From 0c49255d5290c3795cd3a43bf1514cceacb9a2e8 Mon Sep 17 00:00:00 2001
From: mwish <maplewish117@gmail.com>
Date: Tue, 26 Dec 2023 19:35:08 +0800
Subject: [PATCH] Minor: style enhancement for CompressedInputStream

---
 cpp/src/arrow/io/compressed.cc | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/cpp/src/arrow/io/compressed.cc b/cpp/src/arrow/io/compressed.cc
index 6c484242a4fc8..39f90e8bc6246 100644
--- a/cpp/src/arrow/io/compressed.cc
+++ b/cpp/src/arrow/io/compressed.cc
@@ -201,7 +201,7 @@ Result<std::shared_ptr<CompressedOutputStream>> CompressedOutputStream::Make(
     util::Codec* codec, const std::shared_ptr<OutputStream>& raw, MemoryPool* pool) {
   // CAUTION: codec is not owned
   std::shared_ptr<CompressedOutputStream> res(new CompressedOutputStream);
-  res->impl_.reset(new Impl(pool, std::move(raw)));
+  res->impl_ = std::make_unique<Impl>(pool, std::move(raw));
   RETURN_NOT_OK(res->impl_->Init(codec));
   return res;
 }
@@ -277,7 +277,7 @@ class CompressedInputStream::Impl {
   }
 
   // Decompress some data from the compressed_ buffer.
-  // Call this function only if the decompressed_ buffer is empty.
+  // Call this function only if the decompressed_ buffer is empty or exhausted.
   Status DecompressData() {
     DCHECK_NE(compressed_->data(), nullptr);
 
@@ -300,7 +300,8 @@ class CompressedInputStream::Impl {
         fresh_decompressor_ = false;
       }
       if (result.bytes_written > 0 || !result.need_more_output || input_len == 0) {
-        RETURN_NOT_OK(decompressed_->Resize(result.bytes_written));
+        RETURN_NOT_OK(
+            decompressed_->Resize(result.bytes_written, /*shrink_to_fit=*/false));
         break;
       }
       DCHECK_EQ(result.bytes_written, 0);
@@ -318,11 +319,6 @@ class CompressedInputStream::Impl {
     if (read_bytes > 0) {
       memcpy(out, decompressed_->data() + decompressed_pos_, read_bytes);
       decompressed_pos_ += read_bytes;
-
-      if (decompressed_pos_ == decompressed_->size()) {
-        // Decompressed data is exhausted, release buffer
-        decompressed_.reset();
-      }
     }
 
     return read_bytes;
@@ -339,7 +335,8 @@ class CompressedInputStream::Impl {
       }
       RETURN_NOT_OK(DecompressData());
     }
-    if (!decompressed_ || decompressed_->size() == 0) {
+    if (decompressed_ == nullptr || decompressed_->size() == 0 ||
+        decompressed_->size() == decompressed_pos_) {
       // Got nothing, need to read more compressed data
       RETURN_NOT_OK(EnsureCompressedData());
       if (compressed_pos_ == compressed_->size()) {
@@ -413,10 +410,9 @@ Result<std::shared_ptr<CompressedInputStream>> CompressedInputStream::Make(
     Codec* codec, const std::shared_ptr<InputStream>& raw, MemoryPool* pool) {
   // CAUTION: codec is not owned
   std::shared_ptr<CompressedInputStream> res(new CompressedInputStream);
-  res->impl_.reset(new Impl(pool, std::move(raw)));
+  res->impl_ = std::make_unique<Impl>(pool, std::move(raw));
   RETURN_NOT_OK(res->impl_->Init(codec));
   return res;
-  return Status::OK();
 }
 
 CompressedInputStream::~CompressedInputStream() { internal::CloseFromDestructor(this); }