introduce ParsingContext

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>

src/buffer.rs

@@ -1,3 +1,4 @@
+use crate::parsing::ParsingContext;
 use amq_protocol::frame::{BackToTheBuffer, GenError, GenResult, WriteContext};
 use std::{
     cmp,
@@ -135,6 +136,14 @@ impl Buffer {
         }
     }
 
+    pub(crate) fn parsing_context(&self) -> ParsingContext<'_> {
+        if self.end > self.position {
+            self.memory[self.position..self.end].into()
+        } else {
+            [&self.memory[self.position..], &self.memory[..self.end]].into()
+        }
+    }
+
     pub(crate) fn data(&self) -> &[u8] {
         // FIXME: drop
         &self.memory[self.position..self.end]

src/lib.rs

@@ -137,6 +137,7 @@ mod exchange;
 mod frames;
 mod id_sequence;
 mod io_loop;
+mod parsing;
 mod promises;
 mod queue;
 mod queues;

src/parsing.rs

@@ -0,0 +1,17 @@
+pub(crate) struct ParsingContext<'a> {
+    buffers: [&'a [u8]; 2],
+}
+
+impl<'a> From<&'a [u8]> for ParsingContext<'a> {
+    fn from(buffer: &'a [u8]) -> Self {
+        Self {
+            buffers: [buffer, &buffer[..0]],
+        }
+    }
+}
+
+impl<'a> From<[&'a [u8]; 2]> for ParsingContext<'a> {
+    fn from(buffers: [&'a [u8]; 2]) -> Self {
+        Self { buffers }
+    }
+}