---
config:
packet:
bitsPerRow: 32
showBits: true
---
packet-beta
0-31: "checksum (uint32, crc32c)"
32-47: "length (uint16)"
48-55: "type (uint8)"
56-255: "data[0..length-1]"
block := record* trailer?
record :=
checksum: uint32 // crc32c of type and data[] ; little-endian
length: uint16 // little-endian
type: uint8 // One of FULL, FIRST, MIDDLE, LAST
data: uint8[length]
Record Fragmentation
The log format supports fragmentation for records larger than the available space in a block (32KB).
Record Types
- FULL (1): Complete record fits in one block
- FIRST (2): First fragment of a multi-block record
- MIDDLE (3): Middle fragment of a multi-block record
- LAST (4): Last fragment of a multi-block record
- ZERO (0): Reserved for padding at end of block
Fragmentation Algorithm
When writing a record:
- If record fits in current block → write as FULL
- If record spans blocks:
- First fragment → FIRST type
- Middle fragments → MIDDLE type
- Last fragment → LAST type
Example: 50KB Record in 32KB Blocks
Block 1 (32KB):
Header: type=FIRST, length=32753 (32KB - 7 byte header)
Data: bytes [0..32752]
Block 2 (32KB):
Header: type=LAST, length=17247 (remaining bytes)
Data: bytes [32753..49999]
Block Boundary Handling
When less than 7 bytes remain in a block (not enough for header):
- Pad with zero bytes (type=ZERO)
- Start next record in new block
This ensures all records have complete headers.
