Merge pull request #13 from terrastruct/tmpfs

tmpfs: Add

Author: nhooyr

README.md

@@ -27,6 +27,9 @@ own repo from this collection we will. Feel free to open an issue to request.
 - [./xexec](#xexec)
 - [./xhttp](#xhttp)
 - [./xmain](#xmain)
+- [./tmpfs](#tmpfs)
+
+
 
 godoc is the canonical reference but we've provided this index as the godoc UI is frankly
 garbage after the move to pkg.go.dev. It's nowhere near as clear and responsive as the old
@@ -115,3 +118,7 @@ xhttp provides HTTP helpers.
 ### [./xmain](./xmain)
 
 xmain implements helpers for building CLI tools.
+
+### [./tmpfs](./tmpfs)
+
+Package tmpfs takes in an memory description of a filesystem and writes it to a temp directory so that it may be used as an io/fs.FS.

ci

@@ -0,0 +1,49 @@
+// Package tmpfs takes in an memory description of a filesystem
+// and writes it to a temp directory so that it may be used as an io/fs.FS.
+package tmpfs
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+)
+
+type FS struct {
+	dir string
+	fs.FS
+}
+
+func Make(m map[string]string) (*FS, error) {
+	tempDir, err := os.MkdirTemp("", "tmpfs-*")
+	if err != nil {
+		return nil, fmt.Errorf("failed to create root tmpfs dir: %w", err)
+	}
+	for p, s := range m {
+		p = path.Join(tempDir, p)
+		err = os.MkdirAll(path.Dir(p), 0755)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create tmpfs dir %q: %w", path.Dir(p), err)
+		}
+		err = os.WriteFile(p, []byte(s), 0644)
+		if err != nil {
+			return nil, fmt.Errorf("failed to write tmpfs file %q: %w", p, err)
+		}
+	}
+	return &FS{
+		dir: tempDir,
+		FS:  os.DirFS(tempDir),
+	}, nil
+}
+
+func (fs *FS) Close() error {
+	err := os.RemoveAll(fs.dir)
+	if errors.Is(err, os.ErrNotExist) {
+		return nil
+	}
+	if err != nil {
+		return fmt.Errorf("failed to close tmpfs.FS: %w", err)
+	}
+	return nil
+}

tmpfs/tmpfs.go

@@ -0,0 +1,38 @@
+package tmpfs_test
+
+import (
+	"io/fs"
+	"testing"
+
+	"oss.terrastruct.com/util-go/assert"
+	"oss.terrastruct.com/util-go/tmpfs"
+)
+
+func TestMemFS(t *testing.T) {
+	t.Parallel()
+
+	m := map[string]string{
+		"index":                       "<Espy_on_crack> I installed 'Linux 6.1', doesn't that make me a unix",
+		"d2/imports":                  "Do your part to help preserve life on Earth -- by trying to preserve your own.",
+		"d2/globs":                    "I'm going to raise an issue and stick it in your ear.",
+		"nested/nested/nested/nested": "Yuppie Wannabes",
+	}
+
+	tmpfs, err := tmpfs.Make(m)
+	assert.Success(t, err)
+	t.Cleanup(func() {
+		err := tmpfs.Close()
+		assert.Success(t, err)
+	})
+
+	for p, s := range m {
+		b, err := fs.ReadFile(tmpfs, p)
+		assert.Success(t, err)
+		assert.Equal(t, s, string(b))
+	}
+
+	_, err = fs.ReadFile(tmpfs, "../escape")
+	assert.ErrorString(t, err, "stat ../escape: invalid argument")
+	_, err = fs.ReadFile(tmpfs, "/root")
+	assert.ErrorString(t, err, "stat /root: invalid argument")
+}