mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-11-12 18:49:07 +00:00
41 lines
1.5 KiB
Markdown
41 lines
1.5 KiB
Markdown
# Add-on Block
|
|
|
|
Fixed storage which stores an immutable binary-search tree of items.
|
|
Each item consists of a pair of pointers to binary data of arbitrary length.
|
|
These two pointers are interpreted as a `key` and a `value`.
|
|
Since items contain only pointers, multiple instances of data are stored just once.
|
|
|
|
Block contains 3 logical parts:
|
|
a) header (256 bytes)
|
|
b) binary-search tree (variable size)
|
|
c) item data (variable size)
|
|
|
|
## Header
|
|
|
|
| offset | length | name | description |
|
|
|-------:|---------:|--------------|--------------|
|
|
| 0x0000 | 4 | magic | magic `TRAB` |
|
|
| 0x0004 | 64 | sig | signature of the whole blob (except magic and sig) |
|
|
| 0x0044 | 4 | tree_count | number of elements in the tree |
|
|
| 0x0048 | 4 | items_size | length of the item section |
|
|
| 0x004A | 182 | reserved | - |
|
|
|
|
## Binary-Search Tree
|
|
|
|
Each node of the tree has the following structure:
|
|
|
|
| offset | length | name | description |
|
|
|-------:|---------:|--------------|--------------|
|
|
| ... | 2 | key_offset | key offset (divided by 4) |
|
|
| ... | 2 | value_offset | value offset (divided by 4) |
|
|
|
|
# Item Data
|
|
|
|
Each item has the following structure:
|
|
|
|
| offset | length | name | description |
|
|
|-------:|---------:|--------------|--------------|
|
|
| ... | 2 | item_len | item (key or value) length |
|
|
| ... | 2 | item_flags | item (key or value) flags |
|
|
| ... | item_len | item_data | item (key or value) data (padded to multiple of 4) |
|