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path: root/src/pkg/index/suffixarray/suffixarray.go
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Diffstat (limited to 'src/pkg/index/suffixarray/suffixarray.go')
-rw-r--r--src/pkg/index/suffixarray/suffixarray.go307
1 files changed, 0 insertions, 307 deletions
diff --git a/src/pkg/index/suffixarray/suffixarray.go b/src/pkg/index/suffixarray/suffixarray.go
deleted file mode 100644
index c59ae6eef..000000000
--- a/src/pkg/index/suffixarray/suffixarray.go
+++ /dev/null
@@ -1,307 +0,0 @@
-// 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"
- "io"
- "regexp"
- "sort"
-)
-
-// Index implements a suffix array for fast substring search.
-type Index struct {
- data []byte
- sa []int // suffix array for data; len(sa) == len(data)
-}
-
-// New creates a new Index for data.
-// Index creation time is O(N*log(N)) for N = len(data).
-func New(data []byte) *Index {
- return &Index{data, qsufsort(data)}
-}
-
-// 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) (int, error) {
- _, err := io.ReadFull(r, buf[0:binary.MaxVarintLen64]) // ok to continue with error
- x, _ := binary.Varint(buf)
- return int(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 []int) (n int, err error) {
- // encode as many elements as fit into buf
- p := binary.MaxVarintLen64
- for ; n < len(data) && p+binary.MaxVarintLen64 <= len(buf); n++ {
- p += binary.PutUvarint(buf[p:], uint64(data[n]))
- }
-
- // update buffer size
- binary.PutVarint(buf, int64(p))
-
- // write buffer
- _, err = w.Write(buf[0:p])
- return
-}
-
-// readSlice reads data[:n] from r and returns n.
-// It uses buf to buffer the read.
-func readSlice(r io.Reader, buf []byte, data []int) (n int, err error) {
- // read buffer size
- var size int
- size, err = readInt(r, buf)
- if err != nil {
- return
- }
-
- // 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[n] = int(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
- n, err := readInt(r, buf)
- if err != nil {
- return err
- }
-
- // allocate space
- if 2*n < cap(x.data) || cap(x.data) < n {
- // new data is significantly smaller or larger then
- // existing buffers - allocate new ones
- x.data = make([]byte, n)
- x.sa = make([]int, n)
- } else {
- // re-use existing buffers
- x.data = x.data[0:n]
- x.sa = x.sa[0:n]
- }
-
- // read data
- if _, err := io.ReadFull(r, x.data); err != nil {
- return err
- }
-
- // read index
- for sa := x.sa; len(sa) > 0; {
- n, err := readSlice(r, buf, sa)
- if err != nil {
- return err
- }
- sa = sa[n:]
- }
- 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
- for sa := x.sa; len(sa) > 0; {
- n, err := writeSlice(w, buf, sa)
- if err != nil {
- return err
- }
- sa = sa[n:]
- }
- 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[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) []int {
- // find matching suffix index range [i:j]
- // find the first index where s would be the prefix
- i := sort.Search(len(x.sa), 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(len(x.sa)-i, func(j int) bool { return !bytes.HasPrefix(x.at(j+i), s) })
- return x.sa[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)
- if n < 0 || len(matches) < n {
- n = len(matches)
- }
- // 0 <= n <= len(matches)
- if n > 0 {
- result = make([]int, n)
- copy(result, matches)
- }
- }
- 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
-}