From 25695b39ea75969342d3f689965e3fcc627f765d Mon Sep 17 00:00:00 2001
From: Robin Mueller <robin.mueller.m@gmail.com>
Date: Wed, 7 Dec 2022 08:14:55 +0100
Subject: [PATCH] add error impls for feature std

---
 src/ecss.rs | 43 ++++++++++++++++++++++++++++++++++++++++++-
 src/lib.rs  | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/src/ecss.rs b/src/ecss.rs
index 06e40f4..f06b4c7 100644
--- a/src/ecss.rs
+++ b/src/ecss.rs
@@ -1,11 +1,13 @@
 //! Common definitions and helpers required to create PUS TMTC packets according to
 //! [ECSS-E-ST-70-41C](https://ecss.nl/standard/ecss-e-st-70-41c-space-engineering-telemetry-and-telecommand-packet-utilization-15-april-2016/)
 use crate::{ByteConversionError, CcsdsPacket, SizeMissmatch};
-use core::fmt::Debug;
+use core::fmt::{Debug, Display, Formatter};
 use core::mem::size_of;
 use crc::{Crc, CRC_16_IBM_3740};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
+#[cfg(feature = "std")]
+use std::error::Error;
 
 pub type CrcType = u16;
 
@@ -65,6 +67,45 @@ pub enum PusError {
     ByteConversionError(ByteConversionError),
 }
 
+impl Display for PusError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        match self {
+            PusError::VersionNotSupported(v) => {
+                write!(f, "PUS version {:?} not supported", v)
+            }
+            PusError::IncorrectCrc(crc) => {
+                write!(f, "crc16 {:#04x} is incorrect", crc)
+            }
+            PusError::RawDataTooShort(size) => {
+                write!(
+                    f,
+                    "deserialization error, provided raw data with size {} too short",
+                    size
+                )
+            }
+            PusError::NoRawData => {
+                write!(f, "no raw data provided")
+            }
+            PusError::CrcCalculationMissing => {
+                write!(f, "crc16 was not calculated")
+            }
+            PusError::ByteConversionError(e) => {
+                write!(f, "low level byte conversion error: {}", e)
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for PusError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        if let PusError::ByteConversionError(e) = self {
+            return Some(e);
+        }
+        None
+    }
+}
+
 impl From<ByteConversionError> for PusError {
     fn from(e: ByteConversionError) -> Self {
         PusError::ByteConversionError(e)
diff --git a/src/lib.rs b/src/lib.rs
index 9aa7955..1ca6fdd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -53,7 +53,10 @@ extern crate alloc;
 extern crate std;
 
 use crate::ecss::CCSDS_HEADER_LEN;
+use core::fmt::{Display, Formatter};
 use delegate::delegate;
+#[cfg(feature = "std")]
+use std::error::Error;
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -85,6 +88,36 @@ pub enum ByteConversionError {
     ZeroCopyFromError,
 }
 
+impl Display for ByteConversionError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        match self {
+            ByteConversionError::ToSliceTooSmall(missmatch) => {
+                write!(
+                    f,
+                    "target slice with size {} is too small, expected size of at least {}",
+                    missmatch.found, missmatch.expected
+                )
+            }
+            ByteConversionError::FromSliceTooSmall(missmatch) => {
+                write!(
+                    f,
+                    "source slice with size {} too small, expected at least {} bytes",
+                    missmatch.found, missmatch.expected
+                )
+            }
+            ByteConversionError::ZeroCopyToError => {
+                write!(f, "zerocopy serialization error")
+            }
+            ByteConversionError::ZeroCopyFromError => {
+                write!(f, "zerocopy deserialization error")
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for ByteConversionError {}
+
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum PacketType {