Bug 1473202 - Part 1: Skip overwriting BinAST auto-generated file if the content is same. r=Yoric

use std::collections::{ HashMap, HashSet };

use std::fs::*;

use std::io::{ Read, Write };

use std::path::Path;

use clap::{ App, Arg };

    let global_rules = GlobalRules::new(&new_syntax, &yaml[0]);

    let exporter = CPPExporter::new(new_syntax, global_rules);

    let get_file_content = |path: &str| {

        if !Path::new(path).is_file() {

            return None;

        }

        let mut f = File::open(path)

            .expect("File not found");

        let mut contents = String::new();

        f.read_to_string(&mut contents)

            .expect("Failed to read file");

        Some(contents)

    };

    let write_to = |description, arg, data: &String| {

        let dest_path = matches.value_of(arg)

            .unwrap();

        println!("...exporting {description}: {path}",

        print!("...exporting {description}: {path} ... ",

            description = description,

            path = dest_path);

        if let Some(old_data) = get_file_content(dest_path) {

            if old_data == *data {

                // To avoid unnecessary rebuild, do not touch the file if the

                // content is not updated.

                println!("skip");

                return;

            }

        };

        let mut dest = File::create(&dest_path)

            .unwrap_or_else(|e| panic!("Could not create {description} at {path}: {error}",

                            description = description,

                            description = description,

                            path = dest_path,

                            error = e));

        println!("done");

    };

    write_to("C++ class header code", "OUT_HEADER_CLASS_FILE",