pitrou commented on code in PR #13640:
URL: https://github.com/apache/arrow/pull/13640#discussion_r961809524
##########
cpp/src/arrow/io/file.cc:
##########
@@ -378,6 +378,109 @@ Status FileOutputStream::Write(const void* data, int64_t
length) {
int FileOutputStream::file_descriptor() const { return impl_->fd(); }
+// ----------------------------------------------------------------------
+// DirectFileOutputStream, change the Open, Write and Close methods from
FileOutputStream
+// Uses DirectIO for writes. Will only write out things in 4096 byte blocks.
Buffers
+// leftover bytes in an internal data structure, which will be padded to 4096
bytes and
+// flushed upon call to close.
+
+class DirectFileOutputStream::DirectFileOutputStreamImpl : public OSFile {
+ public:
+ Status Open(const std::string& path) {
+ return OpenWritable(path, true, false, true /* write_only */, true);
+ }
+ Status Open(int fd) { return OpenWritable(fd); }
+};
+
+DirectFileOutputStream::DirectFileOutputStream() {
+ uintptr_t mask = (uintptr_t)(4095);
+
+ cached_data_.reserve(4096 + 4095);
+ aligned_cached_data_ = reinterpret_cast<uint8_t*>(
+ reinterpret_cast<uintptr_t>(&cached_data_[0] + 4095) & ~(mask));
Review Comment:
No strong feeling from me. I'm ok with `std::vector` and manual alignment
given that this is quite a small memory area anyway.
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