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authorEelco Dolstra <eelco.dolstra@logicblox.com>2016-03-29T12·29+0200
committerEelco Dolstra <eelco.dolstra@logicblox.com>2016-03-29T14·37+0200
commit784ee35c80774c5f073b6b8be6ab3d4d7e38e2f1 (patch)
tree1442cbfe72d75f5cb1dd8d68706220e5821ab374 /src/libutil/thread-pool.hh
parent0ebe69dc67853e9e2b2b7b22069e766a7cbc057d (diff)
Add "nix verify-paths" command
Unlike "nix-store --verify-path", this command verifies signatures in
addition to store path contents, is multi-threaded (especially useful
when verifying binary caches), and has a progress indicator.

Example use:

$ nix verify-paths --store https://cache.nixos.org -r $(type -p thunderbird)
...
[17/132 checked] checking ‘/nix/store/rawakphadqrqxr6zri2rmnxh03gqkrl3-autogen-5.18.6’
Diffstat (limited to 'src/libutil/thread-pool.hh')
-rw-r--r--src/libutil/thread-pool.hh52
1 files changed, 52 insertions, 0 deletions
diff --git a/src/libutil/thread-pool.hh b/src/libutil/thread-pool.hh
new file mode 100644
index 000000000000..77641d88ba4e
--- /dev/null
+++ b/src/libutil/thread-pool.hh
@@ -0,0 +1,52 @@
+#pragma once
+
+#include "sync.hh"
+#include "util.hh"
+
+#include <queue>
+#include <functional>
+#include <thread>
+
+namespace nix {
+
+/* A simple thread pool that executes a queue of work items
+   (lambdas). */
+class ThreadPool
+{
+public:
+
+    ThreadPool(size_t nrThreads = 0);
+
+    // FIXME: use std::packaged_task?
+    typedef std::function<void()> work_t;
+
+    /* Enqueue a function to be executed by the thread pool. */
+    void enqueue(const work_t & t);
+
+    /* Execute work items until the queue is empty. Note that work
+       items are allowed to add new items to the queue; this is
+       handled correctly. Queue processing stops prematurely if any
+       work item throws an exception. This exception is propagated to
+       the calling thread. If multiple work items throw an exception
+       concurrently, only one item is propagated; the others are
+       printed on stderr and otherwise ignored. */
+    void process();
+
+private:
+
+    size_t nrThreads;
+
+    struct State
+    {
+        std::queue<work_t> left;
+        size_t pending = 0;
+        std::exception_ptr exception;
+    };
+
+    Sync<State> state;
+
+    std::condition_variable wakeup;
+
+};
+
+}