marsupialtail commented on code in PR #13640:
URL: https://github.com/apache/arrow/pull/13640#discussion_r960978713
##########
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:
The use of std vector is not just to implement the alignment, but also
resolve memory freeing issues especially if the function fails in the middle
and returns some Invalid status in the future. If you use std vector they will
automatically be destroyed, if you had used posix_memalign that memory region
will not be freed.
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