You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
cloudreve/bootstrap/embed.go

433 lines
13 KiB

This file contains ambiguous Unicode characters!

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

// Copyright 2020 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 embed provides access to files embedded in the running Go program.
//
// Go source files that import "embed" can use the //go:embed directive
// to initialize a variable of type string, []byte, or FS with the contents of
// files read from the package directory or subdirectories at compile time.
//
// For example, here are three ways to embed a file named hello.txt
// and then print its contents at run time.
//
// Embedding one file into a string:
//
// import _ "embed"
//
// //go:embed hello.txt
// var s string
// print(s)
//
// Embedding one file into a slice of bytes:
//
// import _ "embed"
//
// //go:embed hello.txt
// var b []byte
// print(string(b))
//
// Embedded one or more files into a file system:
//
// import "embed"
//
// //go:embed hello.txt
// var f embed.FS
// data, _ := f.ReadFile("hello.txt")
// print(string(data))
//
// # Directives
//
// A //go:embed directive above a variable declaration specifies which files to embed,
// using one or more path.Match patterns.
//
// The directive must immediately precede a line containing the declaration of a single variable.
// Only blank lines and // line comments are permitted between the directive and the declaration.
//
// The type of the variable must be a string type, or a slice of a byte type,
// or FS (or an alias of FS).
//
// For example:
//
// package server
//
// import "embed"
//
// // content holds our static web server content.
// //go:embed image/* template/*
// //go:embed html/index.html
// var content embed.FS
//
// The Go build system will recognize the directives and arrange for the declared variable
// (in the example above, content) to be populated with the matching files from the file system.
//
// The //go:embed directive accepts multiple space-separated patterns for
// brevity, but it can also be repeated, to avoid very long lines when there are
// many patterns. The patterns are interpreted relative to the package directory
// containing the source file. The path separator is a forward slash, even on
// Windows systems. Patterns may not contain . or .. or empty path elements,
// nor may they begin or end with a slash. To match everything in the current
// directory, use * instead of .. To allow for naming files with spaces in
// their names, patterns can be written as Go double-quoted or back-quoted
// string literals.
//
// If a pattern names a directory, all files in the subtree rooted at that directory are
// embedded (recursively), except that files with names beginning with . or _
// are excluded. So the variable in the above example is almost equivalent to:
//
// // content is our static web server content.
// //go:embed image template html/index.html
// var content embed.FS
//
// The difference is that image/* embeds image/.tempfile while image does not.
// Neither embeds image/dir/.tempfile.
//
// If a pattern begins with the prefix all:, then the rule for walking directories is changed
// to include those files beginning with . or _. For example, all:image embeds
// both image/.tempfile and image/dir/.tempfile.
//
// The //go:embed directive can be used with both exported and unexported variables,
// depending on whether the package wants to make the data available to other packages.
// It can only be used with variables at package scope, not with local variables.
//
// Patterns must not match files outside the package's module, such as .git/* or symbolic links.
// Patterns must not match files whose names include the special punctuation characters " * < > ? ` ' | / \ and :.
// Matches for empty directories are ignored. After that, each pattern in a //go:embed line
// must match at least one file or non-empty directory.
//
// If any patterns are invalid or have invalid matches, the build will fail.
//
// # Strings and Bytes
//
// The //go:embed line for a variable of type string or []byte can have only a single pattern,
// and that pattern can match only a single file. The string or []byte is initialized with
// the contents of that file.
//
// The //go:embed directive requires importing "embed", even when using a string or []byte.
// In source files that don't refer to embed.FS, use a blank import (import _ "embed").
//
// # File Systems
//
// For embedding a single file, a variable of type string or []byte is often best.
// The FS type enables embedding a tree of files, such as a directory of static
// web server content, as in the example above.
//
// FS implements the io/fs package's FS interface, so it can be used with any package that
// understands file systems, including net/http, text/template, and html/template.
//
// For example, given the content variable in the example above, we can write:
//
// http.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.FS(content))))
//
// template.ParseFS(content, "*.tmpl")
//
// # Tools
//
// To support tools that analyze Go packages, the patterns found in //go:embed lines
// are available in “go list” output. See the EmbedPatterns, TestEmbedPatterns,
// and XTestEmbedPatterns fields in the “go help list” output.
package bootstrap
import (
"errors"
"io"
"io/fs"
"time"
)
// An FS is a read-only collection of files, usually initialized with a //go:embed directive.
// When declared without a //go:embed directive, an FS is an empty file system.
//
// An FS is a read-only value, so it is safe to use from multiple goroutines
// simultaneously and also safe to assign values of type FS to each other.
//
// FS implements fs.FS, so it can be used with any package that understands
// file system interfaces, including net/http, text/template, and html/template.
//
// See the package documentation for more details about initializing an FS.
type FS struct {
// The compiler knows the layout of this struct.
// See cmd/compile/internal/staticdata's WriteEmbed.
//
// The files list is sorted by name but not by simple string comparison.
// Instead, each file's name takes the form "dir/elem" or "dir/elem/".
// The optional trailing slash indicates that the file is itself a directory.
// The files list is sorted first by dir (if dir is missing, it is taken to be ".")
// and then by base, so this list of files:
//
// p
// q/
// q/r
// q/s/
// q/s/t
// q/s/u
// q/v
// w
//
// is actually sorted as:
//
// p # dir=. elem=p
// q/ # dir=. elem=q
// w/ # dir=. elem=w
// q/r # dir=q elem=r
// q/s/ # dir=q elem=s
// q/v # dir=q elem=v
// q/s/t # dir=q/s elem=t
// q/s/u # dir=q/s elem=u
//
// This order brings directory contents together in contiguous sections
// of the list, allowing a directory read to use binary search to find
// the relevant sequence of entries.
files *[]file
}
// split splits the name into dir and elem as described in the
// comment in the FS struct above. isDir reports whether the
// final trailing slash was present, indicating that name is a directory.
func split(name string) (dir, elem string, isDir bool) {
if name[len(name)-1] == '/' {
isDir = true
name = name[:len(name)-1]
}
i := len(name) - 1
for i >= 0 && name[i] != '/' {
i--
}
if i < 0 {
return ".", name, isDir
}
return name[:i], name[i+1:], isDir
}
// trimSlash trims a trailing slash from name, if present,
// returning the possibly shortened name.
func trimSlash(name string) string {
if len(name) > 0 && name[len(name)-1] == '/' {
return name[:len(name)-1]
}
return name
}
var (
_ fs.ReadDirFS = FS{}
_ fs.ReadFileFS = FS{}
)
// A file is a single file in the FS.
// It implements fs.FileInfo and fs.DirEntry.
type file struct {
// The compiler knows the layout of this struct.
// See cmd/compile/internal/staticdata's WriteEmbed.
name string
data string
hash [16]byte // truncated SHA256 hash
}
var (
_ fs.FileInfo = (*file)(nil)
_ fs.DirEntry = (*file)(nil)
)
func (f *file) Name() string { _, elem, _ := split(f.name); return elem }
func (f *file) Size() int64 { return int64(len(f.data)) }
func (f *file) ModTime() time.Time { return time.Time{} }
func (f *file) IsDir() bool { _, _, isDir := split(f.name); return isDir }
func (f *file) Sys() any { return nil }
func (f *file) Type() fs.FileMode { return f.Mode().Type() }
func (f *file) Info() (fs.FileInfo, error) { return f, nil }
func (f *file) Mode() fs.FileMode {
if f.IsDir() {
return fs.ModeDir | 0555
}
return 0444
}
// dotFile is a file for the root directory,
// which is omitted from the files list in a FS.
var dotFile = &file{name: "./"}
// lookup returns the named file, or nil if it is not present.
func (f FS) lookup(name string) *file {
if !fs.ValidPath(name) {
// The compiler should never emit a file with an invalid name,
// so this check is not strictly necessary (if name is invalid,
// we shouldn't find a match below), but it's a good backstop anyway.
return nil
}
if name == "." {
return dotFile
}
if f.files == nil {
return nil
}
// Binary search to find where name would be in the list,
// and then check if name is at that position.
dir, elem, _ := split(name)
files := *f.files
i := sortSearch(len(files), func(i int) bool {
idir, ielem, _ := split(files[i].name)
return idir > dir || idir == dir && ielem >= elem
})
if i < len(files) && trimSlash(files[i].name) == name {
return &files[i]
}
return nil
}
// readDir returns the list of files corresponding to the directory dir.
func (f FS) readDir(dir string) []file {
if f.files == nil {
return nil
}
// Binary search to find where dir starts and ends in the list
// and then return that slice of the list.
files := *f.files
i := sortSearch(len(files), func(i int) bool {
idir, _, _ := split(files[i].name)
return idir >= dir
})
j := sortSearch(len(files), func(j int) bool {
jdir, _, _ := split(files[j].name)
return jdir > dir
})
return files[i:j]
}
// Open opens the named file for reading and returns it as an fs.File.
//
// The returned file implements io.Seeker when the file is not a directory.
func (f FS) Open(name string) (fs.File, error) {
file := f.lookup(name)
if file == nil {
return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
}
if file.IsDir() {
return &openDir{file, f.readDir(name), 0}, nil
}
return &openFile{file, 0}, nil
}
// ReadDir reads and returns the entire named directory.
func (f FS) ReadDir(name string) ([]fs.DirEntry, error) {
file, err := f.Open(name)
if err != nil {
return nil, err
}
dir, ok := file.(*openDir)
if !ok {
return nil, &fs.PathError{Op: "read", Path: name, Err: errors.New("not a directory")}
}
list := make([]fs.DirEntry, len(dir.files))
for i := range list {
list[i] = &dir.files[i]
}
return list, nil
}
// ReadFile reads and returns the content of the named file.
func (f FS) ReadFile(name string) ([]byte, error) {
file, err := f.Open(name)
if err != nil {
return nil, err
}
ofile, ok := file.(*openFile)
if !ok {
return nil, &fs.PathError{Op: "read", Path: name, Err: errors.New("is a directory")}
}
return []byte(ofile.f.data), nil
}
// An openFile is a regular file open for reading.
type openFile struct {
f *file // the file itself
offset int64 // current read offset
}
var (
_ io.Seeker = (*openFile)(nil)
)
func (f *openFile) Close() error { return nil }
func (f *openFile) Stat() (fs.FileInfo, error) { return f.f, nil }
func (f *openFile) Read(b []byte) (int, error) {
if f.offset >= int64(len(f.f.data)) {
return 0, io.EOF
}
if f.offset < 0 {
return 0, &fs.PathError{Op: "read", Path: f.f.name, Err: fs.ErrInvalid}
}
n := copy(b, f.f.data[f.offset:])
f.offset += int64(n)
return n, nil
}
func (f *openFile) Seek(offset int64, whence int) (int64, error) {
switch whence {
case 0:
// offset += 0
case 1:
offset += f.offset
case 2:
offset += int64(len(f.f.data))
}
if offset < 0 || offset > int64(len(f.f.data)) {
return 0, &fs.PathError{Op: "seek", Path: f.f.name, Err: fs.ErrInvalid}
}
f.offset = offset
return offset, nil
}
// An openDir is a directory open for reading.
type openDir struct {
f *file // the directory file itself
files []file // the directory contents
offset int // the read offset, an index into the files slice
}
func (d *openDir) Close() error { return nil }
func (d *openDir) Stat() (fs.FileInfo, error) { return d.f, nil }
func (d *openDir) Read([]byte) (int, error) {
return 0, &fs.PathError{Op: "read", Path: d.f.name, Err: errors.New("is a directory")}
}
func (d *openDir) ReadDir(count int) ([]fs.DirEntry, error) {
n := len(d.files) - d.offset
if n == 0 {
if count <= 0 {
return nil, nil
}
return nil, io.EOF
}
if count > 0 && n > count {
n = count
}
list := make([]fs.DirEntry, n)
for i := range list {
list[i] = &d.files[d.offset+i]
}
d.offset += n
return list, nil
}
// sortSearch is like sort.Search, avoiding an import.
func sortSearch(n int, f func(int) bool) int {
// Define f(-1) == false and f(n) == true.
// Invariant: f(i-1) == false, f(j) == true.
i, j := 0, n
for i < j {
h := int(uint(i+j) >> 1) // avoid overflow when computing h
// i ≤ h < j
if !f(h) {
i = h + 1 // preserves f(i-1) == false
} else {
j = h // preserves f(j) == true
}
}
// i == j, f(i-1) == false, and f(j) (= f(i)) == true => answer is i.
return i
}