diff options
Diffstat (limited to 'src/libstore/derivations.hh')
| -rw-r--r-- | src/libstore/derivations.hh | 37 |
1 files changed, 35 insertions, 2 deletions
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh index 36ac09210..c57468fac 100644 --- a/src/libstore/derivations.hh +++ b/src/libstore/derivations.hh @@ -6,6 +6,7 @@ #include "content-address.hh" #include <map> +#include <variant> namespace nix { @@ -114,10 +115,42 @@ Derivation readDerivation(const Store & store, const Path & drvPath, std::string // FIXME: remove bool isDerivation(const string & fileName); -Hash hashDerivationModulo(Store & store, const Derivation & drv, bool maskOutputs); +// known CA drv's output hashes, current just for fixed-output derivations +// whose output hashes are always known since they are fixed up-front. +typedef std::map<std::string, Hash> CaOutputHashes; + +typedef std::variant< + Hash, // regular DRV normalized hash + CaOutputHashes +> DrvHashModulo; + +/* Returns hashes with the details of fixed-output subderivations + expunged. + + A fixed-output derivation is a derivation whose outputs have a + specified content hash and hash algorithm. (Currently they must have + exactly one output (`out'), which is specified using the `outputHash' + and `outputHashAlgo' attributes, but the algorithm doesn't assume + this.) We don't want changes to such derivations to propagate upwards + through the dependency graph, changing output paths everywhere. + + For instance, if we change the url in a call to the `fetchurl' + function, we do not want to rebuild everything depending on it---after + all, (the hash of) the file being downloaded is unchanged. So the + *output paths* should not change. On the other hand, the *derivation + paths* should change to reflect the new dependency graph. + + For fixed-output derivations, this returns a map from the name of + each output to its hash, unique up to the output's contents. + + For regular derivations, it returns a single hash of the derivation + ATerm, after subderivations have been likewise expunged from that + derivation. + */ +DrvHashModulo hashDerivationModulo(Store & store, const Derivation & drv, bool maskOutputs); /* Memoisation of hashDerivationModulo(). */ -typedef std::map<StorePath, Hash> DrvHashes; +typedef std::map<StorePath, DrvHashModulo> DrvHashes; extern DrvHashes drvHashes; // FIXME: global, not thread-safe |