From 2d6df16849ebcf237d17c919727756d90974daba Mon Sep 17 00:00:00 2001
From: Nicole Mazzuca <t-nimaz@microsoft.com>
Date: Wed, 10 Jul 2019 14:35:10 -0700
Subject: [PATCH] remove_all parallelized, and fix the issues with symlink

---
 toolsrc/include/vcpkg/base/files.h      |  38 ++++-
 toolsrc/include/vcpkg/base/rng.h        | 165 ++++++++++++++++----
 toolsrc/include/vcpkg/base/work_queue.h | 183 +++++++++++++++++++++++
 toolsrc/src/vcpkg/base/files.cpp        | 190 +++++++++++++++++++-----
 toolsrc/src/vcpkg/base/rng.cpp          |   4 +-
 5 files changed, 508 insertions(+), 72 deletions(-)
 create mode 100644 toolsrc/include/vcpkg/base/work_queue.h

diff --git a/toolsrc/include/vcpkg/base/files.h b/toolsrc/include/vcpkg/base/files.h
index 3ea0d6036..178fae541 100644
--- a/toolsrc/include/vcpkg/base/files.h
+++ b/toolsrc/include/vcpkg/base/files.h
@@ -12,14 +12,50 @@ namespace fs
     using stdfs::copy_options;
     using stdfs::file_status;
     using stdfs::file_type;
+    using stdfs::perms;
     using stdfs::path;
     using stdfs::u8path;
 
+    /*
+        std::experimental::filesystem's file_status and file_type are broken in
+        the presence of symlinks -- a symlink is treated as the object it points
+        to for `symlink_status` and `symlink_type`
+    */
+
+    using stdfs::status;
+
+    // we want to poison ADL with these niebloids
+    constexpr struct {
+        file_status operator()(const path& p, std::error_code& ec) const noexcept;
+        file_status operator()(const path& p) const noexcept;
+    } symlink_status{};
+
+    constexpr struct {
+        inline bool operator()(file_status s) const {
+            return stdfs::is_symlink(s);
+        }
+
+        inline bool operator()(const path& p) const {
+            return stdfs::is_symlink(symlink_status(p));
+        }
+        inline bool operator()(const path& p, std::error_code& ec) const {
+            return stdfs::is_symlink(symlink_status(p, ec));
+        }
+    } is_symlink{};
+
     inline bool is_regular_file(file_status s) { return stdfs::is_regular_file(s); }
     inline bool is_directory(file_status s) { return stdfs::is_directory(s); }
-    inline bool is_symlink(file_status s) { return stdfs::is_symlink(s); }
 }
 
+/*
+    if someone attempts to use unqualified `symlink_status` or `is_symlink`,
+    they might get the ADL version, which is broken.
+    Therefore, put `symlink_status` in the global namespace, so that they get
+    our symlink_status.
+*/
+using fs::symlink_status;
+using fs::is_symlink;
+
 namespace vcpkg::Files
 {
     struct Filesystem
diff --git a/toolsrc/include/vcpkg/base/rng.h b/toolsrc/include/vcpkg/base/rng.h
index 1bcab05b3..4a0411f64 100644
--- a/toolsrc/include/vcpkg/base/rng.h
+++ b/toolsrc/include/vcpkg/base/rng.h
@@ -4,17 +4,56 @@
 #include <limits>
 #include <random>
 
-namespace vcpkg {
+namespace vcpkg::Rng {
+
+    namespace detail {
+        template <class T>
+        constexpr std::size_t bitsize = sizeof(T) * CHAR_BITS;
+
+        template <class T>
+        constexpr bool is_valid_shift(int k) {
+            return 0 <= k && k <= bitsize<T>;
+        }
+
+        // precondition: 0 <= k < bitsize<T>
+        template <class T>
+        constexpr T ror(T x, int k) {
+            if (k == 0) {
+                return x;
+            }
+            return (x >> k) | (x << (bitsize<T> - k));
+        }
+
+        // precondition: 0 <= k < bitsize<T>
+        template <class T>
+        constexpr T rol(T x, int k) {
+            if (k == 0) {
+                return x;
+            }
+            return (x << k) | (x >> (bitsize<T> - k));
+        }
+
+        // there _is_ a way to do this generally, but I don't know how to
+        template <class UIntType, int e>
+        struct XoshiroJumpTable;
+
+        template <>
+        struct XoshiroJumpTable<std::uint64_t, 128> {
+            constexpr static std::uint64_t value[4] = {
+                0x180ec6d33cfd0aba, 0xd5a61266f0c9392c, 0xa9582618e03fc9aa, 0x39abdc4529b1661c
+            };
+        };
+    }
 
     /*
         NOTE(ubsan): taken from the xoshiro paper
         initialized from random_device by default
         actual code is copied from wikipedia, since I wrote that code
     */
-    struct splitmix64_engine {
-        splitmix64_engine() noexcept;
+    struct splitmix {
+        splitmix() noexcept;
 
-        constexpr splitmix64_engine(std::uint64_t seed) noexcept
+        constexpr splitmix(std::uint64_t seed) noexcept
             : state(seed) {}
 
         constexpr std::uint64_t operator()() noexcept {
@@ -35,62 +74,126 @@ namespace vcpkg {
             return std::numeric_limits<std::uint64_t>::min();
         }
 
+        template <class T>
+        constexpr void fill(T* first, T* last) {
+            constexpr auto mask =
+                static_cast<std::uint64_t>(std::numeric_limits<T>::max());
+
+            const auto remaining =
+                (last - first) % (sizeof(std::uint64_t) / sizeof(T));
+
+            for (auto it = first; it != last - remaining;) {
+                const auto item = (*this)();
+                for (
+                    int shift = 0;
+                    shift < 64;
+                    shift += detail::bitsize<T>, ++it
+                ) {
+                    *it = static_cast<T>((item >> shift) & mask);
+                }
+            }
+
+            if (remaining == 0) return;
+
+            int shift = 0;
+            const auto item = (*this)();
+            for (auto it = last - remaining;
+                it != last;
+                shift += detail::bitsize<T>, ++it
+            ) {
+                *it = static_cast<T>((item >> shift) & mask);
+            }
+        }
+
     private:
         std::uint64_t state;
     };
 
-    // Sebastian Vigna's xorshift-based xoshiro xoshiro256** engine
+    template <class UIntType, int S, int R, int T>
+    struct starstar_scrambler {
+        constexpr static UIntType scramble(UIntType n) noexcept {
+            return detail::rol(n * S, R) * T;
+        }
+    };
+
+    // Sebastian Vigna's xorshift-based xoshiro engine
     // fast and really good
-    // uses the splitmix64_engine to initialize state
-    struct xoshiro256ss_engine {
-        // splitmix64_engine will be initialized with random_device
-        xoshiro256ss_engine() noexcept {
-            splitmix64_engine sm64{};
+    // uses the splitmix to initialize state
+    template <class UIntType, class Scrambler, int A, int B>
+    struct xoshiro_engine {
+        static_assert(detail::is_valid_shift<UIntType>(A));
+        static_assert(detail::is_valid_shift<UIntType>(B));
+        static_assert(std::is_unsigned_v<UIntType>);
 
-            for (std::uint64_t& s : this->state) {
-                s = sm64();
-            }
+        // splitmix will be initialized with random_device
+        xoshiro_engine() noexcept {
+            splitmix sm{};
+
+            sm.fill(&state[0], &state[4]);
         }
 
-        constexpr xoshiro256ss_engine(std::uint64_t seed) noexcept : state() {
-            splitmix64_engine sm64{seed};
+        constexpr xoshiro_engine(std::uint64_t seed) noexcept : state() {
+            splitmix sm{seed};
 
-            for (std::uint64_t& s : this->state) {
-                s = sm64();
-            }
+            sm.fill(&state[0], &state[4]);
         }
 
-        constexpr std::uint64_t operator()() noexcept {
-            std::uint64_t const result = rol(state[1] * 5, 7) * 9;
+        constexpr UIntType operator()() noexcept {
+            const UIntType result = Scrambler::scramble(state[0]);
 
-            std::uint64_t const t = state[1] << 17;
+            const UIntType t = state[1] << A;
 
-            // state[i] = state[i] ^ state[i + 4 mod 4]
             state[2] ^= state[0];
             state[3] ^= state[1];
             state[1] ^= state[2];
             state[0] ^= state[3];
 
             state[2] ^= t;
-            state[3] ^= rol(state[3], 45);
+            state[3] ^= detail::rol(state[3], B);
 
             return result;
         }
 
-        constexpr std::uint64_t max() const noexcept {
-            return std::numeric_limits<std::uint64_t>::max();
+        constexpr UIntType max() const noexcept {
+            return std::numeric_limits<UIntType>::max();
         }
 
         constexpr std::uint64_t min() const noexcept {
-            return std::numeric_limits<std::uint64_t>::min();
+            return std::numeric_limits<UIntType>::min();
+        }
+
+        // quickly jump ahead 2^e steps
+        // takes 4 * bitsize<UIntType> rng next operations
+        template <int e>
+        constexpr void discard_e() noexcept {
+            using JT = detail::XoshiroJumpTable<UIntType, e>;
+
+            UIntType s[4] = {};
+            for (const auto& jump : JT::value) {
+                for (std::size_t i = 0; i < bitsize<UIntType>; ++i) {
+                    if ((jump >> i) & 1) {
+                        s[0] ^= state[0];
+                        s[1] ^= state[1];
+                        s[2] ^= state[2];
+                        s[3] ^= state[3];
+                    }
+                    (*this)();
+                }
+            }
+
+            state[0] = s[0];
+            state[1] = s[1];
+            state[2] = s[2];
+            state[3] = s[3];
         }
     private:
         // rotate left
-        constexpr std::uint64_t rol(std::uint64_t x, int k) {
-            return (x << k) | (x >> (64 - k));
-        }
-
-        std::uint64_t state[4];
+        UIntType state[4];
     };
 
+    using xoshiro256ss = xoshiro_engine<
+        std::uint64_t,
+        starstar_scrambler<std::uint64_t, 5, 7, 9>,
+        17,
+        45>;
 }
diff --git a/toolsrc/include/vcpkg/base/work_queue.h b/toolsrc/include/vcpkg/base/work_queue.h
new file mode 100644
index 000000000..4db167fa6
--- /dev/null
+++ b/toolsrc/include/vcpkg/base/work_queue.h
@@ -0,0 +1,183 @@
+#pragma once
+
+#include <memory>
+#include <queue>
+
+namespace vcpkg {
+    namespace detail {
+        template <class Action, class ThreadLocalData>
+        auto call_action(
+            Action& action,
+            const WorkQueue<Action, ThreadLocalData>& work_queue,
+            ThreadLocalData& tld
+        ) -> decltype(static_cast<void>(std::move(action)(tld, work_queue)))
+        {
+            std::move(action)(tld, work_queue);
+        }
+
+        template <class Action, class ThreadLocalData>
+        auto call_action(
+            Action& action,
+            const WorkQueue<Action, ThreadLocalData>&,
+            ThreadLocalData& tld
+        ) -> decltype(static_cast<void>(std::move(action)(tld)))
+        {
+            std::move(action)(tld);
+        }
+    }
+
+    template <class Action, class ThreadLocalData>
+    struct WorkQueue {
+        template <class F>
+        explicit WorkQueue(const F& initializer) noexcept {
+            state = State::Joining;
+
+            std::size_t num_threads = std::thread::hardware_concurrency();
+            if (num_threads == 0) {
+                num_threads = 4;
+            }
+
+            m_threads.reserve(num_threads);
+            for (std::size_t i = 0; i < num_threads; ++i) {
+                m_threads.emplace_back(this, initializer);
+            }
+        }
+
+        WorkQueue(WorkQueue const&) = delete;
+        WorkQueue(WorkQueue&&) = delete;
+
+        ~WorkQueue() = default;
+
+        // runs all remaining tasks, and blocks on their finishing
+        // if this is called in an existing task, _will block forever_
+        // DO NOT DO THAT
+        // thread-unsafe
+        void join() {
+            {
+                auto lck = std::unique_lock<std::mutex>(m_mutex);
+                if (m_state == State::Running) {
+                    m_state = State::Joining;
+                } else if (m_state == State::Joining) {
+                    Checks::exit_with_message(VCPKG_LINE_INFO, "Attempted to join more than once");
+                }
+            }
+            for (auto& thrd : m_threads) {
+                thrd.join();
+            }
+        }
+
+        // useful in the case of errors
+        // doesn't stop any existing running tasks
+        // returns immediately, so that one can call this in a task
+        void terminate() const {
+            {
+                auto lck = std::unique_lock<std::mutex>(m_mutex);
+                m_state = State::Terminated;
+            }
+            m_cv.notify_all();
+        }
+
+        void enqueue_action(Action a) const {
+            {
+                auto lck = std::unique_lock<std::mutex>(m_mutex);
+                m_actions.push_back(std::move(a));
+            }
+            m_cv.notify_one();
+        }
+
+        template <class Rng>
+        void enqueue_all_actions_by_move(Rng&& rng) const {
+            {
+                using std::begin;
+                using std::end;
+
+                auto lck = std::unique_lock<std::mutex>(m_mutex);
+
+                auto first = begin(rng);
+                auto last = end(rng);
+
+                m_actions.reserve(m_actions.size() + (end - begin));
+
+                std::move(first, last, std::back_insert_iterator(rng));
+            }
+
+            m_cv.notify_all();
+        }
+
+        template <class Rng>
+        void enqueue_all_actions(Rng&& rng) const {
+            {
+                using std::begin;
+                using std::end;
+
+                auto lck = std::unique_lock<std::mutex>(m_mutex);
+
+                auto first = begin(rng);
+                auto last = end(rng);
+
+                m_actions.reserve(m_actions.size() + (end - begin));
+
+                std::copy(first, last, std::back_insert_iterator(rng));
+            }
+
+            m_cv.notify_all();
+        }
+
+    private:
+        friend struct WorkQueueWorker {
+            const WorkQueue* work_queue;
+            ThreadLocalData tld;
+
+            template <class F>
+            WorkQueueWorker(const WorkQueue* work_queue, const F& initializer)
+                : work_queue(work_queue), tld(initializer())
+            { }
+
+            void operator()() {
+                for (;;) {
+                    auto lck = std::unique_lock<std::mutex>(work_queue->m_mutex);
+                    ++work_queue->running_workers;
+
+                    const auto state = work_queue->m_state;
+
+                    if (state == State::Terminated) {
+                        --work_queue->running_workers;
+                        return;
+                    }
+
+                    if (work_queue->m_actions.empty()) {
+                        --work_queue->running_workers;
+                        if (state == State::Running || work_queue->running_workers > 0) {
+                            work_queue->m_cv.wait(lck);
+                            continue;
+                        }
+
+                        // state == State::Joining and we are the only worker
+                        // no more work!
+                        return;
+                    }
+
+                    Action action = work_queue->m_actions.pop_back();
+                    lck.unlock();
+
+                    detail::call_action(action, *work_queue, tld);
+                }
+            }
+        };
+
+        enum class State : std::uint16_t {
+            Running,
+            Joining,
+            Terminated,
+        };
+
+        mutable std::mutex m_mutex;
+        // these four are under m_mutex
+        mutable State m_state;
+        mutable std::uint16_t running_workers;
+        mutable std::vector<Action> m_actions;
+        mutable std::condition_variable condition_variable;
+
+        std::vector<std::thread> m_threads;
+    };
+}
diff --git a/toolsrc/src/vcpkg/base/files.cpp b/toolsrc/src/vcpkg/base/files.cpp
index d0926bb4c..e89c531be 100644
--- a/toolsrc/src/vcpkg/base/files.cpp
+++ b/toolsrc/src/vcpkg/base/files.cpp
@@ -6,6 +6,7 @@
 #include <vcpkg/base/system.h>
 #include <vcpkg/base/system.print.h>
 #include <vcpkg/base/system.process.h>
+#include <vcpkg/base/work_queue.h>
 #include <vcpkg/base/util.h>
 
 #if defined(__linux__) || defined(__APPLE__)
@@ -21,6 +22,45 @@
 #include <copyfile.h>
 #endif
 
+namespace fs {
+    file_status decltype(symlink_status)::operator()(const path& p, std::error_code& ec) const noexcept {
+#if defined(_WIN32)
+        /*
+            do not find the permissions of the file -- it's unnecessary for the
+            things that vcpkg does.
+            if one were to add support for this in the future, one should look
+            into GetFileSecurityW
+        */
+        perms permissions = perms::unknown;
+
+        WIN32_FILE_ATTRIBUTE_DATA file_attributes;
+        file_type ft = file_type::unknown;
+        if (!GetFileAttributesExW(p.c_str(), GetFileExInfoStandard, &file_attributes)) {
+            ft = file_type::not_found;
+        } else if (file_attributes.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
+            // check for reparse point -- if yes, then symlink
+            ft = file_type::symlink;
+        } else if (file_attributes.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
+            ft = file_type::directory;
+        } else {
+            // otherwise, the file is a regular file
+            ft = file_type::regular;
+        }
+
+        return file_status(ft, permissions);
+
+#else
+        return stdfs::symlink_status(p, ec);
+#endif
+    }
+
+    file_status decltype(symlink_status)::operator()(const path& p) const noexcept {
+        std::error_code ec;
+        auto result = symlink_status(p, ec);
+        if (ec) vcpkg::Checks::exit_with_message(VCPKG_LINE_INFO, "error getting status of path %s: %s", p, ec.message());
+    }
+}
+
 namespace vcpkg::Files
 {
     static const std::regex FILESYSTEM_INVALID_CHARACTERS_REGEX = std::regex(R"([\/:*?"<>|])");
@@ -263,55 +303,129 @@ namespace vcpkg::Files
                 (as well as on macOS and Linux), this is just as fast and will have
                 fewer spurious errors due to locks.
             */
-            struct recursive {
-                const fs::path& tmp_directory;
-                std::error_code& ec;
-                xoshiro256ss_engine& rng;
 
-                void operator()(const fs::path& current) const {
-                    const auto type = fs::stdfs::symlink_status(current, ec).type();
-                    if (ec) return;
+            /*
+                `remove` doesn't actually remove anything -- it simply moves the
+                files into a parent directory (which ends up being at `path`),
+                and then inserts `actually_remove{current_path}` into the work
+                queue.
+            */
+            struct remove {
+                struct tld {
+                    const fs::path& tmp_directory;
+                    std::uint64_t index;
 
-                    const auto tmp_name = Strings::b64url_encode(rng());
-                    const auto tmp_path = tmp_directory / tmp_name;
+                    std::atomic<std::uintmax_t>& files_deleted;
 
-                    switch (type) {
-                    case fs::file_type::directory: {
-                        fs::stdfs::rename(current, tmp_path, ec);
-                        if (ec) return;
-                        for (const auto& entry : fs::stdfs::directory_iterator(tmp_path)) {
-                            (*this)(entry);
+                    std::mutex& ec_mutex;
+                    std::error_code& ec;
+                };
+
+                struct actually_remove;
+                using queue = WorkQueue<actually_remove, tld>;
+
+                /*
+                    if `current_path` is a directory, first `remove`s all
+                    elements of the directory, then calls remove.
+
+                    else, just calls remove.
+                */
+                struct actually_remove {
+                    fs::path current_path;
+
+                    void operator()(tld& info, const queue& queue) const {
+                        std::error_code ec;
+                        const auto path_type = fs::symlink_status(current_path, ec).type();
+
+                        if (check_ec(ec, info, queue)) return;
+
+                        if (path_type == fs::file_type::directory) {
+                            for (const auto& entry : fs::stdfs::directory_iterator(current_path)) {
+                                remove{}(entry, info, queue);
+                            }
+                        }
+
+                        if (fs::stdfs::remove(current_path, ec)) {
+                            info.files_deleted.fetch_add(1, std::memory_order_relaxed);
+                        } else {
+                            check_ec(ec, info, queue);
                         }
-                        fs::stdfs::remove(tmp_path, ec);
-                    } break;
-                    case fs::file_type::symlink:
-                    case fs::file_type::regular: {
-                        fs::stdfs::rename(current, tmp_path, ec);
-                        fs::stdfs::remove(current, ec);
-                    } break;
-                    case fs::file_type::not_found: return;
-                    case fs::file_type::none: {
-                        Checks::exit_with_message(VCPKG_LINE_INFO, "Error occurred when evaluating file type of file: %s", current);
-                    }
-                    default: {
-                        Checks::exit_with_message(VCPKG_LINE_INFO, "Attempted to delete special file: %s", current);
                     }
+                };
+
+                static bool check_ec(const std::error_code& ec, tld& info, const queue& queue) {
+                    if (ec) {
+                        queue.terminate();
+
+                        auto lck = std::unique_lock<std::mutex>(info.ec_mutex);
+                        if (!info.ec) {
+                            info.ec = ec;
+                        }
+
+                        return true;
+                    } else {
+                        return false;
                     }
                 }
+
+                void operator()(const fs::path& current_path, tld& info, const queue& queue) const {
+                    std::error_code ec;
+
+                    const auto type = fs::symlink_status(current_path, ec).type();
+                    if (check_ec(ec, info, queue)) return;
+
+                    const auto tmp_name = Strings::b64url_encode(info.index++);
+                    const auto tmp_path = info.tmp_directory / tmp_name;
+
+                    fs::stdfs::rename(current_path, tmp_path, ec);
+                    if (check_ec(ec, info, queue)) return;
+
+                    queue.enqueue_action(actually_remove{std::move(tmp_path)});
+                }
             };
 
-            auto const real_path = fs::stdfs::absolute(path);
+            const auto path_type = fs::symlink_status(path, ec).type();
 
-            if (! real_path.has_parent_path()) {
-                Checks::exit_with_message(VCPKG_LINE_INFO, "Attempted to remove_all the base directory");
+            std::atomic<std::uintmax_t> files_deleted = 0;
+
+            if (path_type == fs::file_type::directory) {
+                std::uint64_t index = 0;
+                std::mutex ec_mutex;
+
+                auto queue = remove::queue([&] {
+                    index += 1 << 32;
+                    return remove::tld{path, index, files_deleted, ec_mutex, ec};
+                });
+
+                index += 1 << 32;
+                auto main_tld = remove::tld{path, index, files_deleted, ec_mutex, ec};
+                for (const auto& entry : fs::stdfs::directory_iterator(path)) {
+                    remove{}(entry, main_tld, queue);
+                }
+
+                queue.join();
             }
 
-            // thoughts: is this fine? or should we do something different?
-            // maybe a temporary directory?
-            auto const base_path = real_path.parent_path();
+            /*
+                we need to do backoff on the removal of the top level directory,
+                since we need to place all moved files into that top level
+                directory, and so we can only delete the directory after all the
+                lower levels have been deleted.
+            */
+            for (int backoff = 0; backoff < 5; ++backoff) {
+                if (backoff) {
+                    using namespace std::chrono_literals;
+                    auto backoff_time = 100ms * backoff;
+                    std::this_thread::sleep_for(backoff_time);
+                }
 
-            xoshiro256ss_engine rng{};
-            recursive{base_path, ec, rng}(real_path);
+                if (fs::stdfs::remove(path, ec)) {
+                    files_deleted.fetch_add(1, std::memory_order_relaxed);
+                    break;
+                }
+            }
+
+            return files_deleted;
         }
         virtual bool exists(const fs::path& path) const override { return fs::stdfs::exists(path); }
         virtual bool is_directory(const fs::path& path) const override { return fs::stdfs::is_directory(path); }
@@ -343,11 +457,11 @@ namespace vcpkg::Files
 
         virtual fs::file_status status(const fs::path& path, std::error_code& ec) const override
         {
-            return fs::stdfs::status(path, ec);
+            return fs::status(path, ec);
         }
         virtual fs::file_status symlink_status(const fs::path& path, std::error_code& ec) const override
         {
-            return fs::stdfs::symlink_status(path, ec);
+            return fs::symlink_status(path, ec);
         }
         virtual void write_contents(const fs::path& file_path, const std::string& data, std::error_code& ec) override
         {
diff --git a/toolsrc/src/vcpkg/base/rng.cpp b/toolsrc/src/vcpkg/base/rng.cpp
index 9fe2ea3b4..40ff646b7 100644
--- a/toolsrc/src/vcpkg/base/rng.cpp
+++ b/toolsrc/src/vcpkg/base/rng.cpp
@@ -1,11 +1,11 @@
 #include <base/rng.h>
 
-namespace vcpkg {
+namespace vcpkg::Rng {
     namespace {
         std::random_device system_entropy{};
     }
 
-    splitmix64_engine::splitmix64_engine() {
+    splitmix::splitmix() {
         std::uint64_t top_half = system_entropy();
         std::uint64_t bottom_half = system_entropy();