136 lines
5.0 KiB
Go
136 lines
5.0 KiB
Go
// Mgmt
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// Copyright (C) 2013-2024+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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// Package embedded embeds mcl modules into the system import namespace.
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// Typically these are made available via an `import "embedded/foo"` style stmt.
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package embedded
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import (
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"fmt"
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"io/fs"
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"runtime"
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"strings"
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"github.com/purpleidea/mgmt/engine"
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"github.com/purpleidea/mgmt/util"
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"github.com/spf13/afero"
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"github.com/yalue/merged_fs"
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)
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const (
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// Scheme is the string used to represent the scheme used by the
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// embedded filesystem URI.
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Scheme = "embeddedfs"
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)
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var registeredEmbeds = make(map[string]fs.ReadFileFS) // must initialize
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// ModuleRegister takes a filesystem and stores a reference to it in our
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// embedded module system along with a name. Future lookups to that name will
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// pull out that filesystem.
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func ModuleRegister(module string, fs fs.ReadFileFS) {
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if _, exists := registeredEmbeds[module]; exists {
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panic(fmt.Sprintf("an embed in module %s is already registered", module))
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}
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// we currently set the fs URI when we return an fs with the Lookup func
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registeredEmbeds[module] = fs
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}
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// Lookup pulls out an embedded filesystem module which will contain a valid URI
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// method. The returned fs is read-only.
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// XXX: Update the interface to remove the afero part leaving this all read-only
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func Lookup(module string) (engine.Fs, error) {
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fs, exists := registeredEmbeds[module]
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if !exists {
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return nil, fmt.Errorf("could not lookup embedded module: %s", module)
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}
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// XXX: All this horrible filesystem transformation mess happens because
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// golang doesn't have a writeable io/fs.WriteableFS interface... We can
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// eventually port this further away from Afero though...
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fromIOFS := afero.FromIOFS{FS: fs} // fulfills afero.Fs interface
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rp := util.NewRelPathFs(fromIOFS, "/") // calls to `/foo` turn into `foo`
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afs := &afero.Afero{Fs: rp} // wrap so that we're implementing ioutil
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engineFS := &util.AferoFs{ // fulfills engine.Fs interface
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Scheme: Scheme, // pick the scheme!
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Path: "/" + module, // need a leading slash
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Afero: afs,
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}
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return engineFS, nil
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}
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// MergeFS merges multiple filesystems and returns an fs.FS. It is provided as a
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// helper function to abstract away the underlying implementation in case we
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// ever wish to replace it with something more performant or ergonomic.
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// TODO: add a new interface that combines ReadFileFS and ReadDirFS and use that
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// as the signature everywhere so we could catch those issues at the very start!
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func MergeFS(filesystems ...fs.ReadFileFS) fs.ReadFileFS {
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l := []fs.FS{}
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for _, x := range filesystems {
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f, ok := x.(fs.FS)
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if !ok {
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// programming error
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panic("fs does not support basic FS")
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}
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l = append(l, f)
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}
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// runs NewMergedFS(a, b) in a balanced way recursively
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ret, ok := merged_fs.MergeMultiple(l...).(fs.ReadFileFS)
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if !ok {
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// programming error
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panic("fs does not support ReadFileFS")
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}
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return ret
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}
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// FullModuleName is a helper function that returns the embedded module name.
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// This is the parent directory that an embedded code base should use as prefix.
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func FullModuleName(moduleName string) string {
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pc, _, _, ok := runtime.Caller(1)
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if !ok {
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panic("caller info not found")
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}
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s := runtime.FuncForPC(pc).Name()
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chunks := strings.Split(s, "/")
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if len(chunks) < 2 {
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// programming error
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panic("split pattern not found")
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}
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name := chunks[len(chunks)-2]
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if name == "" {
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panic("name not found")
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}
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if moduleName == "" { // in case we only want to know the module name
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return name
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}
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return name + "/" + moduleName // do the concat for the user!
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}
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