Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10' r/724

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1adf74a3706efbcb0ea4625da106fb2
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

1 files changed, 266 insertions, 0 deletions

diff --git a/third_party/nix/src/libstore/nar-accessor.cc b/third_party/nix/src/libstore/nar-accessor.cc
new file mode 100644
index 000000000000..b74480684f2a
--- /dev/null
+++ b/third_party/nix/src/libstore/nar-accessor.cc
@@ -0,0 +1,266 @@
+#include "nar-accessor.hh"
+#include "archive.hh"
+#include "json.hh"
+
+#include <map>
+#include <stack>
+#include <algorithm>
+
+#include <nlohmann/json.hpp>
+
+namespace nix {
+
+struct NarMember
+{
+    FSAccessor::Type type = FSAccessor::Type::tMissing;
+
+    bool isExecutable = false;
+
+    /* If this is a regular file, position of the contents of this
+       file in the NAR. */
+    size_t start = 0, size = 0;
+
+    std::string target;
+
+    /* If this is a directory, all the children of the directory. */
+    std::map<std::string, NarMember> children;
+};
+
+struct NarAccessor : public FSAccessor
+{
+    std::shared_ptr<const std::string> nar;
+
+    GetNarBytes getNarBytes;
+
+    NarMember root;
+
+    struct NarIndexer : ParseSink, StringSource
+    {
+        NarAccessor & acc;
+
+        std::stack<NarMember *> parents;
+
+        std::string currentStart;
+        bool isExec = false;
+
+        NarIndexer(NarAccessor & acc, const std::string & nar)
+            : StringSource(nar), acc(acc)
+        { }
+
+        void createMember(const Path & path, NarMember member) {
+            size_t level = std::count(path.begin(), path.end(), '/');
+            while (parents.size() > level) parents.pop();
+
+            if (parents.empty()) {
+                acc.root = std::move(member);
+                parents.push(&acc.root);
+            } else {
+                if (parents.top()->type != FSAccessor::Type::tDirectory)
+                    throw Error("NAR file missing parent directory of path '%s'", path);
+                auto result = parents.top()->children.emplace(baseNameOf(path), std::move(member));
+                parents.push(&result.first->second);
+            }
+        }
+
+        void createDirectory(const Path & path) override
+        {
+            createMember(path, {FSAccessor::Type::tDirectory, false, 0, 0});
+        }
+
+        void createRegularFile(const Path & path) override
+        {
+            createMember(path, {FSAccessor::Type::tRegular, false, 0, 0});
+        }
+
+        void isExecutable() override
+        {
+            parents.top()->isExecutable = true;
+        }
+
+        void preallocateContents(unsigned long long size) override
+        {
+            currentStart = string(s, pos, 16);
+            assert(size <= std::numeric_limits<size_t>::max());
+            parents.top()->size = (size_t)size;
+            parents.top()->start = pos;
+        }
+
+        void receiveContents(unsigned char * data, unsigned int len) override
+        {
+            // Sanity check
+            if (!currentStart.empty()) {
+                assert(len < 16 || currentStart == string((char *) data, 16));
+                currentStart.clear();
+            }
+        }
+
+        void createSymlink(const Path & path, const string & target) override
+        {
+            createMember(path,
+                NarMember{FSAccessor::Type::tSymlink, false, 0, 0, target});
+        }
+    };
+
+    NarAccessor(ref<const std::string> nar) : nar(nar)
+    {
+        NarIndexer indexer(*this, *nar);
+        parseDump(indexer, indexer);
+    }
+
+    NarAccessor(const std::string & listing, GetNarBytes getNarBytes)
+        : getNarBytes(getNarBytes)
+    {
+        using json = nlohmann::json;
+
+        std::function<void(NarMember &, json &)> recurse;
+
+        recurse = [&](NarMember & member, json & v) {
+            std::string type = v["type"];
+
+            if (type == "directory") {
+                member.type = FSAccessor::Type::tDirectory;
+                for (auto i = v["entries"].begin(); i != v["entries"].end(); ++i) {
+                    std::string name = i.key();
+                    recurse(member.children[name], i.value());
+                }
+            } else if (type == "regular") {
+                member.type = FSAccessor::Type::tRegular;
+                member.size = v["size"];
+                member.isExecutable = v.value("executable", false);
+                member.start = v["narOffset"];
+            } else if (type == "symlink") {
+                member.type = FSAccessor::Type::tSymlink;
+                member.target = v.value("target", "");
+            } else return;
+        };
+
+        json v = json::parse(listing);
+        recurse(root, v);
+    }
+
+    NarMember * find(const Path & path)
+    {
+        Path canon = path == "" ? "" : canonPath(path);
+        NarMember * current = &root;
+        auto end = path.end();
+        for (auto it = path.begin(); it != end; ) {
+            // because it != end, the remaining component is non-empty so we need
+            // a directory
+            if (current->type != FSAccessor::Type::tDirectory) return nullptr;
+
+            // skip slash (canonPath above ensures that this is always a slash)
+            assert(*it == '/');
+            it += 1;
+
+            // lookup current component
+            auto next = std::find(it, end, '/');
+            auto child = current->children.find(std::string(it, next));
+            if (child == current->children.end()) return nullptr;
+            current = &child->second;
+
+            it = next;
+        }
+
+        return current;
+    }
+
+    NarMember & get(const Path & path) {
+        auto result = find(path);
+        if (result == nullptr)
+            throw Error("NAR file does not contain path '%1%'", path);
+        return *result;
+    }
+
+    Stat stat(const Path & path) override
+    {
+        auto i = find(path);
+        if (i == nullptr)
+            return {FSAccessor::Type::tMissing, 0, false};
+        return {i->type, i->size, i->isExecutable, i->start};
+    }
+
+    StringSet readDirectory(const Path & path) override
+    {
+        auto i = get(path);
+
+        if (i.type != FSAccessor::Type::tDirectory)
+            throw Error(format("path '%1%' inside NAR file is not a directory") % path);
+
+        StringSet res;
+        for (auto & child : i.children)
+            res.insert(child.first);
+
+        return res;
+    }
+
+    std::string readFile(const Path & path) override
+    {
+        auto i = get(path);
+        if (i.type != FSAccessor::Type::tRegular)
+            throw Error(format("path '%1%' inside NAR file is not a regular file") % path);
+
+        if (getNarBytes) return getNarBytes(i.start, i.size);
+
+        assert(nar);
+        return std::string(*nar, i.start, i.size);
+    }
+
+    std::string readLink(const Path & path) override
+    {
+        auto i = get(path);
+        if (i.type != FSAccessor::Type::tSymlink)
+            throw Error(format("path '%1%' inside NAR file is not a symlink") % path);
+        return i.target;
+    }
+};
+
+ref<FSAccessor> makeNarAccessor(ref<const std::string> nar)
+{
+    return make_ref<NarAccessor>(nar);
+}
+
+ref<FSAccessor> makeLazyNarAccessor(const std::string & listing,
+    GetNarBytes getNarBytes)
+{
+    return make_ref<NarAccessor>(listing, getNarBytes);
+}
+
+void listNar(JSONPlaceholder & res, ref<FSAccessor> accessor,
+    const Path & path, bool recurse)
+{
+    auto st = accessor->stat(path);
+
+    auto obj = res.object();
+
+    switch (st.type) {
+    case FSAccessor::Type::tRegular:
+        obj.attr("type", "regular");
+        obj.attr("size", st.fileSize);
+        if (st.isExecutable)
+            obj.attr("executable", true);
+        if (st.narOffset)
+            obj.attr("narOffset", st.narOffset);
+        break;
+    case FSAccessor::Type::tDirectory:
+        obj.attr("type", "directory");
+        {
+            auto res2 = obj.object("entries");
+            for (auto & name : accessor->readDirectory(path)) {
+                if (recurse) {
+                    auto res3 = res2.placeholder(name);
+                    listNar(res3, accessor, path + "/" + name, true);
+                } else
+                    res2.object(name);
+            }
+        }
+        break;
+    case FSAccessor::Type::tSymlink:
+        obj.attr("type", "symlink");
+        obj.attr("target", accessor->readLink(path));
+        break;
+    default:
+        throw Error("path '%s' does not exist in NAR", path);
+    }
+}
+
+}