Add --buffered and same stream check

Before this, running the program with the same input and output file
would destroy the file's contents. Now, it isn't allowed without the new
--buffered option, which reads the whole file into memory before opening
it for writing.

This requires stevedonovan/lapp#1 to be merged so for now this version
is not publishable to crates.io as it is using my fork of lapp.

Cargo.lock

@@ -3,7 +3,7 @@
 [[package]]
 name = "lapp"
 version = "0.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
+source = "git+https://github.com/NoraCodes/lapp?branch=nora/iofile_paths#0fb2df69ce5262958401214fca0d0f31d62b1062"
 
 [[package]]
 name = "smallvec"
@@ -20,13 +20,13 @@ dependencies = [
 
 [[package]]
 name = "utf8-norm"
-version = "1.0.1"
+version = "1.1.0"
 dependencies = [
- "lapp 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lapp 0.4.0 (git+https://github.com/NoraCodes/lapp?branch=nora/iofile_paths)",
  "unicode-normalization 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [metadata]
-"checksum lapp 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "60bf485afeba9437a275ad29a9383b03f2978450e7feceffb55be8c0dbad9829"
+"checksum lapp 0.4.0 (git+https://github.com/NoraCodes/lapp?branch=nora/iofile_paths)" = "<none>"
 "checksum smallvec 0.6.10 (registry+https://github.com/rust-lang/crates.io-index)" = "ab606a9c5e214920bb66c458cd7be8ef094f813f20fe77a54cc7dbfff220d4b7"
 "checksum unicode-normalization 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "141339a08b982d942be2ca06ff8b076563cbe223d1befd5450716790d44e2426"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "utf8-norm"
-version = "1.0.1"
+version = "1.1.0"
 authors = ["Leonora Tindall <nora@nora.codes>"]
 edition = "2018"
 license = "GPL-3.0-only"
@@ -12,6 +12,6 @@ keywords = ["unicode", "normalize"]
 categories = ["command-line-utilities", "internationalization", "localization", "text-processing"]
 
 [dependencies]
-lapp = "0.4"
+lapp = { git = "https://github.com/NoraCodes/lapp", branch = "nora/iofile_paths" }
 unicode-normalization = "0.1"
 

README

@@ -1,9 +1,13 @@
 utf8-norm, validate and normalize UTF-8 Unicode data
 
-Version 1.0.1 licensed GPLv3. (C) 2019 Leonora Tindall <nora@nora.codes>
+ABOUT
+
+Version 1.1.0 licensed GPLv3. (C) 2019 Leonora Tindall <nora@nora.codes>
 Fast command line Unicode normalization, supporting stream safety transformations as well
 as NFC, NFD, NFKD, and NFKC. Exits with failure if the incoming stream is not valid UTF-8.
 
+USAGE
+
 Usage: utf8-norm [--nfc | --nfd | --nfkc | --nfkd] [--stream-safe] [--crlf] <infile> <outfile>
 
     <infile> (default stdin) - file from which to read bytes.
@@ -14,7 +18,12 @@ Usage: utf8-norm [--nfc | --nfd | --nfkc | --nfkd] [--stream-safe] [--crlf] <inf
     -c, --nfc   - write NFC (canonical composition computed from NFD). This is the default.
     -C, --nfkc  - write NFKC (canonical composition computed from NFC).
     -s, --stream-safe   - write stream-safe bytes (Conjoining Grapheme Joiners, UAX15-D4).
-    -V, --version - output version information and exit
+    -b, --buffered  - read the entire input file into memory before operating on it.
+    -V, --version - output version information and exit.
+
+The --buffered option is primarily useful for reading and writing to the same file. It will
+read bytes from the input until end of file and only then begin processing lines of the
+input.
 
 utf8-norm was created at Rust Belt Rust 2019 in Dayton, OH. Thanks to @j41manning for her
 excellent talk regarding Unicode handling in Rust.

src/main.rs

@@ -1,6 +1,6 @@
 extern crate lapp;
 extern crate unicode_normalization;
-use std::io::{BufRead, BufReader, BufWriter, Write};
+use std::io::{BufRead, BufReader, BufWriter, Write, Cursor};
 use unicode_normalization::UnicodeNormalization;
 
 // usize because that's the max number of bools in the slice
@@ -16,8 +16,6 @@ fn main() {
     let usage = include_str!("../README");
     let args = lapp::parse_args(&usage);
 
-    let infile = BufReader::new(args.get_infile("infile"));
-    let mut outfile = BufWriter::new(args.get_outfile("outfile"));    
 
     if args.get_bool("version") {
         println!("Version {} licensed GPLv3. (C) 2019 Leonora Tindall <nora@nora.codes>",
@@ -25,6 +23,11 @@ fn main() {
         std::process::exit(0);
     }
 
+    if !args.get_bool("buffered") && args.get_path("infile") == args.get_path("outfile") {
+        eprintln!("Warning: input and output file are the same. This is not supported without using --buffered, because it would result in removing the file without processing any input.");
+        std::process::exit(128);
+    } 
+
     let nfd = args.get_bool("nfd");
     let nfkd = args.get_bool("nfkd");
     let nfc = args.get_bool("nfc");
@@ -33,10 +36,26 @@ fn main() {
 
     if trues(&[nfd, nfkd, nfc, nfkc]) > 1 {
         eprintln!("--nfd, --nfkd, --nfc, and --nfkc are mutually exclusive.");
-        std::process::exit(1);
+        std::process::exit(128);
     } 
 
-    for line in infile.lines() {
+    // If buffering is needed, we have to read the whole file BEFORE opening it for
+    // writing, or else it will be truncated and all the contents will be lost.
+    let instream: Box<dyn BufRead> = {
+        if args.get_bool("buffered") {
+            let mut buffer = Vec::new();
+            args.get_infile("infile")
+                .read_to_end(&mut buffer)
+                .expect("Could not read input file into buffer. Error");
+            Box::new(Cursor::new(buffer))
+        } else {
+            Box::new(BufReader::new(args.get_infile("infile")))
+        }
+    };
+
+    let mut outfile = BufWriter::new(args.get_outfile("outfile"));    
+
+    for line in instream.lines() {
         let mut line = line.expect("Could not read line from file. Error").clone();
         if args.get_bool("crlf") {
             line.push('\x0D');