ceremonyclient/pebble/sstable/raw_block.go

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2024-01-03 07:31:42 +00:00
// Copyright 2018 The LevelDB-Go and Pebble Authors. All rights reserved. Use
// of this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
package sstable
import (
"encoding/binary"
"sort"
"unsafe"
"github.com/cockroachdb/pebble/internal/base"
)
type rawBlockWriter struct {
blockWriter
}
func (w *rawBlockWriter) add(key InternalKey, value []byte) {
w.curKey, w.prevKey = w.prevKey, w.curKey
size := len(key.UserKey)
if cap(w.curKey) < size {
w.curKey = make([]byte, 0, size*2)
}
w.curKey = w.curKey[:size]
copy(w.curKey, key.UserKey)
w.storeWithOptionalValuePrefix(
size, value, len(key.UserKey), false, 0, false)
}
// rawBlockIter is an iterator over a single block of data. Unlike blockIter,
// keys are stored in "raw" format (i.e. not as internal keys). Note that there
// is significant similarity between this code and the code in blockIter. Yet
// reducing duplication is difficult due to the blockIter being performance
// critical. rawBlockIter must only be used for blocks where the value is
// stored together with the key.
type rawBlockIter struct {
cmp Compare
offset int32
nextOffset int32
restarts int32
numRestarts int32
ptr unsafe.Pointer
data []byte
key, val []byte
ikey InternalKey
cached []blockEntry
cachedBuf []byte
}
func newRawBlockIter(cmp Compare, block block) (*rawBlockIter, error) {
i := &rawBlockIter{}
return i, i.init(cmp, block)
}
func (i *rawBlockIter) init(cmp Compare, block block) error {
numRestarts := int32(binary.LittleEndian.Uint32(block[len(block)-4:]))
if numRestarts == 0 {
return base.CorruptionErrorf("pebble/table: invalid table (block has no restart points)")
}
i.cmp = cmp
i.restarts = int32(len(block)) - 4*(1+numRestarts)
i.numRestarts = numRestarts
i.ptr = unsafe.Pointer(&block[0])
i.data = block
if i.key == nil {
i.key = make([]byte, 0, 256)
} else {
i.key = i.key[:0]
}
i.val = nil
i.clearCache()
return nil
}
func (i *rawBlockIter) readEntry() {
ptr := unsafe.Pointer(uintptr(i.ptr) + uintptr(i.offset))
shared, ptr := decodeVarint(ptr)
unshared, ptr := decodeVarint(ptr)
value, ptr := decodeVarint(ptr)
i.key = append(i.key[:shared], getBytes(ptr, int(unshared))...)
i.key = i.key[:len(i.key):len(i.key)]
ptr = unsafe.Pointer(uintptr(ptr) + uintptr(unshared))
i.val = getBytes(ptr, int(value))
i.nextOffset = int32(uintptr(ptr)-uintptr(i.ptr)) + int32(value)
}
func (i *rawBlockIter) loadEntry() {
i.readEntry()
i.ikey.UserKey = i.key
}
func (i *rawBlockIter) clearCache() {
i.cached = i.cached[:0]
i.cachedBuf = i.cachedBuf[:0]
}
func (i *rawBlockIter) cacheEntry() {
var valStart int32
valSize := int32(len(i.val))
if valSize > 0 {
valStart = int32(uintptr(unsafe.Pointer(&i.val[0])) - uintptr(i.ptr))
}
i.cached = append(i.cached, blockEntry{
offset: i.offset,
keyStart: int32(len(i.cachedBuf)),
keyEnd: int32(len(i.cachedBuf) + len(i.key)),
valStart: valStart,
valSize: valSize,
})
i.cachedBuf = append(i.cachedBuf, i.key...)
}
// SeekGE implements internalIterator.SeekGE, as documented in the pebble
// package.
func (i *rawBlockIter) SeekGE(key []byte) bool {
// Find the index of the smallest restart point whose key is > the key
// sought; index will be numRestarts if there is no such restart point.
i.offset = 0
index := sort.Search(int(i.numRestarts), func(j int) bool {
offset := int32(binary.LittleEndian.Uint32(i.data[int(i.restarts)+4*j:]))
// For a restart point, there are 0 bytes shared with the previous key.
// The varint encoding of 0 occupies 1 byte.
ptr := unsafe.Pointer(uintptr(i.ptr) + uintptr(offset+1))
// Decode the key at that restart point, and compare it to the key sought.
v1, ptr := decodeVarint(ptr)
_, ptr = decodeVarint(ptr)
s := getBytes(ptr, int(v1))
return i.cmp(key, s) < 0
})
// Since keys are strictly increasing, if index > 0 then the restart point at
// index-1 will be the largest whose key is <= the key sought. If index ==
// 0, then all keys in this block are larger than the key sought, and offset
// remains at zero.
if index > 0 {
i.offset = int32(binary.LittleEndian.Uint32(i.data[int(i.restarts)+4*(index-1):]))
}
i.loadEntry()
// Iterate from that restart point to somewhere >= the key sought.
for valid := i.Valid(); valid; valid = i.Next() {
if i.cmp(key, i.key) <= 0 {
break
}
}
return i.Valid()
}
// First implements internalIterator.First, as documented in the pebble
// package.
func (i *rawBlockIter) First() bool {
i.offset = 0
i.loadEntry()
return i.Valid()
}
// Last implements internalIterator.Last, as documented in the pebble package.
func (i *rawBlockIter) Last() bool {
// Seek forward from the last restart point.
i.offset = int32(binary.LittleEndian.Uint32(i.data[i.restarts+4*(i.numRestarts-1):]))
i.readEntry()
i.clearCache()
i.cacheEntry()
for i.nextOffset < i.restarts {
i.offset = i.nextOffset
i.readEntry()
i.cacheEntry()
}
i.ikey.UserKey = i.key
return i.Valid()
}
// Next implements internalIterator.Next, as documented in the pebble
// package.
func (i *rawBlockIter) Next() bool {
i.offset = i.nextOffset
if !i.Valid() {
return false
}
i.loadEntry()
return true
}
// Prev implements internalIterator.Prev, as documented in the pebble
// package.
func (i *rawBlockIter) Prev() bool {
if n := len(i.cached) - 1; n > 0 && i.cached[n].offset == i.offset {
i.nextOffset = i.offset
e := &i.cached[n-1]
i.offset = e.offset
i.val = getBytes(unsafe.Pointer(uintptr(i.ptr)+uintptr(e.valStart)), int(e.valSize))
i.ikey.UserKey = i.cachedBuf[e.keyStart:e.keyEnd]
i.cached = i.cached[:n]
return true
}
if i.offset == 0 {
i.offset = -1
i.nextOffset = 0
return false
}
targetOffset := i.offset
index := sort.Search(int(i.numRestarts), func(j int) bool {
offset := int32(binary.LittleEndian.Uint32(i.data[int(i.restarts)+4*j:]))
return offset >= targetOffset
})
i.offset = 0
if index > 0 {
i.offset = int32(binary.LittleEndian.Uint32(i.data[int(i.restarts)+4*(index-1):]))
}
i.readEntry()
i.clearCache()
i.cacheEntry()
for i.nextOffset < targetOffset {
i.offset = i.nextOffset
i.readEntry()
i.cacheEntry()
}
i.ikey.UserKey = i.key
return true
}
// Key implements internalIterator.Key, as documented in the pebble package.
func (i *rawBlockIter) Key() InternalKey {
return i.ikey
}
// Value implements internalIterator.Value, as documented in the pebble
// package.
func (i *rawBlockIter) Value() []byte {
return i.val
}
// Valid implements internalIterator.Valid, as documented in the pebble
// package.
func (i *rawBlockIter) Valid() bool {
return i.offset >= 0 && i.offset < i.restarts
}
// Error implements internalIterator.Error, as documented in the pebble
// package.
func (i *rawBlockIter) Error() error {
return nil
}
// Close implements internalIterator.Close, as documented in the pebble
// package.
func (i *rawBlockIter) Close() error {
i.val = nil
return nil
}