rewrite

README.md

@@ -1,2 +1,29 @@
 # persist
 Persist loads and saves Go objects to files
+
+## Usage
+
+First get it:
+
+```
+go get github.com/matryer/persist
+```
+
+Then save objects like this:
+
+```
+var conf Config
+if err := persist.Save("./project.conf", &conf); err != nil {
+	log.Fatalln("failed to save config:", err)
+}
+```
+
+And load them like this:
+
+
+```
+var conf Config
+if err := persist.Load("./project.conf", &conf); err != nil {
+	log.Fatalln("failed to load config:", err)
+}
+```

doc.go

@@ -0,0 +1,2 @@
+// Package persist loads and saves Go objects to files.
+package persist

persist.go

@@ -0,0 +1,60 @@
+package persist
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"os"
+	"sync"
+)
+
+var lock sync.Mutex
+
+// Marshal is a function that marshals the object into an
+// io.Reader.
+// By default, it uses the JSON marshaller.
+var Marshal = func(v interface{}) (io.Reader, error) {
+	b, err := json.MarshalIndent(v, "", "\t")
+	if err != nil {
+		return nil, err
+	}
+	return bytes.NewReader(b), nil
+}
+
+// Unmarshal is a function that unmarshals the data from the
+// reader into the specified value.
+// By default, it uses the JSON unmarshaller.
+var Unmarshal = func(r io.Reader, v interface{}) error {
+	return json.NewDecoder(r).Decode(v)
+}
+
+// Save saves a representation of v to the file at path.
+func Save(path string, v interface{}) error {
+	lock.Lock()
+	defer lock.Unlock()
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	r, err := Marshal(v)
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(f, r)
+	return err
+}
+
+// Load loads the file at path into v.
+// Use os.IsNotExist() to see if the returned error is due
+// to the file being missing.
+func Load(path string, v interface{}) error {
+	lock.Lock()
+	defer lock.Unlock()
+	f, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return Unmarshal(f, v)
+}

persist_test.go

@@ -0,0 +1,50 @@
+package persist_test
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"github.com/cheekybits/is"
+	"github.com/matryer/persist"
+)
+
+type obj struct {
+	Name   string
+	Number int
+	When   time.Time
+}
+
+func TestNoFile(t *testing.T) {
+	is := is.New(t)
+
+	var v interface{}
+	err := persist.Load("no-such-file.conf", &v)
+	is.Equal(true, os.IsNotExist(err))
+
+}
+
+func TestPersist(t *testing.T) {
+	is := is.New(t)
+	defer os.Remove("./file.tmp")
+
+	o := &obj{
+		Name:   "Mat",
+		Number: 47,
+		When:   time.Now(),
+	}
+
+	// save it
+	err := persist.Save("./file.tmp", o)
+	is.NoErr(err)
+
+	// load it
+	var o2 obj
+	err = persist.Load("./file.tmp", &o2)
+	is.NoErr(err)
+
+	is.Equal(o.Name, o2.Name)
+	is.Equal(o.Number, o2.Number)
+	is.Equal(o.When, o2.When)
+
+}