Moving away from goamz to use minio-go instead. (#4193)

minio-go does fully managed way of handling S3 API requests

  - Automatic bucket location management across all s3 regions.
  - Transparently upload large files in multipart if file 64MB
    or larger.
  - Right GetObject() API provides compatibility with
    io.ReadWriteSeeker interface.
  - Various other APIs including bulk deletes, server side object
    copy, bucket policies and bucket notifications.

Fixes #4182

vendor/github.com/minio/minio-go/api-stat.go

@@ -0,0 +1,120 @@
+/*
+ * Minio Go Library for Amazon S3 Compatible Cloud Storage (C) 2015, 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package minio
+
+import (
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// BucketExists verify if bucket exists and you have permission to access it.
+func (c Client) BucketExists(bucketName string) (bool, error) {
+	// Input validation.
+	if err := isValidBucketName(bucketName); err != nil {
+		return false, err
+	}
+
+	// Execute HEAD on bucketName.
+	resp, err := c.executeMethod("HEAD", requestMetadata{
+		bucketName: bucketName,
+	})
+	defer closeResponse(resp)
+	if err != nil {
+		if ToErrorResponse(err).Code == "NoSuchBucket" {
+			return false, nil
+		}
+		return false, err
+	}
+	if resp != nil {
+		if resp.StatusCode != http.StatusOK {
+			return false, httpRespToErrorResponse(resp, bucketName, "")
+		}
+	}
+	return true, nil
+}
+
+// StatObject verifies if object exists and you have permission to access.
+func (c Client) StatObject(bucketName, objectName string) (ObjectInfo, error) {
+	// Input validation.
+	if err := isValidBucketName(bucketName); err != nil {
+		return ObjectInfo{}, err
+	}
+	if err := isValidObjectName(objectName); err != nil {
+		return ObjectInfo{}, err
+	}
+
+	// Execute HEAD on objectName.
+	resp, err := c.executeMethod("HEAD", requestMetadata{
+		bucketName: bucketName,
+		objectName: objectName,
+	})
+	defer closeResponse(resp)
+	if err != nil {
+		return ObjectInfo{}, err
+	}
+	if resp != nil {
+		if resp.StatusCode != http.StatusOK {
+			return ObjectInfo{}, httpRespToErrorResponse(resp, bucketName, objectName)
+		}
+	}
+
+	// Trim off the odd double quotes from ETag in the beginning and end.
+	md5sum := strings.TrimPrefix(resp.Header.Get("ETag"), "\"")
+	md5sum = strings.TrimSuffix(md5sum, "\"")
+
+	// Parse content length.
+	size, err := strconv.ParseInt(resp.Header.Get("Content-Length"), 10, 64)
+	if err != nil {
+		return ObjectInfo{}, ErrorResponse{
+			Code:       "InternalError",
+			Message:    "Content-Length is invalid. " + reportIssue,
+			BucketName: bucketName,
+			Key:        objectName,
+			RequestID:  resp.Header.Get("x-amz-request-id"),
+			HostID:     resp.Header.Get("x-amz-id-2"),
+			Region:     resp.Header.Get("x-amz-bucket-region"),
+		}
+	}
+	// Parse Last-Modified has http time format.
+	date, err := time.Parse(http.TimeFormat, resp.Header.Get("Last-Modified"))
+	if err != nil {
+		return ObjectInfo{}, ErrorResponse{
+			Code:       "InternalError",
+			Message:    "Last-Modified time format is invalid. " + reportIssue,
+			BucketName: bucketName,
+			Key:        objectName,
+			RequestID:  resp.Header.Get("x-amz-request-id"),
+			HostID:     resp.Header.Get("x-amz-id-2"),
+			Region:     resp.Header.Get("x-amz-bucket-region"),
+		}
+	}
+	// Fetch content type if any present.
+	contentType := strings.TrimSpace(resp.Header.Get("Content-Type"))
+	if contentType == "" {
+		contentType = "application/octet-stream"
+	}
+	// Save object metadata info.
+	var objectStat ObjectInfo
+	objectStat.ETag = md5sum
+	objectStat.Key = objectName
+	objectStat.Size = size
+	objectStat.LastModified = date
+	objectStat.ContentType = contentType
+	return objectStat, nil
+}