Merge pull request #9 from scottlamb/pr-max-rows

Support limiting printed bytes

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "pretty-hex"
-version = "0.2.1"
+version = "0.3.0"
 authors = ["Andrei Volnin <[email protected]>"]
 license = "MIT"
 description = "Pretty hex dump of bytes slice in the common style."

src/pretty_hex.rs

@@ -60,6 +60,8 @@ pub struct HexConfig {
     pub group: usize,
     /// Source bytes per chunk (word). 0 for single word.
     pub chunk: usize,
+    /// Maximum bytes to print.
+    pub max_bytes: usize,
 }
 
 /// Default configuration with `title`, `ascii`, 16 source bytes `width` grouped to 4 separate
@@ -72,6 +74,7 @@ impl Default for HexConfig {
             width: 16,
             group: 4,
             chunk: 1,
+            max_bytes: usize::MAX,
         }
     }
 }
@@ -112,18 +115,23 @@ where
     T: AsRef<[u8]> + ?Sized,
     W: fmt::Write,
 {
+    let mut source = source.as_ref();
     if cfg.title {
-        writeln!(writer, "Length: {0} (0x{0:x}) bytes", source.as_ref().len())?;
+        writeln!(writer, "Length: {0} (0x{0:x}) bytes", source.len())?;
     }
 
-    if source.as_ref().is_empty() {
+    if source.is_empty() {
         return Ok(());
     }
 
-    let lines = source.as_ref().chunks(if cfg.width > 0 {
+    let omitted = source.len().checked_sub(cfg.max_bytes);
+    if omitted.is_some() {
+        source = &source[..cfg.max_bytes];
+    }
+    let lines = source.chunks(if cfg.width > 0 {
         cfg.width
     } else {
-        source.as_ref().len()
+        source.len()
     });
     let lines_len = lines.len();
     for (i, row) in lines.enumerate() {
@@ -150,6 +158,9 @@ where
             writeln!(writer)?;
         }
     }
+    if let Some(o) = omitted {
+        write!(writer, "\n...{0} (0x{0:x}) bytes not shown...", o)?;
+    }
     Ok(())
 }
 

tests/tests.rs

@@ -56,6 +56,7 @@ fn test_config() {
         width: 0,
         group: 0,
         chunk: 0,
+        max_bytes: usize::MAX,
     };
     assert!(config_hex(&vec![], cfg).is_empty());
     assert_eq!("2425262728", config_hex(&"$%&'(", cfg));
@@ -108,7 +109,8 @@ fn test_config() {
                 ascii: true,
                 width: 11,
                 group: 2,
-                chunk: 3
+                chunk: 3,
+                max_bytes: usize::MAX,
             }),
         "0000:   000102 030405  060708 090a   ...........\n\
          000b:   0b0c                         .."
@@ -122,7 +124,8 @@ fn test_config() {
                 ascii: true,
                 width: 16,
                 group: 3,
-                chunk: 3
+                chunk: 3,
+                max_bytes: usize::MAX,
             }
         ),
         "0000:   000102 030405 060708  090a0b 0c0d0e 0f   ................\n\
@@ -143,6 +146,27 @@ fn test_config() {
         format!("{}", v.hex_conf(cfg)),
         "00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12"
     );
+
+    let cfg = HexConfig {
+        max_bytes: 16,
+        ..HexConfig::default()
+    };
+    assert_eq!(
+        format!("{:?}", v.hex_conf(cfg)),
+        "Length: 19 (0x13) bytes\n\
+         0000:   00 01 02 03  04 05 06 07  08 09 0a 0b  0c 0d 0e 0f   ................\n\
+         ...3 (0x3) bytes not shown..."
+    );
+    let cfg = HexConfig {
+        max_bytes: 4,
+        ..HexConfig::default()
+    };
+    assert_eq!(
+        format!("{:?}", v.hex_conf(cfg)),
+        "Length: 19 (0x13) bytes\n\
+         0000:   00 01 02 03                                          ....\n\
+         ...15 (0xf) bytes not shown..."
+    );
 }
 
 #[cfg(feature = "alloc")]