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#pragma once
#include <cstdint>
#include <string>
#include <utility>
#include <vector>
namespace downloader
{
/// Single-threaded code
class ChunksDownloadStrategy
{
public:
enum ChunkStatusT { CHUNK_FREE = 0, CHUNK_DOWNLOADING = 1, CHUNK_COMPLETE = 2, CHUNK_AUX = -1 };
private:
#pragma pack(push, 1)
struct ChunkT
{
/// position of chunk in file
int64_t m_pos;
/// @see ChunkStatusT
int8_t m_status;
ChunkT() : m_pos(-1), m_status(-1)
{
static_assert(sizeof(ChunkT) == 9, "Be sure to avoid overhead in writing to file.");
}
ChunkT(int64_t pos, int8_t st) : m_pos(pos), m_status(st) {}
};
#pragma pack(pop)
struct LessChunks
{
bool operator() (ChunkT const & r1, ChunkT const & r2) const { return r1.m_pos < r2.m_pos; }
bool operator() (ChunkT const & r1, int64_t const & r2) const { return r1.m_pos < r2; }
bool operator() (int64_t const & r1, ChunkT const & r2) const { return r1 < r2.m_pos; }
};
using RangeT = std::pair<int64_t, int64_t>;
static const int SERVER_READY = -1;
struct ServerT
{
std::string m_url;
int m_chunkIndex;
ServerT(std::string const & url, int ind) : m_url(url), m_chunkIndex(ind) {}
};
std::vector<ChunkT> m_chunks;
std::vector<ServerT> m_servers;
/// @return Chunk pointer and it's index for given file offsets range.
std::pair<ChunkT *, int> GetChunk(RangeT const & range);
public:
ChunksDownloadStrategy(std::vector<std::string> const & urls);
/// Init chunks vector for fileSize.
void InitChunks(int64_t fileSize, int64_t chunkSize, ChunkStatusT status = CHUNK_FREE);
/// Used in unit tests only!
void AddChunk(RangeT const & range, ChunkStatusT status);
void SaveChunks(int64_t fileSize, std::string const & fName);
/// @return Already downloaded size.
int64_t LoadOrInitChunks(std::string const & fName, int64_t fileSize, int64_t chunkSize);
/// Should be called for every completed chunk (no matter successful or not).
/// @returns url of the chunk
std::string ChunkFinished(bool success, RangeT const & range);
size_t ActiveServersCount() const { return m_servers.size(); }
enum ResultT
{
ENextChunk,
ENoFreeServers,
EDownloadFailed,
EDownloadSucceeded
};
/// Should be called until returns ENextChunk
ResultT NextChunk(std::string & outUrl, RangeT & range);
};
} // namespace downloader
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