westonpace commented on a change in pull request #11486:
URL: https://github.com/apache/arrow/pull/11486#discussion_r740642909
##########
File path: cpp/src/arrow/ipc/reader.cc
##########
@@ -1358,6 +1398,62 @@ Future<std::shared_ptr<RecordBatchFileReader>>
RecordBatchFileReader::OpenAsync(
.Then([=]() -> Result<std::shared_ptr<RecordBatchFileReader>> { return
result; });
}
+Result<int64_t> IoRecordedRandomAccessFile::GetSize() { return file_size_; }
+
+Result<int64_t> IoRecordedRandomAccessFile::ReadAt(int64_t position, int64_t
nbytes,
+ void* out) {
+ auto num_bytes_read = std::min(file_size_, position + nbytes) - position;
+
+ if (!recorded_reads_.empty() &&
+ position == recorded_reads_.back().offset +
recorded_reads_.back().length) {
+ // merge continuous IOs into one if possible
+ recorded_reads_.back().length += num_bytes_read;
+ } else {
+ // no real IO is performed, it is only saved into a vector for replaying
later
+ recorded_reads_.emplace_back(io::ReadRange{position, num_bytes_read});
+ }
+ return num_bytes_read;
+}
Review comment:
I'm not sure if it matters or not but I think read calls should advance
the position. For example:
```
Read(10) // Reads bytes 0-9
Read(10) // Reads bytes 10-19
```
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