Add the DeviceInfo struct

In the next patch, we will add support for the NK_list_devices functions
that returns a list of NK_device_info structs with information about the
connected devices.  This patch introduces the DeviceInfo struct that
holds the information returned by NK_list_devices and that can be
created from a NK_device_info struct.

2 files changed, 105 insertions, 4 deletions

diff --git a/src/device/mod.rs b/src/device/mod.rs
index a3a0255..e015886 100644
--- a/src/device/mod.rs
+++ b/src/device/mod.rs
@@ -5,7 +5,9 @@ mod pro;
 mod storage;
 mod wrapper;
 
-use std::convert::TryFrom;
+use std::cmp;
+use std::convert::{TryFrom, TryInto};
+use std::ffi;
 use std::fmt;
 
 use libc;
@@ -17,7 +19,8 @@ use crate::error::{CommunicationError, Error};
 use crate::otp::GenerateOtp;
 use crate::pws::GetPasswordSafe;
 use crate::util::{
-    get_command_result, get_cstring, get_last_error, result_from_string, result_or_error,
+    get_command_result, get_cstring, get_last_error, owned_str_from_ptr, result_from_string,
+    result_or_error,
 };
 
 pub use pro::Pro;
@@ -68,6 +71,73 @@ impl TryFrom<nitrokey_sys::NK_device_model> for Model {
     }
 }
 
+/// Connection information for a Nitrokey device.
+#[derive(Clone, Debug, PartialEq)]
+pub struct DeviceInfo {
+    /// The model of the Nitrokey device, or `None` if the model is not supported by this crate.
+    pub model: Option<Model>,
+    /// The USB device path.
+    pub path: String,
+    /// The serial number as a 8-character hex string, or `None` if the device does not expose its
+    /// serial number.
+    pub serial_number: Option<String>,
+}
+
+impl TryFrom<&nitrokey_sys::NK_device_info> for DeviceInfo {
+    type Error = Error;
+
+    fn try_from(device_info: &nitrokey_sys::NK_device_info) -> Result<DeviceInfo, Error> {
+        let model_result = device_info.model.try_into();
+        let model_option = model_result.map(Some).or_else(|err| match err {
+            Error::UnsupportedModelError => Ok(None),
+            _ => Err(err),
+        })?;
+        let serial_number = unsafe { ffi::CStr::from_ptr(device_info.serial_number) }
+            .to_str()
+            .map_err(Error::from)?;
+        Ok(DeviceInfo {
+            model: model_option,
+            path: owned_str_from_ptr(device_info.path)?,
+            serial_number: get_hidapi_serial_number(serial_number),
+        })
+    }
+}
+
+impl fmt::Display for DeviceInfo {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.model {
+            Some(model) => write!(f, "Nitrokey {}", model)?,
+            None => write!(f, "Unsupported Nitrokey model")?,
+        }
+        write!(f, " at {} with ", self.path)?;
+        match &self.serial_number {
+            Some(ref serial_number) => write!(f, "serial no. {}", serial_number),
+            None => write!(f, "an unknown serial number"),
+        }
+    }
+}
+
+/// Parses a serial number returned by hidapi and transforms it to the Nitrokey format.
+///
+/// If the serial number is all zero, this function returns `None`.  Otherwise, all leading zeros
+/// (except the last eight characters) are stripped and `Some(_)` is returned.  If the serial
+/// number has less than eight characters, leading zeros are added.
+fn get_hidapi_serial_number(serial_number: &str) -> Option<String> {
+    let mut iter = serial_number.char_indices().skip_while(|(_, c)| *c == '0');
+    let first_non_null = iter.next();
+    if let Some((i, _)) = first_non_null {
+        // keep at least the last 8 characters
+        let len = serial_number.len();
+        let cut = cmp::min(len.saturating_sub(8), i);
+        let (_, suffix) = serial_number.split_at(cut);
+        // if necessary, add leading zeros to reach 8 characters
+        let fill = 8usize.saturating_sub(len);
+        Some("0".repeat(fill) + suffix)
+    } else {
+        None
+    }
+}
+
 /// A firmware version for a Nitrokey device.
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct FirmwareVersion {
@@ -476,3 +546,34 @@ pub(crate) fn get_connected_device(
 pub(crate) fn connect_enum(model: Model) -> bool {
     unsafe { nitrokey_sys::NK_login_enum(model.into()) == 1 }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::get_hidapi_serial_number;
+
+    #[test]
+    fn hidapi_serial_number() {
+        assert_eq!(None, get_hidapi_serial_number(""));
+        assert_eq!(None, get_hidapi_serial_number("00000000000000000"));
+        assert_eq!(
+            Some("00001234".to_string()),
+            get_hidapi_serial_number("1234")
+        );
+        assert_eq!(
+            Some("00001234".to_string()),
+            get_hidapi_serial_number("00001234")
+        );
+        assert_eq!(
+            Some("00001234".to_string()),
+            get_hidapi_serial_number("000000001234")
+        );
+        assert_eq!(
+            Some("100000001234".to_string()),
+            get_hidapi_serial_number("100000001234")
+        );
+        assert_eq!(
+            Some("10000001234".to_string()),
+            get_hidapi_serial_number("010000001234")
+        );
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 0eb4f40..dad4a20 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -118,8 +118,8 @@ use nitrokey_sys;
 pub use crate::auth::{Admin, Authenticate, User};
 pub use crate::config::Config;
 pub use crate::device::{
-    Device, DeviceWrapper, Model, Pro, SdCardData, Storage, StorageProductionInfo, StorageStatus,
-    VolumeMode, VolumeStatus,
+    Device, DeviceInfo, DeviceWrapper, Model, Pro, SdCardData, Storage, StorageProductionInfo,
+    StorageStatus, VolumeMode, VolumeStatus,
 };
 pub use crate::error::{CommandError, CommunicationError, Error, LibraryError};
 pub use crate::otp::{ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData};