//! HDF5 Link Info message parsing (message type 0x0002). use crate::error::FormatError; /// Parsed Link Info message from a v2 group object header. #[derive(Debug, Clone, PartialEq)] pub struct LinkInfoMessage { /// Maximum creation order value (if tracking is enabled). pub max_creation_order: Option, /// Address of fractal heap for dense link storage. None means compact storage only. pub fractal_heap_address: Option, /// Address of B-tree v2 for name-ordered link index. pub btree_name_index_address: Option, /// Address of B-tree v2 for creation-order link index. pub btree_creation_order_address: Option, } fn read_offset(data: &[u8], pos: usize, size: u8) -> Result { let s = size as usize; if pos.checked_add(s).is_none_or(|end| end > data.len()) { return Err(FormatError::UnexpectedEof { expected: pos.saturating_add(s), available: data.len(), }); } Ok(match size { 2 => u16::from_le_bytes([data[pos], data[pos + 1]]) as u64, 4 => u32::from_le_bytes([data[pos], data[pos + 1], data[pos + 2], data[pos + 3]]) as u64, 8 => u64::from_le_bytes([ data[pos], data[pos + 1], data[pos + 2], data[pos + 3], data[pos + 4], data[pos + 5], data[pos + 6], data[pos + 7], ]), _ => return Err(FormatError::InvalidOffsetSize(size)), }) } fn is_undefined(val: u64, offset_size: u8) -> bool { match offset_size { 2 => val == 0xFFFF, 4 => val == 0xFFFF_FFFF, 8 => val == 0xFFFF_FFFF_FFFF_FFFF, _ => false, } } fn ensure_len(data: &[u8], pos: usize, needed: usize) -> Result<(), FormatError> { match pos.checked_add(needed) { Some(end) if end <= data.len() => Ok(()), _ => Err(FormatError::UnexpectedEof { expected: pos.saturating_add(needed), available: data.len(), }), } } impl LinkInfoMessage { /// Parse a Link Info message from raw message data. pub fn parse(data: &[u8], offset_size: u8) -> Result { ensure_len(data, 0, 2)?; let version = data[0]; if version != 0 { return Err(FormatError::InvalidLinkInfoVersion(version)); } let flags = data[1]; let has_max_creation_order = flags & 0x01 != 0; let has_creation_order_index = flags & 0x02 != 0; let mut pos = 2; let max_creation_order = if has_max_creation_order { ensure_len(data, pos, 8)?; let v = u64::from_le_bytes([ data[pos], data[pos + 1], data[pos + 2], data[pos + 3], data[pos + 4], data[pos + 5], data[pos + 6], data[pos + 7], ]); pos += 8; Some(v) } else { None }; let fh_addr = read_offset(data, pos, offset_size)?; pos += offset_size as usize; let fractal_heap_address = if is_undefined(fh_addr, offset_size) { None } else { Some(fh_addr) }; let btree_addr = read_offset(data, pos, offset_size)?; pos += offset_size as usize; let btree_name_index_address = if is_undefined(btree_addr, offset_size) { None } else { Some(btree_addr) }; let btree_creation_order_address = if has_creation_order_index { let addr = read_offset(data, pos, offset_size)?; if is_undefined(addr, offset_size) { None } else { Some(addr) } } else { None }; Ok(LinkInfoMessage { max_creation_order, fractal_heap_address, btree_name_index_address, btree_creation_order_address, }) } } #[cfg(test)] mod tests { use super::*; #[test] fn compact_storage() { // version=0, flags=0, fractal_heap=undef, btree=undef let mut data = vec![0u8; 2 + 8 + 8]; data[0] = 0; // version data[1] = 0; // flags // fractal heap address = undefined data[2..10].copy_from_slice(&0xFFFF_FFFF_FFFF_FFFFu64.to_le_bytes()); // btree name index = undefined data[10..18].copy_from_slice(&0xFFFF_FFFF_FFFF_FFFFu64.to_le_bytes()); let msg = LinkInfoMessage::parse(&data, 8).unwrap(); assert_eq!(msg.fractal_heap_address, None); assert_eq!(msg.btree_name_index_address, None); assert_eq!(msg.max_creation_order, None); assert_eq!(msg.btree_creation_order_address, None); } #[test] fn dense_storage_with_creation_order() { // flags: bit 0 (max creation order) + bit 1 (creation order index) let mut data = Vec::new(); data.push(0); // version data.push(0x03); // flags data.extend_from_slice(&42u64.to_le_bytes()); // max_creation_order data.extend_from_slice(&0x1000u64.to_le_bytes()); // fractal heap data.extend_from_slice(&0x2000u64.to_le_bytes()); // btree name data.extend_from_slice(&0x3000u64.to_le_bytes()); // btree creation order let msg = LinkInfoMessage::parse(&data, 8).unwrap(); assert_eq!(msg.max_creation_order, Some(42)); assert_eq!(msg.fractal_heap_address, Some(0x1000)); assert_eq!(msg.btree_name_index_address, Some(0x2000)); assert_eq!(msg.btree_creation_order_address, Some(0x3000)); } #[test] fn no_creation_order_tracking() { let mut data = Vec::new(); data.push(0); // version data.push(0x00); // flags: nothing data.extend_from_slice(&0x500u64.to_le_bytes()); // fractal heap data.extend_from_slice(&0x600u64.to_le_bytes()); // btree name let msg = LinkInfoMessage::parse(&data, 8).unwrap(); assert_eq!(msg.max_creation_order, None); assert_eq!(msg.fractal_heap_address, Some(0x500)); assert_eq!(msg.btree_name_index_address, Some(0x600)); assert_eq!(msg.btree_creation_order_address, None); } #[test] fn invalid_version() { let data = vec![1, 0, 0, 0]; let err = LinkInfoMessage::parse(&data, 8).unwrap_err(); assert_eq!(err, FormatError::InvalidLinkInfoVersion(1)); } #[test] fn four_byte_offsets() { let mut data = Vec::new(); data.push(0); // version data.push(0x00); // flags data.extend_from_slice(&0x100u32.to_le_bytes()); // fractal heap data.extend_from_slice(&0x200u32.to_le_bytes()); // btree name let msg = LinkInfoMessage::parse(&data, 4).unwrap(); assert_eq!(msg.fractal_heap_address, Some(0x100)); assert_eq!(msg.btree_name_index_address, Some(0x200)); } }