arg: parse start

Cargo.toml

@@ -8,6 +8,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+mapcat = { path = "." }
 memmap = "0.7.0"
 num_cpus = "1.13.0"
 smallvec = "1.5.1"

src/arg.rs

@@ -0,0 +1,65 @@
+use std::{fmt,error};
+
+/// Print help message then exit with code `2`.
+pub fn usage() -> !
+{
+    eprintln!("uasge: {} <output file> <input files...>", std::env::args().next().unwrap());
+
+    eprintln!();
+    eprintln!("mapcat v{}: mmap() based file concatenation", env!("CARGO_PKG_VERSION"));
+    eprintln!(" by {} with <3 (licensed GPL3+)", env!("CARGO_PKG_AUTHORS"));
+    eprintln!();
+
+    eprintln!("NOTES:");
+    eprintln!("The output file is required, if one is not provided, we will just print this message and exit with error code `2`. If there are no input files, it will just create an empty output and return with error code `0` (unless there were other errors)");
+    eprintln!("Output files are always clobbered regardless if there are any inputs, or if the concatenation operation succeeds / fails");
+    eprintln!();
+    eprintln!(" (compiled with write parallelisation enabled)"); //TODO: we will eventually feature gate the threaded scheduler based solution. but for now, it is the only one implemented so we'll just print this always
+    
+    std::process::exit(2)
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Operation
+{
+    pub output: String,
+    pub inputs: Vec<String>,
+}
+
+/// Parse the arguments passed to the process
+#[inline] pub fn parse_args() -> Result<Operation, ArgParseError>
+{
+    parse(std::env::args().skip(1))
+}
+
+fn parse<J: Into<String>, I: IntoIterator<Item = J>>(args: I) -> Result<Operation, ArgParseError>
+{
+    let mut args = args.into_iter().map(Into::into);
+
+    let output = args.next().ok_or(ArgParseError::NoOutput)?;
+
+    Ok(
+	Operation {
+	    output,
+	    inputs: args.collect(),
+	}
+    )
+}
+
+#[derive(Debug)]
+pub enum ArgParseError
+{
+    NoOutput,
+}
+
+impl error::Error for ArgParseError{}
+impl fmt::Display for ArgParseError
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	match self {
+	    Self::NoOutput => write!(f, "output file was not provided"),
+	}
+    }
+}
+

src/main.rs

@@ -1,33 +1,38 @@
 #![allow(dead_code)]
 
+
+#[macro_export] macro_rules! unwrap {
+    (return $($code:expr)?; $err:expr) => {
+	{
+	    match $err {
+		Ok(v) => v,
+		Err(e) => {
+		    eprintln!("Error: {}", e);
+		    
+		    #[allow(unused_variables)]
+		    let rc = -1;
+		    $(let rc = $code;)?
+			
+			std::process::exit(rc)
+		},
+	    }
+	}
+    };
+}
+
 mod state;
 mod pool;
 mod map;
 mod job;
 mod work;
+mod arg;
 
 mod consts;
 
-fn usage() -> !
-{
-    eprintln!("uasge: {} <output file> <input files...>", std::env::args().next().unwrap());
 
-    eprintln!();
-    eprintln!("mapcat v{}: mmap() based file concatenation", env!("CARGO_PKG_VERSION"));
-    eprintln!(" by {} with <3 (licensed GPL3+)", env!("CARGO_PKG_AUTHORS"));
-    eprintln!();
-
-    eprintln!("NOTES:");
-    eprintln!("The output file is required, if one is not provided, we will just exit with error code `2`. If there are no input files, it will just create an empty output and return with error code `0` (unless there were other errors)");
-    eprintln!("Output files are always clobbered regardless if there are any inputs, or if the concatenation operation succeeds / fails");
-    eprintln!();
-    eprintln!(" (compiled with write parallelisation enabled)"); //TODO: we will eventually feature gate the threaded scheduler based solution. but for now, it is the only one implemented so we'll just print this always
-    
-    std::process::exit(0)
-}
 
-fn main() {
+fn work(arg::Operation{output, inputs}: arg::Operation) -> Result<(), Box<dyn std::error::Error>>
-    usage()
+{
     // todo:
     //  - create and open output file
     //  - open and stat all input files in order (`job::create_from_file`).
@@ -41,4 +46,14 @@ fn main() {
     //  - Read the completion stream receiver until all file jobs have been signaled as completed
     //  - wait on all worker threads to complete.
     //  - ensure all data was written.
+
+    Ok(())
+}
+
+fn main() {
+    match arg::parse_args() {
+	Ok(op) => unwrap!(return 1; work(op)),
+	Err(arg::ArgParseError::NoOutput) => arg::usage(),
+    }
+    
 }