Code cleanup and simplification

- Print in human-readable not amazon format
   - Send stat() before accessing object, error gracefully
   - Move client and bucket API operations to their own files
   - Remove unused functions, constants and variables
   - Rename API operations to sensible names
        * GetBucket --> ListObjects
        * Buckets --> ListBuckets

pkg/s3/object.go

@@ -0,0 +1,141 @@
+package s3
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"time"
+
+	"crypto/md5"
+	"encoding/base64"
+	"io/ioutil"
+	"net/http"
+)
+
+/// Object API operations
+
+// Put - upload new object to bucket
+func (c *Client) Put(bucket, key string, size int64, contents io.Reader) error {
+	req := newReq(c.keyURL(bucket, key))
+	req.Method = "PUT"
+	req.ContentLength = size
+
+	h := md5.New()
+	// Memory where data is present
+	sink := new(bytes.Buffer)
+	mw := io.MultiWriter(h, sink)
+	written, err := io.Copy(mw, contents)
+	if written != size {
+		return fmt.Errorf("Data read mismatch")
+	}
+	if err != nil {
+		return err
+	}
+	req.Body = ioutil.NopCloser(sink)
+	b64 := base64.StdEncoding.EncodeToString(h.Sum(nil))
+	req.Header.Set("Content-MD5", b64)
+	c.Auth.signRequest(req)
+
+	res, err := c.transport().RoundTrip(req)
+	if res != nil && res.Body != nil {
+		defer res.Body.Close()
+	}
+
+	if err != nil {
+		return err
+	}
+	if res.StatusCode != http.StatusOK {
+		// res.Write(os.Stderr)
+		return fmt.Errorf("Got response code %d from s3", res.StatusCode)
+	}
+	return nil
+}
+
+// Stat - returns 0, "", os.ErrNotExist if not on S3
+func (c *Client) Stat(key, bucket string) (size int64, date time.Time, reterr error) {
+	req := newReq(c.keyURL(bucket, key))
+	req.Method = "HEAD"
+	c.Auth.signRequest(req)
+	res, err := c.transport().RoundTrip(req)
+	if res != nil && res.Body != nil {
+		defer res.Body.Close()
+	}
+	if err != nil {
+		return 0, date, err
+	}
+
+	switch res.StatusCode {
+	case http.StatusNotFound:
+		return 0, date, os.ErrNotExist
+	case http.StatusOK:
+		size, err = strconv.ParseInt(res.Header.Get("Content-Length"), 10, 64)
+		if err != nil {
+			return 0, date, err
+		}
+		if dateStr := res.Header.Get("Last-Modified"); dateStr != "" {
+			// AWS S3 uses RFC1123 standard for Date in HTTP header, unlike XML content
+			date, err := time.Parse(time.RFC1123, dateStr)
+			if err != nil {
+				return 0, date, err
+			}
+			return size, date, nil
+		}
+	default:
+		return 0, date, fmt.Errorf("s3: Unexpected status code %d statting object %v", res.StatusCode, key)
+	}
+	return
+}
+
+// Get - download a requested object from a given bucket
+func (c *Client) Get(bucket, key string) (body io.ReadCloser, size int64, err error) {
+	req := newReq(c.keyURL(bucket, key))
+	c.Auth.signRequest(req)
+	res, err := c.transport().RoundTrip(req)
+	if err != nil {
+		return
+	}
+	switch res.StatusCode {
+	case http.StatusOK:
+		return res.Body, res.ContentLength, nil
+	case http.StatusNotFound:
+		res.Body.Close()
+		return nil, 0, os.ErrNotExist
+	default:
+		res.Body.Close()
+		return nil, 0, fmt.Errorf("Amazon HTTP error on GET: %d", res.StatusCode)
+	}
+}
+
+// GetPartial fetches part of the s3 key object in bucket.
+// If length is negative, the rest of the object is returned.
+// The caller must close rc.
+func (c *Client) GetPartial(bucket, key string, offset, length int64) (rc io.ReadCloser, err error) {
+	if offset < 0 {
+		return nil, fmt.Errorf("invalid negative length")
+	}
+
+	req := newReq(c.keyURL(bucket, key))
+	if length >= 0 {
+		req.Header.Set("Range", fmt.Sprintf("bytes=%d-%d", offset, offset+length-1))
+	} else {
+		req.Header.Set("Range", fmt.Sprintf("bytes=%d-", offset))
+	}
+	c.Auth.signRequest(req)
+
+	res, err := c.transport().RoundTrip(req)
+	if err != nil {
+		return
+	}
+	switch res.StatusCode {
+	case http.StatusOK, http.StatusPartialContent:
+		return res.Body, nil
+	case http.StatusNotFound:
+		res.Body.Close()
+		return nil, os.ErrNotExist
+	default:
+		res.Body.Close()
+		return nil, fmt.Errorf("Amazon HTTP error on GET: %d", res.StatusCode)
+	}
+}