nvs_blob.h

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#pragma once
 
#include <Preferences.h>
#include <cstddef>
#include <cstdint>
#include <span>
 
namespace nvs_blob
{
enum class ReadStatus {
    Absent,   
    Mismatch, 
    Ok        
};
 
inline ReadStatus read(Preferences& prefs, const char* key, std::span<uint8_t> out)
{
    const size_t stored = prefs.getBytesLength(key);
    if (stored == 0)
    {
        return ReadStatus::Absent;
    }
    if (stored != out.size() || prefs.getBytes(key, out.data(), out.size()) != out.size())
    {
        return ReadStatus::Mismatch;
    }
    return ReadStatus::Ok;
}
} // namespace nvs_blob