From d8b91b969c2bbf9155448b5dad36e44ac37b76a1 Mon Sep 17 00:00:00 2001
From: Fabian Reinartz <fab.reinartz@gmail.com>
Date: Mon, 24 Apr 2017 10:33:08 +0200
Subject: [PATCH] docs: add chunk file format

---
 Documentation/format/chunks.md | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 Documentation/format/chunks.md

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+# Chunks Disk Format
+
+The following describes the format of a single chunks file, which is created in the `chunks/` directory of a block.
+
+```
+ ┌────────────────────────────┬──────────────────┐
+ │ magic(0x85BD40DD) <4 byte> | version <1 byte> │
+ ├────────────────────────────┴──────────────────┤
+ │                     Body ...                  │
+ └───────────────────────────────────────────────┘
+```
+
+Available versions:
+* v1 (`1`)
+
+## Body (v1)
+
+The body contains a sequence of chunks, each of which has the following format.
+
+```
+┌─────────────────────────────────────────────────────────┐
+│ ┌──────────────┬───────────────────┬────────────┐       │
+│ │ len <varint> | encoding <1 byte> │    data    │  ...  │
+│ └──────────────┴───────────────────┴────────────┘       │
+└─────────────────────────────────────────────────────────┘
+```
+
+The length marks the length of the encoding byte and data combined.
+The CRC checksum is calculated over the encoding byte and data.
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