Update Rust crate base64 to 0.21.0 (#1709)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [base64](https://github.com/marshallpierce/rust-base64) | dependencies | minor | `0.20.0` -> `0.21.0` |

---

### Release Notes

<details>
<summary>marshallpierce/rust-base64</summary>

### [`v0.21.0`](https://github.com/marshallpierce/rust-base64/blob/HEAD/RELEASE-NOTES.md#&#8203;0210)

[Compare Source](marshallpierce/rust-base64@v0.20.0...v0.21.0)

(not yet released)

#### Migration

##### Functions

| < 0.20 function         | 0.21 equivalent                                                                     |
|-------------------------|-------------------------------------------------------------------------------------|
| `encode()`              | `engine::general_purpose::STANDARD.encode()` or `prelude::BASE64_STANDARD.encode()` |
| `encode_config()`       | `engine.encode()`                                                                   |
| `encode_config_buf()`   | `engine.encode_string()`                                                            |
| `encode_config_slice()` | `engine.encode_slice()`                                                             |
| `decode()`              | `engine::general_purpose::STANDARD.decode()` or `prelude::BASE64_STANDARD.decode()` |
| `decode_config()`       | `engine.decode()`                                                                   |
| `decode_config_buf()`   | `engine.decode_vec()`                                                               |
| `decode_config_slice()` | `engine.decode_slice()`                                                             |

The short-lived 0.20 functions were the 0.13 functions with `config` replaced with `engine`.

##### Padding

If applicable, use the preset engines `engine::STANDARD`, `engine::STANDARD_NO_PAD`, `engine::URL_SAFE`,
or `engine::URL_SAFE_NO_PAD`.
The `NO_PAD` ones require that padding is absent when decoding, and the others require that
canonical padding is present .

If you need the < 0.20 behavior that did not care about padding, or want to recreate < 0.20.0's predefined `Config`s
precisely, see the following table.

| 0.13.1 Config   | 0.20.0+ alphabet | `encode_padding` | `decode_padding_mode` |
|-----------------|------------------|------------------|-----------------------|
| STANDARD        | STANDARD         | true             | Indifferent           |
| STANDARD_NO_PAD | STANDARD         | false            | Indifferent           |
| URL_SAFE        | URL_SAFE         | true             | Indifferent           |
| URL_SAFE_NO_PAD | URL_SAFE         | false            | Indifferent           |

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

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Co-authored-by: cabr2-bot <cabr2.help@gmail.com>
Co-authored-by: crapStone <crapstone01@gmail.com>
Co-authored-by: crapStone <crapstone@noreply.codeberg.org>
Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1709
Reviewed-by: Epsilon_02 <epsilon_02@noreply.codeberg.org>
Co-authored-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
Co-committed-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>

crates/config/Cargo.toml

@@ -10,7 +10,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-base64 = "0.20.0"
+base64 = "0.21.0"
 directories-next = "2.0.0"
 lazy_static = "1.4.0"
 log = "0.4.17"

crates/config/src/handler.rs

@@ -1,5 +1,6 @@
 use std::{collections::HashMap, env, path::PathBuf};
 
+use base64::{prelude::BASE64_STANDARD, Engine};
 use directories_next::ProjectDirs;
 use lazy_static::lazy_static;
 use serde_json::Value;
@@ -15,6 +16,8 @@ use super::{
   types::{BackendConfig, FrontendConfig, GHSSymbols, LocalizedStrings, LocalizedStringsHeader},
 };
 
+const BASE64_IMAGE_TAG: &str = "data:image/image/png;base64,";
+
 lazy_static! {
   pub static ref PROJECT_DIRS: ProjectDirs = ProjectDirs::from("de", "Calciumdibromid", "CaBr2").unwrap();
   pub static ref DATA_DIR: PathBuf = get_program_data_dir();
@@ -81,25 +84,31 @@ pub async fn get_hazard_symbols() -> Result<GHSSymbols> {
 
   let mut symbols = HashMap::new();
   let mut buf = Vec::new();
+  let mut str_buf = BASE64_IMAGE_TAG.to_string();
 
   for filename in symbol_folder
     .read_dir()?
     .filter(|p| p.is_ok())
     .map(|p| p.unwrap().path())
     .filter(|p| p.is_file())
   {
-    buf.clear();
     let mut file = OpenOptions::new().read(true).open(&filename).await?;
+    buf.clear();
     file.read_to_end(&mut buf).await?;
 
+    // trim only base64 data -> reuse buffer
+    str_buf.truncate(BASE64_IMAGE_TAG.len());
+    BASE64_STANDARD.encode_string(&buf, &mut str_buf);
+
     symbols.insert(
       filename
         .file_name()
         .unwrap()
         .to_string_lossy()
         .trim_end_matches(".png")
         .into(),
-      format!("data:image/image/png;base64,{}", base64::encode(&buf)),
+      // clone only allocates .len() bytes
+      str_buf.clone(),
     );
   }