From ba20f457f8de8b14b27f37b65324d81d2f3206c3 Mon Sep 17 00:00:00 2001
From: Nicola Belluti <nicolabelluti@protonmail.com>
Date: Mon, 6 May 2024 11:31:41 +0200
Subject: [PATCH] Reversed the direction of the iterator
---
src/record_iterator.rs | 64 +++++++++++++++++++++++++++---------------
1 file changed, 41 insertions(+), 23 deletions(-)
diff --git a/src/record_iterator.rs b/src/record_iterator.rs
index d9d5efa..bbe0767 100644
--- a/src/record_iterator.rs
+++ b/src/record_iterator.rs
@@ -6,25 +6,36 @@ pub struct RecordIterator<'a> {
r701: &'a mut R701,
input_buffer: Vec<u8>,
sequence_number: u16,
- record_count: u16,
total_records: u16,
+ record_count: u16,
}
impl<'a> RecordIterator<'a> {
pub fn from(r701: &'a mut R701) -> Result<Self> {
- // Ping the endpoint
- r701.ping()?;
-
// Get the total number of records
let total_records = r701.get_total_record_count()?;
+ // The endpoint expects the first block of records to be sent first
+ r701.get_record_bytes(total_records, 0)?;
+
+ // Calculate the sequence number of the last record and the position of
+ // the last useful byte
+ let sequence_number = total_records * 12 / 1024;
+ let last_byte = (total_records * 12 % 1024) as usize;
+
+ // Get the last records and cut out all the trailing `ff` bytes
+ let input_buffer = r701
+ .get_record_bytes(total_records, sequence_number)?
+ .drain(..last_byte)
+ .collect::<Vec<u8>>();
+
// Return a new Iterator
Ok(Self {
r701,
- input_buffer: Vec::new(),
- record_count: 0,
- sequence_number: 0,
+ input_buffer,
+ sequence_number,
total_records,
+ record_count: total_records,
})
}
}
@@ -33,32 +44,39 @@ impl<'a> Iterator for RecordIterator<'a> {
type Item = Record;
fn next(&mut self) -> Option<Self::Item> {
- self.record_count += 1;
-
- // If we exceeded the total number of records, return None
- if self.record_count > self.total_records {
+ // Stop iterating when there are no more records
+ if self.record_count == 0 {
return None;
}
- // If the buffer is empty, make another request to the endpoint asking
- // for more data
+ self.record_count -= 1;
+
+ // If the input buffer is almost empty, make another request to the
+ // endpoint asking for more data
if self.input_buffer.len() < 12 {
- let bytes = &mut self
+ // If the buffer is almost empty but the sequence number is already
+ // zero, stop iterating
+ if self.sequence_number == 0 {
+ return None;
+ }
+
+ self.sequence_number -= 1;
+
+ // Request new bytes
+ let bytes = self
.r701
.get_record_bytes(self.total_records, self.sequence_number)
.ok()?;
- self.input_buffer.append(bytes);
- self.sequence_number += 1;
- }
-
- // If the record bytes are set to `ff ff ff ff ff ff ff ff ff ff ff ff`,
- // return None
- if self.input_buffer[..12] == [0xff_u8; 12] {
- return None;
+ // Put the bytes at the start of the vector
+ self.input_buffer.splice(0..0, bytes.iter().copied());
}
// Return a new Record
- self.input_buffer.drain(..12).as_slice().try_into().ok()
+ self.input_buffer
+ .drain(self.input_buffer.len() - 12..)
+ .as_slice()
+ .try_into()
+ .ok()
}
}