Struct BlobReader

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pub struct BlobReader { /* private fields */ }

Expand description

Streaming reader for large binary objects (LOBs).

BlobReader implements AsyncRead to provide a streaming interface for reading large objects. Data can be read in chunks without allocating additional buffers for each read operation.

§Example

use mssql_client::blob::BlobReader;
use tokio::io::AsyncReadExt;

let data: Bytes = row.get("binary_column")?;
let mut reader = BlobReader::from_bytes(data);

// Read up to 4KB at a time
let mut buffer = vec![0u8; 4096];
let bytes_read = reader.read(&mut buffer).await?;

Implementations§

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impl BlobReader

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pub fn from_bytes(buffer: Bytes) -> Self

Create a new BlobReader from a Bytes buffer.

This is the primary constructor for creating a blob reader from column data retrieved from a query result.

§Example

use bytes::Bytes;
use mssql_client::blob::BlobReader;

let data = Bytes::from_static(b"Hello, World!");
let reader = BlobReader::from_bytes(data);
assert_eq!(reader.len(), Some(13));

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pub fn empty() -> Self

Create an empty BlobReader.

Returns a reader with no data that will immediately return EOF.

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pub fn from_slice(data: &[u8]) -> Self

Create a BlobReader from a byte slice.

This copies the data into an owned Bytes buffer.

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pub fn len(&self) -> Option<u64>

Get the total length of the BLOB in bytes.

Returns Some(length) with the total size of the data. Returns None only for truly streaming implementations where the total length is unknown in advance.

§Example

use bytes::Bytes;
use mssql_client::blob::BlobReader;

let reader = BlobReader::from_bytes(Bytes::from_static(b"test"));
assert_eq!(reader.len(), Some(4));

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pub fn is_empty(&self) -> bool

Check if the BLOB is empty.

Returns true if the BLOB contains no data.

§Example

use bytes::Bytes;
use mssql_client::blob::BlobReader;

let empty = BlobReader::empty();
assert!(empty.is_empty());

let non_empty = BlobReader::from_bytes(Bytes::from_static(b"data"));
assert!(!non_empty.is_empty());

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pub fn bytes_read(&self) -> u64

Get the number of bytes read so far.

This tracks progress through the BLOB and can be used for progress reporting.

§Example

use bytes::Bytes;
use mssql_client::blob::BlobReader;

let reader = BlobReader::from_bytes(Bytes::from_static(b"Hello"));
assert_eq!(reader.bytes_read(), 0);

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pub fn remaining(&self) -> Option<u64>

Get the number of bytes remaining to be read.

Returns Some(remaining) if the total length is known.

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pub fn rewind(&mut self)

Reset the reader position to the beginning.

After calling this, bytes_read() will return 0 and subsequent reads will start from the beginning of the data.

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pub fn into_bytes(self) -> Bytes

Consume the reader and return the underlying Bytes buffer.

This returns the complete data, including any bytes already read. The buffer is not consumed by reads; it remains complete.

§Example

use bytes::Bytes;
use mssql_client::blob::BlobReader;

let data = Bytes::from_static(b"Hello");
let reader = BlobReader::from_bytes(data.clone());
let recovered = reader.into_bytes();
assert_eq!(recovered, data);

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