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Use SSZ object to define header

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Jacek Sieka 2022-10-25 11:13:33 +02:00
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docs/e2store.md
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@ -12,14 +12,14 @@ The `e2store` (extension: `.e2s`) is a simple linear [Type-Length-Value](https:/
The type and length are encoded in an 8-byte header which is directly followed by data. The type and length are encoded in an 8-byte header which is directly followed by data.
``` The header corresponds to an SSZ object defined as such:
record = header | data ```python
header = type | length class Header(Container):
type = Vector[byte, 2] type: Vector[byte, 2]
length = Vector[byte, 6] length: uint48
``` ```
The `length` is the first 6 bytes of a little-endian encoded `uint64`, not including the header itself. For example, the entry with header type `[0x22, 0x32]`, the length `4` and the bytes `[0x01, 0x02, 0x03, 0x04]` will be stored as the byte sequence `[0x22, 0x32, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04]`. The `length` is the length of the data that follows the header, not including the length of the header itself. For example, the entry with header type `[0x22, 0x32]`, the length `4` and the bytes `[0x01, 0x02, 0x03, 0x04]` will be stored as the byte sequence `[0x22, 0x32, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04]`.
`.e2s` files may freely be concatenated, and may contain out-of-order records. `.e2s` files may freely be concatenated, and may contain out-of-order records.