | } |
| 113 | |
| 114 | // BranchPageElements retrieves a list of branch nodes. |
| 115 | func (p *Page) BranchPageElements() []branchPageElement { |
| 116 | if p.count == 0 { |
| 117 | return nil |
| 118 | } |
| 119 | data := UnsafeAdd(unsafe.Pointer(p), unsafe.Sizeof(*p)) |
| 120 | elems := unsafe.Slice((*branchPageElement)(data), int(p.count)) |
| 121 | return elems |
| 122 | } |
| 123 | |
| 124 | func (p *Page) FreelistPageCount() (int, int) { |
| 125 | Assert(p.IsFreelistPage(), fmt.Sprintf("can't get freelist page count from a non-freelist page: %2x", p.flags)) |
| 126 | |
| 127 | // If the page.count is at the max uint16 value (64k) then it's considered |
| 128 | // an overflow and the size of the freelist is stored as the first element. |
| 129 | var idx, count = 0, int(p.count) |
| 130 | if count == 0xFFFF { |
| 131 | idx = 1 |
| 132 | c := *(*Pgid)(UnsafeAdd(unsafe.Pointer(p), unsafe.Sizeof(*p))) |
| 133 | count = int(c) |
| 134 | if count < 0 { |
| 135 | panic(fmt.Sprintf("leading element count %d overflows int", c)) |
| 136 | } |
| 137 | } |
| 138 | |
| 139 | return idx, count |
| 140 | } |
| 141 | |
| 142 | func (p *Page) FreelistPageIds() []Pgid { |
| 143 | Assert(p.IsFreelistPage(), fmt.Sprintf("can't get freelist page IDs from a non-freelist page: %2x", p.flags)) |
| 144 | |
| 145 | idx, count := p.FreelistPageCount() |
| 146 | |
| 147 | if count == 0 { |
| 148 | return nil |
| 149 | } |
| 150 | |
| 151 | data := UnsafeIndex(unsafe.Pointer(p), unsafe.Sizeof(*p), pgidSize, idx) |
| 152 | ids := unsafe.Slice((*Pgid)(data), count) |
| 153 | |
| 154 | return ids |
| 155 | } |
| 156 | |
| 157 | // dump writes n bytes of the page to STDERR as hex output. |
| 158 | func (p *Page) hexdump(n int) { |
| 159 | buf := UnsafeByteSlice(unsafe.Pointer(p), 0, 0, n) |
| 160 | fmt.Fprintf(os.Stderr, "%x\n", buf) |
| 161 | } |
| 162 | |
| 163 | func (p *Page) PageElementSize() uintptr { |
| 164 | if p.IsLeafPage() { |
| 165 | return LeafPageElementSize |
| 166 | } |
| 167 | return BranchPageElementSize |
| 168 | } |
| 169 | |
| 170 | func (p *Page) Id() Pgid { |
| 171 | return p.id |
| 172 | } |
| 173 | |
| 174 | func (p *Page) SetId(target Pgid) { |
| 175 | p.id = target |
| 176 | } |
| 177 | |
| 178 | func (p *Page) Flags() uint16 { |
| 179 | return p.flags |
| 180 | } |
| 181 | |
| 182 | func (p *Page) SetFlags(v uint16) { |
| 183 | p.flags = v |
| 184 | } |
| 185 | |
| 186 | func (p *Page) Count() uint16 { |
| 187 | return p.count |
| 188 | } |
| 189 | |
| 190 | func (p *Page) SetCount(target uint16) { |
| 191 | p.count = target |
| 192 | } |
| 193 | |
| 194 | func (p *Page) Overflow() uint32 { |
| 195 | return p.overflow |
| 196 | } |
| 197 | |
| 198 | func (p *Page) SetOverflow(target uint32) { |
| 199 | p.overflow = target |
| 200 | } |
| 201 | |
| 202 | func (p *Page) String() string { |
| 203 | return fmt.Sprintf("ID: %d, Type: %s, count: %d, overflow: %d", p.id, p.Typ(), p.count, p.overflow) |
| 204 | } |
| 205 | |
| 206 | type Pages []*Page |
| 207 | |
| 208 | func (s Pages) Len() int { return len(s) } |
| 209 | func (s Pages) Swap(i, j int) { s[i], s[j] = s[j], s[i] } |
| 210 | func (s Pages) Less(i, j int) bool { return s[i].id < s[j].id } |
| 211 | |
| 212 | // branchPageElement represents a node on a branch page. |
| 213 | type branchPageElement struct { |
| 214 | pos uint32 |
| 215 | ksize uint32 |
| 216 | pgid Pgid |
| 217 | } |
| 218 | |
| 219 | func (n *branchPageElement) Pos() uint32 { |
| 220 | return n.pos |
| 221 | } |
| 222 | |
| 223 | func (n *branchPageElement) SetPos(v uint32) { |
| 224 | n.pos = v |
| 225 | } |
| 226 | |
| 227 | func (n *branchPageElement) Ksize() uint32 { |
| 228 | return n.ksize |
| 229 | } |
| 230 | |
| 231 | func (n *branchPageElement) SetKsize(v uint32) { |
| 232 | n.ksize = v |
| 233 | } |
| 234 | |
| 235 | func (n *branchPageElement) Pgid() Pgid { |
| 236 | return n.pgid |
| 237 | } |
| 238 | |
| 239 | func (n *branchPageElement) SetPgid(v Pgid) { |
| 240 | n.pgid = v |
| 241 | } |
| 242 | |
| 243 | // Key returns a byte slice of the node key. |
| 244 | func (n *branchPageElement) Key() []byte { |
| 245 | return UnsafeByteSlice(unsafe.Pointer(n), 0, int(n.pos), int(n.pos)+int(n.ksize)) |
| 246 | } |
| 247 | |
| 248 | // leafPageElement represents a node on a leaf page. |
| 249 | type leafPageElement struct { |
| 250 | flags uint32 |
| 251 | pos uint32 |
| 252 | ksize uint32 |
| 253 | vsize uint32 |
| 254 | } |
| 255 | |
| 256 | func NewLeafPageElement(flags, pos, ksize, vsize uint32) *leafPageElement { |
| 257 | return &leafPageElement{ |
| 258 | flags: flags, |
| 259 | pos: pos, |
| 260 | ksize: ksize, |
| 261 | vsize: vsize, |
| 262 | } |
| 263 | } |
| 264 | |
| 265 | func (n *leafPageElement) Flags() uint32 { |
| 266 | return n.flags |
| 267 | } |
| 268 | |
| 269 | func (n *leafPageElement) SetFlags(v uint32) { |
| 270 | n.flags = v |
| 271 | } |
| 272 | |
| 273 | func (n *leafPageElement) Pos() uint32 { |
| 274 | return n.pos |
| 275 | } |
| 276 | |
| 277 | func (n *leafPageElement) SetPos(v uint32) { |
| 278 | n.pos = v |
| 279 | } |
| 280 | |
| 281 | func (n *leafPageElement) Ksize() uint32 { |
| 282 | return n.ksize |
| 283 | } |
| 284 | |
| 285 | func (n *leafPageElement) SetKsize(v uint32) { |
| 286 | n.ksize = v |
| 287 | } |
| 288 | |
| 289 | func (n *leafPageElement) Vsize() uint32 { |
| 290 | return n.vsize |
| 291 | } |
| 292 | |
| 293 | func (n *leafPageElement) SetVsize(v uint32) { |
| 294 | n.vsize = v |
| 295 | } |
| 296 | |
| 297 | // Key returns a byte slice of the node key. |
| 298 | func (n *leafPageElement) Key() []byte { |
| 299 | i := int(n.pos) |
| 300 | j := i + int(n.ksize) |
| 301 | return UnsafeByteSlice(unsafe.Pointer(n), 0, i, j) |
| 302 | } |
| 303 | |
| 304 | // Value returns a byte slice of the node value. |
| 305 | func (n *leafPageElement) Value() []byte { |
| 306 | i := int(n.pos) + int(n.ksize) |
| 307 | j := i + int(n.vsize) |
| 308 | return UnsafeByteSlice(unsafe.Pointer(n), 0, i, j) |
| 309 | } |
| 310 | |
| 311 | func (n *leafPageElement) IsBucketEntry() bool { |
| 312 | return n.flags&uint32(BucketLeafFlag) != 0 |
| 313 | } |
| 314 | |
| 315 | func (n *leafPageElement) Bucket() *InBucket { |
| 316 | if n.IsBucketEntry() { |
| 317 | return LoadBucket(n.Value()) |
| 318 | } else { |
| 319 | return nil |
| 320 | } |
| 321 | } |
| 322 | |
| 323 | // PageInfo represents human readable information about a page. |
| 324 | type PageInfo struct { |
| 325 | ID int |
| 326 | Type string |
| 327 | Count int |
| 328 | OverflowCount int |
| 329 | } |
| 330 | |
| 331 | type Pgids []Pgid |
| 332 | |
| 333 | func (s Pgids) Len() int { return len(s) } |
| 334 | func (s Pgids) Swap(i, j int) { s[i], s[j] = s[j], s[i] } |
| 335 | func (s Pgids) Less(i, j int) bool { return s[i] < s[j] } |
| 336 | |
| 337 | // Merge returns the sorted union of a and b. |
| 338 | func (a Pgids) Merge(b Pgids) Pgids { |
| 339 | // Return the opposite slice if one is nil. |
| 340 | if len(a) == 0 { |
| 341 | return b |
| 342 | } |
| 343 | if len(b) == 0 { |
| 344 | return a |
| 345 | } |
| 346 | merged := make(Pgids, len(a)+len(b)) |
| 347 | Mergepgids(merged, a, b) |
| 348 | return merged |
| 349 | } |
| 350 | |
| 351 | // Mergepgids copies the sorted union of a and b into dst. |
| 352 | // If dst is too small, it panics. |
| 353 | func Mergepgids(dst, a, b Pgids) { |
| 354 | if len(dst) < len(a)+len(b) { |
| 355 | panic(fmt.Errorf("mergepgids bad len %d < %d + %d", len(dst), len(a), len(b))) |
| 356 | } |
| 357 | // Copy in the opposite slice if one is nil. |
| 358 | if len(a) == 0 { |
| 359 | copy(dst, b) |
| 360 | return |
| 361 | } |
| 362 | if len(b) == 0 { |
| 363 | copy(dst, a) |
| 364 | return |
| 365 | } |
| 366 | |
| 367 | // Merged will hold all elements from both lists. |
| 368 | merged := dst[:0] |
| 369 | |
| 370 | // Assign lead to the slice with a lower starting value, follow to the higher value. |
| 371 | lead, follow := a, b |
| 372 | if b[0] < a[0] { |
| 373 | lead, follow = b, a |
| 374 | } |
| 375 | |
| 376 | // Continue while there are elements in the lead. |
| 377 | for len(lead) > 0 { |
| 378 | // Merge largest prefix of lead that is ahead of follow[0]. |
| 379 | n := sort.Search(len(lead), func(i int) bool { return lead[i] > follow[0] }) |
| 380 | merged = append(merged, lead[:n]...) |
| 381 | if n >= len(lead) { |
| 382 | break |
| 383 | } |
| 384 | |
| 385 | // Swap lead and follow. |
| 386 | lead, follow = follow, lead[n:] |
| 387 | } |
| 388 | |
| 389 | // Append what's left in follow. |
| 390 | _ = append(merged, follow...) |
| 391 | } |