mirror of
https://github.com/autc04/Retro68.git
synced 2024-08-31 09:29:37 +00:00
386 lines
9.5 KiB
Go
386 lines
9.5 KiB
Go
// Copyright 2010 The Go 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 suffixarray implements substring search in logarithmic time using
|
|
// an in-memory suffix array.
|
|
//
|
|
// Example use:
|
|
//
|
|
// // create index for some data
|
|
// index := suffixarray.New(data)
|
|
//
|
|
// // lookup byte slice s
|
|
// offsets1 := index.Lookup(s, -1) // the list of all indices where s occurs in data
|
|
// offsets2 := index.Lookup(s, 3) // the list of at most 3 indices where s occurs in data
|
|
//
|
|
package suffixarray
|
|
|
|
import (
|
|
"bytes"
|
|
"encoding/binary"
|
|
"errors"
|
|
"io"
|
|
"math"
|
|
"regexp"
|
|
"sort"
|
|
)
|
|
|
|
// Can change for testing
|
|
var maxData32 int = realMaxData32
|
|
|
|
const realMaxData32 = math.MaxInt32
|
|
|
|
// Index implements a suffix array for fast substring search.
|
|
type Index struct {
|
|
data []byte
|
|
sa ints // suffix array for data; sa.len() == len(data)
|
|
}
|
|
|
|
// An ints is either an []int32 or an []int64.
|
|
// That is, one of them is empty, and one is the real data.
|
|
// The int64 form is used when len(data) > maxData32
|
|
type ints struct {
|
|
int32 []int32
|
|
int64 []int64
|
|
}
|
|
|
|
func (a *ints) len() int {
|
|
return len(a.int32) + len(a.int64)
|
|
}
|
|
|
|
func (a *ints) get(i int) int64 {
|
|
if a.int32 != nil {
|
|
return int64(a.int32[i])
|
|
}
|
|
return a.int64[i]
|
|
}
|
|
|
|
func (a *ints) set(i int, v int64) {
|
|
if a.int32 != nil {
|
|
a.int32[i] = int32(v)
|
|
} else {
|
|
a.int64[i] = v
|
|
}
|
|
}
|
|
|
|
func (a *ints) slice(i, j int) ints {
|
|
if a.int32 != nil {
|
|
return ints{a.int32[i:j], nil}
|
|
}
|
|
return ints{nil, a.int64[i:j]}
|
|
}
|
|
|
|
// New creates a new Index for data.
|
|
// Index creation time is O(N) for N = len(data).
|
|
func New(data []byte) *Index {
|
|
ix := &Index{data: data}
|
|
if len(data) <= maxData32 {
|
|
ix.sa.int32 = make([]int32, len(data))
|
|
text_32(data, ix.sa.int32)
|
|
} else {
|
|
ix.sa.int64 = make([]int64, len(data))
|
|
text_64(data, ix.sa.int64)
|
|
}
|
|
return ix
|
|
}
|
|
|
|
// writeInt writes an int x to w using buf to buffer the write.
|
|
func writeInt(w io.Writer, buf []byte, x int) error {
|
|
binary.PutVarint(buf, int64(x))
|
|
_, err := w.Write(buf[0:binary.MaxVarintLen64])
|
|
return err
|
|
}
|
|
|
|
// readInt reads an int x from r using buf to buffer the read and returns x.
|
|
func readInt(r io.Reader, buf []byte) (int64, error) {
|
|
_, err := io.ReadFull(r, buf[0:binary.MaxVarintLen64]) // ok to continue with error
|
|
x, _ := binary.Varint(buf)
|
|
return x, err
|
|
}
|
|
|
|
// writeSlice writes data[:n] to w and returns n.
|
|
// It uses buf to buffer the write.
|
|
func writeSlice(w io.Writer, buf []byte, data ints) (n int, err error) {
|
|
// encode as many elements as fit into buf
|
|
p := binary.MaxVarintLen64
|
|
m := data.len()
|
|
for ; n < m && p+binary.MaxVarintLen64 <= len(buf); n++ {
|
|
p += binary.PutUvarint(buf[p:], uint64(data.get(n)))
|
|
}
|
|
|
|
// update buffer size
|
|
binary.PutVarint(buf, int64(p))
|
|
|
|
// write buffer
|
|
_, err = w.Write(buf[0:p])
|
|
return
|
|
}
|
|
|
|
var errTooBig = errors.New("suffixarray: data too large")
|
|
|
|
// readSlice reads data[:n] from r and returns n.
|
|
// It uses buf to buffer the read.
|
|
func readSlice(r io.Reader, buf []byte, data ints) (n int, err error) {
|
|
// read buffer size
|
|
var size64 int64
|
|
size64, err = readInt(r, buf)
|
|
if err != nil {
|
|
return
|
|
}
|
|
if int64(int(size64)) != size64 || int(size64) < 0 {
|
|
// We never write chunks this big anyway.
|
|
return 0, errTooBig
|
|
}
|
|
size := int(size64)
|
|
|
|
// read buffer w/o the size
|
|
if _, err = io.ReadFull(r, buf[binary.MaxVarintLen64:size]); err != nil {
|
|
return
|
|
}
|
|
|
|
// decode as many elements as present in buf
|
|
for p := binary.MaxVarintLen64; p < size; n++ {
|
|
x, w := binary.Uvarint(buf[p:])
|
|
data.set(n, int64(x))
|
|
p += w
|
|
}
|
|
|
|
return
|
|
}
|
|
|
|
const bufSize = 16 << 10 // reasonable for BenchmarkSaveRestore
|
|
|
|
// Read reads the index from r into x; x must not be nil.
|
|
func (x *Index) Read(r io.Reader) error {
|
|
// buffer for all reads
|
|
buf := make([]byte, bufSize)
|
|
|
|
// read length
|
|
n64, err := readInt(r, buf)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if int64(int(n64)) != n64 || int(n64) < 0 {
|
|
return errTooBig
|
|
}
|
|
n := int(n64)
|
|
|
|
// allocate space
|
|
if 2*n < cap(x.data) || cap(x.data) < n || x.sa.int32 != nil && n > maxData32 || x.sa.int64 != nil && n <= maxData32 {
|
|
// new data is significantly smaller or larger than
|
|
// existing buffers - allocate new ones
|
|
x.data = make([]byte, n)
|
|
x.sa.int32 = nil
|
|
x.sa.int64 = nil
|
|
if n <= maxData32 {
|
|
x.sa.int32 = make([]int32, n)
|
|
} else {
|
|
x.sa.int64 = make([]int64, n)
|
|
}
|
|
} else {
|
|
// re-use existing buffers
|
|
x.data = x.data[0:n]
|
|
x.sa = x.sa.slice(0, n)
|
|
}
|
|
|
|
// read data
|
|
if _, err := io.ReadFull(r, x.data); err != nil {
|
|
return err
|
|
}
|
|
|
|
// read index
|
|
sa := x.sa
|
|
for sa.len() > 0 {
|
|
n, err := readSlice(r, buf, sa)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
sa = sa.slice(n, sa.len())
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// Write writes the index x to w.
|
|
func (x *Index) Write(w io.Writer) error {
|
|
// buffer for all writes
|
|
buf := make([]byte, bufSize)
|
|
|
|
// write length
|
|
if err := writeInt(w, buf, len(x.data)); err != nil {
|
|
return err
|
|
}
|
|
|
|
// write data
|
|
if _, err := w.Write(x.data); err != nil {
|
|
return err
|
|
}
|
|
|
|
// write index
|
|
sa := x.sa
|
|
for sa.len() > 0 {
|
|
n, err := writeSlice(w, buf, sa)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
sa = sa.slice(n, sa.len())
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// Bytes returns the data over which the index was created.
|
|
// It must not be modified.
|
|
//
|
|
func (x *Index) Bytes() []byte {
|
|
return x.data
|
|
}
|
|
|
|
func (x *Index) at(i int) []byte {
|
|
return x.data[x.sa.get(i):]
|
|
}
|
|
|
|
// lookupAll returns a slice into the matching region of the index.
|
|
// The runtime is O(log(N)*len(s)).
|
|
func (x *Index) lookupAll(s []byte) ints {
|
|
// find matching suffix index range [i:j]
|
|
// find the first index where s would be the prefix
|
|
i := sort.Search(x.sa.len(), func(i int) bool { return bytes.Compare(x.at(i), s) >= 0 })
|
|
// starting at i, find the first index at which s is not a prefix
|
|
j := i + sort.Search(x.sa.len()-i, func(j int) bool { return !bytes.HasPrefix(x.at(j+i), s) })
|
|
return x.sa.slice(i, j)
|
|
}
|
|
|
|
// Lookup returns an unsorted list of at most n indices where the byte string s
|
|
// occurs in the indexed data. If n < 0, all occurrences are returned.
|
|
// The result is nil if s is empty, s is not found, or n == 0.
|
|
// Lookup time is O(log(N)*len(s) + len(result)) where N is the
|
|
// size of the indexed data.
|
|
//
|
|
func (x *Index) Lookup(s []byte, n int) (result []int) {
|
|
if len(s) > 0 && n != 0 {
|
|
matches := x.lookupAll(s)
|
|
count := matches.len()
|
|
if n < 0 || count < n {
|
|
n = count
|
|
}
|
|
// 0 <= n <= count
|
|
if n > 0 {
|
|
result = make([]int, n)
|
|
if matches.int32 != nil {
|
|
for i := range result {
|
|
result[i] = int(matches.int32[i])
|
|
}
|
|
} else {
|
|
for i := range result {
|
|
result[i] = int(matches.int64[i])
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return
|
|
}
|
|
|
|
// FindAllIndex returns a sorted list of non-overlapping matches of the
|
|
// regular expression r, where a match is a pair of indices specifying
|
|
// the matched slice of x.Bytes(). If n < 0, all matches are returned
|
|
// in successive order. Otherwise, at most n matches are returned and
|
|
// they may not be successive. The result is nil if there are no matches,
|
|
// or if n == 0.
|
|
//
|
|
func (x *Index) FindAllIndex(r *regexp.Regexp, n int) (result [][]int) {
|
|
// a non-empty literal prefix is used to determine possible
|
|
// match start indices with Lookup
|
|
prefix, complete := r.LiteralPrefix()
|
|
lit := []byte(prefix)
|
|
|
|
// worst-case scenario: no literal prefix
|
|
if prefix == "" {
|
|
return r.FindAllIndex(x.data, n)
|
|
}
|
|
|
|
// if regexp is a literal just use Lookup and convert its
|
|
// result into match pairs
|
|
if complete {
|
|
// Lookup returns indices that may belong to overlapping matches.
|
|
// After eliminating them, we may end up with fewer than n matches.
|
|
// If we don't have enough at the end, redo the search with an
|
|
// increased value n1, but only if Lookup returned all the requested
|
|
// indices in the first place (if it returned fewer than that then
|
|
// there cannot be more).
|
|
for n1 := n; ; n1 += 2 * (n - len(result)) /* overflow ok */ {
|
|
indices := x.Lookup(lit, n1)
|
|
if len(indices) == 0 {
|
|
return
|
|
}
|
|
sort.Ints(indices)
|
|
pairs := make([]int, 2*len(indices))
|
|
result = make([][]int, len(indices))
|
|
count := 0
|
|
prev := 0
|
|
for _, i := range indices {
|
|
if count == n {
|
|
break
|
|
}
|
|
// ignore indices leading to overlapping matches
|
|
if prev <= i {
|
|
j := 2 * count
|
|
pairs[j+0] = i
|
|
pairs[j+1] = i + len(lit)
|
|
result[count] = pairs[j : j+2]
|
|
count++
|
|
prev = i + len(lit)
|
|
}
|
|
}
|
|
result = result[0:count]
|
|
if len(result) >= n || len(indices) != n1 {
|
|
// found all matches or there's no chance to find more
|
|
// (n and n1 can be negative)
|
|
break
|
|
}
|
|
}
|
|
if len(result) == 0 {
|
|
result = nil
|
|
}
|
|
return
|
|
}
|
|
|
|
// regexp has a non-empty literal prefix; Lookup(lit) computes
|
|
// the indices of possible complete matches; use these as starting
|
|
// points for anchored searches
|
|
// (regexp "^" matches beginning of input, not beginning of line)
|
|
r = regexp.MustCompile("^" + r.String()) // compiles because r compiled
|
|
|
|
// same comment about Lookup applies here as in the loop above
|
|
for n1 := n; ; n1 += 2 * (n - len(result)) /* overflow ok */ {
|
|
indices := x.Lookup(lit, n1)
|
|
if len(indices) == 0 {
|
|
return
|
|
}
|
|
sort.Ints(indices)
|
|
result = result[0:0]
|
|
prev := 0
|
|
for _, i := range indices {
|
|
if len(result) == n {
|
|
break
|
|
}
|
|
m := r.FindIndex(x.data[i:]) // anchored search - will not run off
|
|
// ignore indices leading to overlapping matches
|
|
if m != nil && prev <= i {
|
|
m[0] = i // correct m
|
|
m[1] += i
|
|
result = append(result, m)
|
|
prev = m[1]
|
|
}
|
|
}
|
|
if len(result) >= n || len(indices) != n1 {
|
|
// found all matches or there's no chance to find more
|
|
// (n and n1 can be negative)
|
|
break
|
|
}
|
|
}
|
|
if len(result) == 0 {
|
|
result = nil
|
|
}
|
|
return
|
|
}
|