X-Git-Url: https://piware.de/gitweb/?p=learn-rust.git;a=blobdiff_plain;f=src%2Fmain.rs;h=c07c4051165861365a2176a3c1edec6957d16903;hp=e61306ac95077cf475e0b60fd11d573531a09e2d;hb=dad4fd7e6684ffa911c1298e374a56d63a56710e;hpb=98ca13fb871858f407a9b2682a4e439d0557a4f7

diff --git a/src/main.rs b/src/main.rs
index e61306a..c07c405 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,8 @@
 mod word_utils;
 
 use std::collections::HashMap;
+use std::io::{prelude::*, ErrorKind};
+use std::fs::{self, File};
 
 use word_utils::{first_word, second_word};
 
@@ -67,8 +69,56 @@ fn test_hashmaps() {
     println!("collect_scores after rebuilding with doubling: {:?}", collect_scores);
 }
 
+fn read_file(path: &str) -> Result<String, std::io::Error> {
+    let mut s = String::new();
+    File::open(path)?
+        .read_to_string(&mut s)?;
+    Ok(s)
+}
+
+fn test_files() {
+    if let Ok(mut f) = File::open("Cargo.toml") {
+        let mut contents = String::new();
+        match f.read_to_string(&mut contents) {
+            Ok(len) => println!("successfully opened Cargo.toml: {:?}, contents {} bytes:\n{}\n----------", f, len, contents),
+            Err(e) => panic!("could not read file: {:?}", e)
+        }
+    } else {
+        println!("could not open Cargo.toml");
+    }
+
+    // alternative form, more specific error checking
+    let mut f = File::open("Cargo.toml").unwrap_or_else(|e| {
+        if e.kind() == ErrorKind::NotFound {
+            println!("Cargo.toml not found, falling back to /dev/null");
+            // need to return a File
+            File::open("/dev/null").unwrap()
+        } else {
+            panic!("Could not open Cargo.toml: {:?}", e);
+        }
+    });
+    let mut contents = String::new();
+    let len = f.read_to_string(&mut contents).unwrap_or_else(|e| {
+        panic!("Could not read file: {:?}", e);
+    });
+    println!("successfully opened Cargo.toml with unwrap_or_else: {:?}, contents {} bytes:\n{}\n----------", f, len, contents);
+
+    // using the '?' operator
+    match read_file("Cargo.toml") {
+        Ok(s) => println!("Cargo.toml contents:\n{}\n-------------", s),
+        Err(e) => println!("Could not open Cargo.toml: {:?}", e)
+    }
+
+    // using std API
+    match fs::read_to_string("Cargo.toml") {
+        Ok(s) => println!("Cargo.toml contents:\n{}\n-------------", s),
+        Err(e) => println!("Could not open Cargo.toml: {:?}", e)
+    }
+}
+
 fn main() {
     test_strings();
     test_vectors();
     test_hashmaps();
+    test_files();
 }