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It is fully deterministic: the same logical content\nproduced with the same parameters yields byte-identical blocks and identical\nreferences, regardless of how input was sliced, buffered, or ordered.",[125,156,157,158,162],{},"This specification is self-contained. An implementation can be written from\nthis document and validated against the test vectors in ",[144,159,161],{"href":160},"appendix-a-test-vectors","Appendix A"," without\nreference to any existing implementation.",[132,164,166],{"id":165},"_1-introduction","1. Introduction",[168,169,171],"h3",{"id":170},"_11-data-model-at-a-glance","1.1 Data model at a glance",[125,173,174],{},"A store contains exactly two kinds of things:",[176,177,178,185],"ul",{},[179,180,181,184],"li",{},[128,182,183],{},"Blocks"," — immutable byte strings addressed by their hash. Blocks form a\ndirected acyclic graph (DAG).",[179,186,187,190],{},[128,188,189],{},"Named refs"," — mutable pointers binding a human-readable name to a block\nreference. Names are the only roots of the graph.",[192,193],"mermaid",{"code":194},"graph LR\n  subgraph names[\"names (mutable)\"]\n    main[\"refs:heads:main\"]\n    backup[\"refs:backup\"]\n  end\n  subgraph blocks[\"blocks (immutable, hash-addressed)\"]\n    root[\""r" root\"]\n    entry[\"Entry {t:"d", r}\"]\n    dir[\""d" dir\"]\n    readme[\""README.md" {t:"f", sz,m,mt,uid,gid, d}\u003Cbr\u002F>inline bytes, no block\"]\n    big[\""big.bin" {t:"f", sz, r}\"]\n    link[\""link" {t:"l", tgt}\"]\n    sub[\""sub" {t:"d", r}\"]\n    subdir[\""d" dir\"]\n    fnode[\""f" file node\u003Cbr\u002F>c: [[sz,r-raw],[sz,r-raw], …]\"]\n    chunk1[\"raw chunk\"]\n    chunk2[\"raw chunk\"]\n  end\n  main -->|n| root\n  backup -->|n| dir\n  root -->|e| entry\n  entry -->|n| dir\n  dir --> readme\n  dir --> big\n  dir --> link\n  dir --> sub\n  sub -->|n| subdir\n  big -->|n| fnode\n  fnode -->|r| chunk1\n  fnode -->|r| chunk2\n",[125,196,197,198,202,203,206],{},"Edge labels: ",[199,200,201],"code",{},"n"," = dag-cbor (node) CID link, ",[199,204,205],{},"r"," = raw CID link.",[125,208,209],{},"Three properties fall out of this shape and drive the rest of the\nspecification:",[176,211,212,221,235],{},[179,213,214,217,218,220],{},[128,215,216],{},"Metadata lives in the parent's entry, not the child's block"," (",[144,219,146],{"href":67},").\nChanging a file's mode rewrites the directory that names it; the content\nblocks are untouched. Two files with identical bytes but different\nmodes\u002Fowners share one content block.",[179,222,223,226,227,230,231,234],{},[128,224,225],{},"Every edit rewrites only the spine"," from the root to the changed entry\n(",[144,228,229],{"href":71},"§8",", ",[144,232,233],{"href":83},"§11","). Every untouched subtree carries over by reference. Old roots\nremain valid and readable — snapshots are free.",[179,236,237,240,241,244],{},[128,238,239],{},"A block is stored and deduplicated by its multihash alone, while\ntraversal identity is the full CID"," — content codec + multihash\n(",[144,242,243],{"href":55},"§4","). This single asymmetry must be respected by every\ndeduplication set in a conforming implementation.",[168,246,248],{"id":247},"_12-design-goals","1.2 Design goals",[125,250,251],{},"In priority order: unix fidelity, small size, performance, simplicity.",[168,253,255],{"id":254},"_13-roles-and-trust-model","1.3 Roles and trust model",[125,257,258,259,262,263,266,267,270,271,274,275,278],{},"This specification distinguishes ",[128,260,261],{},"writers"," (produce blocks, refs, and\npacks) and ",[128,264,265],{},"readers"," (consume them). Writers within one store are assumed\ncooperative (trusted to emit only conforming blocks); they need not be\nexclusive — the concurrency properties of each operation are given in ",[144,268,269],{"href":99},"§15.3",",\nand only garbage collection requires exclusive access (",[144,272,273],{"href":99},"§15.2","). Readers MUST\ntreat all input — blocks fetched from a store, pack bytes, ref values — as\npotentially foreign or hostile, and MUST enforce every validation rule in\nthis document (",[144,276,277],{"href":91},"§13.2",").",[168,280,282],{"id":281},"_14-scope-and-non-goals","1.4 Scope and non-goals",[125,284,285,286,288],{},"In scope: block encodings, the entry\u002Fnode data model, chunking algorithms,\nthe key–value storage mapping, the pack interchange format (a CARv1\nprofile, ",[144,287,150],{"href":87},"), and conformance requirements for readers and writers.",[125,290,291],{},"Out of scope: transport protocols, access control, encryption,\nmulti-writer coordination, and any particular host-language API.",[293,294,295],"style",{},"html .light .shiki span {color: var(--shiki-light);background: var(--shiki-light-bg);font-style: var(--shiki-light-font-style);font-weight: var(--shiki-light-font-weight);text-decoration: var(--shiki-light-text-decoration);}html.light .shiki span {color: var(--shiki-light);background: var(--shiki-light-bg);font-style: var(--shiki-light-font-style);font-weight: var(--shiki-light-font-weight);text-decoration: var(--shiki-light-text-decoration);}html .default .shiki span {color: var(--shiki-default);background: var(--shiki-default-bg);font-style: var(--shiki-default-font-style);font-weight: var(--shiki-default-font-weight);text-decoration: var(--shiki-default-text-decoration);}html .shiki span {color: var(--shiki-default);background: var(--shiki-default-bg);font-style: var(--shiki-default-font-style);font-weight: var(--shiki-default-font-weight);text-decoration: var(--shiki-default-text-decoration);}html .dark .shiki span {color: var(--shiki-dark);background: var(--shiki-dark-bg);font-style: var(--shiki-dark-font-style);font-weight: var(--shiki-dark-font-weight);text-decoration: var(--shiki-dark-text-decoration);}html.dark .shiki span {color: var(--shiki-dark);background: var(--shiki-dark-bg);font-style: var(--shiki-dark-font-style);font-weight: var(--shiki-dark-font-weight);text-decoration: var(--shiki-dark-text-decoration);}",{"title":297,"searchDepth":298,"depth":298,"links":299},"",2,[300,301],{"id":134,"depth":298,"text":135},{"id":165,"depth":298,"text":166,"children":302},[303,305,306,307],{"id":170,"depth":304,"text":171},3,{"id":247,"depth":304,"text":248},{"id":254,"depth":304,"text":255},{"id":281,"depth":304,"text":282},"md",{},{"title":44},{"title":120,"description":297},"zM_OSlgcO4uNmqi02NxshgVRt0I87DQHSyRau6AJo-4",[314,315],{"title":33,"path":34,"stem":35,"description":297,"icon":36,"children":-1},{"title":46,"path":47,"stem":48,"description":297,"children":-1},1784656164396]