bkietz commented on a change in pull request #10644:
URL: https://github.com/apache/arrow/pull/10644#discussion_r663119109
##########
File path: cpp/src/arrow/util/io_util.cc
##########
@@ -1734,5 +1665,21 @@ int64_t GetRandomSeed() {
return static_cast<int64_t>(seed_gen());
}
+uint64_t GetThreadId() {
+ uint64_t equiv{0};
+ // std::thread::id is trivially copyable as per C++ spec,
+ // so type punning as a uint64_t should work
+ static_assert(sizeof(std::thread::id) <= sizeof(uint64_t),
+ "std::thread::id can't fit into uint64_t");
+ const auto tid = std::this_thread::get_id();
+ memcpy(&equiv, reinterpret_cast<const void*>(&tid), sizeof(tid));
+ return equiv;
+}
+
+uint64_t GetOptionalThreadId() {
+ auto tid = GetThreadId();
+ return (tid == 0) ? tid - 1 : tid;
Review comment:
If we're going to use -1 in multiple places like this, let's define it
as a global constant:
```suggestion
return (tid == 0) ? kUnlikelyThreadId : tid;
```
##########
File path: cpp/src/arrow/util/io_util.h
##########
@@ -399,5 +338,12 @@ Status SendSignalToThread(int signum, uint64_t thread_id);
ARROW_EXPORT
int64_t GetRandomSeed();
+/// \brief Get the current thread id
Review comment:
It seems odd to put this in io_util.h and not thread_pool.h
##########
File path: cpp/src/arrow/util/io_util.cc
##########
@@ -1734,5 +1665,21 @@ int64_t GetRandomSeed() {
return static_cast<int64_t>(seed_gen());
}
+uint64_t GetThreadId() {
+ uint64_t equiv{0};
+ // std::thread::id is trivially copyable as per C++ spec,
+ // so type punning as a uint64_t should work
+ static_assert(sizeof(std::thread::id) <= sizeof(uint64_t),
+ "std::thread::id can't fit into uint64_t");
+ const auto tid = std::this_thread::get_id();
+ memcpy(&equiv, reinterpret_cast<const void*>(&tid), sizeof(tid));
+ return equiv;
+}
+
+uint64_t GetOptionalThreadId() {
+ auto tid = GetThreadId();
+ return (tid == 0) ? tid - 1 : tid;
Review comment:
Actually I'm not sure I understand the intent of this function and it's
not exported
##########
File path: cpp/src/arrow/util/io_util.h
##########
@@ -399,5 +338,12 @@ Status SendSignalToThread(int signum, uint64_t thread_id);
ARROW_EXPORT
int64_t GetRandomSeed();
+/// \brief Get the current thread id
+///
+/// In addition to having the same properties as std::thread, the returned
value
+/// is a regular integer value, which is more convenient than an opaque type.
+ARROW_EXPORT
+uint64_t GetThreadId();
+
Review comment:
```suggestion
ARROW_EXPORT
uint64_t GetOptionalThreadId();
```
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