segment parser is working

src/error.rs

@@ -0,0 +1,6 @@
+use nom;
+
+#[derive(Debug, PartialEq)]
+pub enum IMFError<'a> {
+    Segment(nom::Err<nom::error::Error<&'a [u8]>>),
+}

src/lib.rs

@@ -1,2 +1,3 @@
+pub mod error;
 pub mod fragments;
 pub mod multipass;

src/multipass/mod.rs

@@ -0,0 +1 @@
+pub mod segment;

src/multipass/segment.rs

@@ -1,7 +1,61 @@
+use std::convert::TryFrom;
+use nom::{
+    IResult,
+    branch::alt,
+    bytes::complete::{is_not, tag},
+    combinator::recognize,
+    sequence::{pair, terminated},
+    multi::many0,
+};
+
+use crate::error::IMFError;
+
 #[derive(Debug, PartialEq)]
 pub struct Segment<'a> {
     pub header: &'a [u8],
     pub body: &'a [u8],
 }
 
+const cr: u8 = 0x0D;
+const lf: u8 = 0x0A;
+const crlf: &[u8] = &[cr, lf];
 
+impl<'a> TryFrom<&'a [u8]> for Segment<'a> {
+    type Error = IMFError<'a>;
+
+    fn try_from(buffer: &'a [u8]) -> Result<Self, Self::Error> {
+        terminated(
+            recognize(many0(line)), 
+            obs_crlf
+        )(buffer)
+            .map_err(|e| IMFError::Segment(e))
+            .map(|(body, header)| Segment { header, body })
+    }
+}
+
+fn line(input: &[u8]) -> IResult<&[u8], (&[u8], &[u8])> {
+    pair(
+        is_not(crlf), 
+        obs_crlf,
+    )(input)
+}
+
+fn obs_crlf(input: &[u8]) -> IResult<&[u8], &[u8]> {
+    alt((tag(crlf), tag(&[cr]), tag(&[lf])))(input)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_segment() {
+        assert_eq!(
+            Segment::try_from(&b"From: hello@world.com\r\nDate: 12 Mar 1997 07:33:25 Z\r\n\r\nHello world!"[..]),
+            Ok(Segment {
+                body: b"Hello world!", 
+                header: b"From: hello@world.com\r\nDate: 12 Mar 1997 07:33:25 Z\r\n",
+            })
+        );
+    }
+}