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// Copyright 2009 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.
// This file implements the Mapping data structure.
package main
import (
"fmt"
"io"
"os"
pathutil "path"
"sort"
"strings"
)
// A Mapping object maps relative paths (e.g. from URLs)
// to absolute paths (of the file system) and vice versa.
//
// A Mapping object consists of a list of individual mappings
// of the form: prefix -> path which are interpreted as follows:
// A relative path of the form prefix/tail is to be mapped to
// the absolute path/tail, if that absolute path exists in the file
// system. Given a Mapping object, a relative path is mapped to an
// absolute path by trying each of the individual mappings in order,
// until a valid mapping is found. For instance, for the mapping:
//
// user -> /home/user
// public -> /home/user/public
// public -> /home/build/public
//
// the relative paths below are mapped to absolute paths as follows:
//
// user/foo -> /home/user/foo
// public/net/rpc/file1.go -> /home/user/public/net/rpc/file1.go
//
// If there is no /home/user/public/net/rpc/file2.go, the next public
// mapping entry is used to map the relative path to:
//
// public/net/rpc/file2.go -> /home/build/public/net/rpc/file2.go
//
// (assuming that file exists).
//
// Each individual mapping also has a RWValue associated with it that
// may be used to store mapping-specific information. See the Iterate
// method.
//
type Mapping struct {
list []mapping
prefixes []string // lazily computed from list
}
type mapping struct {
prefix, path string
value *RWValue
}
// Init initializes the Mapping from a list of ':'-separated
// paths. Empty paths are ignored; relative paths are assumed
// to be relative to the current working directory and converted
// to absolute paths. For each path of the form:
//
// dirname/localname
//
// a mapping
//
// localname -> path
//
// is added to the Mapping object, in the order of occurrence.
// For instance, the argument:
//
// /home/user:/home/build/public
//
// leads to the following mapping:
//
// user -> /home/user
// public -> /home/build/public
//
func (m *Mapping) Init(paths string) {
pathlist := canonicalizePaths(strings.Split(paths, ":", -1), nil)
list := make([]mapping, len(pathlist))
// create mapping list
for i, path := range pathlist {
_, prefix := pathutil.Split(path)
list[i] = mapping{prefix, path, new(RWValue)}
}
m.list = list
}
// IsEmpty returns true if there are no mappings specified.
func (m *Mapping) IsEmpty() bool { return len(m.list) == 0 }
// PrefixList returns a list of all prefixes, with duplicates removed.
// For instance, for the mapping:
//
// user -> /home/user
// public -> /home/user/public
// public -> /home/build/public
//
// the prefix list is:
//
// user, public
//
func (m *Mapping) PrefixList() []string {
// compute the list lazily
if m.prefixes == nil {
list := make([]string, len(m.list))
// populate list
for i, e := range m.list {
list[i] = e.prefix
}
// sort the list and remove duplicate entries
sort.SortStrings(list)
i := 0
prev := ""
for _, path := range list {
if path != prev {
list[i] = path
i++
prev = path
}
}
m.prefixes = list[0:i]
}
return m.prefixes
}
// Fprint prints the mapping.
func (m *Mapping) Fprint(w io.Writer) {
for _, e := range m.list {
fmt.Fprintf(w, "\t%s -> %s\n", e.prefix, e.path)
}
}
func splitFirst(path string) (head, tail string) {
i := strings.Index(path, "/")
if i > 0 {
// 0 < i < len(path)
return path[0:i], path[i+1:]
}
return "", path
}
// ToAbsolute maps a relative path to an absolute path using the Mapping
// specified by the receiver. If the path cannot be mapped, the empty
// string is returned.
//
func (m *Mapping) ToAbsolute(path string) string {
prefix, tail := splitFirst(path)
for _, e := range m.list {
switch {
case e.prefix == prefix:
// use tail
case e.prefix == "":
tail = path
default:
continue // no match
}
abspath := pathutil.Join(e.path, tail)
if _, err := os.Stat(abspath); err == nil {
return abspath
}
}
return "" // no match
}
// ToRelative maps an absolute path to a relative path using the Mapping
// specified by the receiver. If the path cannot be mapped, the empty
// string is returned.
//
func (m *Mapping) ToRelative(path string) string {
for _, e := range m.list {
if strings.HasPrefix(path, e.path) {
// /absolute/prefix/foo -> prefix/foo
return pathutil.Join(e.prefix, path[len(e.path):]) // Join will remove a trailing '/'
}
}
return "" // no match
}
// Iterate calls f for each path and RWValue in the mapping (in uspecified order)
// until f returns false.
//
func (m *Mapping) Iterate(f func(path string, value *RWValue) bool) {
for _, e := range m.list {
if !f(e.path, e.value) {
return
}
}
}