chore: checkpoint before Python removal

vendor/ssh-key/src/fingerprint/randomart.rs

@@ -0,0 +1,113 @@
+//! Support for the "drunken bishop" fingerprint algorithm, a.k.a. "randomart".
+//!
+//! The algorithm is described in the paper:
+//!
+//! "The drunken bishop: An analysis of the OpenSSH fingerprint visualization algorithm"
+//!
+//! <http://www.dirk-loss.de/sshvis/drunken_bishop.pdf>
+
+use super::Fingerprint;
+use core::fmt;
+
+const WIDTH: usize = 17;
+const HEIGHT: usize = 9;
+const VALUES: &[u8; 17] = b" .o+=*BOX@%&#/^SE";
+const NVALUES: u8 = VALUES.len() as u8 - 1;
+
+type Field = [[u8; WIDTH]; HEIGHT];
+
+/// "randomart" renderer.
+pub(super) struct Randomart<'a> {
+    header: &'a str,
+    field: Field,
+    footer: &'static str,
+}
+
+impl<'a> Randomart<'a> {
+    /// Create new "randomart" from the given fingerprint.
+    // TODO: Remove this when the pipeline toolchain is updated beyond 1.69
+    #[allow(clippy::arithmetic_side_effects)]
+    pub(super) fn new(header: &'a str, fingerprint: Fingerprint) -> Self {
+        let mut field = Field::default();
+        let mut x = WIDTH / 2;
+        let mut y = HEIGHT / 2;
+
+        for mut byte in fingerprint.as_bytes().iter().copied() {
+            for _ in 0..4 {
+                if byte & 0x1 == 0 {
+                    x = x.saturating_sub(1);
+                } else {
+                    x = x.saturating_add(1);
+                }
+
+                if byte & 0x2 == 0 {
+                    y = y.saturating_sub(1);
+                } else {
+                    y = y.saturating_add(1);
+                }
+
+                x = x.min(WIDTH.saturating_sub(1));
+                y = y.min(HEIGHT.saturating_sub(1));
+
+                if field[y][x] < NVALUES - 2 {
+                    field[y][x] = field[y][x].saturating_add(1);
+                }
+
+                byte >>= 2;
+            }
+        }
+
+        field[HEIGHT / 2][WIDTH / 2] = NVALUES - 1;
+        field[y][x] = NVALUES;
+
+        Self {
+            header,
+            field,
+            footer: fingerprint.footer(),
+        }
+    }
+}
+
+impl fmt::Display for Randomart<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        writeln!(f, "+{:-^width$}+", self.header, width = WIDTH)?;
+
+        for row in self.field {
+            write!(f, "|")?;
+
+            for c in row {
+                write!(f, "{}", VALUES[c as usize] as char)?;
+            }
+
+            writeln!(f, "|")?;
+        }
+
+        write!(f, "+{:-^width$}+", self.footer, width = WIDTH)
+    }
+}
+
+#[cfg(all(test, feature = "alloc"))]
+mod tests {
+    use super::Fingerprint;
+
+    const EXAMPLE_FINGERPRINT: &str = "SHA256:UCUiLr7Pjs9wFFJMDByLgc3NrtdU344OgUM45wZPcIQ";
+    const EXAMPLE_RANDOMART: &str = "\
++--[ED25519 256]--+
+|o+oO==+ o..      |
+|.o++Eo+o..       |
+|. +.oO.o . .     |
+| . o..B.. . .    |
+|  ...+ .S. o     |
+|  .o. . . . .    |
+|  o..    o       |
+|   B      .      |
+|  .o*            |
++----[SHA256]-----+";
+
+    #[test]
+    fn generation() {
+        let fingerprint = EXAMPLE_FINGERPRINT.parse::<Fingerprint>().unwrap();
+        let randomart = fingerprint.to_randomart("[ED25519 256]");
+        assert_eq!(EXAMPLE_RANDOMART, randomart);
+    }
+}