niyue commented on a change in pull request #11486:
URL: https://github.com/apache/arrow/pull/11486#discussion_r740648481



##########
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:
       OK. I am not aware of this. I will fix it.

##########
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:
       OK. I was not aware of this. I will fix it.




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