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Impure derivations are derivations that can produce a different result
every time they're built. Example:
stdenv.mkDerivation {
name = "impure";
__impure = true; # marks this derivation as impure
outputHashAlgo = "sha256";
outputHashMode = "recursive";
buildCommand = "date > $out";
};
Some important characteristics:
* This requires the 'impure-derivations' experimental feature.
* Impure derivations are not "cached". Thus, running "nix-build" on
the example above multiple times will cause a rebuild every time.
* They are implemented similar to CA derivations, i.e. the output is
moved to a content-addressed path in the store. The difference is
that we don't register a realisation in the Nix database.
* Pure derivations are not allowed to depend on impure derivations. In
the future fixed-output derivations will be allowed to depend on
impure derivations, thus forming an "impurity barrier" in the
dependency graph.
* When sandboxing is enabled, impure derivations can access the
network in the same way as fixed-output derivations. In relaxed
sandboxing mode, they can access the local filesystem.
94 lines
2.6 KiB
C++
94 lines
2.6 KiB
C++
#include "store-api.hh"
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#include <sodium.h>
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namespace nix {
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static void checkName(std::string_view path, std::string_view name)
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{
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if (name.empty())
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throw BadStorePath("store path '%s' has an empty name", path);
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if (name.size() > 211)
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throw BadStorePath("store path '%s' has a name longer than 211 characters", path);
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for (auto c : name)
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if (!((c >= '0' && c <= '9')
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|| (c >= 'a' && c <= 'z')
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|| (c >= 'A' && c <= 'Z')
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|| c == '+' || c == '-' || c == '.' || c == '_' || c == '?' || c == '='))
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throw BadStorePath("store path '%s' contains illegal character '%s'", path, c);
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}
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StorePath::StorePath(std::string_view _baseName)
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: baseName(_baseName)
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{
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if (baseName.size() < HashLen + 1)
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throw BadStorePath("'%s' is too short to be a valid store path", baseName);
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for (auto c : hashPart())
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if (c == 'e' || c == 'o' || c == 'u' || c == 't'
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|| !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'z')))
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throw BadStorePath("store path '%s' contains illegal base-32 character '%s'", baseName, c);
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checkName(baseName, name());
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}
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StorePath::StorePath(const Hash & hash, std::string_view _name)
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: baseName((hash.to_string(Base32, false) + "-").append(std::string(_name)))
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{
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checkName(baseName, name());
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}
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bool StorePath::isDerivation() const
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{
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return hasSuffix(name(), drvExtension);
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}
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StorePath StorePath::dummy("ffffffffffffffffffffffffffffffff-x");
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StorePath StorePath::random(std::string_view name)
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{
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Hash hash(htSHA1);
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randombytes_buf(hash.hash, hash.hashSize);
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return StorePath(hash, name);
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}
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StorePath Store::parseStorePath(std::string_view path) const
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{
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auto p = canonPath(std::string(path));
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if (dirOf(p) != storeDir)
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throw BadStorePath("path '%s' is not in the Nix store", p);
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return StorePath(baseNameOf(p));
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}
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std::optional<StorePath> Store::maybeParseStorePath(std::string_view path) const
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{
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try {
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return parseStorePath(path);
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} catch (Error &) {
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return {};
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}
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}
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bool Store::isStorePath(std::string_view path) const
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{
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return (bool) maybeParseStorePath(path);
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}
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StorePathSet Store::parseStorePathSet(const PathSet & paths) const
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{
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StorePathSet res;
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for (auto & i : paths) res.insert(parseStorePath(i));
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return res;
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}
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std::string Store::printStorePath(const StorePath & path) const
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{
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return (storeDir + "/").append(path.to_string());
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}
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PathSet Store::printStorePathSet(const StorePathSet & paths) const
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{
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PathSet res;
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for (auto & i : paths) res.insert(printStorePath(i));
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return res;
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}
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}
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