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api-get-object.go
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api-get-object.go
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/*
* 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 (
"errors"
"fmt"
"io"
"net/http"
"strings"
"sync"
"time"
"github.com/minio/minio-go/pkg/encrypt"
)
// GetEncryptedObject deciphers and streams data stored in the server after applying a specifed encryption materiels
func (c Client) GetEncryptedObject(bucketName, objectName string, encryptMaterials encrypt.Materials) (io.Reader, error) {
if encryptMaterials == nil {
return nil, ErrInvalidArgument("Unable to recognize empty encryption properties")
}
// Fetch encrypted object
encReader, err := c.GetObject(bucketName, objectName)
if err != nil {
return nil, err
}
// Stat object to get its encryption metadata
st, err := encReader.Stat()
if err != nil {
return nil, err
}
// Setup object for decrytion, object is transparently
// decrypted as the consumer starts reading.
encryptMaterials.SetupDecryptMode(encReader, st.Metadata.Get(amzHeaderIV), st.Metadata.Get(amzHeaderKey))
// Success.
return encryptMaterials, nil
}
// GetObject - returns an seekable, readable object.
func (c Client) GetObject(bucketName, objectName string) (*Object, error) {
// Input validation.
if err := isValidBucketName(bucketName); err != nil {
return nil, err
}
if err := isValidObjectName(objectName); err != nil {
return nil, err
}
var httpReader io.ReadCloser
var objectInfo ObjectInfo
var err error
// Create request channel.
reqCh := make(chan getRequest)
// Create response channel.
resCh := make(chan getResponse)
// Create done channel.
doneCh := make(chan struct{})
// This routine feeds partial object data as and when the caller reads.
go func() {
defer close(reqCh)
defer close(resCh)
// Loop through the incoming control messages and read data.
for {
select {
// When the done channel is closed exit our routine.
case <-doneCh:
// Close the http response body before returning.
// This ends the connection with the server.
if httpReader != nil {
httpReader.Close()
}
return
// Gather incoming request.
case req := <-reqCh:
// If this is the first request we may not need to do a getObject request yet.
if req.isFirstReq {
// First request is a Read/ReadAt.
if req.isReadOp {
// Differentiate between wanting the whole object and just a range.
if req.isReadAt {
// If this is a ReadAt request only get the specified range.
// Range is set with respect to the offset and length of the buffer requested.
// Do not set objectInfo from the first readAt request because it will not get
// the whole object.
httpReader, _, err = c.getObject(bucketName, objectName, req.Offset, int64(len(req.Buffer)))
} else {
// First request is a Read request.
httpReader, objectInfo, err = c.getObject(bucketName, objectName, req.Offset, 0)
}
if err != nil {
resCh <- getResponse{
Error: err,
}
return
}
// Read at least firstReq.Buffer bytes, if not we have
// reached our EOF.
size, err := io.ReadFull(httpReader, req.Buffer)
if err == io.ErrUnexpectedEOF {
// If an EOF happens after reading some but not
// all the bytes ReadFull returns ErrUnexpectedEOF
err = io.EOF
}
// Send back the first response.
resCh <- getResponse{
objectInfo: objectInfo,
Size: int(size),
Error: err,
didRead: true,
}
} else {
// First request is a Stat or Seek call.
// Only need to run a StatObject until an actual Read or ReadAt request comes through.
objectInfo, err = c.StatObject(bucketName, objectName)
if err != nil {
resCh <- getResponse{
Error: err,
}
// Exit the go-routine.
return
}
// Send back the first response.
resCh <- getResponse{
objectInfo: objectInfo,
}
}
} else if req.settingObjectInfo { // Request is just to get objectInfo.
objectInfo, err := c.StatObject(bucketName, objectName)
if err != nil {
resCh <- getResponse{
Error: err,
}
// Exit the goroutine.
return
}
// Send back the objectInfo.
resCh <- getResponse{
objectInfo: objectInfo,
}
} else {
// Offset changes fetch the new object at an Offset.
// Because the httpReader may not be set by the first
// request if it was a stat or seek it must be checked
// if the object has been read or not to only initialize
// new ones when they haven't been already.
// All readAt requests are new requests.
if req.DidOffsetChange || !req.beenRead {
if httpReader != nil {
// Close previously opened http reader.
httpReader.Close()
}
// If this request is a readAt only get the specified range.
if req.isReadAt {
// Range is set with respect to the offset and length of the buffer requested.
httpReader, _, err = c.getObject(bucketName, objectName, req.Offset, int64(len(req.Buffer)))
} else {
httpReader, objectInfo, err = c.getObject(bucketName, objectName, req.Offset, 0)
}
if err != nil {
resCh <- getResponse{
Error: err,
}
return
}
}
// Read at least req.Buffer bytes, if not we have
// reached our EOF.
size, err := io.ReadFull(httpReader, req.Buffer)
if err == io.ErrUnexpectedEOF {
// If an EOF happens after reading some but not
// all the bytes ReadFull returns ErrUnexpectedEOF
err = io.EOF
}
// Reply back how much was read.
resCh <- getResponse{
Size: int(size),
Error: err,
didRead: true,
objectInfo: objectInfo,
}
}
}
}
}()
// Create a newObject through the information sent back by reqCh.
return newObject(reqCh, resCh, doneCh), nil
}
// get request message container to communicate with internal
// go-routine.
type getRequest struct {
Buffer []byte
Offset int64 // readAt offset.
DidOffsetChange bool // Tracks the offset changes for Seek requests.
beenRead bool // Determines if this is the first time an object is being read.
isReadAt bool // Determines if this request is a request to a specific range
isReadOp bool // Determines if this request is a Read or Read/At request.
isFirstReq bool // Determines if this request is the first time an object is being accessed.
settingObjectInfo bool // Determines if this request is to set the objectInfo of an object.
}
// get response message container to reply back for the request.
type getResponse struct {
Size int
Error error
didRead bool // Lets subsequent calls know whether or not httpReader has been initiated.
objectInfo ObjectInfo // Used for the first request.
}
// Object represents an open object. It implements Read, ReadAt,
// Seeker, Close for a HTTP stream.
type Object struct {
// Mutex.
mutex *sync.Mutex
// User allocated and defined.
reqCh chan<- getRequest
resCh <-chan getResponse
doneCh chan<- struct{}
currOffset int64
objectInfo ObjectInfo
// Ask lower level to initiate data fetching based on currOffset
seekData bool
// Keeps track of closed call.
isClosed bool
// Keeps track of if this is the first call.
isStarted bool
// Previous error saved for future calls.
prevErr error
// Keeps track of if this object has been read yet.
beenRead bool
// Keeps track of if objectInfo has been set yet.
objectInfoSet bool
}
// doGetRequest - sends and blocks on the firstReqCh and reqCh of an object.
// Returns back the size of the buffer read, if anything was read, as well
// as any error encountered. For all first requests sent on the object
// it is also responsible for sending back the objectInfo.
func (o *Object) doGetRequest(request getRequest) (getResponse, error) {
o.reqCh <- request
response := <-o.resCh
// This was the first request.
if !o.isStarted {
// The object has been operated on.
o.isStarted = true
}
// Set the objectInfo if the request was not readAt
// and it hasn't been set before.
if !o.objectInfoSet && !request.isReadAt {
o.objectInfo = response.objectInfo
o.objectInfoSet = true
}
// Set beenRead only if it has not been set before.
if !o.beenRead {
o.beenRead = response.didRead
}
// Return any error to the top level.
if response.Error != nil {
return response, response.Error
}
// Data are ready on the wire, no need to reinitiate connection in lower level
o.seekData = false
return response, nil
}
// setOffset - handles the setting of offsets for
// Read/ReadAt/Seek requests.
func (o *Object) setOffset(bytesRead int64) error {
// Update the currentOffset.
o.currOffset += bytesRead
if o.currOffset >= o.objectInfo.Size {
return io.EOF
}
return nil
}
// Read reads up to len(b) bytes into b. It returns the number of
// bytes read (0 <= n <= len(p)) and any error encountered. Returns
// io.EOF upon end of file.
func (o *Object) Read(b []byte) (n int, err error) {
if o == nil {
return 0, ErrInvalidArgument("Object is nil")
}
// Locking.
o.mutex.Lock()
defer o.mutex.Unlock()
// prevErr is previous error saved from previous operation.
if o.prevErr != nil || o.isClosed {
return 0, o.prevErr
}
// Create a new request.
readReq := getRequest{
isReadOp: true,
beenRead: o.beenRead,
Buffer: b,
}
// Alert that this is the first request.
if !o.isStarted {
readReq.isFirstReq = true
}
// Ask to establish a new data fetch routine based on seekData flag
readReq.DidOffsetChange = o.seekData
readReq.Offset = o.currOffset
// Send and receive from the first request.
response, err := o.doGetRequest(readReq)
if err != nil && err != io.EOF {
// Save the error for future calls.
o.prevErr = err
return response.Size, err
}
// Bytes read.
bytesRead := int64(response.Size)
// Set the new offset.
oerr := o.setOffset(bytesRead)
if oerr != nil {
// Save the error for future calls.
o.prevErr = oerr
return response.Size, oerr
}
// Return the response.
return response.Size, err
}
// Stat returns the ObjectInfo structure describing Object.
func (o *Object) Stat() (ObjectInfo, error) {
if o == nil {
return ObjectInfo{}, ErrInvalidArgument("Object is nil")
}
// Locking.
o.mutex.Lock()
defer o.mutex.Unlock()
if o.prevErr != nil && o.prevErr != io.EOF || o.isClosed {
return ObjectInfo{}, o.prevErr
}
// This is the first request.
if !o.isStarted || !o.objectInfoSet {
statReq := getRequest{
isFirstReq: !o.isStarted,
settingObjectInfo: !o.objectInfoSet,
}
// Send the request and get the response.
_, err := o.doGetRequest(statReq)
if err != nil {
o.prevErr = err
return ObjectInfo{}, err
}
}
return o.objectInfo, nil
}
// ReadAt reads len(b) bytes from the File starting at byte offset
// off. It returns the number of bytes read and the error, if any.
// ReadAt always returns a non-nil error when n < len(b). At end of
// file, that error is io.EOF.
func (o *Object) ReadAt(b []byte, offset int64) (n int, err error) {
if o == nil {
return 0, ErrInvalidArgument("Object is nil")
}
// Locking.
o.mutex.Lock()
defer o.mutex.Unlock()
// prevErr is error which was saved in previous operation.
if o.prevErr != nil || o.isClosed {
return 0, o.prevErr
}
// Can only compare offsets to size when size has been set.
if o.objectInfoSet {
// If offset is negative than we return io.EOF.
// If offset is greater than or equal to object size we return io.EOF.
if offset >= o.objectInfo.Size || offset < 0 {
return 0, io.EOF
}
}
// Create the new readAt request.
readAtReq := getRequest{
isReadOp: true,
isReadAt: true,
DidOffsetChange: true, // Offset always changes.
beenRead: o.beenRead, // Set if this is the first request to try and read.
Offset: offset, // Set the offset.
Buffer: b,
}
// Alert that this is the first request.
if !o.isStarted {
readAtReq.isFirstReq = true
}
// Send and receive from the first request.
response, err := o.doGetRequest(readAtReq)
if err != nil && err != io.EOF {
// Save the error.
o.prevErr = err
return response.Size, err
}
// Bytes read.
bytesRead := int64(response.Size)
// There is no valid objectInfo yet
// to compare against for EOF.
if !o.objectInfoSet {
// Update the currentOffset.
o.currOffset += bytesRead
} else {
// If this was not the first request update
// the offsets and compare against objectInfo
// for EOF.
oerr := o.setOffset(bytesRead)
if oerr != nil {
o.prevErr = oerr
return response.Size, oerr
}
}
return response.Size, err
}
// Seek sets the offset for the next Read or Write to offset,
// interpreted according to whence: 0 means relative to the
// origin of the file, 1 means relative to the current offset,
// and 2 means relative to the end.
// Seek returns the new offset and an error, if any.
//
// Seeking to a negative offset is an error. Seeking to any positive
// offset is legal, subsequent io operations succeed until the
// underlying object is not closed.
func (o *Object) Seek(offset int64, whence int) (n int64, err error) {
if o == nil {
return 0, ErrInvalidArgument("Object is nil")
}
// Locking.
o.mutex.Lock()
defer o.mutex.Unlock()
if o.prevErr != nil {
// At EOF seeking is legal allow only io.EOF, for any other errors we return.
if o.prevErr != io.EOF {
return 0, o.prevErr
}
}
// Negative offset is valid for whence of '2'.
if offset < 0 && whence != 2 {
return 0, ErrInvalidArgument(fmt.Sprintf("Negative position not allowed for %d.", whence))
}
// This is the first request. So before anything else
// get the ObjectInfo.
if !o.isStarted || !o.objectInfoSet {
// Create the new Seek request.
seekReq := getRequest{
isReadOp: false,
Offset: offset,
isFirstReq: true,
}
// Send and receive from the seek request.
_, err := o.doGetRequest(seekReq)
if err != nil {
// Save the error.
o.prevErr = err
return 0, err
}
}
// Switch through whence.
switch whence {
default:
return 0, ErrInvalidArgument(fmt.Sprintf("Invalid whence %d", whence))
case 0:
if offset > o.objectInfo.Size {
return 0, io.EOF
}
o.currOffset = offset
case 1:
if o.currOffset+offset > o.objectInfo.Size {
return 0, io.EOF
}
o.currOffset += offset
case 2:
// Seeking to positive offset is valid for whence '2', but
// since we are backing a Reader we have reached 'EOF' if
// offset is positive.
if offset > 0 {
return 0, io.EOF
}
// Seeking to negative position not allowed for whence.
if o.objectInfo.Size+offset < 0 {
return 0, ErrInvalidArgument(fmt.Sprintf("Seeking at negative offset not allowed for %d", whence))
}
o.currOffset = o.objectInfo.Size + offset
}
// Reset the saved error since we successfully seeked, let the Read
// and ReadAt decide.
if o.prevErr == io.EOF {
o.prevErr = nil
}
// Ask lower level to fetch again from source
o.seekData = true
// Return the effective offset.
return o.currOffset, nil
}
// Close - The behavior of Close after the first call returns error
// for subsequent Close() calls.
func (o *Object) Close() (err error) {
if o == nil {
return ErrInvalidArgument("Object is nil")
}
// Locking.
o.mutex.Lock()
defer o.mutex.Unlock()
// if already closed return an error.
if o.isClosed {
return o.prevErr
}
// Close successfully.
close(o.doneCh)
// Save for future operations.
errMsg := "Object is already closed. Bad file descriptor."
o.prevErr = errors.New(errMsg)
// Save here that we closed done channel successfully.
o.isClosed = true
return nil
}
// newObject instantiates a new *minio.Object*
// ObjectInfo will be set by setObjectInfo
func newObject(reqCh chan<- getRequest, resCh <-chan getResponse, doneCh chan<- struct{}) *Object {
return &Object{
mutex: &sync.Mutex{},
reqCh: reqCh,
resCh: resCh,
doneCh: doneCh,
}
}
// getObject - retrieve object from Object Storage.
//
// Additionally this function also takes range arguments to download the specified
// range bytes of an object. Setting offset and length = 0 will download the full object.
//
// For more information about the HTTP Range header.
// go to http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35.
func (c Client) getObject(bucketName, objectName string, offset, length int64) (io.ReadCloser, ObjectInfo, error) {
// Validate input arguments.
if err := isValidBucketName(bucketName); err != nil {
return nil, ObjectInfo{}, err
}
if err := isValidObjectName(objectName); err != nil {
return nil, ObjectInfo{}, err
}
customHeader := make(http.Header)
// Set ranges if length and offset are valid.
// See https://tools.ietf.org/html/rfc7233#section-3.1 for reference.
if length > 0 && offset >= 0 {
customHeader.Set("Range", fmt.Sprintf("bytes=%d-%d", offset, offset+length-1))
} else if offset > 0 && length == 0 {
customHeader.Set("Range", fmt.Sprintf("bytes=%d-", offset))
} else if length < 0 && offset == 0 {
customHeader.Set("Range", fmt.Sprintf("bytes=%d", length))
}
// Execute GET on objectName.
resp, err := c.executeMethod("GET", requestMetadata{
bucketName: bucketName,
objectName: objectName,
customHeader: customHeader,
})
if err != nil {
return nil, ObjectInfo{}, err
}
if resp != nil {
if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
return nil, 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 the date.
date, err := time.Parse(http.TimeFormat, resp.Header.Get("Last-Modified"))
if err != nil {
msg := "Last-Modified time format not recognized. " + reportIssue
return nil, ObjectInfo{}, ErrorResponse{
Code: "InternalError",
Message: msg,
RequestID: resp.Header.Get("x-amz-request-id"),
HostID: resp.Header.Get("x-amz-id-2"),
Region: resp.Header.Get("x-amz-bucket-region"),
}
}
// Get content-type.
contentType := strings.TrimSpace(resp.Header.Get("Content-Type"))
if contentType == "" {
contentType = "application/octet-stream"
}
var objectStat ObjectInfo
objectStat.ETag = md5sum
objectStat.Key = objectName
objectStat.Size = resp.ContentLength
objectStat.LastModified = date
objectStat.ContentType = contentType
// do not close body here, caller will close
return resp.Body, objectStat, nil
}