/
file.go
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/
file.go
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package main
import (
"bytes"
"context"
"errors"
"fmt"
"io/fs"
"io/ioutil"
"os"
"github.com/aws/aws-sdk-go-v2/service/s3"
"go.uber.org/atomic"
)
const (
ModeMultipartUpload os.FileMode = fs.ModePerm + 1 // Custom os.FileMode for S3 multipart upload
)
var (
ErrLockNotSupported = errors.New("lock not supported by s3")
ErrTruncateNotSupported = errors.New("truncate not supported by s3")
ErrFileClosed = errors.New("file is closed")
ErrCantWriteToReadOnly = errors.New("can't write to read-only file")
ErrCantReadFromWriteOnly = errors.New("can't read from write-only file")
)
// s3ReadFile implements billy.File for S3, and represents a file opened in read mode.
//
// Upon creation, the file is loaded from S3.
type s3ReadFile struct {
client *s3.Client // s3 skd client
bucket string // S3 bucket name
key string // File object's key in S3
closed bool // Is the file closed?
reader *bytes.Reader // Buffer for file contents
}
// newS3ReadFile creates a new s3ReadFile.
func newS3ReadFile(client *s3.Client, bucket, key string) (*s3ReadFile, error) {
// TODO: Check if the file exists
// ...
// Create the context
ctx := context.TODO() // TODO: How can user-supplied contexts be supported?
// Run the GetObject operation
res, err := client.GetObject(ctx, &s3.GetObjectInput{
Bucket: &bucket,
Key: &key,
})
if err != nil {
return nil, fmt.Errorf("unable to perform GetObject operation: %w", err)
}
// Read the file contents and store in a bytes reader
buf, err := ioutil.ReadAll(res.Body)
if err != nil {
return nil, fmt.Errorf("unable to read file body: %w", err)
}
reader := bytes.NewReader(buf)
// Return the file
return &s3ReadFile{
client: client,
bucket: bucket,
key: key,
reader: reader,
}, nil
}
// Name returns the name of the file as presented to Open.
func (f *s3ReadFile) Name() string {
return f.key
}
// Write implements os.Writer for billy.File
func (f *s3ReadFile) Write(p []byte) (n int, err error) {
return 0, ErrCantWriteToReadOnly
}
// Read implements os.Reader for billy.File
func (f *s3ReadFile) Read(p []byte) (n int, err error) {
return f.reader.Read(p)
}
// ReadAt implements io.ReaderAt for billy.File
func (f *s3ReadFile) ReadAt(p []byte, off int64) (n int, err error) {
return f.reader.ReadAt(p, off)
}
// Seek implements io.Seeker for billy.File
func (f *s3ReadFile) Seek(offset int64, whence int) (int64, error) {
return f.reader.Seek(offset, whence)
}
// Close implements io.Closer for billy.File
func (f *s3ReadFile) Close() error {
// Was the file already closed?
if f.closed {
return ErrFileClosed
}
// Close the underlying file
f.reader = nil
// Mark the file as closed
f.closed = true
return nil
}
// Lock locks the file like e.g. flock. It protects against access from
// other processes.
func (f *s3ReadFile) Lock() error {
return ErrLockNotSupported
}
// Unlock unlocks the file.
func (f *s3ReadFile) Unlock() error {
return ErrLockNotSupported
}
// Truncate the file.
func (f *s3ReadFile) Truncate(size int64) error {
return ErrTruncateNotSupported
}
// s3WriteFile stores a file opened in write mode and implements billy.File
//
// Upon creation, a buffer is created to store the file contents. Upon close,
// the file is uploaded to S3.
type s3WriteFile struct {
client *s3.Client // s3 skd client
bucket string // S3 bucket name
key string // File object's key in S3
closed bool // Is the file closed?
buf *bytes.Buffer // Buffer for storing the file before it's uploaded
}
// newS3WriteFile creates a new s3ReadFile.
func newS3WriteFile(client *s3.Client, bucket, key string) (*s3WriteFile, error) {
// TODO: Validate the key
// ...
return &s3WriteFile{
client: client,
bucket: bucket,
key: key,
buf: bytes.NewBuffer(nil),
}, nil
}
// Name returns the name of the file as presented to Open.
func (f *s3WriteFile) Name() string {
return f.key
}
// Write implements os.Writer for billy.File
func (f *s3WriteFile) Write(p []byte) (n int, err error) {
return 0, nil
}
// Read implements os.Reader for billy.File
func (f *s3WriteFile) Read(p []byte) (n int, err error) {
return 0, ErrCantReadFromWriteOnly
}
// ReadAt implements io.ReaderAt for billy.File
func (f *s3WriteFile) ReadAt(p []byte, off int64) (n int, err error) {
return 0, ErrCantReadFromWriteOnly
}
// Seek implements io.Seeker for billy.File
func (f *s3WriteFile) Seek(offset int64, whence int) (int64, error) {
return 0, errors.New("not implemented")
}
// Close implements io.Closer for billy.File
func (f *s3WriteFile) Close() error {
if f.closed {
return ErrFileClosed
}
// Set to closed
f.closed = true
// Extract the body from the buffer
body := bytes.NewReader(f.buf.Bytes())
// Create the context
ctx := context.TODO() // TODO: How can user-supplied contexts be supported?
// Run the GetObject operation
// TODO: Currently `res` is not used. Should it be?
_, err := f.client.PutObject(ctx, &s3.PutObjectInput{
Bucket: &f.bucket,
Key: &f.key,
Body: body,
})
if err != nil {
return fmt.Errorf("unable to perform GetObject operation: %w", err)
}
return nil
}
// Lock locks the file like e.g. flock. It protects against access from
// other processes.
func (f *s3WriteFile) Lock() error {
return ErrLockNotSupported
}
// Unlock unlocks the file.
func (f *s3WriteFile) Unlock() error {
return ErrLockNotSupported
}
// Truncate the file.
func (f *s3WriteFile) Truncate(size int64) error {
return ErrTruncateNotSupported
}
// s3MultipartUploadFile implements billy.File
type s3MultipartUploadFile struct {
client *s3.Client // s3 skd client
bucket string // S3 bucket name
key string // File object's key in S3
closed bool // Is the file closed?
uploadID string // S3 multipart upload ID
uploadN *atomic.Int32 // Counter tracking the number of uploads
}
// newS3MultipartUploadFile creates a new s3ReadFile.
func newS3MultipartUploadFile(client *s3.Client, bucket, key string) (*s3MultipartUploadFile, error) {
// TODO: Check if the file exists
// ...
// Create the context
ctx := context.TODO() // TODO: How can user-supplied contexts be supported?
// Run the GetObject operation
res, err := client.CreateMultipartUpload(ctx, &s3.CreateMultipartUploadInput{
Bucket: &bucket,
Key: &key,
})
if err != nil {
return nil, fmt.Errorf("unable to create multipart upload: %w", err)
}
// Return the file
return &s3MultipartUploadFile{
client: client,
bucket: bucket,
key: key,
uploadID: *res.UploadId,
uploadN: atomic.NewInt32(1),
}, nil
}
// Name returns the name of the file as presented to Open.
func (f *s3MultipartUploadFile) Name() string {
return f.key
}
// Write implements os.Writer for billy.File
func (f *s3MultipartUploadFile) Write(p []byte) (n int, err error) {
// Get the size of the data being written
n = len(p)
// Create a context for the operation
ctx := context.TODO() // TODO: How can user-supplied contexts be supported?
// Create a reader for the data
r := bytes.NewReader(p)
// Get the part number
pn := f.uploadN.Load()
// Run the UploadPart operation
_, err = f.client.UploadPart(ctx, &s3.UploadPartInput{
Bucket: &f.bucket,
Key: &f.key,
UploadId: &f.uploadID,
PartNumber: pn,
Body: r,
})
if err != nil {
return 0, fmt.Errorf("unable to upload part %d: %w", pn, err)
}
// Increment the part number
f.uploadN.Add(1)
// Return the number of bytes written
return n, nil
}
// Read implements os.Reader for billy.File
func (f *s3MultipartUploadFile) Read(p []byte) (n int, err error) {
return 0, ErrCantReadFromWriteOnly
}
// ReadAt implements io.ReaderAt for billy.File
func (f *s3MultipartUploadFile) ReadAt(p []byte, off int64) (n int, err error) {
return 0, ErrCantReadFromWriteOnly
}
// Seek implements io.Seeker for billy.File
func (f *s3MultipartUploadFile) Seek(offset int64, whence int) (int64, error) {
return 0, errors.New("seek not implemented")
}
// Close implements io.Closer for billy.File
func (f *s3MultipartUploadFile) Close() error {
// Check if the file has been closed
if f.closed {
return ErrFileClosed
}
// Set to closed
f.closed = true
// Create the context
ctx := context.TODO() // TODO: How can user-supplied contexts be supported?
// Complete the multipart upload
// TODO: Currently `res` is not used. Should it be?
_, err := f.client.CompleteMultipartUpload(ctx, &s3.CompleteMultipartUploadInput{
Bucket: &f.bucket,
Key: &f.key,
UploadId: &f.uploadID,
})
if err != nil {
return fmt.Errorf("unable to complete multipart upload: %w", err)
}
return nil
}
// Lock locks the file like e.g. flock. It protects against access from
// other processes.
func (f *s3MultipartUploadFile) Lock() error {
return ErrLockNotSupported
}
// Unlock unlocks the file.
func (f *s3MultipartUploadFile) Unlock() error {
return ErrLockNotSupported
}
// Truncate the file.
func (f *s3MultipartUploadFile) Truncate(size int64) error {
return ErrTruncateNotSupported
}