Added examples and better error reporting

+ The field that errors is now reported
+ The formats/ dir contains all predefined formats
  + Includes CCSDS packet for now
+ There appears to be an issue with bit formatting, the APID field is not being parsed correctly (upper 8 bits is not being factored in

formats/ccsds.toml

@@ -0,0 +1,43 @@
+# Consultative Committee for Space Data Systems (CCSDS) Space Packet Defenition
+# Primary Header + Raw Payload
+# Ref: https://public.ccsds.org/Pubs/133x0b2e1.pdfa
+#
+# Example Packet:
+# [0x08, 0x55, 0xc0, 0x00, 0x00, 0x05, 0x01, 0x02, 0x03, 0x04, 0x05]
+
+[[formats]]
+name = "ccsds"
+
+[[formats.fields]]
+name = "Version Number"
+field_type = {type = "UInt", bit_width = 3}
+
+[[formats.fields]]
+name = "Packet Type"
+field_type = {type = "UInt", bit_width = 1}
+
+[[formats.fields]]
+name = "Secondary Header Flag"
+field_type = {type = "UInt", bit_width = 1}
+
+[[formats.fields]]
+name = "APID"
+field_type = {type = "UInt", bit_width = 11}
+
+[[formats.fields]]
+name = "Sequency Flags"
+field_type = {type = "UInt", bit_width = 2}
+
+[[formats.fields]]
+name = "Packet Sequence Count"
+field_type = {type = "UInt", bit_width = 14}
+
+[[formats.fields]]
+name = "Data Length"
+field_type = {type = "UInt", bit_width = 16}
+
+[[formats.fields]]
+name = "Data"
+# Allow payloads up to the max size that can be specfied in "Data Length"
+field_type = {type = "Bytes", max_len = 65535}
+

src/byte_stream/mod.rs

@@ -8,7 +8,7 @@ pub enum ByteStreamError {
 impl Display for ByteStreamError {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
-            ByteStreamError::OutOfRange => write!(f, "Request values out of range")
+            ByteStreamError::OutOfRange => write!(f, "Requested values out of range")
         }
     }
 }
@@ -44,7 +44,7 @@ impl ByteStream {
             byte_count
         };
 
-        if bytes_needed > self.data.len() || bytes_needed + byte_ndx > self.data.len() {
+        if bytes_needed > self.data.len() || (bytes_needed + byte_ndx) > self.data.len() {
             return Err(ByteStreamError::OutOfRange);
         }
 

src/formatter/format.rs

@@ -30,7 +30,7 @@ impl From<FromUtf8Error> for FormatError {
 impl Display for FormatError {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
-            FormatError::ByteSteamError(e) => writeln!(f, "Byte steam error: {}", e),
+            FormatError::ByteSteamError(e) => writeln!(f, "Byte stream error: {}", e),
             FormatError::NotSupported => write!(f, "Field type not supported"),
             FormatError::StringParseError(e) => write!(f, "String parse error: {}", e)
         }
@@ -165,10 +165,17 @@ impl Format {
         let mut bit_ndx: usize = 0;
 
         for field in &self.fields {
-            let (data_str, bit_width) = field.format_data(&byte_stream, bit_ndx)?;
+            match field.format_data(&byte_stream, bit_ndx) {
+                Ok((data_str, bit_width)) => {
                     bit_ndx += bit_width;
                     writeln!(format_str, "{}: {}", field.name, data_str).unwrap();
                 }
+                Err(e) => {
+                    println!("Error formatting field: \"{}\": {}", field.name, e);
+                    return Err(e);
+                }
+            }
+        }
 
         Ok(format_str)
     }
@@ -278,4 +285,15 @@ mod tests {
 
         assert_eq!(output, "[222, 173]")
     }
+
+    #[test]
+    fn test_format_bytes_max_len_bigger_than_data() {
+        let field = Field {field_type: FieldType::Bytes {max_len: 64}, name: "test".to_string()};
+
+        let byte_steam = ByteStream::from(vec![0xDE, 0xAD]);
+
+        let (output, _) = field.format_data(&byte_steam, 0).unwrap();
+
+        assert_eq!(output, "[222, 173]")
+    }
 }

src/main.rs

@@ -35,6 +35,6 @@ fn main() {
 
     match format.format_data(&data) {
         Ok(data_str) => println!("{}", data_str),
-        Err(e) => println!("Unable to format data: {}", e)
+        Err(_) => println!("Error formatting data")
     }
 }