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writecmd.go
163 lines (136 loc) · 4.13 KB
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writecmd.go
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package commands
import (
"errors"
"fmt"
"github.com/cpssd/paranoid/libpfs/encryption"
"github.com/cpssd/paranoid/libpfs/returncodes"
"io"
"os"
"path"
)
//WriteCommand writes data to the given file
func WriteCommand(paranoidDirectory, filePath string, offset, length int64, data []byte) (returnCode returncodes.Code, returnError error, bytesWrote int) {
Log.Info("write command called")
Log.Verbose("write : given paranoidDirectory =", paranoidDirectory)
err := GetFileSystemLock(paranoidDirectory, SharedLock)
if err != nil {
return returncodes.EUNEXPECTED, err, 0
}
defer func() {
err := UnLockFileSystem(paranoidDirectory)
if err != nil {
returnCode = returncodes.EUNEXPECTED
returnError = err
bytesWrote = 0
}
}()
namepath := getParanoidPath(paranoidDirectory, filePath)
namepathType, err := getFileType(paranoidDirectory, namepath)
if err != nil {
return returncodes.EUNEXPECTED, err, 0
}
if namepathType == typeENOENT {
return returncodes.ENOENT, errors.New(filePath + " does not exist"), 0
}
if namepathType == typeDir {
return returncodes.EISDIR, errors.New(filePath + " is a paranoidDirectory"), 0
}
if namepathType == typeSymlink {
return returncodes.EIO, errors.New(filePath + " is a symlink"), 0
}
fileInodeBytes, code, err := getFileInode(namepath)
if code != returncodes.OK {
return code, err, 0
}
inodeName := string(fileInodeBytes)
err = getFileLock(paranoidDirectory, inodeName, ExclusiveLock)
if err != nil {
return returncodes.EUNEXPECTED, err, 0
}
defer func() {
err := unLockFile(paranoidDirectory, inodeName)
if err != nil {
returnCode = returncodes.EUNEXPECTED
returnError = err
bytesWrote = 0
}
}()
Log.Verbose("write : wrting to " + inodeName)
contentsFile, err := os.OpenFile(path.Join(paranoidDirectory, "contents", inodeName), os.O_RDWR, 0777)
if err != nil {
return returncodes.EUNEXPECTED, fmt.Errorf("error opening contents file: %s", err), 0
}
defer contentsFile.Close()
if offset == -1 {
offset = 0
}
if length == -1 {
err = truncate(contentsFile, offset)
if err != nil {
return returncodes.EUNEXPECTED, fmt.Errorf("error truncating file: %s", err), 0
}
} else if len(data) > int(length) {
data = data[:length]
} else if len(data) < int(length) {
emptyBytes := make([]byte, int(length)-len(data))
data = append(data, emptyBytes...)
}
wroteLen, err := writeAt(contentsFile, data, offset)
if err != nil {
return returncodes.EUNEXPECTED, fmt.Errorf("error writing to file: %s", err), wroteLen
}
return returncodes.OK, nil, wroteLen
}
func writeAt(file *os.File, data []byte, offset int64) (wroteLen int, err error) {
if !encryption.Encrypted {
return file.WriteAt(data, offset)
}
cipherSizeInt64 := int64(encryption.GetCipherSize())
extraStartBytes := offset % cipherSizeInt64
writeStart := offset - extraStartBytes
startBytes := make([]byte, extraStartBytes)
_, readerror, err := readAt(file, startBytes, writeStart)
if err != nil {
return 0, fmt.Errorf("error reading start block: %s", err)
}
if readerror != nil {
return 0, fmt.Errorf("error reading start block: %s", readerror)
}
extraEndBytes := cipherSizeInt64 - ((offset + int64(len(data))) % cipherSizeInt64)
endBytes := make([]byte, extraEndBytes)
fileLength, err := getFileLength(file)
if err != nil {
return 0, err
}
if offset+int64(len(data)) < fileLength {
_, readerror, err := readAt(file, endBytes, offset+int64(len(data)))
if err != nil {
return 0, fmt.Errorf("error reading end block: %s", err)
}
if readerror != nil && readerror != io.EOF {
return 0, fmt.Errorf("error reading end block: %s", err)
}
}
bytesToWrite := append(startBytes, data...)
bytesToWrite = append(bytesToWrite, endBytes...)
err = encryption.Encrypt(bytesToWrite)
if err != nil {
return 0, err
}
n, err := file.WriteAt(bytesToWrite, writeStart+1)
n = n - int(extraStartBytes)
if n > len(data) {
n = len(data)
}
if err != nil {
return n, err
}
if offset+int64(len(data)) > fileLength {
endBlockSize := (offset + int64(len(data))) % cipherSizeInt64
_, err := file.WriteAt([]byte{byte(endBlockSize)}, 0)
if err != nil {
return n, err
}
}
return n, nil
}