b2sum: add support to -l option

src/uu/hashsum/src/hashsum.rs

@@ -65,7 +65,23 @@ fn detect_algo(
         "sha256sum" => ("SHA256", Box::new(Sha256::new()) as Box<dyn Digest>, 256),
         "sha384sum" => ("SHA384", Box::new(Sha384::new()) as Box<dyn Digest>, 384),
         "sha512sum" => ("SHA512", Box::new(Sha512::new()) as Box<dyn Digest>, 512),
-        "b2sum" => ("BLAKE2", Box::new(Blake2b::new()) as Box<dyn Digest>, 512),
+        "b2sum" => match matches.get_one::<usize>("length") {
+            Some(length_in_bits) => {
+                // blake2 output size must be a multiple of 8 bits
+                if length_in_bits % 8 == 0 {
+                    let length_in_bytes = length_in_bits / 8;
+                    (
+                        "BLAKE2",
+                        Box::new(Blake2b::with_output_bytes(length_in_bytes)),
+                        *length_in_bits,
+                    )
+                } else {
+                    crash!(1, "Invalid length (expected a multiple of 8)")
+                }
+            }
+            // by default, blake2 uses 64bytes (512 bits)
+            None => ("BLAKE2", Box::new(Blake2b::new()) as Box<dyn Digest>, 512),
+        },
         "b3sum" => ("BLAKE3", Box::new(Blake3::new()) as Box<dyn Digest>, 256),
         "sha3sum" => match matches.get_one::<usize>("bits") {
             Some(224) => (
@@ -379,6 +395,22 @@ pub fn uu_app_common() -> Command {
         )
 }
 
+pub fn uu_app_length() -> Command {
+    uu_app_opt_length(uu_app_common())
+}
+
+fn uu_app_opt_length(command: Command) -> Command {
+    // Needed for variable-length output sums (e.g. SHAKE)
+    command.arg(
+        Arg::new("length")
+            .short('l')
+            .long("length")
+            .help("digest length in bits; must not exceed the max for the blake2 algorithm (512) and must be a multiple of 8")
+            .value_name("BITS")
+            .value_parser(parse_bit_num),
+    )
+}
+
 pub fn uu_app_b3sum() -> Command {
     uu_app_b3sum_opts(uu_app_common())
 }
@@ -454,7 +486,7 @@ fn uu_app(binary_name: &str) -> Command {
             uu_app_common()
         }
         // b2sum supports the md5sum options plus -l/--length.
-        "b2sum" => uu_app_common(), // TODO: Implement -l/--length
+        "b2sum" => uu_app_length(),
         // These have never been part of GNU Coreutils, but can function with the same
         // options as md5sum.
         "sha3-224sum" | "sha3-256sum" | "sha3-384sum" | "sha3-512sum" => uu_app_common(),

src/uucore/src/lib/features/sum.rs

@@ -38,10 +38,25 @@ pub trait Digest {
     }
 }
 
-pub struct Blake2b(blake2b_simd::State);
+/// first element of the tuple is the blake2b state
+/// second is the number of output bits
+pub struct Blake2b(blake2b_simd::State, usize);
+
+impl Blake2b {
+    /// Return a new Blake2b instance with a custom output bytes length
+    pub fn with_output_bytes(output_bytes: usize) -> Self {
+        let mut params = blake2b_simd::Params::new();
+        params.hash_length(output_bytes);
+
+        let state = params.to_state();
+        Self(state, output_bytes * 8)
+    }
+}
+
 impl Digest for Blake2b {
     fn new() -> Self {
-        Self(blake2b_simd::State::new())
+        // by default, Blake2b output is 512 bits long (= 64B)
+        Self::with_output_bytes(64)
     }
 
     fn hash_update(&mut self, input: &[u8]) {
@@ -54,11 +69,11 @@ impl Digest for Blake2b {
     }
 
     fn reset(&mut self) {
-        *self = Self::new();
+        *self = Self::with_output_bytes(self.output_bytes());
     }
 
     fn output_bits(&self) -> usize {
-        512
+        self.1
     }
 }