fault_tolerant_reader.hpp

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#pragma once
 
#include "bad_block_map.hpp"
#include "disk_reader.hpp"
 
#include <cstddef>
#include <cstdint>
#include <functional>
#include <mutex>
#include <string>
 
struct ReadResult {
    bool success {false};
    size_t bytes_read {0};
    bool partial {false};
    bool timeout {false};
    std::string error;
};
 
struct FaultTolerantReaderConfig {
    size_t initial_chunk_size {1024 * 1024};
    size_t min_chunk_size {4096};
    int max_retries {3};
    bool mark_slow_ranges {true};
};
 
class FaultTolerantReader {
public:
    using CancelCallback = std::function<bool()>;
 
    FaultTolerantReader() = default;
 
    bool open(const std::string& path, std::string& error);
    void close();
 
    bool is_open() const;
    uint64_t size() const;
    uint32_t logical_sector_size() const;
    const std::string& path() const;
 
    void set_config(const FaultTolerantReaderConfig& cfg);
    void set_cancel_callback(CancelCallback cb);
 
    ReadResult read_at(uint64_t offset, void* buffer, size_t size);
    ReadResult read_rescue(uint64_t offset, void* buffer, size_t size);
 
    const BadBlockMap& bad_block_map() const;
    BadBlockMap& bad_block_map();
 
private:
    ReadResult read_rescue_recursive(uint64_t offset, unsigned char* buffer, size_t size);
 
    DiskReader reader_;
    FaultTolerantReaderConfig config_;
    CancelCallback cancel_cb_;
    BadBlockMap bad_map_;
    mutable std::mutex mutex_;
};