From 249eae5f4aad8c90e4e0eae19268fbf74fe05783 Mon Sep 17 00:00:00 2001
From: Lee Clagett <code@leeclagett.com>
Date: Tue, 13 Oct 2020 15:09:18 +0000
Subject: Allow byte_stream->byte_slice conversion to shrink unused buffer
 space

---
 contrib/epee/src/byte_slice.cpp | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

(limited to 'contrib/epee/src')

diff --git a/contrib/epee/src/byte_slice.cpp b/contrib/epee/src/byte_slice.cpp
index faf7689be..453b63a4c 100644
--- a/contrib/epee/src/byte_slice.cpp
+++ b/contrib/epee/src/byte_slice.cpp
@@ -36,6 +36,11 @@
 #include "byte_slice.h"
 #include "byte_stream.h"
 
+namespace
+{
+  const std::size_t page_size = 4096;
+}
+
 namespace epee
 {
   struct byte_slice_data
@@ -173,16 +178,27 @@ namespace epee
     : byte_slice(adapt_buffer{}, std::move(buffer))
   {}
 
-  byte_slice::byte_slice(byte_stream&& stream) noexcept
+  byte_slice::byte_slice(byte_stream&& stream, const bool shrink)
     : storage_(nullptr), portion_(stream.data(), stream.size())
   {
-    if (stream.size())
+    if (portion_.size())
     {
-      std::uint8_t* const data = stream.take_buffer().release() - sizeof(raw_byte_slice);
+      byte_buffer buf;
+      if (shrink && page_size <= stream.available())
+      {
+          buf = byte_buffer_resize(stream.take_buffer(), portion_.size());
+          if (!buf)
+            throw std::bad_alloc{};
+          portion_ = {buf.get(), portion_.size()};
+      }
+      else // no need to shrink buffer
+        buf = stream.take_buffer();
+
+      std::uint8_t* const data = buf.release() - sizeof(raw_byte_slice);
       new (data) raw_byte_slice{};
       storage_.reset(reinterpret_cast<raw_byte_slice*>(data));
     }
-    else
+    else // empty stream
       portion_ = nullptr;
   }
 
-- 
cgit v1.2.3