1// A complete article demonstrating Typst features together
2
3#set document(
4  title: "Content-Addressable Storage for Version Control",
5  author: "sublimated docs",
6)
7#set page(paper: "a4", margin: (x: 2.5cm, y: 3cm), numbering: "1")
8#set text(size: 11pt)
9#set par(justify: true, leading: 0.65em)
10#set heading(numbering: "1.1")
11
12// Custom note block
13#let note(body) = block(
14  width: 100%,
15  fill: rgb("#f0f7ff"),
16  stroke: rgb("#3b82f6") + 0.5pt,
17  inset: 12pt,
18  radius: 4pt,
19)[#text(weight: "bold", size: 9pt, fill: rgb("#3b82f6"))[NOTE ] #body]
20
21// Title
22#align(center)[
23  #text(size: 20pt, weight: "bold")[Content-Addressable Storage\ for Version Control]
24  #v(0.5em)
25  #text(size: 12pt, fill: luma(100))[A practical overview]
26  #v(1em)
27]
28
29= Introduction <intro>
30
31Content-addressable storage (CAS) identifies data by its content hash rather than by location. This approach is fundamental to version control systems like Git, where every object — blob, tree, commit — is addressed by its SHA-1 hash.
32
33#note[This article demonstrates Typst features. Push it to sublimated to see it rendered as a multi-page document.]
34
35= How CAS works
36
37== Hash functions
38
39A hash function $H$ maps arbitrary data $D$ to a fixed-size digest:
40
41$ H: {0, 1}^* -> {0, 1}^n $
42
43For CAS to work, the hash must be:
44
45- *deterministic* — same input always produces same output
46- *collision-resistant* — hard to find $x != y$ where $H(x) = H(y)$
47- *fast* — hashing should not be a bottleneck
48
49== Common algorithms
50
51#figure(
52  table(
53    columns: (1fr, auto, auto, auto),
54    fill: (x, y) => if y == 0 { luma(235) },
55    [*Algorithm*], [*Digest size*], [*Speed*], [*Status*],
56    [SHA-1], [160 bits], [~500 MB/s], [Deprecated],
57    [SHA-256], [256 bits], [~300 MB/s], [Standard],
58    [BLAKE3], [256 bits], [~3 GB/s], [Modern],
59  ),
60  caption: [Hash algorithm comparison],
61) <hash-table>
62
63As shown in @hash-table, BLAKE3 offers significantly better throughput while maintaining security properties equivalent to SHA-256.
64
65== Content identifiers
66
67A self-describing content identifier (CID) includes the algorithm:
68
69```
70blake3-a1b2c3d4e5f6...
71sha256-9f86d081884c...
72```
73
74This makes the system future-proof — new algorithms can be added without breaking existing references.
75
76= Applications
77
78== Deduplication
79
80When two files have identical content, they produce the same hash and are stored once:
81
82$ "store"(f_1) = "store"(f_2) "iff" H(f_1) = H(f_2) $
83
84#let savings(n, d) = calc.round((1 - (n - d) / n) * 100, digits: 1)
85
86#figure(
87  table(
88    columns: 4,
89    fill: (x, y) => if y == 0 { luma(235) },
90    [*Dataset*], [*Total files*], [*Unique*], [*Space saved*],
91    [Source code], [12,450], [8,230], [#savings(12450, 8230)%],
92    [Documents], [3,200], [2,890], [#savings(3200, 2890)%],
93    [Media], [850], [845], [#savings(850, 845)%],
94  ),
95  caption: [Deduplication effectiveness by content type],
96)
97
98== Immutable history
99
100Every version of every file is preserved. A commit is a tree of hashes:
101
102```
103commit abc123
104├── tree def456
105│   ├── blob 1a2b3c  README.md
106│   ├── blob 4d5e6f  src/main.rs
107│   └── tree 7g8h9i  docs/
108│       ├── blob aabbcc  guide.md
109│       └── blob ddeeff  api.md
110└── parent commit 789xyz
111```
112
113Changing any file changes every hash up to the root — integrity is guaranteed.
114
115= Performance
116
117The cost of CAS operations scales with content size, not history depth:
118
119$ T_"lookup" = O(1) quad "hash table lookup" $
120$ T_"store" = O(|D|) quad "hash computation" $
121$ T_"verify" = O(|D|) quad "rehash and compare" $
122
123For a repository with $n$ objects and average size $s$:
124
125$ "Total space" <= n dot s quad "(with dedup: significantly less)" $
126
127= Conclusion
128
129Content-addressable storage provides a foundation for systems that need integrity, deduplication, and immutable history. Combined with a hierarchical commit model, it enables version control at any granularity — from individual files to entire organizations.
130
131See @intro for the overview, and @hash-table for algorithm benchmarks.