httpfile - file.go

  // Package httpfile provides an easy way to create HTTP handlers that respond with static data, possibly gzip compressed if requested by the client.
  package httpfile // import "vimagination.zapto.org/httpfile"
  
  import (
  	"bytes"
  	"compress/gzip"
  	"io"
  	"io/fs"
  	"net/http"
  	"sync"
  	"time"
  
  	"vimagination.zapto.org/httpencoding"
  )
  
  var empty = [20]byte{0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x03, 0x03}
  
  // Type file represents an http.Handler upon which you can set static data.
  type File struct {
  	name string
  
  	mu               sync.RWMutex
  	modtime          time.Time
  	data, compressed []byte
  }
  
  // New creates a new File with the given name, which is used to apply
  // Content-Type headers.
  func New(name string) *File {
  	return &File{name: name, modtime: time.Now(), compressed: empty[:]}
  }
  
  // NewWithData create a new File with the given name, and sets the initial
  // uncompressed data to that provided.
  func NewWithData(name string, data []byte) *File {
  	var buf bytes.Buffer
  
  	f := New(name)
  	f.data = data
  	g := gzip.NewWriter(&buf)
  
  	g.Write(data)
  	g.Close()
  
  	f.compressed = buf.Bytes()
  
  	return f
  }
  
  var isGzip = httpencoding.HandlerFunc(func(enc httpencoding.Encoding) bool { return enc == "gzip" })
  
  // ServeHTTP implements the http.Handler interface.
  func (f *File) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  	var buf bytes.Reader
  
  	wantsGzip := httpencoding.HandleEncoding(r, isGzip)
  
  	f.mu.RLock()
  
  	modtime := f.modtime
  
  	if wantsGzip {
  		buf.Reset(f.compressed)
  		w.Header().Add("Content-Encoding", "gzip")
  	} else {
  		buf.Reset(f.data)
  	}
  
  	f.mu.RUnlock()
  
  	http.ServeContent(w, r, f.name, modtime, &buf)
  }
  
  // ReadFrom reads all of the data from io.Reader and applies it to the file,
  // overwriting any existing data and setting the modtime to Now.
  func (f *File) ReadFrom(r io.Reader) (int64, error) {
  	file := f.Create()
  	defer file.Close()
  
  	return io.Copy(file, r)
  }
  
  // WriteTo writes the uncompressed data to the given writer.
  func (f *File) WriteTo(w io.Writer) (int64, error) {
  	f.mu.RLock()
  	data := f.data
  	f.mu.RUnlock()
  
  	n, err := w.Write(data)
  
  	return int64(n), err
  }
  
  // Chtime sets the modtime to the given time.
  func (f *File) Chtime(t time.Time) {
  	f.mu.Lock()
  	f.modtime = t
  	f.mu.Unlock()
  }
  
  // Name returns the name given during File creation.
  func (f *File) Name() string {
  	return f.name
  }
  
  // A Writer is bound to the File is was created from, buffering data that is
  // written to it.Writer. Upon Closing, that data will be compressed and both
  // the uncompressed and compressed data will be replaced on the File.
  type Writer struct {
  	file *File
  	data []byte
  }
  
  // Create opens a Writer that can be used to write the data for the File. Close
  // must be called on the resulting Writer for the data to be accepted.
  func (f *File) Create() *Writer {
  	return &Writer{
  		file: f,
  	}
  }
  
  // Write is an implementation of the io.Writer interface.
  func (f *Writer) Write(p []byte) (int, error) {
  	if f.file == nil {
  		return 0, fs.ErrClosed
  	}
  
  	f.data = append(f.data, p...)
  
  	return len(p), nil
  }
  
  // WriteString is an implementation of the io.StringWriter interface.
  func (f *Writer) WriteString(str string) (int, error) {
  	if f.file == nil {
  		return 0, fs.ErrClosed
  	}
  
  	f.data = append(f.data, str...)
  
  	return len(str), nil
  }
  
  // Close is an implementation of the io.Close interface.
  //
  // This method must be called for the written data to be accepted on the File.
  func (f *Writer) Close() error {
  	if f.file == nil {
  		return fs.ErrClosed
  	}
  
  	var compressed bytes.Buffer
  
  	g := gzip.NewWriter(&compressed)
  
  	g.Write(f.data)
  	g.Close()
  
  	f.file.mu.Lock()
  
  	f.file.data = f.data
  	f.file.compressed = compressed.Bytes()
  	f.file.modtime = time.Now()
  
  	f.file.mu.Unlock()
  
  	*f = Writer{}
  
  	return nil
  }