nuts_backend

Trait Backend

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pub trait Backend: ReceiveHeader<Self>
where
    Self: Sized,
{
    type Settings: Binary + Clone;
    type Err: Error + Send + Sync;
    type Id: Binary + Clone + Display + FromStr + IdSize + PartialEq;
    type Info;

    // Required methods
    fn info(&self) -> Result<Self::Info, Self::Err>;
    fn block_size(&self) -> u32;
    fn aquire(&mut self, buf: &[u8]) -> Result<Self::Id, Self::Err>;
    fn release(&mut self, id: Self::Id) -> Result<(), Self::Err>;
    fn read(
        &mut self,
        id: &Self::Id,
        buf: &mut [u8],
    ) -> Result<usize, Self::Err>;
    fn write(&mut self, id: &Self::Id, buf: &[u8]) -> Result<usize, Self::Err>;
    fn write_header(&mut self, buf: &[u8; 512]) -> Result<(), Self::Err>;
    fn delete(self);
}
Expand description

Trait that describes a backend of a container.

Required Associated Types§

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type Settings: Binary + Clone

Runtime configuration used by the backend.

It should contain all settings/information needed by the backend. It is loaded from the header when the backend is opened. See the Open trait for more information on how the backend is opened.

The Create trait is used to create the settings of a backend.

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type Err: Error + Send + Sync

The error type used by methods of this trait.

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type Id: Binary + Clone + Display + FromStr + IdSize + PartialEq

The id identifies a block in the storage. It is used everywhere you need a pointer to a block.

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type Info

Information of the backend.

It includes information like public settings. The difference to Backend::Settings is that Backend::Settings might include sensible information which are removed from Backend::Info.

Required Methods§

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fn info(&self) -> Result<Self::Info, Self::Err>

Returns information from the backend.

It includes information like public settings. The difference to Backend::Settings is that Backend::Settings might include sensible information which are removed from Backend::Info.

§Errors

On any error a self-defined Backend::Err is returned.

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fn block_size(&self) -> u32

Returns the block size of the backend.

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fn aquire(&mut self, buf: &[u8]) -> Result<Self::Id, Self::Err>

Aquires a new block in the backend.

Once aquired you should be able to read and write from/to it.

buf contains the initial data, which should be copied into the block.

  • A buf which is not large enough to fill the whole block must be rejected and an error must be returned.
  • If buf holds more data than the block-size, then only the first block-size bytes are copied into the block.

By default an aquired block, which is not written yet, should return an all-zero buffer.

Returns the id if the block.

§Errors

On any error a self-defined Backend::Err is returned.

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fn release(&mut self, id: Self::Id) -> Result<(), Self::Err>

Releases a block again.

A released block cannot be read and written, the id cannot be used afterwards.

§Errors

On any error a self-defined Backend::Err is returned.

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fn read(&mut self, id: &Self::Id, buf: &mut [u8]) -> Result<usize, Self::Err>

Reads a block from the backend.

Reads the block with the given id and places the data in buf.

You cannot read not more data than the block-size bytes. If buf is larger, than not the whole buffer is filled. In the other direction, if buf is not large enough to store the whole block, buf is filled with the first buf.len() bytes.

The methods returns the number of bytes actually read, which cannot be greater than the block-size.

§Errors

On any error a self-defined Backend::Err is returned.

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fn write(&mut self, id: &Self::Id, buf: &[u8]) -> Result<usize, Self::Err>

Writes a block into the backend.

Writes up to buf.len() bytes from the unencrypted buf buffer into the block with the given id.

  • A buf which is not large enough to fill the whole block must be rejected and an error must be returned.
  • If buf holds more data than the block-size, then only the first block-size bytes are copied into the block.

The method returns the number of bytes actually written.

§Errors

On any error a self-defined Backend::Err is returned.

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fn write_header(&mut self, buf: &[u8; 512]) -> Result<(), Self::Err>

Puts the given buf into the header of the backend.

The container uses this method to ask the backend to put data into the header. The container does not know where the backend stores the header, that’s why such a method is used. Not more than HEADER_MAX_SIZE bytes can be stored in the header.

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fn delete(self)

Deletes the entire instance and all traces.

The method must not fail!

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors§