Refactored library to take buffers, not Paths

Also made the binary return fancy exit codes and respect debug flag a
bit more.

Author: Pascal Hertleif

Cargo.lock

@@ -5,9 +5,9 @@ authors = ["Pascal Hertleif <[email protected]>"]
 edition = "2018"
 
 [dependencies]
-anyhow = "1.0.33"
 heck = "0.3.1"
 structopt = "0.3.20"
+exitcode = "1.1.2"
 dbc-codegen = { path = ".." }
 
 [[bin]]

dbc-codegen-cli/Cargo.toml

@@ -1,8 +1,8 @@
-use anyhow::Result;
-use std::path::PathBuf;
+use std::fs::File;
+use std::{path::PathBuf, process::exit};
 use structopt::StructOpt;
 
-/// Generate Rust structs from a `dbc` file.
+/// Generate Rust `struct`s from a `dbc` file.
 #[derive(Debug, StructOpt)]
 struct Cli {
     /// Path to a `.dbc` file
@@ -14,8 +14,43 @@ struct Cli {
     debug: bool,
 }
 
-fn main() -> Result<()> {
+fn main() {
     let args = Cli::from_args();
-    dbc_codegen::codegen(args.dbc_path, args.out_path, args.debug)?;
-    Ok(())
+    let dbc_file = std::fs::read(&args.dbc_path).unwrap_or_else(|e| {
+        eprintln!("could not read `{}`: {}", args.dbc_path.display(), e);
+        exit(exitcode::NOINPUT);
+    });
+    let dbc_file_name = args
+        .dbc_path
+        .file_name()
+        .unwrap_or_else(|| args.dbc_path.as_ref())
+        .to_string_lossy();
+
+    if !args.out_path.is_dir() {
+        eprintln!(
+            "Output path needs to point to a directory (checked {})",
+            args.out_path.display()
+        );
+        exit(exitcode::CANTCREAT);
+    }
+
+    let messages_path = args.out_path.join("messages.rs");
+    let mut messages_code = File::create(messages_path).unwrap_or_else(|e| {
+        eprintln!(
+            "Could not create `messages.rs` file in {}: {:?}",
+            args.out_path.display(),
+            e
+        );
+        exit(exitcode::CANTCREAT);
+    });
+
+    dbc_codegen::codegen(&dbc_file_name, &dbc_file, &mut messages_code, args.debug).unwrap_or_else(
+        |e| {
+            eprintln!("could not convert `{}`: {}", args.dbc_path.display(), e);
+            if args.debug {
+                eprintln!("details: {:?}", e);
+            }
+            exit(exitcode::NOINPUT)
+        },
+    )
 }

dbc-codegen-cli/src/main.rs

@@ -1,31 +1,26 @@
-use anyhow::{anyhow, ensure, Context, Result};
+use anyhow::{anyhow, Context, Result};
 use can_dbc::{Message, Signal, ValDescription, ValueDescription, DBC};
 use heck::{CamelCase, SnakeCase};
 use pad::PadAdapter;
-use std::{fs::File, io::BufWriter, io::Write, path::PathBuf};
+use std::io::{BufWriter, Write};
 
 mod includes;
 mod keywords;
 mod pad;
 
-pub fn codegen(dbc_path: PathBuf, out_path: PathBuf, debug: bool) -> Result<()> {
-    let dbc = std::fs::read(&dbc_path)
-        .with_context(|| format!("could not read `{}`", dbc_path.display()))?;
-    let dbc = can_dbc::DBC::from_slice(&dbc)
-        .map_err(|e| anyhow!("Could not parse dbc file: {:#?}", e))?;
+pub fn codegen(dbc_name: &str, dbc_content: &[u8], out: impl Write, debug: bool) -> Result<()> {
+    let dbc = can_dbc::DBC::from_slice(dbc_content).map_err(|e| {
+        let msg = "Could not parse dbc file";
+        if debug {
+            anyhow!("{}: {:#?}", msg, e)
+        } else {
+            anyhow!("{}", msg)
+        }
+    })?;
     if debug {
         eprintln!("{:#?}", dbc);
     }
-
-    ensure!(
-        out_path.is_dir(),
-        "Output path needs to point to a directory"
-    );
-
-    let messages_path = out_path.join("messages.rs");
-    let messages_code =
-        File::create(messages_path).context("Could not create `messages.rs` file")?;
-    let mut w = BufWriter::new(messages_code);
+    let mut w = BufWriter::new(out);
 
     writeln!(&mut w, "// Generated code!")?;
     writeln!(&mut w, "#![no_std]")?;
@@ -34,12 +29,7 @@ pub fn codegen(dbc_path: PathBuf, out_path: PathBuf, debug: bool) -> Result<()>
         "#![allow(unused, clippy::let_and_return, clippy::eq_op)]"
     )?;
     writeln!(&mut w)?;
-    let dbc_file_name = dbc_path.file_name().unwrap_or_else(|| dbc_path.as_ref());
-    writeln!(
-        &mut w,
-        "//! Message definitions from file `{:?}`",
-        dbc_file_name
-    )?;
+    writeln!(&mut w, "//! Message definitions from file `{:?}`", dbc_name)?;
     writeln!(&mut w, "//!")?;
     writeln!(&mut w, "//! - Version: `{:?}`", dbc.version())?;
     writeln!(&mut w)?;

src/lib.rs

@@ -1,11 +1,14 @@
-use std::path::PathBuf;
-
 use anyhow::Result;
+use std::{
+    fs::{self, File},
+    io::BufWriter,
+};
 
 fn main() -> Result<()> {
-    let dbc_file: PathBuf = PathBuf::from("../dbc-examples/example.dbc");
-    let out: PathBuf = PathBuf::from("src/");
+    let dbc_file = fs::read("../dbc-examples/example.dbc")?;
+    let mut out = BufWriter::new(File::create("src/messages.rs")?);
     println!("cargo:rerun-if-changed=../dbc-examples/example.dbc");
-    dbc_codegen::codegen(dbc_file, out, true)?;
+
+    dbc_codegen::codegen("example.dbc", &dbc_file, &mut out, true)?;
     Ok(())
 }