Struct ObjectDescriptor 

pub struct ObjectDescriptor { /* private fields */ }

An open object ready to read one or more ranges.

Example

use google_cloud_storage::{client::Storage, model_ext::ReadRange};
let client = Storage::builder().build().await?;
let open: ObjectDescriptor = client
    .open_object("projects/_/buckets/my-bucket", "my-object")
    .send().await?;
println!("metadata = {:?}", open.object());
// Read 2000 bytes starting at offset 1000.
let mut reader = open.read_range(ReadRange::segment(1000, 2000)).await;
while let Some(data) = reader.next().await.transpose()? {
  println!("received {} bytes", data.len());
}

This is analogous to a “file descriptor”. It represents an object in Cloud Storage that has been “opened” and is ready for more read operations. An object descriptor can have multiple concurrent read operations at a time. You may call read_range() even if previous reads have not completed.

There are no guarantees about the order of the responses. All the data for a read_range() may be returned before any data of earlier read_range() calls, or the data may arrive in any interleaved order. Naturally, the data for a single ranged read arrives in order.

You should actively read from all concurrent reads: the client library uses separate buffers for each read_range() call, but once a buffer is full the library will stop delivering data to all the concurrent reads.

Implementations

impl ObjectDescriptor

pub fn object(&self) -> Object

Returns the metadata for the open object.

Example

let descriptor = open();
println!("object generation = {}", descriptor.object().generation);

fn open() -> ObjectDescriptor {
// ... details omitted ...
}

pub async fn read_range(&self, range: ReadRange) -> ReadObjectResponse

Start reading a range.

Example

use google_cloud_storage::{model_ext::ReadRange, read_object::ReadObjectResponse};
const MIB: u64 = 1024 * 1024;
let descriptor = open();
println!("object generation = {}", descriptor.object().generation);

// Read 2 MiB starting at offset 0.
let read1 = descriptor.read_range(ReadRange::segment(0, 2 * MIB)).await;
// Concurrently read 2 MiB starting at offset 4 MiB.
let read2 = descriptor.read_range(ReadRange::segment(4 * MIB, 2 * MIB)).await;

let t1 = tokio::spawn(async move { do_read(read1) });
let t2 = tokio::spawn(async move { do_read(read2) });

async fn do_read(mut reader: ReadObjectResponse) {
// ... details omitted ...
}
fn open() -> ObjectDescriptor {
// ... details omitted ...
}

pub fn headers(&self) -> HeaderMap

Returns metadata about the original open_object() request.

Example

let descriptor = open();
// Often useful when troubleshooting problems with Google Support.
let headers = descriptor.headers();
println!("debugging header = {:?}", headers.get("x-guploader-uploadid"));

fn open() -> ObjectDescriptor {
// ... details omitted ...
}

pub fn new<T>(inner: T) -> Self

where T: ObjectDescriptor + 'static,

Create a new instance.

Application developers should only need to create an ObjectDescriptor in unit tests.

Trait Implementations

impl Clone for ObjectDescriptor

fn clone(&self) -> ObjectDescriptor

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ObjectDescriptor

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.