Notes on CAS and git.
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@ -89,7 +89,7 @@
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"algorithms/index.md": "cd7c7ba91fb2f961c9f2437777e8e2ac",
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"algorithms/sorting/index.md": "2d5a18a3079d96fa9e3d4289181a8b6c",
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"algorithms/sorting/insertion-sort.md": "00e4edb132d473b0516fde3307ebae30",
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"bash/index.md": "3dfeb538d781e4645e3aaaf32beb1034",
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"bash/index.md": "3e4738d8d3531bb7a5afc53a2d73036c",
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"bash/prompts.md": "61cb877e68da040a15b85af76b1f68ba",
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"bash/quoting.md": "b1d8869a91001f8b22f0cdc54d806f61",
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"bash/robustness.md": "7ab094b95ba2bfa885adba8e9efedf68",
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@ -122,7 +122,7 @@
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"_journal/2024-02-02.md": "a3b222daee8a50bce4cbac699efc7180",
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"_journal/2024-02-01.md": "3aa232387d2dc662384976fd116888eb",
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"_journal/2024-01-31.md": "7c7fbfccabc316f9e676826bf8dfe970",
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"logic/equiv-trans.md": "4a781f0d21ee0942445cd31da3ec396f",
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"logic/equiv-trans.md": "1f2d5823f128b8fdb526436e83a206ff",
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"_journal/2024-02-07.md": "8d81cd56a3b33883a7706d32e77b5889",
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"algorithms/loop-invariants.md": "cbefc346842c21a6cce5c5edce451eb2",
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"algorithms/loop-invariant.md": "29f9f9090a3109890d333a78acc18b50",
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@ -190,7 +190,7 @@
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"combinatorics/inclusion-exclusion.md": "ca5c967be774ce204f1ca47cc8df14b8",
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"_journal/2024-02-21.md": "b9d944ecebe625da5dd72aeea6a916a2",
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"_journal/2024-02/2024-02-20.md": "af2ef10727726200c4defe2eafc7d841",
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"algebra/radices.md": "88c6c5657eca99f3d274f0c3fc0e3af0",
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"algebra/radices.md": "4ffc8525f2b877c0d17e3359870797fe",
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"_journal/2024-02-22.md": "e01f1d4bd2f7ac2a667cdfd500885a2a",
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"_journal/2024-02/2024-02-21.md": "f423137ae550eb958378750d1f5e98c7",
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"_journal/2024-02-23.md": "219ce9ad15a8733edd476c97628b71fd",
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@ -208,8 +208,15 @@
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"_journal/2024-02/2024-02-25.md": "426be827fe8483e4ab432304a2aa6df3",
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"_journal/2024-02-27.md": "851180f1f7c1aaacd4c0b0ec2639bdf2",
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"_journal/2024-02/2024-02-26.md": "417b84be5d96f9d8adcdedca3b68b141",
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"_journal/2024-02-28.md": "3d69115853814aaff435b3a4c05f97b7",
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"_journal/2024-02/2024-02-27.md": "f75a0d04a875aeee932343dae0c78768"
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"_journal/2024-02-28.md": "7489377c014a2ff3c535d581961b5b82",
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"_journal/2024-02/2024-02-27.md": "f75a0d04a875aeee932343dae0c78768",
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"filesystems/index.md": "cbd2b0290a3ba3b32abec4bd8bfefad5",
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"filesystems/cas.md": "34906013a2a60fe5ee0e31809b4838aa",
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"git/objects.md": "b49015b8ebffc2c976d97b2484c74448",
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"git/index.md": "83d2d95fc549d9e8436946c7bd058d15",
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"encoding/integer.md": "5dd3a961bf259e53da207209051b8335",
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"_journal/2024-02-29.md": "f610f3caed659c1de3eed5f226cab508",
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"_journal/2024-02/2024-02-28.md": "7489377c014a2ff3c535d581961b5b82"
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},
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"fields_dict": {
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"Basic": [
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---
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title: "2024-02-29"
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---
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- [x] Anki Flashcards
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- [x] KoL
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- [ ] Sheet Music (10 min.)
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- [x] Go (1 Life & Death Problem)
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- [ ] Korean (Read 1 Story)
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- [ ] Interview Prep (1 Practice Problem)
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- [ ] Log Work Hours (Max 3 hours)
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* 101weiqi (serial numbers)
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* Q-349924
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* Q-99982
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* Q-285489
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* Q-85874
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* Q-265576
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* Q-11420
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* TODO
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* Watch database courses and read
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@ -5,10 +5,10 @@ title: "2024-02-28"
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- [x] Anki Flashcards
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- [x] KoL
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- [ ] Sheet Music (10 min.)
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- [ ] Go (1 Life & Death Problem)
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- [x] Go (1 Life & Death Problem)
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- [ ] Korean (Read 1 Story)
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- [ ] Interview Prep (1 Practice Problem)
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- [ ] Log Work Hours (Max 3 hours)
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- [x] Log Work Hours (Max 3 hours)
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* 101weiqi (serial numbers)
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* Q-314990
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@ -16,4 +16,6 @@ title: "2024-02-28"
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* Q-305178
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* Q-51685
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* Q-11821
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* Q-5014
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* Q-5014
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* Add notes on `SIGABRT`.
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* First pass on "Git Internals" in "Pro Git".
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@ -276,7 +276,7 @@ END%%
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%%ANKI
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Basic
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Which hexadecimal digits have a leading `1` bit?
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Which hexadecimal digits encode binary with a leading `1` bit?
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Back: `8` through `F`
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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Tags: binary::hex
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@ -285,7 +285,7 @@ END%%
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%%ANKI
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Basic
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Which hexadecimal digits have a leading `0` bit?
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Which hexadecimal digits encode binary with a leading `0` bit?
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Back: `0` through `7`
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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Tags: binary::hex
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@ -126,8 +126,8 @@ END%%
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%%ANKI
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Basic
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*Why* is it $UMax = 2 \cdot TMax + 1$?
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Back: All bit strings representing negative numbers in two's-complement are positive in unsigned encoding.
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Provide a combinatorial explanation on why $UMax$ equals $2 \cdot TMax + 1$.
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Back: There is one more negative number than positive numbers represented in two's-complement.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1708613447880-->
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END%%
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---
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title: Content-Addressable Storage
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TARGET DECK: Obsidian::STEM
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FILE TAGS: fs::cas
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tags:
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- cas
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- fs
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---
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## Overview
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CAS (**c**ontent-**a**ddressed **s**torage) refers to storage that allows retrieval based on content (as opposed to name or location). Usually the contents of a file are passed through a cryptographic hash function to generate a key that can be used for subsequent retrieval.
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%%ANKI
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Basic
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What is content-addressed storage?
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Back: A method for storing information such that it can be retrieved based on its content.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255543-->
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END%%
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%%ANKI
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Basic
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What is considered the "opposite" of content-addressed storage?
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Back: Location-addressed storage.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255547-->
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END%%
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%%ANKI
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Basic
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What is CAS an acronym for?
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Back: **C**ontent-**a**ddressed **s**torage.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255550-->
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END%%
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%%ANKI
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Cloze
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{1:Content}-addressed is to {2:URNs} whereas {2:location}-addressed is to {1:URLs}.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255553-->
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END%%
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%%ANKI
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Basic
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Interpreted as a key-value store, what is a "key" in a CAS system?
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Back: The digest produced when running content through a cryptographic hash function.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255556-->
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END%%
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%%ANKI
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Basic
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Interpreted as a key-value store, what is a "value" in a CAS system?
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Back: The actual content being stored.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255559-->
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END%%
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%%ANKI
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Basic
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In the context of CAS, what is a "content address"?
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Back: A digest produced when running content through a cryptographic hash function.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255562-->
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END%%
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%%ANKI
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Cloze
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Content addresses are an alternative to {location} addresses found in traditional filesystems.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255565-->
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END%%
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%%ANKI
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Basic
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Why are CAS systems sometimes called "fixed content storage"?
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Back: CAS is normally used for files that are not frequently edited.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255567-->
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END%%
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%%ANKI
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Basic
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How is it CAS systems ensure file uniqueness?
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Back: An attempt to store an already stored file will generate the same key as before.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255570-->
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END%%
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%%ANKI
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Basic
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How is it CAS systems ensure file's remain unchanged?
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Back: A file's key will always be the same provided the content has not changed.
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Reference: “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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<!--ID: 1709177255573-->
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END%%
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## References
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* “Content-Addressable Storage,” in _Wikipedia_, February 27, 2024, [https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681](https://en.wikipedia.org/w/index.php?title=Content-addressable_storage&oldid=1210669681).
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* Scott Chacon, _Pro Git_, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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---
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title: Filesystems
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---
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---
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title: Git
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---
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---
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title: Objects
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TARGET DECK: Obsidian::STEM
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FILE TAGS: fs::cas git
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tags:
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- cas
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- fs
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- git
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---
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## Overview
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%%ANKI
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Basic
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What cryptographic hash function does git use internally?
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Back: SHA-1
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255577-->
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END%%
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%%ANKI
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Basic
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How many bytes make up a SHA-1 digest?
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Back: 20
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255580-->
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END%%
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%%ANKI
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Basic
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How many hexadecimal digits make up a SHA-1 digest?
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Back: 40
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255584-->
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END%%
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%%ANKI
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Basic
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How is a SHA-1 digest typically represented?
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Back: As a string of 40 hexadecimal digits.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255589-->
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END%%
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%%ANKI
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Basic
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What is "oid" an acronym for?
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Back: **O**bject **id**.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255594-->
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END%%
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%%ANKI
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Basic
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What *is* an object id?
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Back: The digest produced when hashing/storing content.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255599-->
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END%%
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%%ANKI
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Basic
|
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What does it mean for git to be a content-addressed storage system?
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Back: Keys generated from hashing content are used to later retrieve said content.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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Tags: fs::cas
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<!--ID: 1709177255603-->
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END%%
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||||
%%ANKI
|
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Cloze
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Interpreted as a key-value store, {oids} are to keys as {objects} are to values.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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Tags: fs::cas
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<!--ID: 1709177255607-->
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END%%
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%%ANKI
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Basic
|
||||
Why prefer term "oid" over e.g. "SHA-1 digest" or similar?
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Back: Git is transitioning to the use of other cryptographic hash functions.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255612-->
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END%%
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%%ANKI
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Basic
|
||||
What is a "porcelain" command?
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Back: A user-friendly command.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255618-->
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END%%
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%%ANKI
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Basic
|
||||
What is a "plumbing" command?
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Back: A lower-level command.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255622-->
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END%%
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%%ANKI
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Cloze
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{Porcelain} commands are more user-friendly than {plumbing} commands.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255627-->
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END%%
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%%ANKI
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Basic
|
||||
What plumbing subcommand is used to generate an oid?
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Back: `hash-object`
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255632-->
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END%%
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%%ANKI
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Basic
|
||||
The `hash-object` subcommand optionally stores the resulting object in what directory?
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Back: `.git/objects`
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255637-->
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END%%
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%%ANKI
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Cloze
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The {object database} refers to the {`.git/objects`} directory.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255644-->
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END%%
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%%ANKI
|
||||
Basic
|
||||
What does the `hash-object` subcommand return?
|
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Back: The computed object id.
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Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
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<!--ID: 1709177255651-->
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END%%
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||||
%%ANKI
|
||||
Basic
|
||||
What optional functionality does the `hash-object` subcommand support?
|
||||
Back: It can write an object into the object database.
|
||||
Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
|
||||
<!--ID: 1709177255659-->
|
||||
END%%
|
||||
|
||||
%%ANKI
|
||||
Basic
|
||||
What flag lets the `hash-object` subcommand write to the object database?
|
||||
Back: `-w`
|
||||
Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
|
||||
<!--ID: 1709177255664-->
|
||||
END%%
|
||||
|
||||
%%ANKI
|
||||
Basic
|
||||
Where does object e.g. `d670460b4b4aece5915caf5c68d12f560a9fe3e4` live in the object database?
|
||||
Back: At `.git/objects/d6/70460b4b4aece5915caf5c68d12f560a9fe3e4`.
|
||||
Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
|
||||
<!--ID: 1709177255668-->
|
||||
END%%
|
||||
|
||||
%%ANKI
|
||||
Basic
|
||||
What regular files exist in the object database after `git init`?
|
||||
Back: None.
|
||||
Reference: Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
|
||||
<!--ID: 1709177255672-->
|
||||
END%%
|
||||
|
||||
## References
|
||||
|
||||
* Scott Chacon, *Pro Git*, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).
|
||||
|
|
@ -863,7 +863,7 @@ END%%
|
|||
|
||||
%%ANKI
|
||||
Basic
|
||||
How do define $s'$ such that $s(E_e^x) = s'(E)$?
|
||||
How do you define $s'$ such that $s(E_e^x) = s'(E)$?
|
||||
Back: $s' = (s; x{:}s(e))$.
|
||||
Reference: Gries, David. *The Science of Programming*. Texts and Monographs in Computer Science. New York: Springer-Verlag, 1981.
|
||||
<!--ID: 1707939006292-->
|
||||
|
|
|
|||
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Reference in New Issue