base58: Add error module

In preparation for improving the `base58` error types crate an `error`
module and move the single current error type there. Make the module
public and reexport the type.

base58/src/error.rs

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: CC0-1.0
+
+//! Error code for the `base58` crate.
+
+use core::fmt;
+
+/// An error that might occur during base58 decoding.
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum Error {
+    /// Invalid character encountered.
+    BadByte(u8),
+    /// Checksum was not correct (expected, actual).
+    BadChecksum(u32, u32),
+    /// The length (in bytes) of the object was not correct.
+    ///
+    /// Note that if the length is excessively long the provided length may be an estimate (and the
+    /// checksum step may be skipped).
+    InvalidLength(usize),
+    /// Extended Key version byte(s) were not recognized.
+    InvalidExtendedKeyVersion([u8; 4]),
+    /// Address version byte were not recognized.
+    InvalidAddressVersion(u8),
+    /// Checked data was less than 4 bytes.
+    TooShort(usize),
+}
+
+internals::impl_from_infallible!(Error);
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use Error::*;
+
+        match *self {
+            BadByte(b) => write!(f, "invalid base58 character {:#x}", b),
+            BadChecksum(exp, actual) =>
+                write!(f, "base58ck checksum {:#x} does not match expected {:#x}", actual, exp),
+            InvalidLength(ell) => write!(f, "length {} invalid for this base58 type", ell),
+            InvalidExtendedKeyVersion(ref v) =>
+                write!(f, "extended key version {:#04x?} is invalid for this base58 type", v),
+            InvalidAddressVersion(ref v) =>
+                write!(f, "address version {} is invalid for this base58 type", v),
+            TooShort(_) => write!(f, "base58ck data not even long enough for a checksum"),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for Error {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        use Error::*;
+
+        match self {
+            BadByte(_)
+            | BadChecksum(_, _)
+            | InvalidLength(_)
+            | InvalidExtendedKeyVersion(_)
+            | InvalidAddressVersion(_)
+            | TooShort(_) => None,
+        }
+    }
+}

base58/src/lib.rs

@@ -24,6 +24,8 @@ extern crate std;
 
 static BASE58_CHARS: &[u8] = b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
 
+pub mod error;
+
 #[cfg(not(feature = "std"))]
 pub use alloc::{string::String, vec::Vec};
 use core::{fmt, iter, slice, str};
@@ -32,6 +34,10 @@ pub use std::{string::String, vec::Vec};
 
 use hashes::{sha256d, Hash};
 
+#[rustfmt::skip]                // Keep public re-exports separate.
+#[doc(inline)]
+pub use self::error::Error;
+
 #[rustfmt::skip]
 static BASE58_DIGITS: [Option<u8>; 128] = [
     None,     None,     None,     None,     None,     None,     None,     None,     // 0-7
@@ -207,63 +213,6 @@ impl<T: Default + Copy> SmallVec<T> {
     }
 }
 
-/// An error that might occur during base58 decoding.
-#[derive(Debug, Clone, PartialEq, Eq)]
-#[non_exhaustive]
-pub enum Error {
-    /// Invalid character encountered.
-    BadByte(u8),
-    /// Checksum was not correct (expected, actual).
-    BadChecksum(u32, u32),
-    /// The length (in bytes) of the object was not correct.
-    ///
-    /// Note that if the length is excessively long the provided length may be an estimate (and the
-    /// checksum step may be skipped).
-    InvalidLength(usize),
-    /// Extended Key version byte(s) were not recognized.
-    InvalidExtendedKeyVersion([u8; 4]),
-    /// Address version byte were not recognized.
-    InvalidAddressVersion(u8),
-    /// Checked data was less than 4 bytes.
-    TooShort(usize),
-}
-
-internals::impl_from_infallible!(Error);
-
-impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        use Error::*;
-
-        match *self {
-            BadByte(b) => write!(f, "invalid base58 character {:#x}", b),
-            BadChecksum(exp, actual) =>
-                write!(f, "base58ck checksum {:#x} does not match expected {:#x}", actual, exp),
-            InvalidLength(ell) => write!(f, "length {} invalid for this base58 type", ell),
-            InvalidExtendedKeyVersion(ref v) =>
-                write!(f, "extended key version {:#04x?} is invalid for this base58 type", v),
-            InvalidAddressVersion(ref v) =>
-                write!(f, "address version {} is invalid for this base58 type", v),
-            TooShort(_) => write!(f, "base58ck data not even long enough for a checksum"),
-        }
-    }
-}
-
-#[cfg(feature = "std")]
-impl std::error::Error for Error {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        use Error::*;
-
-        match self {
-            BadByte(_)
-            | BadChecksum(_, _)
-            | InvalidLength(_)
-            | InvalidExtendedKeyVersion(_)
-            | InvalidAddressVersion(_)
-            | TooShort(_) => None,
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use hex::test_hex_unwrap as hex;