refactor: Utility to load CPU template

There are (or will be) multiple places that load CPU template. Makes it
as a utility function.

Signed-off-by: Takahiro Itazuri <[email protected]>

Author: zulinx86

src/cpu-template-helper/src/main.rs

@@ -7,8 +7,6 @@ use std::path::PathBuf;
 use clap::{Parser, Subcommand, ValueEnum};
 use vmm::cpu_config::templates::{GetCpuTemplate, GetCpuTemplateError};
 
-use crate::utils::UtilsError;
-
 mod fingerprint;
 mod template;
 mod utils;
@@ -26,7 +24,7 @@ enum HelperError {
     /// Failed to serialize/deserialize JSON file: {0}
     Serde(#[from] serde_json::Error),
     /// {0}
-    Utils(#[from] UtilsError),
+    Utils(#[from] utils::UtilsError),
     /// {0}
     TemplateDump(#[from] template::dump::DumpError),
     /// {0}
@@ -127,12 +125,10 @@ fn run(cli: Cli) -> Result<(), HelperError> {
                 write(output, cpu_config_json)?;
             }
             TemplateOperation::Strip { paths, suffix } => {
-                let mut templates = Vec::with_capacity(paths.len());
-                for path in &paths {
-                    let template_json = read_to_string(path)?;
-                    let template = serde_json::from_str(&template_json)?;
-                    templates.push(template);
-                }
+                let templates = paths
+                    .iter()
+                    .map(utils::load_cpu_template)
+                    .collect::<Result<Vec<_>, utils::UtilsError>>()?;
 
                 let stripped_templates = template::strip::strip(templates)?;
 
@@ -144,13 +140,10 @@ fn run(cli: Cli) -> Result<(), HelperError> {
             }
             TemplateOperation::Verify { config, template } => {
                 let config = config.map(read_to_string).transpose()?;
-                let template = match template {
-                    Some(path) => {
-                        let template_json = read_to_string(path)?;
-                        Some(serde_json::from_str(&template_json)?)
-                    }
-                    None => None,
-                };
+                let template = template
+                    .as_ref()
+                    .map(utils::load_cpu_template)
+                    .transpose()?;
                 let (vmm, vm_resources) = utils::build_microvm_from_config(config, template)?;
 
                 let cpu_template = vm_resources

src/cpu-template-helper/src/utils/mod.rs

@@ -3,6 +3,7 @@
 
 use std::ffi::OsString;
 use std::fmt::Display;
+use std::fs::read_to_string;
 use std::hash::Hash;
 use std::io::Write;
 use std::path::{Path, PathBuf};
@@ -70,6 +71,14 @@ pub enum UtilsError {
     CreateTempFile(#[from] vmm_sys_util::errno::Error),
     /// Failed to operate file: {0}
     FileIo(#[from] std::io::Error),
+    /// Failed to serialize/deserialize JSON file: {0}
+    Serde(#[from] serde_json::Error),
+}
+
+pub fn load_cpu_template(path: &PathBuf) -> Result<CustomCpuTemplate, UtilsError> {
+    let template_json = read_to_string(path)?;
+    let template = serde_json::from_str(&template_json)?;
+    Ok(template)
 }
 
 // Utility function to prepare scratch kernel image and rootfs and build mock Firecracker config.