add base32 read and write

Cargo.toml

@@ -12,5 +12,16 @@ description = "library for generating TOTP codes (tokens) defined in RFC 6238"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
+[package.metadata.docs.rs]
+features = [ "oathuri" ]
+
+[features]
+default = []
+oathuri = [ "data-encoding", "url", "percent-encoding" ]
+
 [dependencies]
 ring = '0.16'
+data-encoding = { version = "2.3", optional = true }
+percent-encoding = { version = "2.1", optional = true }
+url = { version = "2.2", optional = true }
+zeroize = { version = "1.3", optional = true }

src/lib.rs

@@ -19,6 +19,8 @@
 //! * Read or write QR codes.
 pub mod high_level;
 pub mod low_level;
+#[cfg(feature = "oathuri")]
+pub mod oath_uri;
 
 pub use high_level::TotpGenerator;
 pub use low_level::HashAlgorithm;

src/oath_uri.rs

@@ -0,0 +1,28 @@
+//! Read or write URIs start with `otpauth://totp/`.
+use data_encoding::{DecodeError, BASE32_NOPAD};
+use zeroize::Zeroize;
+
+/// Read key bytes from a base32-encoded String.
+pub fn key_from_base32(mut encoded: String) -> Result<Vec<u8>, DecodeError> {
+    let mut tmp = encoded.to_ascii_uppercase();
+    encoded.zeroize();
+    let output = BASE32_NOPAD.decode(tmp.as_bytes());
+    tmp.zeroize();
+    output
+}
+
+/// Write key bytes to a base32-encoded String in uppercase.
+pub fn key_to_base32_uppercase<T: AsRef<[u8]> + Zeroize>(mut key: T) -> String {
+    let output = BASE32_NOPAD.encode(key.as_ref());
+    key.zeroize();
+    output
+}
+
+/// Write key bytes to a base32-encoded String in lowercase.
+pub fn key_to_base32_lowercase<T: AsRef<[u8]> + Zeroize>(key: T) -> String {
+    let mut uppercase = key_to_base32_uppercase(key);
+    let output = uppercase.to_ascii_lowercase();
+    uppercase.zeroize();
+    output
+}
+