- package bbolt
-
- import (
- "fmt"
- "os"
- "reflect"
- "sort"
- "unsafe"
- )
-
- const pageHeaderSize = unsafe.Sizeof(page{})
-
- const minKeysPerPage = 2
-
- const branchPageElementSize = unsafe.Sizeof(branchPageElement{})
- const leafPageElementSize = unsafe.Sizeof(leafPageElement{})
-
- const (
- branchPageFlag = 0x01
- leafPageFlag = 0x02
- metaPageFlag = 0x04
- freelistPageFlag = 0x10
- )
-
- const (
- bucketLeafFlag = 0x01
- )
-
- type pgid uint64
-
- type page struct {
- id pgid
- flags uint16
- count uint16
- overflow uint32
- }
-
- // typ returns a human readable page type string used for debugging.
- func (p *page) typ() string {
- if (p.flags & branchPageFlag) != 0 {
- return "branch"
- } else if (p.flags & leafPageFlag) != 0 {
- return "leaf"
- } else if (p.flags & metaPageFlag) != 0 {
- return "meta"
- } else if (p.flags & freelistPageFlag) != 0 {
- return "freelist"
- }
- return fmt.Sprintf("unknown<%02x>", p.flags)
- }
-
- // meta returns a pointer to the metadata section of the page.
- func (p *page) meta() *meta {
- return (*meta)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p)))
- }
-
- // leafPageElement retrieves the leaf node by index
- func (p *page) leafPageElement(index uint16) *leafPageElement {
- off := uintptr(index) * unsafe.Sizeof(leafPageElement{})
- return (*leafPageElement)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p) + off))
- }
-
- // leafPageElements retrieves a list of leaf nodes.
- func (p *page) leafPageElements() []leafPageElement {
- if p.count == 0 {
- return nil
- }
- return *(*[]leafPageElement)(unsafe.Pointer(&reflect.SliceHeader{
- Data: uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p),
- Len: int(p.count),
- Cap: int(p.count),
- }))
- }
-
- // branchPageElement retrieves the branch node by index
- func (p *page) branchPageElement(index uint16) *branchPageElement {
- off := uintptr(index) * unsafe.Sizeof(branchPageElement{})
- return (*branchPageElement)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p) + off))
- }
-
- // branchPageElements retrieves a list of branch nodes.
- func (p *page) branchPageElements() []branchPageElement {
- if p.count == 0 {
- return nil
- }
- return *(*[]branchPageElement)(unsafe.Pointer(&reflect.SliceHeader{
- Data: uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p),
- Len: int(p.count),
- Cap: int(p.count),
- }))
- }
-
- // dump writes n bytes of the page to STDERR as hex output.
- func (p *page) hexdump(n int) {
- buf := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
- Data: uintptr(unsafe.Pointer(p)),
- Len: n,
- Cap: n,
- }))
- fmt.Fprintf(os.Stderr, "%x\n", buf)
- }
-
- type pages []*page
-
- func (s pages) Len() int { return len(s) }
- func (s pages) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
- func (s pages) Less(i, j int) bool { return s[i].id < s[j].id }
-
- // branchPageElement represents a node on a branch page.
- type branchPageElement struct {
- pos uint32
- ksize uint32
- pgid pgid
- }
-
- // key returns a byte slice of the node key.
- func (n *branchPageElement) key() []byte {
- return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
- Data: uintptr(unsafe.Pointer(n)) + uintptr(n.pos),
- Len: int(n.ksize),
- Cap: int(n.ksize),
- }))
- }
-
- // leafPageElement represents a node on a leaf page.
- type leafPageElement struct {
- flags uint32
- pos uint32
- ksize uint32
- vsize uint32
- }
-
- // key returns a byte slice of the node key.
- func (n *leafPageElement) key() []byte {
- return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
- Data: uintptr(unsafe.Pointer(n)) + uintptr(n.pos),
- Len: int(n.ksize),
- Cap: int(n.ksize),
- }))
- }
-
- // value returns a byte slice of the node value.
- func (n *leafPageElement) value() []byte {
- return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
- Data: uintptr(unsafe.Pointer(n)) + uintptr(n.pos) + uintptr(n.ksize),
- Len: int(n.vsize),
- Cap: int(n.vsize),
- }))
- }
-
- // PageInfo represents human readable information about a page.
- type PageInfo struct {
- ID int
- Type string
- Count int
- OverflowCount int
- }
-
- type pgids []pgid
-
- func (s pgids) Len() int { return len(s) }
- func (s pgids) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
- func (s pgids) Less(i, j int) bool { return s[i] < s[j] }
-
- // merge returns the sorted union of a and b.
- func (a pgids) merge(b pgids) pgids {
- // Return the opposite slice if one is nil.
- if len(a) == 0 {
- return b
- }
- if len(b) == 0 {
- return a
- }
- merged := make(pgids, len(a)+len(b))
- mergepgids(merged, a, b)
- return merged
- }
-
- // mergepgids copies the sorted union of a and b into dst.
- // If dst is too small, it panics.
- func mergepgids(dst, a, b pgids) {
- if len(dst) < len(a)+len(b) {
- panic(fmt.Errorf("mergepgids bad len %d < %d + %d", len(dst), len(a), len(b)))
- }
- // Copy in the opposite slice if one is nil.
- if len(a) == 0 {
- copy(dst, b)
- return
- }
- if len(b) == 0 {
- copy(dst, a)
- return
- }
-
- // Merged will hold all elements from both lists.
- merged := dst[:0]
-
- // Assign lead to the slice with a lower starting value, follow to the higher value.
- lead, follow := a, b
- if b[0] < a[0] {
- lead, follow = b, a
- }
-
- // Continue while there are elements in the lead.
- for len(lead) > 0 {
- // Merge largest prefix of lead that is ahead of follow[0].
- n := sort.Search(len(lead), func(i int) bool { return lead[i] > follow[0] })
- merged = append(merged, lead[:n]...)
- if n >= len(lead) {
- break
- }
-
- // Swap lead and follow.
- lead, follow = follow, lead[n:]
- }
-
- // Append what's left in follow.
- _ = append(merged, follow...)
- }
|