storj/pkg/piecestore/pstore.go

// Copyright (C) 2018 Storj Labs, Inc.
// See LICENSE for copying information.

package pstore

import (
	"io"
	"os"
	"path"
	"path/filepath"

	"github.com/zeebo/errs"

	"storj.io/storj/pkg/filepiece"
)

// Errors
var (
	ArgError = errs.Class("argError")
	FSError  = errs.Class("fsError")
)

// PathByHash -- creates datapath from hash and dir
func PathByHash(hash, dir string) (string, error) {
	if len(hash) < 20 {
		return "", ArgError.New("Invalid hash length")
	}

	folder1 := string(hash[0:2])
	folder2 := string(hash[2:4])
	fileName := string(hash[4:])

	return path.Join(dir, folder1, folder2, fileName), nil
}

// Store -- Store data into piece store
// 	hash 					(string)		Hash of the data to be stored
// 	r 			  		(io.Reader)	File/Stream that contains the contents of the data to be stored
// 	length 				(length)		Size of the data to be stored
// 	psFileOffset 	(offset)  	Offset of the data that you are writing. Useful for multiple connections to split the data transfer
// 	dir 					(string)		pstore directory containing all other data stored
// 	returns 			(error) 		error if failed and nil if successful
func Store(hash string, r io.Reader, length int64, psFileOffset int64, dir string) (int64, error) {
	if psFileOffset < 0 {
		return 0, ArgError.New("Offset is less than 0. Must be greater than or equal to 0")
	}
	if length < 0 {
		return 0, ArgError.New("Length is less than 0. Must be greater than or equal to 0")
	}
	if dir == "" {
		return 0, ArgError.New("No path provided")
	}

	dataPath, err := PathByHash(hash, dir)
	if err != nil {
		return 0, err
	}

	// Create directory path on file system
	if err = os.MkdirAll(filepath.Dir(dataPath), 0700); err != nil {
		return 0, err
	}

	// Create File on file system
	dataFile, err := os.OpenFile(dataPath, os.O_RDWR|os.O_CREATE, 0755)
	if err != nil {
		return 0, err
	}

	dataFileChunk, _ := fpiece.NewChunk(dataFile, psFileOffset, length)

	// Close when finished
	defer dataFile.Close()

	return io.CopyN(dataFileChunk, r, length)
}

// Retrieve -- Retrieve data from pstore directory
//	hash 					(string)		   Hash of the stored data
//	w 						(io.Writer)	   Stream that recieves the stored data
//	length 				(length)		   Amount of data to read. Read all data if -1
//	readPosOffset	(offset)	   	 Offset of the data that you are reading. Useful for multiple connections to split the data transfer
//	dir 					(string)		   pstore directory containing all other data stored
//	returns 			(int64, error) returns err if failed and the number of bytes retrieved if successful
func Retrieve(hash string, w io.Writer, length int64, readPosOffset int64, dir string) (int64, error) {
	if dir == "" {
		return 0, ArgError.New("No path provided")
	}

	dataPath, err := PathByHash(hash, dir)
	if err != nil {
		return 0, err
	}

	fileInfo, err := os.Stat(dataPath)
	if err != nil {
		return 0, err
	}

	// If offset is greater than file size return
	if readPosOffset >= fileInfo.Size() || readPosOffset < 0 {
		return 0, ArgError.New("Invalid offset: %v", readPosOffset)
	}

	// If length less than 0 read the entire file
	if length <= -1 {
		length = fileInfo.Size()
	}

	// If trying to read past the end of the file, just read to the end
	if fileInfo.Size() < readPosOffset+length {
		length = fileInfo.Size() - readPosOffset
	}

	dataFile, err := os.OpenFile(dataPath, os.O_RDONLY, 0755)
	if err != nil {
		return 0, err
	}
	// Close when finished
	defer dataFile.Close()

	// Created a section reader so that we can concurrently retrieve the same file.
	dataFileChunk, _ := fpiece.NewChunk(dataFile, readPosOffset, length)

	total, err := io.CopyN(w, dataFileChunk, length)

	return total, err
}

// Delete -- Delete data from farmer
//	hash 		(string) 	Hash of the data to be stored
//	dir 		(string) 	pstore directory containing all other data stored
//	returns (error) 	if failed and nil if successful
func Delete(hash string, dir string) error {
	if dir == "" {
		return ArgError.New("No path provided")
	}

	dataPath, err := PathByHash(hash, dir)
	if err != nil {
		return err
	}

	if _, err = os.Stat(dataPath); os.IsNotExist(err) {
		return nil
	}

	if err = os.Remove(dataPath); err != nil {
		return err
	}

	return nil
}