--- /dev/null
+// Copyright 2012 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 present
+
+import (
+ "errors"
+ "regexp"
+ "strconv"
+ "unicode/utf8"
+)
+
+// This file is stolen from go/src/cmd/godoc/codewalk.go.
+// It's an evaluator for the file address syntax implemented by acme and sam,
+// but using Go-native regular expressions.
+// To keep things reasonably close, this version uses (?m:re) for all user-provided
+// regular expressions. That is the only change to the code from codewalk.go.
+// See http://9p.io/sys/doc/sam/sam.html Table II for details on the syntax.
+
+// addrToByte evaluates the given address starting at offset start in data.
+// It returns the lo and hi byte offset of the matched region within data.
+func addrToByteRange(addr string, start int, data []byte) (lo, hi int, err error) {
+ if addr == "" {
+ lo, hi = start, len(data)
+ return
+ }
+ var (
+ dir byte
+ prevc byte
+ charOffset bool
+ )
+ lo = start
+ hi = start
+ for addr != "" && err == nil {
+ c := addr[0]
+ switch c {
+ default:
+ err = errors.New("invalid address syntax near " + string(c))
+ case ',':
+ if len(addr) == 1 {
+ hi = len(data)
+ } else {
+ _, hi, err = addrToByteRange(addr[1:], hi, data)
+ }
+ return
+
+ case '+', '-':
+ if prevc == '+' || prevc == '-' {
+ lo, hi, err = addrNumber(data, lo, hi, prevc, 1, charOffset)
+ }
+ dir = c
+
+ case '$':
+ lo = len(data)
+ hi = len(data)
+ if len(addr) > 1 {
+ dir = '+'
+ }
+
+ case '#':
+ charOffset = true
+
+ case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+ var i int
+ for i = 1; i < len(addr); i++ {
+ if addr[i] < '0' || addr[i] > '9' {
+ break
+ }
+ }
+ var n int
+ n, err = strconv.Atoi(addr[0:i])
+ if err != nil {
+ break
+ }
+ lo, hi, err = addrNumber(data, lo, hi, dir, n, charOffset)
+ dir = 0
+ charOffset = false
+ prevc = c
+ addr = addr[i:]
+ continue
+
+ case '/':
+ var i, j int
+ Regexp:
+ for i = 1; i < len(addr); i++ {
+ switch addr[i] {
+ case '\\':
+ i++
+ case '/':
+ j = i + 1
+ break Regexp
+ }
+ }
+ if j == 0 {
+ j = i
+ }
+ pattern := addr[1:i]
+ lo, hi, err = addrRegexp(data, lo, hi, dir, pattern)
+ prevc = c
+ addr = addr[j:]
+ continue
+ }
+ prevc = c
+ addr = addr[1:]
+ }
+
+ if err == nil && dir != 0 {
+ lo, hi, err = addrNumber(data, lo, hi, dir, 1, charOffset)
+ }
+ if err != nil {
+ return 0, 0, err
+ }
+ return lo, hi, nil
+}
+
+// addrNumber applies the given dir, n, and charOffset to the address lo, hi.
+// dir is '+' or '-', n is the count, and charOffset is true if the syntax
+// used was #n. Applying +n (or +#n) means to advance n lines
+// (or characters) after hi. Applying -n (or -#n) means to back up n lines
+// (or characters) before lo.
+// The return value is the new lo, hi.
+func addrNumber(data []byte, lo, hi int, dir byte, n int, charOffset bool) (int, int, error) {
+ switch dir {
+ case 0:
+ lo = 0
+ hi = 0
+ fallthrough
+
+ case '+':
+ if charOffset {
+ pos := hi
+ for ; n > 0 && pos < len(data); n-- {
+ _, size := utf8.DecodeRune(data[pos:])
+ pos += size
+ }
+ if n == 0 {
+ return pos, pos, nil
+ }
+ break
+ }
+ // find next beginning of line
+ if hi > 0 {
+ for hi < len(data) && data[hi-1] != '\n' {
+ hi++
+ }
+ }
+ lo = hi
+ if n == 0 {
+ return lo, hi, nil
+ }
+ for ; hi < len(data); hi++ {
+ if data[hi] != '\n' {
+ continue
+ }
+ switch n--; n {
+ case 1:
+ lo = hi + 1
+ case 0:
+ return lo, hi + 1, nil
+ }
+ }
+
+ case '-':
+ if charOffset {
+ // Scan backward for bytes that are not UTF-8 continuation bytes.
+ pos := lo
+ for ; pos > 0 && n > 0; pos-- {
+ if data[pos]&0xc0 != 0x80 {
+ n--
+ }
+ }
+ if n == 0 {
+ return pos, pos, nil
+ }
+ break
+ }
+ // find earlier beginning of line
+ for lo > 0 && data[lo-1] != '\n' {
+ lo--
+ }
+ hi = lo
+ if n == 0 {
+ return lo, hi, nil
+ }
+ for ; lo >= 0; lo-- {
+ if lo > 0 && data[lo-1] != '\n' {
+ continue
+ }
+ switch n--; n {
+ case 1:
+ hi = lo
+ case 0:
+ return lo, hi, nil
+ }
+ }
+ }
+
+ return 0, 0, errors.New("address out of range")
+}
+
+// addrRegexp searches for pattern in the given direction starting at lo, hi.
+// The direction dir is '+' (search forward from hi) or '-' (search backward from lo).
+// Backward searches are unimplemented.
+func addrRegexp(data []byte, lo, hi int, dir byte, pattern string) (int, int, error) {
+ // We want ^ and $ to work as in sam/acme, so use ?m.
+ re, err := regexp.Compile("(?m:" + pattern + ")")
+ if err != nil {
+ return 0, 0, err
+ }
+ if dir == '-' {
+ // Could implement reverse search using binary search
+ // through file, but that seems like overkill.
+ return 0, 0, errors.New("reverse search not implemented")
+ }
+ m := re.FindIndex(data[hi:])
+ if len(m) > 0 {
+ m[0] += hi
+ m[1] += hi
+ } else if hi > 0 {
+ // No match. Wrap to beginning of data.
+ m = re.FindIndex(data)
+ }
+ if len(m) == 0 {
+ return 0, 0, errors.New("no match for " + pattern)
+ }
+ return m[0], m[1], nil
+}
projects / dotfiles / .git / blobdiff