echo/context_fs.go

package echo

import (
	"errors"
	"io"
	"io/fs"
	"net/http"
	"path/filepath"
)

func (c *context) File(file string) error {
	return fsFile(c, file, c.echo.Filesystem)
}

// FileFS serves file from given file system.
//
// When dealing with `embed.FS` use `fs := echo.MustSubFS(fs, "rootDirectory") to create sub fs which uses necessary
// prefix for directory path. This is necessary as `//go:embed assets/images` embeds files with paths
// including `assets/images` as their prefix.
func (c *context) FileFS(file string, filesystem fs.FS) error {
	return fsFile(c, file, filesystem)
}

func fsFile(c Context, file string, filesystem fs.FS) error {
	f, err := filesystem.Open(file)
	if err != nil {
		return ErrNotFound
	}
	defer f.Close()

	fi, _ := f.Stat()
	if fi.IsDir() {
		file = filepath.ToSlash(filepath.Join(file, indexPage)) // ToSlash is necessary for Windows. fs.Open and os.Open are different in that aspect.
		f, err = filesystem.Open(file)
		if err != nil {
			return ErrNotFound
		}
		defer f.Close()
		if fi, err = f.Stat(); err != nil {
			return err
		}
	}
	ff, ok := f.(io.ReadSeeker)
	if !ok {
		return errors.New("file does not implement io.ReadSeeker")
	}
	http.ServeContent(c.Response(), c.Request(), fi.Name(), fi.ModTime(), ff)
	return nil
}