primops: add builtins.convertHash

doc/manual/src/release-notes/rl-next.md

@@ -8,4 +8,6 @@
 
 - Introduce new flake installable syntax `flakeref#.attrPath` where the "." prefix denotes no searching of default attribute prefixes like `packages.<SYSTEM>` or `legacyPackages.<SYSTEM>`.
 
+- Introduce a new built-in function [`builtins.convertHash`](@docroot@/language/builtins.md#builtins-convertHash).
+
 - `builtins.fetchTree` is now marked as stable.

perl/lib/Nix/Store.xs

@@ -78,7 +78,7 @@ SV * queryReferences(char * path)
 SV * queryPathHash(char * path)
     PPCODE:
         try {
-            auto s = store()->queryPathInfo(store()->parseStorePath(path))->narHash.to_string(Base32, true);
+            auto s = store()->queryPathInfo(store()->parseStorePath(path))->narHash.to_string(HashFormat::Base32, true);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -104,7 +104,7 @@ SV * queryPathInfo(char * path, int base32)
                 XPUSHs(&PL_sv_undef);
             else
                 XPUSHs(sv_2mortal(newSVpv(store()->printStorePath(*info->deriver).c_str(), 0)));
-            auto s = info->narHash.to_string(base32 ? Base32 : Base16, true);
+            auto s = info->narHash.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, true);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
             mXPUSHi(info->registrationTime);
             mXPUSHi(info->narSize);
@@ -206,7 +206,7 @@ SV * hashPath(char * algo, int base32, char * path)
     PPCODE:
         try {
             Hash h = hashPath(parseHashType(algo), path).first;
-            auto s = h.to_string(base32 ? Base32 : Base16, false);
+            auto s = h.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -217,7 +217,7 @@ SV * hashFile(char * algo, int base32, char * path)
     PPCODE:
         try {
             Hash h = hashFile(parseHashType(algo), path);
-            auto s = h.to_string(base32 ? Base32 : Base16, false);
+            auto s = h.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -228,7 +228,7 @@ SV * hashString(char * algo, int base32, char * s)
     PPCODE:
         try {
             Hash h = hashString(parseHashType(algo), s);
-            auto s = h.to_string(base32 ? Base32 : Base16, false);
+            auto s = h.to_string(base32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());
@@ -239,7 +239,7 @@ SV * convertHash(char * algo, char * s, int toBase32)
     PPCODE:
         try {
             auto h = Hash::parseAny(s, parseHashType(algo));
-            auto s = h.to_string(toBase32 ? Base32 : Base16, false);
+            auto s = h.to_string(toBase32 ? HashFormat::Base32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());

src/libexpr/eval-cache.cc

@@ -50,7 +50,7 @@ struct AttrDb
         Path cacheDir = getCacheDir() + "/nix/eval-cache-v5";
         createDirs(cacheDir);
 
-        Path dbPath = cacheDir + "/" + fingerprint.to_string(Base16, false) + ".sqlite";
+        Path dbPath = cacheDir + "/" + fingerprint.to_string(HashFormat::Base16, false) + ".sqlite";
 
         state->db = SQLite(dbPath);
         state->db.isCache();

src/libexpr/primops.cc

@@ -1758,7 +1758,7 @@ static void prim_hashFile(EvalState & state, const PosIdx pos, Value * * args, V
 
     auto path = realisePath(state, pos, *args[1]);
 
-    v.mkString(hashString(*ht, path.readFile()).to_string(Base16, false));
+    v.mkString(hashString(*ht, path.readFile()).to_string(HashFormat::Base16, false));
 }
 
 static RegisterPrimOp primop_hashFile({
@@ -3760,7 +3760,7 @@ static void prim_hashString(EvalState & state, const PosIdx pos, Value * * args,
     NixStringContext context; // discarded
     auto s = state.forceString(*args[1], context, pos, "while evaluating the second argument passed to builtins.hashString");
 
-    v.mkString(hashString(*ht, s).to_string(Base16, false));
+    v.mkString(hashString(*ht, s).to_string(HashFormat::Base16, false));
 }
 
 static RegisterPrimOp primop_hashString({
@@ -3774,6 +3774,101 @@ static RegisterPrimOp primop_hashString({
     .fun = prim_hashString,
 });
 
+static void prim_convertHash(EvalState & state, const PosIdx pos, Value * * args, Value & v)
+{
+    state.forceAttrs(*args[0], pos, "while evaluating the first argument passed to builtins.convertHash");
+    auto &inputAttrs = args[0]->attrs;
+
+    Bindings::iterator iteratorHash = getAttr(state, state.symbols.create("hash"), inputAttrs, "while locating the attribute 'hash'");
+    auto hash = state.forceStringNoCtx(*iteratorHash->value, pos, "while evaluating the attribute 'hash'");
+
+    Bindings::iterator iteratorHashAlgo = inputAttrs->find(state.symbols.create("hashAlgo"));
+    std::optional<HashType> ht = std::nullopt;
+    if (iteratorHashAlgo != inputAttrs->end()) {
+        ht = parseHashType(state.forceStringNoCtx(*iteratorHashAlgo->value, pos, "while evaluating the attribute 'hashAlgo'"));
+    }
+
+    Bindings::iterator iteratorToHashFormat = getAttr(state, state.symbols.create("toHashFormat"), args[0]->attrs, "while locating the attribute 'toHashFormat'");
+    HashFormat hf = parseHashFormat(state.forceStringNoCtx(*iteratorToHashFormat->value, pos, "while evaluating the attribute 'toHashFormat'"));
+
+    v.mkString(Hash::parseAny(hash, ht).to_string(hf, hf == HashFormat::SRI));
+}
+
+static RegisterPrimOp primop_convertHash({
+    .name = "__convertHash",
+    .args = {"args"},
+    .doc = R"(
+      Return the specified representation of a hash string, based on the attributes presented in *args*:
+
+      - `hash`
+
+        The hash to be converted.
+        The hash format is detected automatically.
+
+      - `hashAlgo`
+
+        The algorithm used to create the hash. Must be one of
+        - `"md5"`
+        - `"sha1"`
+        - `"sha256"`
+        - `"sha512"`
+
+        The attribute may be omitted when `hash` is an [SRI hash](https://www.w3.org/TR/SRI/#the-integrity-attribute) or when the hash is prefixed with the hash algorithm name followed by a colon.
+        That `<hashAlgo>:<hashBody>` syntax is supported for backwards compatibility with existing tooling.
+
+      - `toHashFormat`
+
+        The format of the resulting hash. Must be one of
+        - `"base16"`
+        - `"base32"`
+        - `"base64"`
+        - `"sri"`
+
+      The result hash is the *toHashFormat* representation of the hash *hash*.
+
+      > **Example**
+      >
+      >   Convert a SHA256 hash in Base16 to SRI:
+      >
+      > ```nix
+      > builtins.convertHash {
+      >   hash = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
+      >   toHashFormat = "sri";
+      >   hashAlgo = "sha256";
+      > }
+      > ```
+      >
+      >     "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU="
+
+      > **Example**
+      >
+      >   Convert a SHA256 hash in SRI to Base16:
+      >
+      > ```nix
+      > builtins.convertHash {
+      >   hash = "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=";
+      >   toHashFormat = "base16";
+      > }
+      > ```
+      >
+      >     "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+
+      > **Example**
+      >
+      >   Convert a hash in the form `<hashAlgo>:<hashBody>` in Base16 to SRI:
+      >
+      > ```nix
+      > builtins.convertHash {
+      >   hash = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
+      >   toHashFormat = "sri";
+      > }
+      > ```
+      >
+      >     "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU="
+    )",
+    .fun = prim_convertHash,
+});
+
 struct RegexCache
 {
     // TODO use C++20 transparent comparison when available

src/libexpr/primops/fetchTree.cc

@@ -31,7 +31,7 @@ void emitTreeAttrs(
 
     auto narHash = input.getNarHash();
     assert(narHash);
-    attrs.alloc("narHash").mkString(narHash->to_string(SRI, true));
+    attrs.alloc("narHash").mkString(narHash->to_string(HashFormat::SRI, true));
 
     if (input.getType() == "git")
         attrs.alloc("submodules").mkBool(
@@ -297,7 +297,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
             : hashFile(htSHA256, state.store->toRealPath(storePath));
         if (hash != *expectedHash)
             state.debugThrowLastTrace(EvalError((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n  specified: %s\n  got:       %s",
-                *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true)));
+                *url, expectedHash->to_string(HashFormat::Base32, true), hash.to_string(HashFormat::Base32, true)));
     }
 
     state.allowAndSetStorePathString(storePath, v);

src/libexpr/tests/error_traces.cc

@@ -1084,7 +1084,7 @@ namespace nix {
 
         ASSERT_TRACE1("hashString \"foo\" \"content\"",
                       UsageError,
-                      hintfmt("unknown hash algorithm '%s'", "foo"));
+                      hintfmt("unknown hash algorithm '%s', expect 'md5', 'sha1', 'sha256', or 'sha512'", "foo"));
 
         ASSERT_TRACE2("hashString \"sha256\" {}",
                       TypeError,

src/libfetchers/fetchers.cc

@@ -147,12 +147,12 @@ std::pair<Tree, Input> Input::fetch(ref<Store> store) const
     };
 
     auto narHash = store->queryPathInfo(tree.storePath)->narHash;
-    input.attrs.insert_or_assign("narHash", narHash.to_string(SRI, true));
+    input.attrs.insert_or_assign("narHash", narHash.to_string(HashFormat::SRI, true));
 
     if (auto prevNarHash = getNarHash()) {
         if (narHash != *prevNarHash)
             throw Error((unsigned int) 102, "NAR hash mismatch in input '%s' (%s), expected '%s', got '%s'",
-                to_string(), tree.actualPath, prevNarHash->to_string(SRI, true), narHash.to_string(SRI, true));
+                to_string(), tree.actualPath, prevNarHash->to_string(HashFormat::SRI, true), narHash.to_string(HashFormat::SRI, true));
     }
 
     if (auto prevLastModified = getLastModified()) {

src/libfetchers/git.cc

@@ -46,7 +46,7 @@ bool touchCacheFile(const Path & path, time_t touch_time)
 Path getCachePath(std::string_view key)
 {
     return getCacheDir() + "/nix/gitv3/" +
-        hashString(htSHA256, key).to_string(Base32, false);
+        hashString(htSHA256, key).to_string(HashFormat::Base32, false);
 }
 
 // Returns the name of the HEAD branch.
@@ -417,7 +417,7 @@ struct GitInputScheme : InputScheme
         auto checkHashType = [&](const std::optional<Hash> & hash)
         {
             if (hash.has_value() && !(hash->type == htSHA1 || hash->type == htSHA256))
-                throw Error("Hash '%s' is not supported by Git. Supported types are sha1 and sha256.", hash->to_string(Base16, true));
+                throw Error("Hash '%s' is not supported by Git. Supported types are sha1 and sha256.", hash->to_string(HashFormat::Base16, true));
         };
 
         auto getLockedAttrs = [&]()

src/libfetchers/github.cc

@@ -125,7 +125,7 @@ struct GitArchiveInputScheme : InputScheme
         auto path = owner + "/" + repo;
         assert(!(ref && rev));
         if (ref) path += "/" + *ref;
-        if (rev) path += "/" + rev->to_string(Base16, false);
+        if (rev) path += "/" + rev->to_string(HashFormat::Base16, false);
         return ParsedURL {
             .scheme = type(),
             .path = path,
@@ -296,7 +296,7 @@ struct GitHubInputScheme : GitArchiveInputScheme
             : "https://api.%s/repos/%s/%s/tarball/%s";
 
         const auto url = fmt(urlFmt, host, getOwner(input), getRepo(input),
-            input.getRev()->to_string(Base16, false));
+            input.getRev()->to_string(HashFormat::Base16, false));
 
         return DownloadUrl { url, headers };
     }
@@ -362,7 +362,7 @@ struct GitLabInputScheme : GitArchiveInputScheme
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("gitlab.com");
         auto url = fmt("https://%s/api/v4/projects/%s%%2F%s/repository/archive.tar.gz?sha=%s",
             host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"),
-            input.getRev()->to_string(Base16, false));
+            input.getRev()->to_string(HashFormat::Base16, false));
 
         Headers headers = makeHeadersWithAuthTokens(host);
         return DownloadUrl { url, headers };
@@ -449,7 +449,7 @@ struct SourceHutInputScheme : GitArchiveInputScheme
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("git.sr.ht");
         auto url = fmt("https://%s/%s/%s/archive/%s.tar.gz",
             host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"),
-            input.getRev()->to_string(Base16, false));
+            input.getRev()->to_string(HashFormat::Base16, false));
 
         Headers headers = makeHeadersWithAuthTokens(host);
         return DownloadUrl { url, headers };

src/libfetchers/mercurial.cc

@@ -206,7 +206,7 @@ struct MercurialInputScheme : InputScheme
         auto checkHashType = [&](const std::optional<Hash> & hash)
         {
             if (hash.has_value() && hash->type != htSHA1)
-                throw Error("Hash '%s' is not supported by Mercurial. Only sha1 is supported.", hash->to_string(Base16, true));
+                throw Error("Hash '%s' is not supported by Mercurial. Only sha1 is supported.", hash->to_string(HashFormat::Base16, true));
         };
 
 
@@ -252,7 +252,7 @@ struct MercurialInputScheme : InputScheme
             }
         }
 
-        Path cacheDir = fmt("%s/nix/hg/%s", getCacheDir(), hashString(htSHA256, actualUrl).to_string(Base32, false));
+        Path cacheDir = fmt("%s/nix/hg/%s", getCacheDir(), hashString(htSHA256, actualUrl).to_string(HashFormat::Base32, false));
 
         /* If this is a commit hash that we already have, we don't
            have to pull again. */

src/libfetchers/tarball.cc

@@ -250,7 +250,7 @@ struct CurlInputScheme : InputScheme
         // NAR hashes are preferred over file hashes since tar/zip
         // files don't have a canonical representation.
         if (auto narHash = input.getNarHash())
-            url.query.insert_or_assign("narHash", narHash->to_string(SRI, true));
+            url.query.insert_or_assign("narHash", narHash->to_string(HashFormat::SRI, true));
         return url;
     }
 

src/libstore/binary-cache-store.cc

@@ -164,7 +164,7 @@ ref<const ValidPathInfo> BinaryCacheStore::addToStoreCommon(
     auto [fileHash, fileSize] = fileHashSink.finish();
     narInfo->fileHash = fileHash;
     narInfo->fileSize = fileSize;
-    narInfo->url = "nar/" + narInfo->fileHash->to_string(Base32, false) + ".nar"
+    narInfo->url = "nar/" + narInfo->fileHash->to_string(HashFormat::Base32, false) + ".nar"
         + (compression == "xz" ? ".xz" :
            compression == "bzip2" ? ".bz2" :
            compression == "zstd" ? ".zst" :

src/libstore/build/local-derivation-goal.cc

@@ -1066,7 +1066,7 @@ void LocalDerivationGoal::initTmpDir() {
                 env[i.first] = i.second;
             } else {
                 auto hash = hashString(htSHA256, i.first);
-                std::string fn = ".attr-" + hash.to_string(Base32, false);
+                std::string fn = ".attr-" + hash.to_string(HashFormat::Base32, false);
                 Path p = tmpDir + "/" + fn;
                 writeFile(p, rewriteStrings(i.second, inputRewrites));
                 chownToBuilder(p);
@@ -2583,8 +2583,8 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
                     delayedException = std::make_exception_ptr(
                         BuildError("hash mismatch in fixed-output derivation '%s':\n  specified: %s\n     got:    %s",
                             worker.store.printStorePath(drvPath),
-                            wanted.to_string(SRI, true),
-                            got.to_string(SRI, true)));
+                            wanted.to_string(HashFormat::SRI, true),
+                            got.to_string(HashFormat::SRI, true)));
                 }
                 if (!newInfo0.references.empty())
                     delayedException = std::make_exception_ptr(

src/libstore/builtins/fetchurl.cc

@@ -65,7 +65,7 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
                 if (!hasSuffix(hashedMirror, "/")) hashedMirror += '/';
                 std::optional<HashType> ht = parseHashTypeOpt(getAttr("outputHashAlgo"));
                 Hash h = newHashAllowEmpty(getAttr("outputHash"), ht);
-                fetch(hashedMirror + printHashType(h.type) + "/" + h.to_string(Base16, false));
+                fetch(hashedMirror + printHashType(h.type) + "/" + h.to_string(HashFormat::Base16, false));
                 return;
             } catch (Error & e) {
                 debug(e.what());

src/libstore/content-address.cc

@@ -60,7 +60,7 @@ std::string ContentAddress::render() const
                 + makeFileIngestionPrefix(method);
         },
     }, method.raw)
-        + this->hash.to_string(Base32, true);
+        + this->hash.to_string(HashFormat::Base32, true);
 }
 
 /**

src/libstore/daemon.cc

@@ -334,7 +334,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         logger->startWork();
         auto hash = store->queryPathInfo(path)->narHash;
         logger->stopWork();
-        to << hash.to_string(Base16, false);
+        to << hash.to_string(HashFormat::Base16, false);
         break;
     }