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eleksir
2024-09-17 23:58:51 +03:00
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/*
Copyright 2013 The Perkeep Authors
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package testkeys
import (
"strconv"
"github.com/cockroachdb/errors"
)
// parseUintBytes is like strconv.ParseUint, but using a []byte. Use of this
// function avoids an allocation when parsing an integer out of a []byte.
//
// This function is copied from go4.org/strconv.
func parseUintBytes(s []byte, base int, bitSize int) (n uint64, err error) {
var cutoff, maxVal uint64
if bitSize == 0 {
bitSize = int(strconv.IntSize)
}
s0 := s
switch {
case len(s) < 1:
err = strconv.ErrSyntax
goto Error
case 2 <= base && base <= 36:
// valid base; nothing to do
case base == 0:
// Look for octal, hex prefix.
switch {
case s[0] == '0' && len(s) > 1 && (s[1] == 'x' || s[1] == 'X'):
base = 16
s = s[2:]
if len(s) < 1 {
err = strconv.ErrSyntax
goto Error
}
case s[0] == '0':
base = 8
default:
base = 10
}
default:
err = errors.New("invalid base " + strconv.Itoa(base))
goto Error
}
n = 0
cutoff = cutoff64(base)
maxVal = 1<<uint(bitSize) - 1
for i := 0; i < len(s); i++ {
var v byte
d := s[i]
switch {
case '0' <= d && d <= '9':
v = d - '0'
case 'a' <= d && d <= 'z':
v = d - 'a' + 10
case 'A' <= d && d <= 'Z':
v = d - 'A' + 10
default:
n = 0
err = strconv.ErrSyntax
goto Error
}
if int(v) >= base {
n = 0
err = strconv.ErrSyntax
goto Error
}
if n >= cutoff {
// n*base overflows
n = 1<<64 - 1
err = strconv.ErrRange
goto Error
}
n *= uint64(base)
n1 := n + uint64(v)
if n1 < n || n1 > maxVal {
// n+v overflows
n = 1<<64 - 1
err = strconv.ErrRange
goto Error
}
n = n1
}
return n, nil
Error:
return n, &strconv.NumError{Func: "ParseUint", Num: string(s0), Err: err}
}
// Return the first number n such that n*base >= 1<<64.
func cutoff64(base int) uint64 {
if base < 2 {
return 0
}
return (1<<64-1)/uint64(base) + 1
}

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// Copyright 2021 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 testkeys provides facilities for generating and comparing
// human-readable test keys for use in tests and benchmarks. This package
// provides a single Comparer implementation that compares all keys generated
// by this package.
//
// Keys generated by this package may optionally have a 'suffix' encoding an
// MVCC timestamp. This suffix is of the form "@<integer>". Comparisons on the
// suffix are performed using integer value, not the byte representation.
package testkeys
import (
"bytes"
"fmt"
"math"
"strconv"
"strings"
"github.com/cockroachdb/pebble/internal/base"
"golang.org/x/exp/constraints"
"golang.org/x/exp/rand"
)
const alpha = "abcdefghijklmnopqrstuvwxyz"
const suffixDelim = '@'
var inverseAlphabet = make(map[byte]int64, len(alpha))
func init() {
for i := range alpha {
inverseAlphabet[alpha[i]] = int64(i)
}
}
// MaxSuffixLen is the maximum length of a suffix generated by this package.
var MaxSuffixLen = 1 + len(fmt.Sprintf("%d", int64(math.MaxInt64)))
// Comparer is the comparer for test keys generated by this package.
var Comparer = &base.Comparer{
Compare: compare,
Equal: func(a, b []byte) bool { return compare(a, b) == 0 },
AbbreviatedKey: func(k []byte) uint64 {
return base.DefaultComparer.AbbreviatedKey(k[:split(k)])
},
FormatKey: base.DefaultFormatter,
Separator: func(dst, a, b []byte) []byte {
ai := split(a)
if ai == len(a) {
return append(dst, a...)
}
bi := split(b)
if bi == len(b) {
return append(dst, a...)
}
// If the keys are the same just return a.
if bytes.Equal(a[:ai], b[:bi]) {
return append(dst, a...)
}
n := len(dst)
dst = base.DefaultComparer.Separator(dst, a[:ai], b[:bi])
// Did it pick a separator different than a[:ai] -- if not we can't do better than a.
buf := dst[n:]
if bytes.Equal(a[:ai], buf) {
return append(dst[:n], a...)
}
// The separator is > a[:ai], so return it
return dst
},
Successor: func(dst, a []byte) []byte {
ai := split(a)
if ai == len(a) {
return append(dst, a...)
}
n := len(dst)
dst = base.DefaultComparer.Successor(dst, a[:ai])
// Did it pick a successor different than a[:ai] -- if not we can't do better than a.
buf := dst[n:]
if bytes.Equal(a[:ai], buf) {
return append(dst[:n], a...)
}
// The successor is > a[:ai], so return it.
return dst
},
ImmediateSuccessor: func(dst, a []byte) []byte {
// TODO(jackson): Consider changing this Comparer to only support
// representable prefix keys containing characters a-z.
ai := split(a)
if ai != len(a) {
panic("pebble: ImmediateSuccessor invoked with a non-prefix key")
}
return append(append(dst, a...), 0x00)
},
Split: split,
Name: "pebble.internal.testkeys",
}
func compare(a, b []byte) int {
ai, bi := split(a), split(b)
if v := bytes.Compare(a[:ai], b[:bi]); v != 0 {
return v
}
if len(a[ai:]) == 0 {
if len(b[bi:]) == 0 {
return 0
}
return -1
} else if len(b[bi:]) == 0 {
return +1
}
return compareTimestamps(a[ai:], b[bi:])
}
func split(a []byte) int {
i := bytes.LastIndexByte(a, suffixDelim)
if i >= 0 {
return i
}
return len(a)
}
func compareTimestamps(a, b []byte) int {
ai, err := parseUintBytes(bytes.TrimPrefix(a, []byte{suffixDelim}), 10, 64)
if err != nil {
panic(fmt.Sprintf("invalid test mvcc timestamp %q", a))
}
bi, err := parseUintBytes(bytes.TrimPrefix(b, []byte{suffixDelim}), 10, 64)
if err != nil {
panic(fmt.Sprintf("invalid test mvcc timestamp %q", b))
}
switch {
case ai < bi:
return +1
case ai > bi:
return -1
default:
return 0
}
}
// Keyspace describes a finite keyspace of unsuffixed test keys.
type Keyspace interface {
// Count returns the number of keys that exist within this keyspace.
Count() int64
// MaxLen returns the maximum length, in bytes, of a key within this
// keyspace. This is only guaranteed to return an upper bound.
MaxLen() int
// Slice returns the sub-keyspace from index i, inclusive, to index j,
// exclusive. The receiver is unmodified.
Slice(i, j int64) Keyspace
// EveryN returns a key space that includes 1 key for every N keys in the
// original keyspace. The receiver is unmodified.
EveryN(n int64) Keyspace
// key writes the i-th key to the buffer and returns the length.
key(buf []byte, i int64) int
}
// Divvy divides the provided keyspace into N equal portions, containing
// disjoint keys evenly distributed across the keyspace.
func Divvy(ks Keyspace, n int64) []Keyspace {
ret := make([]Keyspace, n)
for i := int64(0); i < n; i++ {
ret[i] = ks.Slice(i, ks.Count()).EveryN(n)
}
return ret
}
// Alpha constructs a keyspace consisting of all keys containing characters a-z,
// with at most `maxLength` characters.
func Alpha(maxLength int) Keyspace {
return alphabet{
alphabet: []byte(alpha),
maxLength: maxLength,
increment: 1,
}
}
// KeyAt returns the i-th key within the keyspace with a suffix encoding the
// timestamp t.
func KeyAt(k Keyspace, i int64, t int64) []byte {
b := make([]byte, k.MaxLen()+MaxSuffixLen)
return b[:WriteKeyAt(b, k, i, t)]
}
// WriteKeyAt writes the i-th key within the keyspace to the buffer dst, with a
// suffix encoding the timestamp t suffix. It returns the number of bytes
// written.
func WriteKeyAt(dst []byte, k Keyspace, i int64, t int64) int {
n := WriteKey(dst, k, i)
n += WriteSuffix(dst[n:], t)
return n
}
// Suffix returns the test keys suffix representation of timestamp t.
func Suffix(t int64) []byte {
b := make([]byte, MaxSuffixLen)
return b[:WriteSuffix(b, t)]
}
// SuffixLen returns the exact length of the given suffix when encoded.
func SuffixLen(t int64) int {
// Begin at 1 for the '@' delimiter, 1 for a single digit.
n := 2
t /= 10
for t > 0 {
t /= 10
n++
}
return n
}
// ParseSuffix returns the integer representation of the encoded suffix.
func ParseSuffix(s []byte) (int64, error) {
return strconv.ParseInt(strings.TrimPrefix(string(s), string(suffixDelim)), 10, 64)
}
// WriteSuffix writes the test keys suffix representation of timestamp t to dst,
// returning the number of bytes written.
func WriteSuffix(dst []byte, t int64) int {
dst[0] = suffixDelim
n := 1
n += len(strconv.AppendInt(dst[n:n], t, 10))
return n
}
// Key returns the i-th unsuffixed key within the keyspace.
func Key(k Keyspace, i int64) []byte {
b := make([]byte, k.MaxLen())
return b[:k.key(b, i)]
}
// WriteKey writes the i-th unsuffixed key within the keyspace to the buffer dst. It
// returns the number of bytes written.
func WriteKey(dst []byte, k Keyspace, i int64) int {
return k.key(dst, i)
}
type alphabet struct {
alphabet []byte
maxLength int
headSkip int64
tailSkip int64
increment int64
}
func (a alphabet) Count() int64 {
// Calculate the total number of keys, ignoring the increment.
total := keyCount(len(a.alphabet), a.maxLength) - a.headSkip - a.tailSkip
// The increment dictates that we take every N keys, where N = a.increment.
// Consider a total containing the 5 keys:
// a b c d e
// ^ ^ ^
// If the increment is 2, this keyspace includes 'a', 'c' and 'e'. After
// dividing by the increment, there may be remainder. If there is, there's
// one additional key in the alphabet.
count := total / a.increment
if total%a.increment > 0 {
count++
}
return count
}
func (a alphabet) MaxLen() int {
return a.maxLength
}
func (a alphabet) Slice(i, j int64) Keyspace {
s := a
s.headSkip += i
s.tailSkip += a.Count() - j
return s
}
func (a alphabet) EveryN(n int64) Keyspace {
s := a
s.increment *= n
return s
}
func keyCount(n, l int) int64 {
if n == 0 {
return 0
} else if n == 1 {
return int64(l)
}
// The number of representable keys in the keyspace is a function of the
// length of the alphabet n and the max key length l. Consider how the
// number of representable keys grows as l increases:
//
// l = 1: n
// l = 2: n + n^2
// l = 3: n + n^2 + n^3
// ...
// Σ i=(1...l) n^i = n*(n^l - 1)/(n-1)
return (int64(n) * (int64(math.Pow(float64(n), float64(l))) - 1)) / int64(n-1)
}
func (a alphabet) key(buf []byte, idx int64) int {
// This function generates keys of length 1..maxKeyLength, pulling
// characters from the alphabet. The idx determines which key to generate,
// generating the i-th lexicographically next key.
//
// The index to use is advanced by `headSkip`, allowing a keyspace to encode
// a subregion of the keyspace.
//
// Eg, alphabet = `ab`, maxKeyLength = 3:
//
// aaa aab aba abb baa bab bba bbb
// aa ab ba bb
// a b
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13
//
return generateAlphabetKey(buf, a.alphabet, (idx*a.increment)+a.headSkip,
keyCount(len(a.alphabet), a.maxLength))
}
func generateAlphabetKey(buf, alphabet []byte, i, keyCount int64) int {
if keyCount == 0 || i > keyCount || i < 0 {
return 0
}
// Of the keyCount keys in the generative keyspace, how many are there
// starting with a particular character?
keysPerCharacter := keyCount / int64(len(alphabet))
// Find the character that the key at index i starts with and set it.
characterIdx := i / keysPerCharacter
buf[0] = alphabet[characterIdx]
// Consider characterIdx = 0, pointing to 'a'.
//
// aaa aab aba abb baa bab bba bbb
// aa ab ba bb
// a b
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13
// \_________________________/
// |keysPerCharacter| keys
//
// In our recursive call, we reduce the problem to:
//
// aaa aab aba abb
// aa ab
// 0 1 2 3 4 5
// \________________________/
// |keysPerCharacter-1| keys
//
// In the subproblem, there are keysPerCharacter-1 keys (eliminating the
// just 'a' key, plus any keys beginning with any other character).
//
// The index i is also offset, reduced by the count of keys beginning with
// characters earlier in the alphabet (keysPerCharacter*characterIdx) and
// the key consisting of just the 'a' (-1).
i = i - keysPerCharacter*characterIdx - 1
return 1 + generateAlphabetKey(buf[1:], alphabet, i, keysPerCharacter-1)
}
// computeAlphabetKeyIndex computes the inverse of generateAlphabetKey,
// returning the index of a particular key, given the provided alphabet and max
// length of a key.
//
// len(key) must be ≥ 1.
func computeAlphabetKeyIndex(key []byte, alphabet map[byte]int64, n int) int64 {
i, ok := alphabet[key[0]]
if !ok {
panic(fmt.Sprintf("unrecognized alphabet character %v", key[0]))
}
// How many keys exist that start with the preceding i characters? Each of
// the i characters themselves are a key, plus the count of all the keys
// with one less character for each.
ret := i + i*keyCount(len(alphabet), n-1)
if len(key) > 1 {
ret += 1 + computeAlphabetKeyIndex(key[1:], alphabet, n-1)
}
return ret
}
func abs(a int64) int64 {
if a < 0 {
return -a
}
return a
}
// RandomSeparator returns a random alphabetic key k such that a < k < b,
// pulling randomness from the provided random number generator. If dst is
// provided and the generated key fits within dst's capacity, the returned slice
// will use dst's memory.
//
// If a prefix P exists such that Prefix(a) < P < Prefix(b), the generated key
// will consist of the prefix P appended with the provided suffix. A zero suffix
// generates an unsuffixed key. If no such prefix P exists, RandomSeparator will
// try to find a key k with either Prefix(a) or Prefix(b) such that a < k < b,
// but the generated key will not use the provided suffix. Note that it's
// possible that no separator key exists (eg, a='a@2', b='a@1'), in which case
// RandomSeparator returns nil.
//
// If RandomSeparator generates a new prefix, the generated prefix will have
// length at most MAX(maxLength, len(Prefix(a)), len(Prefix(b))).
//
// RandomSeparator panics if a or b fails to decode.
func RandomSeparator(dst, a, b []byte, suffix int64, maxLength int, rng *rand.Rand) []byte {
if Comparer.Compare(a, b) >= 0 {
return nil
}
// Determine both keys' logical prefixes and suffixes.
ai := Comparer.Split(a)
bi := Comparer.Split(b)
ap := a[:ai]
bp := b[:bi]
maxLength = max[int](maxLength, max[int](len(ap), len(bp)))
var as, bs int64
var err error
if ai != len(a) {
as, err = ParseSuffix(a[ai:])
if err != nil {
panic(fmt.Sprintf("failed to parse suffix of %q", a))
}
}
if bi != len(b) {
bs, err = ParseSuffix(b[bi:])
if err != nil {
panic(fmt.Sprintf("failed to parse suffix of %q", b))
}
}
apIdx := computeAlphabetKeyIndex(ap, inverseAlphabet, maxLength)
bpIdx := computeAlphabetKeyIndex(bp, inverseAlphabet, maxLength)
diff := bpIdx - apIdx
generatedIdx := bpIdx
if diff > 0 {
var add int64 = diff + 1
var start int64 = apIdx
if as == 1 {
// There's no expressible key with prefix a greater than a@1. So,
// exclude ap.
start = apIdx + 1
add = diff
}
if bs == 0 {
// No key with prefix b can sort before b@0. We don't want to pick b.
add--
}
// We're allowing generated id to be in the range [start, start + add - 1].
if start > start+add-1 {
return nil
}
// If we can generate a key which is actually in the middle of apIdx
// and bpIdx use it so that we don't have to bother about timestamps.
generatedIdx = rng.Int63n(add) + start
for diff > 1 && generatedIdx == apIdx || generatedIdx == bpIdx {
generatedIdx = rng.Int63n(add) + start
}
}
switch {
case generatedIdx == apIdx && generatedIdx == bpIdx:
if abs(bs-as) <= 1 {
// There's no expressible suffix between the two, and there's no
// possible separator key.
return nil
}
// The key b is >= key a, but has the same prefix, so b must have the
// smaller timestamp, unless a has timestamp of 0.
//
// NB: The zero suffix (suffix-less) sorts before all other suffixes, so
// any suffix we generate will be greater than it.
if as == 0 {
// bs > as
suffix = bs + rng.Int63n(10) + 1
} else {
// bs < as.
// Generate suffix in range [bs + 1, as - 1]
suffix = bs + 1 + rng.Int63n(as-bs-1)
}
case generatedIdx == apIdx:
// NB: The zero suffix (suffix-less) sorts before all other suffixes, so
// any suffix we generate will be greater than it.
if as == 0 && suffix == 0 {
suffix++
} else if as != 0 && suffix >= as {
suffix = rng.Int63n(as)
}
case generatedIdx == bpIdx:
if suffix <= bs {
suffix = bs + rng.Int63n(10) + 1
}
}
if sz := maxLength + SuffixLen(suffix); cap(dst) < sz {
dst = make([]byte, sz)
} else {
dst = dst[:cap(dst)]
}
var w int
if suffix == 0 {
w = WriteKey(dst, Alpha(maxLength), generatedIdx)
} else {
w = WriteKeyAt(dst, Alpha(maxLength), generatedIdx, suffix)
}
return dst[:w]
}
func max[I constraints.Ordered](a, b I) I {
if b > a {
return b
}
return a
}