Adding exif to files downloaded using reqwest and saved from bytes does not work.

[Bkmd100]

When reading or writing metadata from files using this code

bytes= client.get(&url).send().await.unwrap().bytes().await.unwrap();
let mut dest = File::create(&save_path).await.unwrap();
dest.write_all(&bytes).await;

let image_path = std::path::Path::new(&save_path);
let mut metadata = Metadata::new();
 metadata.set_tag(
                ExifTag::ImageDescription(&description)
            );
 metadata.write_to_file(&image_path);

A panic and following error occurs:

thread 'main' panicked at  xxxx\little_exif-0.6.2\src\jpg.rs:59:41:
range end index 2 out of range for slice of length 0

I managed to bypass this by converting the bytes to an image first :

let img = image::load_from_memory(&content).unwrap();
let image_path = std::path::Path::new(&save_path);
img.save(image_path);
let image_path = std::path::Path::new(&save_path);
let mut metadata = Metadata::new();
 metadata.set_tag(
                ExifTag::ImageDescription(&description)
            );
 metadata.write_to_file(&image_path);

Also I would like to note that "Metadata::new_from_path" does not work in both cases, and files saved as bytes seems to be working fine in all apps.
Please ignore all the unwraps/async and mix of stdio/async_std.

[TechnikTobi]

Hi,

thanks for the issue! Could you please provide me with some example data to reproduce this? Ideally this would be the data as bytes that you are writing in dest.write_all(&bytes).await;

[Bkmd100]

Thanks for your quick reply, here is a full demo to easily copy/paste to replicate the problem

cargo :

[dependencies]
reqwest = { version = "0.12.9", features = ["full"] }
tokio = { version = "1.0.0", features = ["full"] }
async-std = "1.13.0"
image = "0.25.5"
little_exif ="0.6.2"

code :

use async_std::fs::{File};
use async_std::io::prelude::*;
use little_exif::exif_tag::ExifTag;
use little_exif::metadata::Metadata;

#[tokio::main]
async fn main() {
    let bytes_version = "image_bytes.jpeg";
    let image_version = "image.jpeg";
    let pic_url="https://picsum.photos/id/237/200/300";
    
    
    //let's fetch the picture
    let bytes = reqwest::get(pic_url)
        .await
        .unwrap()
        .bytes()
        .await
        .unwrap();


    //let's save it using image cargo
    let img = image::load_from_memory(&bytes).unwrap();
    let image_path = std::path::Path::new(image_version);
    img.save(image_path);

    //lets save it directly from the bytes
    let mut dest = File::create(bytes_version).await.unwrap();
    dest.write_all(&bytes);


    //create the metadata
    let mut metadata = Metadata::new();
    metadata.set_tag(ExifTag::ImageDescription("test".to_string()));

    //let us write to the regular version
    let metadata_image_path = std::path::Path::new(image_version);
    metadata.write_to_file(&metadata_image_path);//works fine

    //let us write to the bytes version
    let metadata_image_path = std::path::Path::new(bytes_version);
    metadata.write_to_file(&metadata_image_path); //should panic here
 
}

[TechnikTobi]

As far as I can tell this has to do something with the async write operation. Replacing

    //lets save it directly from the bytes
    let mut dest = File::create(bytes_version).await.unwrap();
    dest.write_all(&bytes);

with

    //lets save it directly from the bytes
    let mut dest = std::fs::OpenOptions::new()
        .write(true)
        .create(true)
        .truncate(true)
        .open(bytes_version)
        .unwrap();
    dest.write_all(&bytes);

(and adding use std::io::Write;) both options seem to work. From my current point of view this has something to do with the async write operation not being done when we want to perform the metadata.write_to_file operation. Now, I'm not an expert on async and await, so I guess you have a strong reason for preferring this in your code over the "classic" I/O-stuff?