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// Copyright 2021 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package assets
import (
"compress/gzip"
"embed"
"io"
"io/fs"
"time"
)
const (
gzipSuffix = ".gz"
)
type FileSystem struct {
embed embed.FS
}
func New(fs embed.FS) FileSystem {
return FileSystem{fs}
}
// Open implements the fs.FS interface.
func (compressed FileSystem) Open(path string) (fs.File, error) {
// If we have the file in our embed FS, just return that as it could be a dir.
var f fs.File
if f, err := compressed.embed.Open(path); err == nil {
return f, nil
}
f, err := compressed.embed.Open(path + gzipSuffix)
if err != nil {
return f, err
}
// Read the decompressed content into a buffer.
gr, err := gzip.NewReader(f)
if err != nil {
return f, err
}
defer gr.Close()
c, err := io.ReadAll(gr)
if err != nil {
return f, err
}
// Wrap everything in our custom File.
return &File{file: f, content: c}, nil
}
type File struct {
// The underlying file.
file fs.File
// The decrompressed content, needed to return an accurate size.
content []byte
// Offset for calls to Read().
offset int
}
// Stat implements the fs.File interface.
func (f File) Stat() (fs.FileInfo, error) {
stat, err := f.file.Stat()
if err != nil {
return stat, err
}
return FileInfo{stat, int64(len(f.content))}, nil
}
// Read implements the fs.File interface.
func (f *File) Read(buf []byte) (int, error) {
if len(buf) > len(f.content)-f.offset {
buf = buf[0:len(f.content[f.offset:])]
}
n := copy(buf, f.content[f.offset:])
if n == len(f.content)-f.offset {
return n, io.EOF
}
f.offset += n
return n, nil
}
// Close implements the fs.File interface.
func (f File) Close() error {
return f.file.Close()
}
type FileInfo struct {
fi fs.FileInfo
actualSize int64
}
// Name implements the fs.FileInfo interface.
func (fi FileInfo) Name() string {
name := fi.fi.Name()
return name[:len(name)-len(gzipSuffix)]
}
// Size implements the fs.FileInfo interface.
func (fi FileInfo) Size() int64 { return fi.actualSize }
// Mode implements the fs.FileInfo interface.
func (fi FileInfo) Mode() fs.FileMode { return fi.fi.Mode() }
// ModTime implements the fs.FileInfo interface.
func (fi FileInfo) ModTime() time.Time { return fi.fi.ModTime() }
// IsDir implements the fs.FileInfo interface.
func (fi FileInfo) IsDir() bool { return fi.fi.IsDir() }
// Sys implements the fs.FileInfo interface.
func (fi FileInfo) Sys() interface{} { return nil }
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