split: add support for -x option (hex suffixes)

Add support for the `-x` command-line option to `split`. This option
causes `split` to produce filenames with hexadecimal suffixes instead
of the default alphabetic suffixes.

src/uu/split/src/split.rs

@@ -32,6 +32,7 @@ static OPT_ADDITIONAL_SUFFIX: &str = "additional-suffix";
 static OPT_FILTER: &str = "filter";
 static OPT_NUMBER: &str = "number";
 static OPT_NUMERIC_SUFFIXES: &str = "numeric-suffixes";
+static OPT_HEX_SUFFIXES: &str = "hex-suffixes";
 static OPT_SUFFIX_LENGTH: &str = "suffix-length";
 static OPT_DEFAULT_SUFFIX_LENGTH: &str = "0";
 static OPT_VERBOSE: &str = "verbose";
@@ -140,6 +141,14 @@ pub fn uu_app<'a>() -> App<'a> {
                 .default_value(OPT_DEFAULT_SUFFIX_LENGTH)
                 .help("use suffixes of length N (default 2)"),
         )
+        .arg(
+            Arg::new(OPT_HEX_SUFFIXES)
+                .short('x')
+                .long(OPT_HEX_SUFFIXES)
+                .takes_value(true)
+                .default_missing_value("0")
+                .help("use hex suffixes starting at 0, not alphabetic"),
+        )
         .arg(
             Arg::new(OPT_VERBOSE)
                 .long(OPT_VERBOSE)
@@ -245,6 +254,8 @@ impl Strategy {
 fn suffix_type_from(matches: &ArgMatches) -> SuffixType {
     if matches.occurrences_of(OPT_NUMERIC_SUFFIXES) > 0 {
         SuffixType::NumericDecimal
+    } else if matches.occurrences_of(OPT_HEX_SUFFIXES) > 0 {
+        SuffixType::NumericHexadecimal
     } else {
         SuffixType::Alphabetic
     }

tests/by-util/test_split.rs

@@ -2,7 +2,7 @@
 //  *
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
-// spell-checker:ignore xzaaa sixhundredfiftyonebytes ninetyonebytes asciilowercase fghij klmno pqrst uvwxyz fivelines
+// spell-checker:ignore xzaaa sixhundredfiftyonebytes ninetyonebytes asciilowercase fghij klmno pqrst uvwxyz fivelines twohundredfortyonebytes
 extern crate rand;
 extern crate regex;
 
@@ -409,6 +409,28 @@ fn test_numeric_dynamic_suffix_length() {
     assert_eq!(file_read(&at, "x9000"), "a");
 }
 
+#[test]
+fn test_hex_dynamic_suffix_length() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    // Split into chunks of one byte each, use hexadecimal digits
+    // instead of letters as file suffixes.
+    //
+    // The input file has (16^2) - 16 + 1 = 241 bytes. This is just
+    // enough to force `split` to dynamically increase the length of
+    // the filename for the very last chunk.
+    //
+    //     x00, x01, x02, ..., xed, xee, xef, xf000
+    //
+    ucmd.args(&["-x", "-b", "1", "twohundredfortyonebytes.txt"])
+        .succeeds();
+    for i in 0..240 {
+        let filename = format!("x{:02x}", i);
+        let contents = file_read(&at, &filename);
+        assert_eq!(contents, "a");
+    }
+    assert_eq!(file_read(&at, "xf000"), "a");
+}
+
 #[test]
 fn test_suffixes_exhausted() {
     new_ucmd!()

tests/fixtures/split/twohundredfortyonebytes.txt

@@ -0,0 +1 @@
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa