Introduce file inspector and add FileSystemInspectedEnv (#216)

Introduce `FileSystemInspector` interface and `FileSystemInspectedEnv`. With
`FileSystemInspectedEnv`, each file operation must first consult
`FileSystemInspector` before reaching actual IO logic.

Signed-off-by: tabokie <xy.tao@outlook.com>

CMakeLists.txt

@@ -722,6 +722,7 @@ set(SOURCES
  env/env_chroot.cc
  env/env_encryption.cc
  env/env_hdfs.cc
+ env/env_inspected.cc
  env/file_system.cc
  env/file_system_tracer.cc
  env/fs_remap.cc

TARGETS

@@ -230,6 +230,7 @@ cpp_library(
  "env/env_chroot.cc",
  "env/env_encryption.cc",
  "env/env_hdfs.cc",
+ "env/env_inspected.cc",
  "env/env_posix.cc",
  "env/file_system.cc",
  "env/file_system_tracer.cc",
@@ -562,6 +563,7 @@ cpp_library(
  "env/env_chroot.cc",
  "env/env_encryption.cc",
  "env/env_hdfs.cc",
+ "env/env_inspected.cc",
  "env/env_posix.cc",
  "env/file_system.cc",
  "env/file_system_tracer.cc",

env/env_basic_test.cc

@@ -14,6 +14,7 @@
 #include "rocksdb/convenience.h"
 #include "rocksdb/env.h"
 #include "rocksdb/env_encryption.h"
+#include "rocksdb/env_inspected.h"
 #include "test_util/testharness.h"
 
 namespace ROCKSDB_NAMESPACE {
@@ -81,6 +82,41 @@ static Env* GetTestFS() {
  EXPECT_NE(fs_env, nullptr);
  return fs_env;
 }
+
+class DummyFileSystemInspector : public FileSystemInspector {
+ public:
+ DummyFileSystemInspector(size_t refill_bytes = 0)
+ : refill_bytes_(refill_bytes) {}
+
+ Status Read(size_t len, size_t* allowed) override {
+ assert(allowed);
+ if (refill_bytes_ == 0) {
+ *allowed = len;
+ } else {
+ *allowed = std::min(refill_bytes_, len);
+ }
+ return Status::OK();
+ }
+
+ Status Write(size_t len, size_t* allowed) override {
+ assert(allowed);
+ if (refill_bytes_ == 0) {
+ *allowed = len;
+ } else {
+ *allowed = std::min(refill_bytes_, len);
+ }
+ return Status::OK();
+ }
+
+ private:
+ size_t refill_bytes_;
+};
+
+static Env* GetInspectedEnv() {
+ static std::unique_ptr<Env> inspected_env(NewFileSystemInspectedEnv(
+ Env::Default(), std::make_shared<DummyFileSystemInspector>(1)));
+ return inspected_env.get();
+}
 #endif // ROCKSDB_LITE
 
 } // namespace
@@ -121,6 +157,9 @@ INSTANTIATE_TEST_CASE_P(EncryptedEnv, EnvMoreTestWithParam,
 INSTANTIATE_TEST_CASE_P(MemEnv, EnvBasicTestWithParam,
  ::testing::Values(&GetMemoryEnv));
 
+INSTANTIATE_TEST_CASE_P(InspectedEnv, EnvBasicTestWithParam,
+ ::testing::Values(&GetInspectedEnv));
+
 namespace {
 
 // Returns a vector of 0 or 1 Env*, depending whether an Env is registered for