From 15a9e678c648076e3f88fff0272b6f9a3f410e7e Mon Sep 17 00:00:00 2001
From: matcap <matcap94@gmail.com>
Date: Sun, 16 Jul 2023 16:16:25 +0200
Subject: [PATCH 1/3] optional offset added to displayed address prefix

---
 src/pretty_hex.rs |  5 ++++-
 tests/tests.rs    | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/pretty_hex.rs b/src/pretty_hex.rs
index 1337812..97f6f5a 100644
--- a/src/pretty_hex.rs
+++ b/src/pretty_hex.rs
@@ -62,6 +62,8 @@ pub struct HexConfig {
     pub chunk: usize,
     /// Maximum bytes to print.
     pub max_bytes: usize,
+    /// Offset added to displayed address prefix
+    pub display_offset: usize,
 }
 
 /// Default configuration with `title`, `ascii`, 16 source bytes `width` grouped to 4 separate
@@ -75,6 +77,7 @@ impl Default for HexConfig {
             group: 4,
             chunk: 1,
             max_bytes: usize::MAX,
+            display_offset: 0,
         }
     }
 }
@@ -136,7 +139,7 @@ where
     let lines_len = lines.len();
     for (i, row) in lines.enumerate() {
         if cfg.width > 0 {
-            write!(writer, "{:04x}:   ", i * cfg.width)?;
+            write!(writer, "{:04x}:   ", i * cfg.width + cfg.display_offset)?;
         }
         for (i, x) in row.as_ref().iter().enumerate() {
             write!(writer, "{}{:02x}", cfg.delimiter(i), x)?;
diff --git a/tests/tests.rs b/tests/tests.rs
index 4d5b5d0..3d01907 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -57,6 +57,7 @@ fn test_config() {
         group: 0,
         chunk: 0,
         max_bytes: usize::MAX,
+        display_offset: 0
     };
     assert!(config_hex(&vec![], cfg).is_empty());
     assert_eq!("2425262728", config_hex(&"$%&'(", cfg));
@@ -95,6 +96,18 @@ fn test_config() {
          0010:   89d5 cf90 2367 4b48  dbb1 bc35 bfee"
     );
 
+    assert_eq!(
+        config_hex(&v,
+            HexConfig {
+                ascii: false,
+                display_offset: 0x200,
+                ..cfg
+            }
+        ),
+        "0200:   6b 4e 1a c3 af 03 d2 1e  7e 73 ba c8 bd 84 0f 83\n\
+         0210:   89 d5 cf 90 23 67 4b 48  db b1 bc 35 bf ee"
+    );
+
     let v: Vec<u8> = (0..21).collect();
     let want = r##"Length: 21 (0x15) bytes
 0000:   00 01 02 03  04 05 06 07  08 09 0a 0b  0c 0d 0e 0f   ................
@@ -111,6 +124,7 @@ fn test_config() {
                 group: 2,
                 chunk: 3,
                 max_bytes: usize::MAX,
+                display_offset: 0
             }),
         "0000:   000102 030405  060708 090a   ...........\n\
          000b:   0b0c                         .."
@@ -126,6 +140,7 @@ fn test_config() {
                 group: 3,
                 chunk: 3,
                 max_bytes: usize::MAX,
+                display_offset: 0
             }
         ),
         "0000:   000102 030405 060708  090a0b 0c0d0e 0f   ................\n\

From 78e0aad90b72f51fdcda4f1d29a698567b94fd8b Mon Sep 17 00:00:00 2001
From: matcap <matcap94@gmail.com>
Date: Sun, 16 Jul 2023 17:35:12 +0200
Subject: [PATCH 2/3] variable address prefix width

---
 src/pretty_hex.rs | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/pretty_hex.rs b/src/pretty_hex.rs
index 97f6f5a..fc284c2 100644
--- a/src/pretty_hex.rs
+++ b/src/pretty_hex.rs
@@ -112,6 +112,18 @@ impl HexConfig {
 
 const NON_ASCII: char = '.';
 
+
+type AddressWriter = dyn Fn(&mut dyn fmt::Write, usize) -> fmt::Result;
+
+fn get_address_writer(max_addr: usize) -> &'static AddressWriter{
+    match max_addr {
+        0x0000..=0xffff => &|w: &mut dyn fmt::Write, a| write!(w, "{:04x}:   ", a),
+        0x010000..=0xffffff => &|w: &mut dyn fmt::Write, a|  write!(w, "{:06x}:   ", a),
+        0x01000000..=0xffffffff => &|w: &mut dyn fmt::Write, a|  write!(w, "{:08x}:   ", a),
+        _ => &|w: &mut dyn fmt::Write, a|  write!(w, "{:016x}:   ", a)
+    }
+}
+
 /// Write hex dump in specified format.
 pub fn hex_write<T, W>(writer: &mut W, source: &T, cfg: HexConfig) -> fmt::Result
 where
@@ -136,10 +148,15 @@ where
     } else {
         source.len()
     });
+
     let lines_len = lines.len();
+
+    let max_address = source.len() - cfg.width + cfg.display_offset;
+    let write_address = get_address_writer(max_address);
+
     for (i, row) in lines.enumerate() {
         if cfg.width > 0 {
-            write!(writer, "{:04x}:   ", i * cfg.width + cfg.display_offset)?;
+            write_address(writer, i * cfg.width + cfg.display_offset)?;
         }
         for (i, x) in row.as_ref().iter().enumerate() {
             write!(writer, "{}{:02x}", cfg.delimiter(i), x)?;

From 4d7902036881a5d93286c72fffc3a7b10e16644d Mon Sep 17 00:00:00 2001
From: matcap <matcap94@gmail.com>
Date: Sun, 23 Jul 2023 20:00:01 +0200
Subject: [PATCH 3/3] check for underflow when calculating maximum address
 prefix

---
 src/pretty_hex.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/pretty_hex.rs b/src/pretty_hex.rs
index fc284c2..28a2db0 100644
--- a/src/pretty_hex.rs
+++ b/src/pretty_hex.rs
@@ -151,7 +151,11 @@ where
 
     let lines_len = lines.len();
 
-    let max_address = source.len() - cfg.width + cfg.display_offset;
+    let max_address = if source.len() <= cfg.width {
+        source.len() + cfg.display_offset
+    } else {
+        source.len() - cfg.width + cfg.display_offset
+    };
     let write_address = get_address_writer(max_address);
 
     for (i, row) in lines.enumerate() {