C++ migration: add AsyncQueue, the C++ version of FSTDispatchQueue (#1176)

AsyncQueue is a queue that executes given operations asynchronously,
enforcing that only a single operation is executing at any given time,
and that in-progress operations don't spawn more operations. The actual
execution is delegated to a platform-specific executor. Executor is an
interface for a FIFO queue that executes given operations serially. Two
implementations of Executor, one using libdispatch and the other using
C++11 standard library, are provided.

AsyncQueue is not used anywhere in the code base at this point.

1 files changed, 30 insertions, 0 deletions

diff --git a/Firestore/Example/Firestore.xcodeproj/project.pbxproj b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
index 54205f0..6738e74 100644
--- a/Firestore/Example/Firestore.xcodeproj/project.pbxproj
+++ b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
@@ -161,6 +161,12 @@
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+		B6FB4684208EA0EC00554BA2 /* async_queue_test_libdispatch.cc in Sources */ = {isa = PBXBuildFile; fileRef = B6FB4680208EA0BE00554BA2 /* async_queue_test_libdispatch.cc */; };
+		B6FB4685208EA0F000554BA2 /* async_queue_test_std.cc in Sources */ = {isa = PBXBuildFile; fileRef = B6FB4681208EA0BE00554BA2 /* async_queue_test_std.cc */; };
+		B6FB468E208F9BAB00554BA2 /* executor_libdispatch_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = B6FB4689208F9B9100554BA2 /* executor_libdispatch_test.cc */; };
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+		B6FB4690208F9BB300554BA2 /* executor_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = B6FB4688208F9B9100554BA2 /* executor_test.cc */; };
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@@ -404,6 +410,15 @@
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+		B6FB467B208E9A8200554BA2 /* async_queue_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = async_queue_test.cc; path = ../../core/test/firebase/firestore/util/async_queue_test.cc; sourceTree = "<group>"; };
+		B6FB4680208EA0BE00554BA2 /* async_queue_test_libdispatch.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = async_queue_test_libdispatch.cc; path = ../../core/test/firebase/firestore/util/async_queue_test_libdispatch.cc; sourceTree = "<group>"; };
+		B6FB4681208EA0BE00554BA2 /* async_queue_test_std.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = async_queue_test_std.cc; path = ../../core/test/firebase/firestore/util/async_queue_test_std.cc; sourceTree = "<group>"; };
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+		B6FB4688208F9B9100554BA2 /* executor_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = executor_test.cc; path = ../../core/test/firebase/firestore/util/executor_test.cc; sourceTree = "<group>"; };
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@@ -494,6 +509,15 @@
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+				B6FB4689208F9B9100554BA2 /* executor_libdispatch_test.cc */,
+				B6FB4687208F9B9100554BA2 /* executor_std_test.cc */,
+				B6FB4688208F9B9100554BA2 /* executor_test.cc */,
+				B6FB468A208F9B9100554BA2 /* executor_test.h */,
+				B6FB4680208EA0BE00554BA2 /* async_queue_test_libdispatch.cc */,
+				B6FB4681208EA0BE00554BA2 /* async_queue_test_std.cc */,
+				B6FB467B208E9A8200554BA2 /* async_queue_test.cc */,
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@@ -1433,12 +1457,15 @@
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 				B686F2AF2023DDEE0028D6BE /* field_path_test.cc in Sources */,
 				5492E03120213FFC00B64F25 /* FSTLevelDBSpecTests.mm in Sources */,
+				B6FB468F208F9BAE00554BA2 /* executor_std_test.cc in Sources */,
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 				5492E0A62021552D00B64F25 /* FSTPersistenceTestHelpers.mm in Sources */,
+				B6FB468E208F9BAB00554BA2 /* executor_libdispatch_test.cc in Sources */,
 				5467FB01203E5717009C9584 /* FIRFirestoreTests.mm in Sources */,
+				B6FB4684208EA0EC00554BA2 /* async_queue_test_libdispatch.cc in Sources */,
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@@ -1462,6 +1489,7 @@
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 				5492E0A32021552D00B64F25 /* FSTLocalSerializerTests.mm in Sources */,
 				5492E0A72021552D00B64F25 /* FSTLevelDBKeyTests.mm in Sources */,
+				B6FB4685208EA0F000554BA2 /* async_queue_test_std.cc in Sources */,
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@@ -1471,6 +1499,7 @@
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 				54995F6F205B6E12004EFFA0 /* leveldb_key_test.cc in Sources */,
 				5492E065202154B900B64F25 /* FSTViewTests.mm in Sources */,
+				B6FB467D208E9D3C00554BA2 /* async_queue_test.cc in Sources */,
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@@ -1498,6 +1527,7 @@
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 				5492E0C72021557E00B64F25 /* FSTSerializerBetaTests.mm in Sources */,
+				B6FB4690208F9BB300554BA2 /* executor_test.cc in Sources */,
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 				5492E057202154AB00B64F25 /* FIRSnapshotMetadataTests.mm in Sources */,
 				54740A571FC914BA00713A1A /* secure_random_test.cc in Sources */,