Separate parsing of options functionality

src/hasher/options/common.rs

@@ -1 +1,24 @@
+use std::{collections::BTreeMap, str::FromStr};
+
+use anyhow::Context;
+
 pub const OUTPUT_SIZE_KEY: &str = "output-size";
+
+pub fn parse_option<T: FromStr>(
+    options: &BTreeMap<String, String>,
+    option_key: impl AsRef<str>,
+    default_value: T,
+) -> anyhow::Result<T>
+where
+    <T as FromStr>::Err: std::error::Error + Send + Sync + 'static,
+{
+    let parsed: T = options
+        .get(option_key.as_ref())
+        .cloned()
+        .map(|s| s.parse())
+        .transpose()
+        .context(format!("While parsing option `{}`", option_key.as_ref()))?
+        .unwrap_or(default_value);
+
+    Ok(parsed)
+}

src/hasher/options/k12_options.rs

@@ -1,8 +1,9 @@
 use std::{collections::BTreeMap, num::NonZeroUsize};
 
-use anyhow::Context;
-
-use super::{common::OUTPUT_SIZE_KEY, traits::HashingOptions};
+use super::{
+    common::{parse_option, OUTPUT_SIZE_KEY},
+    traits::HashingOptions,
+};
 
 pub const DEFAULT_OUTPUT_SIZE: NonZeroUsize = match NonZeroUsize::new(32) {
     Some(v) => v,
@@ -17,12 +18,8 @@ impl TryFrom<BTreeMap<String, String>> for K12Options {
     type Error = anyhow::Error;
 
     fn try_from(options: BTreeMap<String, String>) -> Result<Self, Self::Error> {
-        let output_size: NonZeroUsize = options
-            .get(OUTPUT_SIZE_KEY)
-            .cloned()
-            .unwrap_or(DEFAULT_OUTPUT_SIZE.to_string())
-            .parse()
-            .context(format!("While parsing option `{OUTPUT_SIZE_KEY}`"))?;
+        let output_size =
+            parse_option::<NonZeroUsize>(&options, OUTPUT_SIZE_KEY, DEFAULT_OUTPUT_SIZE)?;
 
         Ok(Self { output_size })
     }