Add a Git-based content-addressed tarball cache

src/libfetchers/attrs.cc

@@ -104,4 +104,9 @@ std::map<std::string, std::string> attrsToQuery(const Attrs & attrs)
     return query;
 }
 
+Hash getRevAttr(const Attrs & attrs, const std::string & name)
+{
+    return Hash::parseAny(getStrAttr(attrs, name), HashAlgorithm::SHA1);
+}
+
 }

src/libfetchers/attrs.hh

@@ -39,4 +39,6 @@ bool getBoolAttr(const Attrs & attrs, const std::string & name);
 
 std::map<std::string, std::string> attrsToQuery(const Attrs & attrs);
 
+Hash getRevAttr(const Attrs & attrs, const std::string & name);
+
 }

src/libfetchers/git-utils.cc

@@ -6,8 +6,8 @@
 #include "finally.hh"
 #include "processes.hh"
 #include "signals.hh"
-
-#include <boost/core/span.hpp>
+#include "users.hh"
+#include "fs-sink.hh"
 
 #include <git2/attr.h>
 #include <git2/blob.h>
@@ -28,6 +28,7 @@
 #include <unordered_set>
 #include <queue>
 #include <regex>
+#include <span>
 
 namespace std {
 
@@ -356,6 +357,8 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
 
     ref<InputAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError e) override;
 
+    ref<GitFileSystemObjectSink> getFileSystemObjectSink() override;
+
     static int sidebandProgressCallback(const char * str, int len, void * payload)
     {
         auto act = (Activity *) payload;
@@ -770,6 +773,154 @@ struct GitExportIgnoreInputAccessor : CachingFilteringInputAccessor {
 
 };
 
+struct GitFileSystemObjectSinkImpl : GitFileSystemObjectSink
+{
+    ref<GitRepoImpl> repo;
+
+    struct PendingDir
+    {
+        std::string name;
+        TreeBuilder builder;
+    };
+
+    std::vector<PendingDir> pendingDirs;
+
+    size_t componentsToStrip = 1;
+
+    void pushBuilder(std::string name)
+    {
+        git_treebuilder * b;
+        if (git_treebuilder_new(&b, *repo, nullptr))
+            throw Error("creating a tree builder: %s", git_error_last()->message);
+        pendingDirs.push_back({ .name = std::move(name), .builder = TreeBuilder(b) });
+    };
+
+    GitFileSystemObjectSinkImpl(ref<GitRepoImpl> repo) : repo(repo)
+    {
+        pushBuilder("");
+    }
+
+    std::pair<git_oid, std::string> popBuilder()
+    {
+        assert(!pendingDirs.empty());
+        auto pending = std::move(pendingDirs.back());
+        git_oid oid;
+        if (git_treebuilder_write(&oid, pending.builder.get()))
+            throw Error("creating a tree object: %s", git_error_last()->message);
+        pendingDirs.pop_back();
+        return {oid, pending.name};
+    };
+
+    void addToTree(const std::string & name, const git_oid & oid, git_filemode_t mode)
+    {
+        assert(!pendingDirs.empty());
+        auto & pending = pendingDirs.back();
+        if (git_treebuilder_insert(nullptr, pending.builder.get(), name.c_str(), &oid, mode))
+            throw Error("adding a file to a tree builder: %s", git_error_last()->message);
+    };
+
+    void updateBuilders(std::span<const std::string> names)
+    {
+        // Find the common prefix of pendingDirs and names.
+        size_t prefixLen = 0;
+        for (; prefixLen < names.size() && prefixLen + 1 < pendingDirs.size(); ++prefixLen)
+            if (names[prefixLen] != pendingDirs[prefixLen + 1].name)
+                break;
+
+        // Finish the builders that are not part of the common prefix.
+        for (auto n = pendingDirs.size(); n > prefixLen + 1; --n) {
+            auto [oid, name] = popBuilder();
+            addToTree(name, oid, GIT_FILEMODE_TREE);
+        }
+
+        // Create builders for the new directories.
+        for (auto n = prefixLen; n < names.size(); ++n)
+            pushBuilder(names[n]);
+    };
+
+    bool prepareDirs(const std::vector<std::string> & pathComponents, bool isDir)
+    {
+        std::span<const std::string> pathComponents2{pathComponents};
+
+        if (pathComponents2.size() <= componentsToStrip) return false;
+        pathComponents2 = pathComponents2.subspan(componentsToStrip);
+
+        updateBuilders(
+            isDir
+            ? pathComponents2
+            : pathComponents2.first(pathComponents2.size() - 1));
+
+        return true;
+    }
+
+    void createRegularFile(
+        const Path & path,
+        std::function<void(CreateRegularFileSink &)> func) override
+    {
+        auto pathComponents = tokenizeString<std::vector<std::string>>(path, "/");
+        if (!prepareDirs(pathComponents, false)) return;
+
+        git_writestream * stream = nullptr;
+        if (git_blob_create_from_stream(&stream, *repo, nullptr))
+            throw Error("creating a blob stream object: %s", git_error_last()->message);
+
+        struct CRF : CreateRegularFileSink {
+            const Path & path;
+            GitFileSystemObjectSinkImpl & back;
+            git_writestream * stream;
+            bool executable = false;
+            CRF(const Path & path, GitFileSystemObjectSinkImpl & back, git_writestream * stream)
+                : path(path), back(back), stream(stream)
+            {}
+            void operator () (std::string_view data) override
+            {
+                if (stream->write(stream, data.data(), data.size()))
+                    throw Error("writing a blob for tarball member '%s': %s", path, git_error_last()->message);
+            }
+            void isExecutable() override
+            {
+                executable = true;
+            }
+        } crf { path, *this, stream };
+        func(crf);
+
+        git_oid oid;
+        if (git_blob_create_from_stream_commit(&oid, stream))
+            throw Error("creating a blob object for tarball member '%s': %s", path, git_error_last()->message);
+
+        addToTree(*pathComponents.rbegin(), oid,
+            crf.executable
+            ? GIT_FILEMODE_BLOB_EXECUTABLE
+            : GIT_FILEMODE_BLOB);
+    }
+
+    void createDirectory(const Path & path) override
+    {
+        auto pathComponents = tokenizeString<std::vector<std::string>>(path, "/");
+        (void) prepareDirs(pathComponents, true);
+    }
+
+    void createSymlink(const Path & path, const std::string & target) override
+    {
+        auto pathComponents = tokenizeString<std::vector<std::string>>(path, "/");
+        if (!prepareDirs(pathComponents, false)) return;
+
+        git_oid oid;
+        if (git_blob_create_from_buffer(&oid, *repo, target.c_str(), target.size()))
+            throw Error("creating a blob object for tarball symlink member '%s': %s", path, git_error_last()->message);
+
+        addToTree(*pathComponents.rbegin(), oid, GIT_FILEMODE_LINK);
+    }
+
+    Hash sync() override {
+        updateBuilders({});
+
+        auto [oid, _name] = popBuilder();
+
+        return toHash(oid);
+    }
+};
+
 ref<GitInputAccessor> GitRepoImpl::getRawAccessor(const Hash & rev)
 {
     auto self = ref<GitRepoImpl>(shared_from_this());
@@ -804,6 +955,11 @@ ref<InputAccessor> GitRepoImpl::getAccessor(const WorkdirInfo & wd, bool exportI
     }
 }
 
+ref<GitFileSystemObjectSink> GitRepoImpl::getFileSystemObjectSink()
+{
+    return make_ref<GitFileSystemObjectSinkImpl>(ref<GitRepoImpl>(shared_from_this()));
+}
+
 std::vector<std::tuple<GitRepoImpl::Submodule, Hash>> GitRepoImpl::getSubmodules(const Hash & rev, bool exportIgnore)
 {
     /* Read the .gitmodules files from this revision. */
@@ -830,5 +986,11 @@ std::vector<std::tuple<GitRepoImpl::Submodule, Hash>> GitRepoImpl::getSubmodules
     return result;
 }
 
+ref<GitRepo> getTarballCache()
+{
+    static auto repoDir = std::filesystem::path(getCacheDir()) / "nix" / "tarball-cache";
+
+    return GitRepo::openRepo(repoDir, true, true);
+}
 
 }

src/libfetchers/git-utils.hh

@@ -2,11 +2,20 @@
 
 #include "filtering-input-accessor.hh"
 #include "input-accessor.hh"
+#include "fs-sink.hh"
 
 namespace nix {
 
 namespace fetchers { struct PublicKey; }
 
+struct GitFileSystemObjectSink : FileSystemObjectSink
+{
+    /**
+     * Flush builder and return a final Git hash.
+     */
+    virtual Hash sync() = 0;
+};
+
 struct GitRepo
 {
     virtual ~GitRepo()
@@ -64,18 +73,14 @@ struct GitRepo
         const std::string & url,
         const std::string & base) = 0;
 
-    struct TarballInfo
-    {
-        Hash treeHash;
-        time_t lastModified;
-    };
-
     virtual bool hasObject(const Hash & oid) = 0;
 
     virtual ref<InputAccessor> getAccessor(const Hash & rev, bool exportIgnore) = 0;
 
     virtual ref<InputAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError makeNotAllowedError) = 0;
 
+    virtual ref<GitFileSystemObjectSink> getFileSystemObjectSink() = 0;
+
     virtual void fetch(
         const std::string & url,
         const std::string & refspec,
@@ -90,4 +95,6 @@ struct GitRepo
         const std::vector<fetchers::PublicKey> & publicKeys) = 0;
 };
 
+ref<GitRepo> getTarballCache();
+
 }