68 lines
1.9 KiB
C++
68 lines
1.9 KiB
C++
#ifndef __GLOBALS_H
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#define __GLOBALS_H
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#include <string>
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using namespace std;
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/* Database names. */
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/* dbHash2Paths :: Hash -> [Path]
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Maintains a mapping from hashes to lists of paths. This is what we
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use to resolve Hash(hash) content descriptors. */
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extern string dbHash2Paths;
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/* dbSuccessors :: Hash -> Hash
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Each pair (h1, h2) in this mapping records the fact that a
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successor of an fstate expression with hash h1 is stored in a file
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with hash h2.
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Note that a term $y$ is successor of $x$ iff there exists a
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sequence of rewrite steps that rewrites $x$ into $y$.
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Also note that instead of a successor, $y$ can be any term
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equivalent to $x$, that is, reducing to the same result, as long as
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$x$ is equal to or a successor of $y$. (This is useful, e.g., for
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shared derivate caching over the network).
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*/
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extern string dbSuccessors;
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/* dbSubstitutes :: Hash -> [Hash]
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Each pair $(h, [hs])$ tells Nix that it can realise any of the
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fstate expressions referenced by the hashes in $hs$ to obtain a Nix
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archive that, when unpacked, will produce a path with hash $h$.
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The main purpose of this is for distributed caching of derivates.
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One system can compute a derivate with hash $h$ and put it on a
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website (as a Nix archive), for instance, and then another system
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can register a substitute for that derivate. The substitute in
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this case might be an fstate expression that fetches the Nix
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archive.
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*/
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extern string dbSubstitutes;
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/* Path names. */
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/* nixStore is the directory where we generally store atomic and
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derived files. */
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extern string nixStore;
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/* nixLogDir is the directory where we log various operations. */
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extern string nixLogDir;
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/* nixDB is the file name of the Berkeley DB database where we
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maintain the dbXXX mappings. */
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extern string nixDB;
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/* Initialize the databases. */
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void initDB();
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#endif /* !__GLOBALS_H */
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