mirror of
https://github.com/go-gitea/gitea.git
synced 2024-08-24 21:27:27 +02:00
198 lines
4.8 KiB
Go
198 lines
4.8 KiB
Go
package bolt
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import (
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"fmt"
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"os"
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"sort"
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"unsafe"
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)
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const pageHeaderSize = int(unsafe.Offsetof(((*page)(nil)).ptr))
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const minKeysPerPage = 2
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const branchPageElementSize = int(unsafe.Sizeof(branchPageElement{}))
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const leafPageElementSize = int(unsafe.Sizeof(leafPageElement{}))
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const (
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branchPageFlag = 0x01
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leafPageFlag = 0x02
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metaPageFlag = 0x04
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freelistPageFlag = 0x10
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)
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const (
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bucketLeafFlag = 0x01
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)
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type pgid uint64
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type page struct {
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id pgid
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flags uint16
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count uint16
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overflow uint32
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ptr uintptr
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}
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// typ returns a human readable page type string used for debugging.
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func (p *page) typ() string {
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if (p.flags & branchPageFlag) != 0 {
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return "branch"
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} else if (p.flags & leafPageFlag) != 0 {
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return "leaf"
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} else if (p.flags & metaPageFlag) != 0 {
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return "meta"
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} else if (p.flags & freelistPageFlag) != 0 {
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return "freelist"
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}
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return fmt.Sprintf("unknown<%02x>", p.flags)
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}
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// meta returns a pointer to the metadata section of the page.
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func (p *page) meta() *meta {
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return (*meta)(unsafe.Pointer(&p.ptr))
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}
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// leafPageElement retrieves the leaf node by index
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func (p *page) leafPageElement(index uint16) *leafPageElement {
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n := &((*[0x7FFFFFF]leafPageElement)(unsafe.Pointer(&p.ptr)))[index]
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return n
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}
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// leafPageElements retrieves a list of leaf nodes.
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func (p *page) leafPageElements() []leafPageElement {
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if p.count == 0 {
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return nil
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}
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return ((*[0x7FFFFFF]leafPageElement)(unsafe.Pointer(&p.ptr)))[:]
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}
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// branchPageElement retrieves the branch node by index
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func (p *page) branchPageElement(index uint16) *branchPageElement {
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return &((*[0x7FFFFFF]branchPageElement)(unsafe.Pointer(&p.ptr)))[index]
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}
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// branchPageElements retrieves a list of branch nodes.
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func (p *page) branchPageElements() []branchPageElement {
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if p.count == 0 {
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return nil
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}
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return ((*[0x7FFFFFF]branchPageElement)(unsafe.Pointer(&p.ptr)))[:]
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}
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// dump writes n bytes of the page to STDERR as hex output.
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func (p *page) hexdump(n int) {
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buf := (*[maxAllocSize]byte)(unsafe.Pointer(p))[:n]
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fmt.Fprintf(os.Stderr, "%x\n", buf)
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}
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type pages []*page
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func (s pages) Len() int { return len(s) }
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func (s pages) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
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func (s pages) Less(i, j int) bool { return s[i].id < s[j].id }
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// branchPageElement represents a node on a branch page.
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type branchPageElement struct {
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pos uint32
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ksize uint32
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pgid pgid
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}
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// key returns a byte slice of the node key.
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func (n *branchPageElement) key() []byte {
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buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
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return (*[maxAllocSize]byte)(unsafe.Pointer(&buf[n.pos]))[:n.ksize]
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}
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// leafPageElement represents a node on a leaf page.
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type leafPageElement struct {
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flags uint32
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pos uint32
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ksize uint32
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vsize uint32
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}
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// key returns a byte slice of the node key.
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func (n *leafPageElement) key() []byte {
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buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
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return (*[maxAllocSize]byte)(unsafe.Pointer(&buf[n.pos]))[:n.ksize:n.ksize]
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}
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// value returns a byte slice of the node value.
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func (n *leafPageElement) value() []byte {
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buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
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return (*[maxAllocSize]byte)(unsafe.Pointer(&buf[n.pos+n.ksize]))[:n.vsize:n.vsize]
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}
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// PageInfo represents human readable information about a page.
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type PageInfo struct {
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ID int
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Type string
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Count int
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OverflowCount int
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}
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type pgids []pgid
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func (s pgids) Len() int { return len(s) }
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func (s pgids) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
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func (s pgids) Less(i, j int) bool { return s[i] < s[j] }
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// merge returns the sorted union of a and b.
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func (a pgids) merge(b pgids) pgids {
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// Return the opposite slice if one is nil.
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if len(a) == 0 {
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return b
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}
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if len(b) == 0 {
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return a
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}
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merged := make(pgids, len(a)+len(b))
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mergepgids(merged, a, b)
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return merged
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}
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// mergepgids copies the sorted union of a and b into dst.
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// If dst is too small, it panics.
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func mergepgids(dst, a, b pgids) {
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if len(dst) < len(a)+len(b) {
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panic(fmt.Errorf("mergepgids bad len %d < %d + %d", len(dst), len(a), len(b)))
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}
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// Copy in the opposite slice if one is nil.
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if len(a) == 0 {
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copy(dst, b)
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return
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}
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if len(b) == 0 {
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copy(dst, a)
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return
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}
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// Merged will hold all elements from both lists.
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merged := dst[:0]
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// Assign lead to the slice with a lower starting value, follow to the higher value.
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lead, follow := a, b
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if b[0] < a[0] {
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lead, follow = b, a
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}
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// Continue while there are elements in the lead.
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for len(lead) > 0 {
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// Merge largest prefix of lead that is ahead of follow[0].
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n := sort.Search(len(lead), func(i int) bool { return lead[i] > follow[0] })
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merged = append(merged, lead[:n]...)
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if n >= len(lead) {
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break
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}
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// Swap lead and follow.
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lead, follow = follow, lead[n:]
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}
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// Append what's left in follow.
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_ = append(merged, follow...)
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}
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