From fc890181464be7d76f4f36a3345cc6bf48ce4fdc Mon Sep 17 00:00:00 2001
From: Benny Halevy <bhalevy@scylladb.com>
Date: Mon, 29 Jun 2020 15:27:04 +0300
Subject: [PATCH] sstables: random_access_reader: make methods noexcept

handle all exceptions in read_exactly, seek, and close
and specify them as noexcept.

Also, specify eof() as noexcept as it trivially is.

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
---
 sstables/random_access_reader.cc | 21 +++++++++++++--------
 sstables/random_access_reader.hh | 10 +++++-----
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/sstables/random_access_reader.cc b/sstables/random_access_reader.cc
index f9e05c450d..713cc5c3e1 100644
--- a/sstables/random_access_reader.cc
+++ b/sstables/random_access_reader.cc
@@ -29,8 +29,12 @@ namespace sstables {
 
 extern logging::logger sstlog;
 
-future <temporary_buffer<char>> random_access_reader::read_exactly(size_t n) {
+future <temporary_buffer<char>> random_access_reader::read_exactly(size_t n) noexcept {
+  try {
     return _in->read_exactly(n);
+  } catch (...) {
+    return current_exception_as_future<temporary_buffer<char>>();
+  }
 }
 
 static future<> close_if_needed(std::unique_ptr<input_stream<char>> in) {
@@ -40,17 +44,18 @@ static future<> close_if_needed(std::unique_ptr<input_stream<char>> in) {
     return in->close().finally([in = std::move(in)] {});
 }
 
-future<> random_access_reader::seek(uint64_t pos) {
-        // FIXME: temporary bad indentation.
-        // A following patch will enclose the body of this function
-        // in a try/catch block.
+future<> random_access_reader::seek(uint64_t pos) noexcept {
+    try {
         auto tmp = std::make_unique<input_stream<char>>(open_at(pos));
         std::swap(tmp, _in);
         return close_if_needed(std::move(tmp));
+    } catch (...) {
+        return current_exception_as_future();
+    }
 }
 
-future<> random_access_reader::close() {
-    return close_if_needed(std::move(_in));
+future<> random_access_reader::close() noexcept {
+    return futurize_invoke(close_if_needed, std::move(_in));
 }
 
 file_random_access_reader::file_random_access_reader(file f, uint64_t file_size, size_t buffer_size, unsigned read_ahead)
@@ -67,7 +72,7 @@ input_stream<char> file_random_access_reader::open_at(uint64_t pos) {
     return make_file_input_stream(_file, pos, len, std::move(options));
 }
 
-future<> file_random_access_reader::close() {
+future<> file_random_access_reader::close() noexcept {
     return random_access_reader::close().finally([this] {
         return _file.close().handle_exception([save = _file](auto ep) {
             sstlog.warn("sstable close failed: {}", ep);
diff --git a/sstables/random_access_reader.hh b/sstables/random_access_reader.hh
index 5434d3d489..b179229edd 100644
--- a/sstables/random_access_reader.hh
+++ b/sstables/random_access_reader.hh
@@ -41,13 +41,13 @@ protected:
     }
 
 public:
-    future <temporary_buffer<char>> read_exactly(size_t n);
+    future <temporary_buffer<char>> read_exactly(size_t n) noexcept;
 
-    future<> seek(uint64_t pos);
+    future<> seek(uint64_t pos) noexcept;
 
-    bool eof() const { return _in->eof(); }
+    bool eof() const noexcept { return _in->eof(); }
 
-    virtual future<> close();
+    virtual future<> close() noexcept;
 
     virtual ~random_access_reader() {}
 };
@@ -62,7 +62,7 @@ public:
 
     explicit file_random_access_reader(file f, uint64_t file_size, size_t buffer_size = 8192, unsigned read_ahead = 4);
 
-    virtual future<> close() override;
+    virtual future<> close() noexcept override;
 };
 
 }