mirror of https://github.com/hak5/bolt.git
130 lines
3.3 KiB
Go
130 lines
3.3 KiB
Go
package bolt
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import (
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"fmt"
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"os"
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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 maxAllocSize = 0xFFFFFFF
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const minKeysPerPage = 2
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const maxNodesPerPage = 65535
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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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bucketsPageFlag = 0x08
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freelistPageFlag = 0x10
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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 & bucketsPageFlag) != 0 {
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return "buckets"
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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 := &((*[maxNodesPerPage]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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return ((*[maxNodesPerPage]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 &((*[maxNodesPerPage]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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return ((*[maxNodesPerPage]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 buf[n.pos : 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 buf[n.pos : n.pos+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 buf[n.pos+n.ksize : n.pos+n.ksize+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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