Merge pull request #17 from laysakura/section-3_1

3.1: `std::io::Read` を実装した何かから最大1024bytes読み込んで HEX 表示するプログラム

Author: yuk1ty

chapter3/Cargo.toml

@@ -7,3 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+
+[[bin]]
+name = "main_3_1"
+path = "src/3_1/main.rs"

chapter3/src/3_1/bytes_read.rs

@@ -0,0 +1,19 @@
+use std::fmt::Display;
+
+#[derive(Debug)]
+pub(super) struct BytesRead {
+    bytes: Vec<u8>,
+    len: usize,
+}
+
+impl BytesRead {
+    pub(super) fn new(bytes: Vec<u8>, len: usize) -> Self {
+        Self { bytes, len }
+    }
+}
+
+impl Display for BytesRead {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{} bytes read:\n{:02x?}", self.len, self.bytes)
+    }
+}

chapter3/src/3_1/main.rs

@@ -0,0 +1,21 @@
+mod bytes_read;
+
+use std::{fs::File, io};
+
+use bytes_read::BytesRead;
+
+/// Reads up to 1024 bytes from `r`.
+fn read_1024bytes<R: io::Read>(r: &mut R) -> io::Result<BytesRead> {
+    let mut buf = [0u8; 1024];
+    let len = r.read(&mut buf)?;
+    Ok(BytesRead::new(buf.into(), len))
+}
+
+fn main() -> io::Result<()> {
+    let mut f = File::open("Cargo.toml")?;
+
+    let bytes_read = read_1024bytes(&mut f)?;
+    println!("{}", bytes_read);
+
+    Ok(())
+}