i think it works

Cargo.toml

@@ -13,7 +13,7 @@ members = [
 default-members = [".", "members/libpt-bin", "members/libpt-core"]
 [workspace.package]
 publish = true
-version = "0.1.7"
+version = "0.1.8"
 edition = "2021"
 authors = ["Christoph J. Scherr <software@cscherr.de>"]
 license = "MIT"

members/libpt-bin/src/hedu/mod.rs

@@ -63,6 +63,10 @@ pub struct Cli {
     #[arg(short, long, global = true)]
     pub log_meta: bool,
 
+    /// show character representation
+    #[arg(short, long, global = true)]
+    pub chars: bool,
+
     /// a data source, probably a file
     pub data_source: String,
 }
@@ -82,7 +86,7 @@ fn main() {
             std::process::exit(1);
         }
     };
-    match dump(BufReader::new(file)) {
+    match dump(BufReader::new(file), cli.chars) {
         Ok(_) => (),
         Err(err) => {
             error!("Could not dump data of file: {err}");

members/libpt-hedu/src/lib.rs

@@ -5,24 +5,82 @@
 //!
 //! This crate is currently empty.
 
-use anyhow::Result;
+use anyhow::{bail, Result};
-use std::{
+use std::io::{prelude::*, BufReader};
-    fmt::Debug,
-    io::{prelude::*, BufRead, BufReader, Bytes},
-};
 
-pub fn dump<T>(mut data: BufReader<T>) -> Result<()>
+const BYTES_PER_LINE: usize = 16;
+const LINE_SEP_HORIZ: char = '─';
+const LINE_SEP_VERT: char = '│';
+
+pub fn dump<T>(mut data: BufReader<T>, chars: bool) -> Result<()>
 where
     T: Read,
 {
-    for (i, b) in data.bytes().enumerate() {
+    let mut buf: [u8; BYTES_PER_LINE] = [0; BYTES_PER_LINE];
-        if i % 8 == 0 {
+    let mut line_counter: usize = 0;
-            print!("{:08X}\t", i);
+    let mut len: usize;
+    // print the head
+    print!("LINE IDX {LINE_SEP_VERT} DATA AS HEX");
+    if chars {
+        print!("{:width$} {LINE_SEP_VERT} FOO", "", width = 37);
     }
-        print!("{:02X?} ", b.unwrap());
-        if i % 8 == 7 {
     println!();
+    if chars {
+        println!("{}", format!("{LINE_SEP_HORIZ}").repeat(78));
+    } else {
+        println!("{}", format!("{LINE_SEP_HORIZ}").repeat(59));
     }
+    // data dump loop
+    len = rd_data(&mut data, &mut buf).unwrap();
+    while len > 0 {
+        print!("{:08X} {LINE_SEP_VERT} ", line_counter);
+        for i in 0..len {
+            if i as usize % BYTES_PER_LINE == BYTES_PER_LINE / 2 {
+                print!(" ");
+            }
+            print!("{:02X} ", buf[i]);
+        }
+        for i in 0..(BYTES_PER_LINE - len) {
+            if i as usize % BYTES_PER_LINE == BYTES_PER_LINE / 2 {
+                print!(" ");
+            }
+            print!("   ");
+        }
+        if chars {
+            print!("{LINE_SEP_VERT} ");
+            for i in 0..len {
+                print!("{}", mask_chars(buf[i] as char));
+            }
+        }
+        line_counter += 1;
+        println!();
+        len = rd_data(&mut data, &mut buf).unwrap();
     }
     Ok(())
 }
+
+fn mask_chars(c: char) -> char {
+    if c.is_ascii_graphic() {
+        return c;
+    } else if c == '\n' {
+        return '↩';
+    } else if c == ' ' {
+        return '␣';
+    } else if c == '\t' {
+        return '⭾';
+    } else {
+        return '<27>';
+    }
+}
+
+fn rd_data<T>(data: &mut BufReader<T>, mut buf: &mut [u8]) -> Result<usize>
+where
+    T: Read,
+{
+    match data.read(&mut buf) {
+        Ok(len) => Ok(len),
+        Err(err) => {
+            bail!(err)
+        }
+    }
+}