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FileStorage

bacnet_objects::file

Trait FileStorage 

Source 
pub trait FileStorage: Send + Sync {
    // Provided methods
    fn read_stream(
        &self,
        _start: u64,
        _count: u64,
    ) -> Result<FileStreamRead, Error> { ... }
    fn write_stream(
        &mut self,
        _start: FileWriteStart,
        _data: &[u8],
    ) -> Result<u64, Error> { ... }
    fn read_records(
        &self,
        _start: u64,
        _count: u64,
    ) -> Result<FileRecordRead, Error> { ... }
    fn write_records(
        &mut self,
        _start: FileWriteStart,
        _records: &[Vec<u8>],
    ) -> Result<u64, Error> { ... }
}
Expand description

The octet- and record-addressed storage behind a File object.

This is the internal channel AtomicReadFile and AtomicWriteFile use to reach file contents (Clauses 14.1 and 14.2). It is deliberately not a property: Table 12-16 (Clause 12.13) defines no File Data property, so file contents have no network route other than the File Access Services, and nothing here appears in Property_List.

The server reaches an implementation through BACnetObject::file_storage_internal and BACnetObject::file_storage_internal_mut. Every method has a default that refuses with SERVICES / FILE_ACCESS_DENIED — there is no implementation behind it, making the file inaccessible under Clause 18 — and a stream-only implementation overrides only the two stream methods.

Error contract, using the Clause 14 pairs:

  • SERVICES / INVALID_FILE_START_POSITION when a read starts past the current end (Clause 14.1 Service Procedure). Reading at the end is legal and yields an empty window. The built-in empty file reports end_of_file TRUE there; non-empty files report FALSE for such a window.
  • OBJECT / FILE_FULL when a write would grow the file past the most this implementation can hold (Clause 14.2.4.1; Clause 18).
  • SERVICES / INVALID_FILE_ACCESS_METHOD when the method does not match the object’s File_Access_Method; only a genuine mismatch, never a missing implementation, reports this.
  • SERVICES / FILE_ACCESS_DENIED from the defaults above.

A write that returns Err must leave the storage unchanged: the service fails as a whole (Clause 14.2.4), and the server encodes no ACK on the error path. Resolved write positions must fit the ACK’s INTEGER, so implementations keep their limit at or below i32::MAX.

Provided Methods§

Source

fn read_stream(&self, _start: u64, _count: u64) -> Result<FileStreamRead, Error>

Read up to count octets starting start octets into the file.

Source

fn write_stream( &mut self, _start: FileWriteStart, _data: &[u8], ) -> Result<u64, Error>

Write data at start, extending the file first when start is past the end; intervening octets are a local matter. Returns the octet offset the data was written at, which for FileWriteStart::Append is the previous file size.

Source

fn read_records( &self, _start: u64, _count: u64, ) -> Result<FileRecordRead, Error>

Read up to count records starting at record start.

Source

fn write_records( &mut self, _start: FileWriteStart, _records: &[Vec<u8>], ) -> Result<u64, Error>

Write records starting at record start, replacing records in place and extending the file first when start is past the end. Returns the record index the data was written at.

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§