github.com/bazelbuild/bazel-gazelle@v0.36.1-0.20240520142334-61b277ba6fed/pathtools/path.go (about)

     1  /* Copyright 2018 The Bazel Authors. All rights reserved.
     2  
     3  Licensed under the Apache License, Version 2.0 (the "License");
     4  you may not use this file except in compliance with the License.
     5  You may obtain a copy of the License at
     6  
     7     http://www.apache.org/licenses/LICENSE-2.0
     8  
     9  Unless required by applicable law or agreed to in writing, software
    10  distributed under the License is distributed on an "AS IS" BASIS,
    11  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  See the License for the specific language governing permissions and
    13  limitations under the License.
    14  */
    15  
    16  // Package pathtools provides utilities for manipulating paths.  Most paths
    17  // within Gazelle are slash-separated paths, relative to the repository root
    18  // directory. The repository root directory is represented by the empty
    19  // string. Paths in this format may be used directly as package names in labels.
    20  package pathtools
    21  
    22  import (
    23  	"path"
    24  	"path/filepath"
    25  	"strings"
    26  )
    27  
    28  // HasPrefix returns whether the slash-separated path p has the given
    29  // prefix. Unlike strings.HasPrefix, this function respects component
    30  // boundaries, so "/home/foo" is not a prefix is "/home/foobar/baz". If the
    31  // prefix is empty, this function always returns true.
    32  func HasPrefix(p, prefix string) bool {
    33  	p = trimTrailingSlash(p)
    34  	prefix = trimTrailingSlash(prefix)
    35  	return prefix == "" || p == prefix || strings.HasPrefix(p, prefix+"/")
    36  }
    37  
    38  // TrimPrefix returns p without the provided prefix. If p doesn't start
    39  // with prefix, it returns p unchanged. Unlike strings.HasPrefix, this function
    40  // respects component boundaries (assuming slash-separated paths), so
    41  // TrimPrefix("foo/bar", "foo") returns "baz".
    42  func TrimPrefix(p, prefix string) string {
    43  	origPath := p
    44  	p = trimTrailingSlash(p)
    45  	prefix = trimTrailingSlash(prefix)
    46  	if prefix == "" {
    47  		return origPath
    48  	}
    49  	if prefix == p {
    50  		return ""
    51  	}
    52  	return strings.TrimPrefix(p, prefix+"/")
    53  }
    54  
    55  // RelBaseName returns the base name for rel, a slash-separated path relative
    56  // to the repository root. If rel is empty, RelBaseName returns the base name
    57  // of prefix. If prefix is empty, RelBaseName returns the base name of root,
    58  // the absolute file path of the repository root directory. If that's empty
    59  // to, then RelBaseName returns "root".
    60  func RelBaseName(rel, prefix, root string) string {
    61  	base := path.Base(rel)
    62  	if base == "." || base == "/" {
    63  		base = path.Base(prefix)
    64  	}
    65  	if base == "." || base == "/" {
    66  		base = filepath.Base(root)
    67  	}
    68  	if base == "." || base == "/" {
    69  		base = "root"
    70  	}
    71  	return base
    72  }
    73  
    74  // Index returns the starting index of the string sub within the non-absolute
    75  // slash-separated path p. sub must start and end at component boundaries
    76  // within p.
    77  func Index(p, sub string) int {
    78  	if sub == "" {
    79  		return 0
    80  	}
    81  	p = path.Clean(p)
    82  	sub = path.Clean(sub)
    83  	if path.IsAbs(sub) {
    84  		if HasPrefix(p, sub) {
    85  			return 0
    86  		} else {
    87  			return -1
    88  		}
    89  	}
    90  	if p == "" || p == "/" {
    91  		return -1
    92  	}
    93  
    94  	i := 0 // i is the index of the first byte of a path element
    95  	if len(p) > 0 && p[0] == '/' {
    96  		i++
    97  	}
    98  	for {
    99  		suffix := p[i:]
   100  		if len(suffix) < len(sub) {
   101  			return -1
   102  		}
   103  		if suffix[:len(sub)] == sub && (len(suffix) == len(sub) || suffix[len(sub)] == '/') {
   104  			return i
   105  		}
   106  		j := strings.IndexByte(suffix, '/')
   107  		if j < 0 {
   108  			return -1
   109  		}
   110  		i += j + 1
   111  		if i >= len(p) {
   112  			return -1
   113  		}
   114  	}
   115  }
   116  
   117  func trimTrailingSlash(p string) string {
   118  	for len(p) > 1 && p[len(p)-1] == '/' {
   119  		p = p[:len(p)-1]
   120  	}
   121  	return p
   122  }