Add write example (#22)

* Add write example

* Add format in make build

Makefile

@@ -19,7 +19,7 @@ format:
 vet:
 	go vet ./...
 
-build: tidy check
+build: tidy format check
 	go build ./...
 
 test:

README.md

@@ -12,6 +12,9 @@
 - [Read a range of a file](read.go)
 - [Read a file with callback](read.go)
 - [Read a file using signed URL](read.go)
+- [Write a file](write.go)
+- [Write a file with callback](write.go)
+- [Write a file using signed URL](write.go)
 - [Append to a new file](append.go)
 - [Append to an existing file](append.go)
 - [Multipart upload](multipart.go)

multipart.go

@@ -179,4 +179,4 @@ func CancelMultipart(store types.Storager, path string) {
 	}
 
 	log.Printf("cancel multipart: %v", path)
-}
+}

read.go

@@ -82,15 +82,14 @@ func ReadWithSignedURL(store types.Storager, path string, expire time.Duration)
 	}
 
 	// QuerySignHTTPRead needs at least two arguments.
-	//
 	// `path` is the path of object.
 	// `expire` provides the time period, with type time.Duration, for which the generated req.URL is valid.
 	//
 	// QuerySignHTTPRead will return two values.
 	// `req` is the generated `*http.Request`, `req.URL` specifies the URL to access with signature in the query string. And `req.Header` specifies the HTTP headers included in the signature.
 	// `err` is the error during this operation.
 	req, err := signer.QuerySignHTTPRead(path, expire)
-	if err !=nil {
+	if err != nil {
 		log.Fatalf("read %v: %v", path, err)
 	}
 

write.go

@@ -0,0 +1,95 @@
+package example
+
+import (
+	"io"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"net/http"
+	"time"
+
+	"github.com/beyondstorage/go-storage/v4/pairs"
+	"github.com/beyondstorage/go-storage/v4/pkg/randbytes"
+	"github.com/beyondstorage/go-storage/v4/types"
+)
+
+func WriteData(store types.Storager, path string) {
+	// content to write
+	size := rand.Int63n(4 * 1024 * 1024)
+	r := io.LimitReader(randbytes.NewRand(), size)
+
+	// Write needs at least three arguments.
+	// `path` is the path of object.
+	// `r` is io.Reader instance for reading the data for uploading.
+	// `size` is the length, in bytes, of the data for uploading.
+	//
+	// Write will return two values.
+	// `n` is the size of write operation.
+	// `err` is the error during this operation.
+	n, err := store.Write(path, r, size)
+	if err != nil {
+		log.Fatalf("write %v: %v", path, err)
+	}
+
+	log.Printf("write size: %d", n)
+}
+
+func WriteWithCallback(store types.Storager, path string) {
+	// content to write
+	size := rand.Int63n(4 * 1024 * 1024)
+	r := io.LimitReader(randbytes.NewRand(), size)
+
+	cur := int64(0)
+	fn := func(bs []byte) {
+		cur += int64(len(bs))
+		log.Printf("write %d bytes already", cur)
+	}
+
+	// If IoCallback is specified, the storage will call it in every I/O operation.
+	// User could use this feature to implement progress bar.
+	n, err := store.Write(path, r, size, pairs.WithIoCallback(fn))
+	if err != nil {
+		log.Fatalf("write %v: %v", path, err)
+	}
+
+	log.Printf("write size: %d", n)
+}
+
+func WriteWithSignedURL(store types.Storager, path string, expire time.Duration) {
+	signer, ok := store.(types.StorageHTTPSigner)
+	if !ok {
+		log.Fatalf("StorageHTTPSigner unimplemented")
+	}
+
+	size := rand.Int63n(4 * 1024 * 1024)
+	r := io.LimitReader(randbytes.NewRand(), size)
+
+	// QuerySignHTTPWrite needs at least three arguments.
+	// `path` is the path of object.
+	// `size` is the length, in bytes, of the data for uploading.
+	// `expire` provides the time period, with type time.Duration, for which the generated req.URL is valid.
+	//
+	// QuerySignHTTPWrite will return two values.
+	//
+	// `req` is the generated `*http.Request`:
+	// `req.URL` specifies the URL to access with signature in the query string.
+	// `req.Header` specifies the HTTP headers included in the signature.
+	// `req.ContentLength` records the length of the associated content, the value equals to `size`.
+	//
+	// `err` is the error during this operation.
+	req, err := signer.QuerySignHTTPWrite(path, size, expire)
+	if err != nil {
+		log.Fatalf("write %v: %v", path, err)
+	}
+
+	// Set request body.
+	req.Body = ioutil.NopCloser(r)
+
+	client := http.Client{}
+	_, err = client.Do(req)
+	if err != nil {
+		log.Fatalf("send HTTP request for writing %v: %v", path, err)
+	}
+
+	log.Printf("write size: %d", size)
+}