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// Copyright 2023 MaidSafe.net limited.
//
// This SAFE Network Software is licensed to you under The General Public License (GPL), version 3.
// Unless required by applicable law or agreed to in writing, the SAFE Network Software distributed
// under the GPL Licence is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. Please review the Licences for the specific language governing
// permissions and limitations relating to use of the SAFE Network Software.
use crate::{
chunks::{DataMapLevel, Error as ChunksError},
error::{Error as ClientError, Result},
Client, FilesApi, BATCH_SIZE, MAX_UPLOAD_RETRIES,
};
use bytes::Bytes;
use futures::StreamExt;
use itertools::Itertools;
use self_encryption::{decrypt_full_set, DataMap, EncryptedChunk, StreamSelfDecryptor};
use sn_networking::target_arch::Instant;
use sn_protocol::storage::{Chunk, ChunkAddress};
use std::{collections::HashMap, fs, path::PathBuf};
use tokio::sync::mpsc::{self};
use xor_name::XorName;
/// The events emitted from the download process.
pub enum FilesDownloadEvent {
/// Downloaded a Chunk from the network
Downloaded(ChunkAddress),
/// The total number of chunks we are about to download.
/// Note: This count currently is not accurate. It does not take into account how we fetch the initial head chunk.
ChunksCount(usize),
/// The total number of data map chunks that we are about to download. This happens if the datamap file is.
/// very large.
/// Note: This count currently is not accurate. It does not take into account how we fetch the initial head chunk.
DatamapCount(usize),
/// The download process has terminated with an error.
Error,
}
// Internally used to differentiate between the various ways that the downloaded chunks are returned.
enum DownloadReturnType {
EncryptedChunks(Vec<EncryptedChunk>),
DecryptedBytes(Bytes),
WrittenToFileSystem,
}
/// `FilesDownload` provides functionality for downloading chunks with support for retries and queuing.
/// This struct is not cloneable. To create a new instance with default configuration, use the `new` function.
/// To modify the configuration, use the provided setter methods (`set_...` functions).
pub struct FilesDownload {
// Configurations
batch_size: usize,
show_holders: bool,
// todo: controlled by GetRecordCfg, need to expose things.
max_retries: usize,
// API
api: FilesApi,
// Events
event_sender: Option<mpsc::Sender<FilesDownloadEvent>>,
logged_event_sender_absence: bool,
}
impl FilesDownload {
/// Creates a new instance of `FilesDownload` with the default configuration.
/// To modify the configuration, use the provided setter methods (`set_...` functions).
pub fn new(files_api: FilesApi) -> Self {
Self {
batch_size: BATCH_SIZE,
show_holders: false,
max_retries: MAX_UPLOAD_RETRIES,
api: files_api,
event_sender: None,
logged_event_sender_absence: false,
}
}
/// Sets the default batch size that determines the number of chunks that are downloaded in parallel
///
/// By default, this option is set to the constant `BATCH_SIZE: usize = 64`.
pub fn set_batch_size(mut self, batch_size: usize) -> Self {
self.batch_size = batch_size;
self
}
/// Sets the option to display the holders that are expected to be holding a chunk during verification.
///
/// By default, this option is set to false.
pub fn set_show_holders(mut self, show_holders: bool) -> Self {
self.show_holders = show_holders;
self
}
/// Sets the maximum number of retries to perform if a chunk fails to download.
///
/// By default, this option is set to the constant `MAX_UPLOAD_RETRIES: usize = 3`.
pub fn set_max_retries(mut self, max_retries: usize) -> Self {
self.max_retries = max_retries;
self
}
/// Returns a receiver for file download events.
/// This method is optional and the download process can be performed without it.
pub fn get_events(&mut self) -> mpsc::Receiver<FilesDownloadEvent> {
let (event_sender, event_receiver) = mpsc::channel(10);
// should we return error if an sender is already set?
self.event_sender = Some(event_sender);
event_receiver
}
/// Download bytes from the network. The contents are spread across
/// multiple chunks in the network. This function invokes the self-encryptor and returns
/// the data that was initially stored.
///
/// Takes `position` and `length` arguments which specify the start position
/// and the length of bytes to be read.
/// Passing `0` to position reads the data from the beginning,
/// and the `length` is just an upper limit.
pub async fn download_from(
&mut self,
address: ChunkAddress,
position: usize,
length: usize,
) -> Result<Bytes> {
// clean up the trackers/stats
self.logged_event_sender_absence = false;
let result = self.download_from_inner(address, position, length).await;
// send an event indicating that the download process completed with an error
if result.is_err() {
self.send_event(FilesDownloadEvent::Error).await?;
}
// drop the sender to close the channel.
let sender = self.event_sender.take();
drop(sender);
result
}
pub async fn download_from_inner(
&mut self,
address: ChunkAddress,
position: usize,
length: usize,
) -> Result<Bytes> {
debug!("Reading {length} bytes at: {address:?}, starting from position: {position}");
let chunk = self.api.client.get_chunk(address, false).await?;
// First try to deserialize a LargeFile, if it works, we go and seek it.
// If an error occurs, we consider it to be a SmallFile.
if let Ok(data_map) = self.unpack_chunk(chunk.clone()).await {
let info = self_encryption::seek_info(data_map.file_size(), position, length);
let range = &info.index_range;
let all_infos = data_map.infos();
let to_download = (range.start..range.end + 1)
.clone()
.map(|i| all_infos[i].clone())
.collect_vec();
let to_download = DataMap::new(to_download);
// not written to file and return the encrypted chunks
if let DownloadReturnType::EncryptedChunks(encrypted_chunks) =
self.read(to_download, None, true, false).await?
{
let bytes = self_encryption::decrypt_range(
&data_map,
&encrypted_chunks,
info.relative_pos,
length,
)
.map_err(ChunksError::SelfEncryption)?;
return Ok(bytes);
} else {
error!("IncorrectDownloadOption: expected to get the encrypted chunks back");
return Err(ClientError::IncorrectDownloadOption);
}
}
// The error above is ignored to avoid leaking the storage format detail of SmallFiles and LargeFiles.
// The basic idea is that we're trying to deserialize as one, and then the other.
// The cost of it is that some errors will not be seen without a refactor.
let mut bytes = chunk.value().clone();
let _ = bytes.split_to(position);
bytes.truncate(length);
Ok(bytes)
}
/// Download a file from the network and get the decrypted bytes.
/// If the data_map_chunk is not provided, the DataMap is fetched from the network using the provided address.
pub async fn download_file(
&mut self,
address: ChunkAddress,
data_map_chunk: Option<Chunk>,
) -> Result<Bytes> {
if let Some(bytes) = self
.download_entire_file(address, data_map_chunk, None)
.await?
{
Ok(bytes)
} else {
error!("IncorrectDownloadOption: expected to get decrypted bytes, but we got None");
Err(ClientError::IncorrectDownloadOption)
}
}
/// Download a file from the network and write it to the provided path.
/// If the data_map_chunk is not provided, the DataMap is fetched from the network using the provided address.
pub async fn download_file_to_path(
&mut self,
address: ChunkAddress,
data_map_chunk: Option<Chunk>,
path: PathBuf,
) -> Result<()> {
if self
.download_entire_file(address, data_map_chunk, Some(path))
.await?
.is_none()
{
Ok(())
} else {
error!(
"IncorrectDownloadOption: expected to not get any decrypted bytes, but got Some"
);
Err(ClientError::IncorrectDownloadOption)
}
}
/// Download a file from the network.
/// If you want to track the download progress, use the `get_events` method.
async fn download_entire_file(
&mut self,
address: ChunkAddress,
data_map_chunk: Option<Chunk>,
downloaded_file_path: Option<PathBuf>,
) -> Result<Option<Bytes>> {
// clean up the trackers/stats
self.logged_event_sender_absence = false;
let result = self
.download_entire_file_inner(address, data_map_chunk, downloaded_file_path)
.await;
// send an event indicating that the download process completed with an error
if result.is_err() {
self.send_event(FilesDownloadEvent::Error).await?;
}
// drop the sender to close the channel.
let sender = self.event_sender.take();
drop(sender);
result
}
async fn download_entire_file_inner(
&mut self,
address: ChunkAddress,
data_map_chunk: Option<Chunk>,
downloaded_file_path: Option<PathBuf>,
) -> Result<Option<Bytes>> {
let head_chunk = if let Some(chunk) = data_map_chunk {
info!("Downloading via supplied local datamap");
chunk
} else {
match self.api.client.get_chunk(address, self.show_holders).await {
Ok(chunk) => chunk,
Err(err) => {
error!("Failed to fetch head chunk {address:?}");
return Err(err);
}
}
};
// first try to deserialize a LargeFile, if it works, we go and seek it
if let Ok(data_map) = self.unpack_chunk(head_chunk.clone()).await {
// read_all emits
match self
.read(data_map, downloaded_file_path, false, false)
.await?
{
DownloadReturnType::EncryptedChunks(_) => {
error!("IncorrectDownloadOption: we should not be getting the encrypted chunks back as it is set to false.");
Err(ClientError::IncorrectDownloadOption)
}
DownloadReturnType::DecryptedBytes(bytes) => Ok(Some(bytes)),
DownloadReturnType::WrittenToFileSystem => Ok(None),
}
} else {
self.send_event(FilesDownloadEvent::ChunksCount(1)).await?;
self.send_event(FilesDownloadEvent::Downloaded(address))
.await?;
// if an error occurs, we assume it's a SmallFile
if let Some(path) = downloaded_file_path {
fs::write(path, head_chunk.value().clone())?;
Ok(None)
} else {
Ok(Some(head_chunk.value().clone()))
}
}
}
/// The internal logic to download the provided chunks inside the datamap.
/// If the decrypted_file_path is provided, we return DownloadReturnType::WrittenToFileSystem
/// If return_encrypted_chunks is true, we return DownloadReturnType::EncryptedChunks
/// Else we return DownloadReturnType::DecryptedBytes
///
/// Set we_are_downloading_a_datamap if we want to emit the DatamapCount else we emit ChunksCount
async fn read(
&mut self,
data_map: DataMap,
decrypted_file_path: Option<PathBuf>,
return_encrypted_chunks: bool,
we_are_downloading_a_datamap: bool,
) -> Result<DownloadReturnType> {
// used internally
enum DownloadKind {
FileSystem(StreamSelfDecryptor),
Memory(Vec<EncryptedChunk>),
}
let mut download_kind = {
if let Some(path) = decrypted_file_path {
DownloadKind::FileSystem(StreamSelfDecryptor::decrypt_to_file(
Box::new(path),
&data_map,
)?)
} else {
DownloadKind::Memory(Vec::new())
}
};
let chunk_infos = data_map.infos();
let expected_count = chunk_infos.len();
if we_are_downloading_a_datamap {
self.send_event(FilesDownloadEvent::ChunksCount(expected_count))
.await?;
} else {
// we're downloading the chunks related to a huge datamap
self.send_event(FilesDownloadEvent::DatamapCount(expected_count))
.await?;
}
let now = Instant::now();
let client_clone = self.api.client.clone();
let show_holders = self.show_holders;
// the initial index is not always 0 as we might seek a range of bytes. So fetch the first index
let mut current_index = chunk_infos
.first()
.ok_or_else(|| ClientError::EmptyDataMap)?
.index;
let mut stream = futures::stream::iter(chunk_infos.into_iter())
.map(|chunk_info| {
Self::get_chunk(
client_clone.clone(),
chunk_info.dst_hash,
chunk_info.index,
show_holders,
)
})
.buffer_unordered(self.batch_size);
let mut chunk_download_cache = HashMap::new();
while let Some(result) = stream.next().await {
let (chunk_address, index, encrypted_chunk) = result?;
// notify about the download
self.send_event(FilesDownloadEvent::Downloaded(chunk_address))
.await?;
info!("Downloaded chunk of index {index:?}. We are at current_index {current_index:?}");
// check if current_index is present in the cache before comparing the fetched index.
// try to keep removing from the cache until we run out of sequential chunks to insert.
while let Some(encrypted_chunk) = chunk_download_cache.remove(¤t_index) {
debug!("Got current_index {current_index:?} from the download cache. Incrementing current index");
match &mut download_kind {
DownloadKind::FileSystem(decryptor) => {
let _ = decryptor.next_encrypted(encrypted_chunk)?;
}
DownloadKind::Memory(collector) => collector.push(encrypted_chunk),
}
current_index += 1;
}
// now check if we can process the fetched index, else cache it.
if index == current_index {
debug!("The downloaded chunk's index {index:?} matches the current index {current_index}. Processing it");
match &mut download_kind {
DownloadKind::FileSystem(decryptor) => {
let _ = decryptor.next_encrypted(encrypted_chunk)?;
}
DownloadKind::Memory(collector) => collector.push(encrypted_chunk),
}
current_index += 1;
} else {
// since we download the chunks concurrently without order, we cache the results for an index that
// finished earlier
debug!("The downloaded chunk's index {index:?} does not match with the current_index {current_index}. Inserting into cache");
let _ = chunk_download_cache.insert(index, encrypted_chunk);
}
}
// finally empty out the cache.
debug!("Finally emptying out the download cache");
while let Some(encrypted_chunk) = chunk_download_cache.remove(¤t_index) {
debug!("Got current_index {current_index:?} from the download cache. Incrementing current index");
match &mut download_kind {
DownloadKind::FileSystem(decryptor) => {
let _ = decryptor.next_encrypted(encrypted_chunk)?;
}
DownloadKind::Memory(collector) => collector.push(encrypted_chunk),
}
current_index += 1;
}
if !chunk_download_cache.is_empty() {
error!(
"The chunk download cache is not empty. Current index {current_index:?}. The indices inside the cache: {:?}",
chunk_download_cache.keys()
);
return Err(ClientError::FailedToAssembleDownloadedChunks);
}
let elapsed = now.elapsed();
info!("Client downloaded file in {elapsed:?}");
match download_kind {
DownloadKind::FileSystem(_) => Ok(DownloadReturnType::WrittenToFileSystem),
DownloadKind::Memory(collector) => {
let result = if return_encrypted_chunks {
DownloadReturnType::EncryptedChunks(collector)
} else {
let bytes = decrypt_full_set(&data_map, &collector)
.map_err(ChunksError::SelfEncryption)?;
DownloadReturnType::DecryptedBytes(bytes)
};
Ok(result)
}
}
}
/// Extracts a file DataMapLevel from a chunk.
/// If the DataMapLevel is not the first level mapping directly to the user's contents,
/// the process repeats itself until it obtains the first level DataMapLevel.
pub async fn unpack_chunk(&mut self, mut chunk: Chunk) -> Result<DataMap> {
loop {
match rmp_serde::from_slice(chunk.value()).map_err(ChunksError::Deserialisation)? {
DataMapLevel::First(data_map) => {
return Ok(data_map);
}
DataMapLevel::Additional(data_map) => {
if let DownloadReturnType::DecryptedBytes(serialized_chunk) =
self.read(data_map, None, false, true).await?
{
chunk = rmp_serde::from_slice(&serialized_chunk)
.map_err(ChunksError::Deserialisation)?;
} else {
error!("IncorrectDownloadOption: we should be getting the decrypted bytes back.");
return Err(ClientError::IncorrectDownloadOption);
}
}
}
}
}
async fn send_event(&mut self, event: FilesDownloadEvent) -> Result<()> {
if let Some(sender) = self.event_sender.as_ref() {
sender.send(event).await.map_err(|err| {
error!("Could not send files download event due to {err:?}");
ClientError::CouldNotSendFilesEvent
})?;
} else if !self.logged_event_sender_absence {
info!("Files download event sender is not set. Use get_events() if you need to keep track of the progress");
self.logged_event_sender_absence = true;
}
Ok(())
}
async fn get_chunk(
client: Client,
address: XorName,
index: usize,
show_holders: bool,
) -> std::result::Result<(ChunkAddress, usize, EncryptedChunk), ChunksError> {
let chunk = client
.get_chunk(ChunkAddress::new(address), show_holders)
.await
.map_err(|err| {
error!("Chunk missing {address:?} with {err:?}",);
ChunksError::ChunkMissing(address)
})?;
let encrypted_chunk = EncryptedChunk {
index,
content: chunk.value,
};
Ok((chunk.address, index, encrypted_chunk))
}
}