Merge pull request #828 from bmancini55/reply_channel_range

[rust-lightning] / lightning / src / util / scid_utils.rs

diff --git a/lightning/src/util/scid_utils.rs b/lightning/src/util/scid_utils.rs
new file mode 100644 (file)
index 0000000..7902a52
--- /dev/null
+++ b/lightning/src/util/scid_utils.rs
@@ -0,0 +1,76 @@
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+/// Maximum block height that can be used in a `short_channel_id`. This
+/// value is based on the 3-bytes available for block height.
+pub const MAX_SCID_BLOCK: u64 = 0x00ffffff;
+
+/// Maximum transaction index that can be used in a `short_channel_id`.
+/// This value is based on the 3-bytes available for tx index.
+pub const MAX_SCID_TX_INDEX: u64 = 0x00ffffff;
+
+/// Maximum vout index that can be used in a `short_channel_id`. This
+/// value is based on the 2-bytes available for the vout index.
+pub const MAX_SCID_VOUT_INDEX: u64 = 0xffff;
+
+/// A `short_channel_id` construction error
+#[derive(Debug, PartialEq)]
+pub enum ShortChannelIdError {
+       BlockOverflow,
+       TxIndexOverflow,
+       VoutIndexOverflow,
+}
+
+/// Extracts the block height (most significant 3-bytes) from the `short_channel_id`
+pub fn block_from_scid(short_channel_id: &u64) -> u32 {
+       return (short_channel_id >> 40) as u32;
+}
+
+/// Constructs a `short_channel_id` using the components pieces. Results in an error
+/// if the block height, tx index, or vout index overflow the maximum sizes.
+pub fn scid_from_parts(block: u64, tx_index: u64, vout_index: u64) -> Result<u64, ShortChannelIdError> {
+       if block > MAX_SCID_BLOCK {
+               return Err(ShortChannelIdError::BlockOverflow);
+       }
+
+       if tx_index > MAX_SCID_TX_INDEX {
+               return Err(ShortChannelIdError::TxIndexOverflow);
+       }
+
+       if vout_index > MAX_SCID_VOUT_INDEX {
+               return Err(ShortChannelIdError::VoutIndexOverflow);
+       }
+
+       Ok((block << 40) | (tx_index << 16) | vout_index)
+}
+
+#[cfg(test)]
+mod tests {
+       use super::*;
+
+       #[test]
+       fn test_block_from_scid() {
+               assert_eq!(block_from_scid(&0x000000_000000_0000), 0);
+               assert_eq!(block_from_scid(&0x000001_000000_0000), 1);
+               assert_eq!(block_from_scid(&0x000001_ffffff_ffff), 1);
+               assert_eq!(block_from_scid(&0x800000_ffffff_ffff), 0x800000);
+               assert_eq!(block_from_scid(&0xffffff_ffffff_ffff), 0xffffff);
+       }
+
+       #[test]
+       fn test_scid_from_parts() {
+               assert_eq!(scid_from_parts(0x00000000, 0x00000000, 0x0000).unwrap(), 0x000000_000000_0000);
+               assert_eq!(scid_from_parts(0x00000001, 0x00000002, 0x0003).unwrap(), 0x000001_000002_0003);
+               assert_eq!(scid_from_parts(0x00111111, 0x00222222, 0x3333).unwrap(), 0x111111_222222_3333);
+               assert_eq!(scid_from_parts(0x00ffffff, 0x00ffffff, 0xffff).unwrap(), 0xffffff_ffffff_ffff);
+               assert_eq!(scid_from_parts(0x01ffffff, 0x00000000, 0x0000).err().unwrap(), ShortChannelIdError::BlockOverflow);
+               assert_eq!(scid_from_parts(0x00000000, 0x01ffffff, 0x0000).err().unwrap(), ShortChannelIdError::TxIndexOverflow);
+               assert_eq!(scid_from_parts(0x00000000, 0x00000000, 0x010000).err().unwrap(), ShortChannelIdError::VoutIndexOverflow);
+       }
+}