From a24bf544b58df8041d8d109205d3aa972fe843f2 Mon Sep 17 00:00:00 2001
From: Profpatsch <mail@profpatsch.de>
Date: Mon, 1 Jun 2020 14:39:42 +0200
Subject: pkgs/profpatsch: alpha-grade encode spec

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 pkgs/profpatsch/encode/spec.md | 81 ++++++++++++++++++++++++++++++++++++++++++
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 create mode 100644 pkgs/profpatsch/encode/spec.md

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+# encode 0.1-unreleased
+
+[bencode][] and [netstring][]-inspired pipe format that should be trivial to parse (100 lines of code or less), mostly human-decipherable for easy debugging, and support nested record and sum types.
+
+
+## scalars
+
+Scalars have the format `[type prefix][size]:[value],`.
+
+### unit
+
+The unit (`u`) has only one value.
+
+The unit is: `u,`
+
+### numbers
+
+Naturals (`n`) and Integers (`i`), with a maximum size in bits.
+
+The allowed bit sizes are: 8, 16, 32, 64, 128. (TODO: does that make sense?)
+
+Natural `1234` that fits in 32 bits: `n32:1234,`
+Integer `-42` that fits in 8 bits: `i8:-42,`
+Integer `23` that fits in 64 bits: `i64:23,`
+
+Floats elided by choice.
+
+### text
+
+Text (`t`) that *must* be encoded as UTF-8, starting with its length in bytes:
+
+The string `hello world` (11 bytes): `t11:hello world,`
+The string `今日は` (9 bytes): `t9:今日は,`
+The string `:,` (2 bytes): `t2::,,`
+The empty sting `` (0 bytes): t0:,`
+
+Binary data elided by choice.
+
+
+## tagged values
+
+### tags
+
+A tag (`<`) gives a value a name. The tag is UTF-8 encoded, starting with its length in bytes and proceeding with the value.
+
+The tag `foo` (3 bytes) tagging the text `hello` (5 bytes): `<3:foo|t5:hello,`
+The tag `` (0 bytes) tagging the 8-bit integer 0: `<0:|i8:0,`
+
+### products (dicts/records), also maps
+
+Multiple tags concatenated, if tag names repeat the later ones should be ignored. (TODO: should there be a marker indicating products, and should maps get a different marker? We don’t have a concept of types here, so probably not.)
+Ordering does not matter.
+
+### sums (tagged unions)
+
+Simply a tagged value (TODO: should there be a marker?).
+
+
+## lists
+
+TODO: necessary?
+
+A list (`[`) imposes an ordering on a sequence of values. It needs to be closed with `]`. Values in it are simply concatenated.
+
+The empty list: `[]`
+The list with one element, the string `foo`: `[t3:foo,]`
+The list with text `foo` followed by i8 `-42`: `[t3:foo,i8:-42,]`
+The list with `Some` and `None` tags: `[<4:Some|t3:foo,<4None|u,<4None|u,]`
+
+
+## motivation
+
+Using
+
+## guarantees
+
+TODO: do I want unique representation (bijection like bencode?) This would put more restrictions on the generator, like sorting records in lexicographic order, but would make it possible to compare without decoding
+
+
+[bencode]: https://en.wikipedia.org/wiki/Bencode
+[netstring]: https://en.wikipedia.org/wiki/Netstring
-- 
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