lix/src/libstore/content-address.cc
John Ericson 242f9bf3dc std::visit by reference
I had started the trend of doing `std::visit` by value (because a type
error once mislead me into thinking that was the only form that
existed). While the optomizer in principle should be able to deal with
extra coppying or extra indirection once the lambdas inlined, sticking
with by reference is the conventional default. I hope this might even
improve performance.
2021-09-30 21:35:09 +00:00

150 lines
4.4 KiB
C++

#include "args.hh"
#include "content-address.hh"
#include "split.hh"
namespace nix {
std::string FixedOutputHash::printMethodAlgo() const
{
return makeFileIngestionPrefix(method) + printHashType(hash.type);
}
std::string makeFileIngestionPrefix(const FileIngestionMethod m)
{
switch (m) {
case FileIngestionMethod::Flat:
return "";
case FileIngestionMethod::Recursive:
return "r:";
default:
throw Error("impossible, caught both cases");
}
}
std::string makeFixedOutputCA(FileIngestionMethod method, const Hash & hash)
{
return "fixed:"
+ makeFileIngestionPrefix(method)
+ hash.to_string(Base32, true);
}
std::string renderContentAddress(ContentAddress ca)
{
return std::visit(overloaded {
[](TextHash & th) {
return "text:" + th.hash.to_string(Base32, true);
},
[](FixedOutputHash & fsh) {
return makeFixedOutputCA(fsh.method, fsh.hash);
}
}, ca);
}
std::string renderContentAddressMethod(ContentAddressMethod cam)
{
return std::visit(overloaded {
[](TextHashMethod & th) {
return std::string{"text:"} + printHashType(htSHA256);
},
[](FixedOutputHashMethod & fshm) {
return "fixed:" + makeFileIngestionPrefix(fshm.fileIngestionMethod) + printHashType(fshm.hashType);
}
}, cam);
}
/*
Parses content address strings up to the hash.
*/
static ContentAddressMethod parseContentAddressMethodPrefix(std::string_view & rest)
{
std::string_view wholeInput { rest };
std::string_view prefix;
{
auto optPrefix = splitPrefixTo(rest, ':');
if (!optPrefix)
throw UsageError("not a content address because it is not in the form '<prefix>:<rest>': %s", wholeInput);
prefix = *optPrefix;
}
auto parseHashType_ = [&](){
auto hashTypeRaw = splitPrefixTo(rest, ':');
if (!hashTypeRaw)
throw UsageError("content address hash must be in form '<algo>:<hash>', but found: %s", wholeInput);
HashType hashType = parseHashType(*hashTypeRaw);
return std::move(hashType);
};
// Switch on prefix
if (prefix == "text") {
// No parsing of the ingestion method, "text" only support flat.
HashType hashType = parseHashType_();
if (hashType != htSHA256)
throw Error("text content address hash should use %s, but instead uses %s",
printHashType(htSHA256), printHashType(hashType));
return TextHashMethod {};
} else if (prefix == "fixed") {
// Parse method
auto method = FileIngestionMethod::Flat;
if (splitPrefix(rest, "r:"))
method = FileIngestionMethod::Recursive;
HashType hashType = parseHashType_();
return FixedOutputHashMethod {
.fileIngestionMethod = method,
.hashType = std::move(hashType),
};
} else
throw UsageError("content address prefix '%s' is unrecognized. Recogonized prefixes are 'text' or 'fixed'", prefix);
}
ContentAddress parseContentAddress(std::string_view rawCa) {
auto rest = rawCa;
ContentAddressMethod caMethod = parseContentAddressMethodPrefix(rest);
return std::visit(
overloaded {
[&](TextHashMethod & thm) {
return ContentAddress(TextHash {
.hash = Hash::parseNonSRIUnprefixed(rest, htSHA256)
});
},
[&](FixedOutputHashMethod & fohMethod) {
return ContentAddress(FixedOutputHash {
.method = fohMethod.fileIngestionMethod,
.hash = Hash::parseNonSRIUnprefixed(rest, std::move(fohMethod.hashType)),
});
},
}, caMethod);
}
ContentAddressMethod parseContentAddressMethod(std::string_view caMethod)
{
std::string_view asPrefix {std::string{caMethod} + ":"};
return parseContentAddressMethodPrefix(asPrefix);
}
std::optional<ContentAddress> parseContentAddressOpt(std::string_view rawCaOpt)
{
return rawCaOpt == "" ? std::optional<ContentAddress>() : parseContentAddress(rawCaOpt);
};
std::string renderContentAddress(std::optional<ContentAddress> ca)
{
return ca ? renderContentAddress(*ca) : "";
}
Hash getContentAddressHash(const ContentAddress & ca)
{
return std::visit(overloaded {
[](const TextHash & th) {
return th.hash;
},
[](const FixedOutputHash & fsh) {
return fsh.hash;
}
}, ca);
}
}