From 289244b2d40beda79db806556168c9c654ed4b7e Mon Sep 17 00:00:00 2001
From: Martin Nowak <code@dawg.eu>
Date: Sun, 19 Aug 2018 12:00:20 +0200
Subject: [PATCH] fix #1 - Windows scattered sync read/write incorrectly
 implemented

- must break on partial reads/writes so that newly arriving data/buffer-space
  in between read/write calls doesn't lead to gaps in scatter buffers
---
 src/std/io/driver/sync.d | 14 ++++++++++++--
 src/std/io/file.d        | 11 +++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/std/io/driver/sync.d b/src/std/io/driver/sync.d
index 3bd0e61..284a915 100644
--- a/src/std/io/driver/sync.d
+++ b/src/std/io/driver/sync.d
@@ -143,7 +143,12 @@ shared @safe @nogc:
         {
             size_t total;
             foreach (b; bufs)
-                total += read(f, b);
+            {
+                immutable len = read(f, b);
+                total += len;
+                if (len < b.length)
+                    break;
+            }
             return total;
         }
     }
@@ -179,7 +184,12 @@ shared @safe @nogc:
         {
             size_t total;
             foreach (b; bufs)
-                total += write(f, b);
+            {
+                immutable len = write(f, b);
+                total += len;
+                if (len < b.length)
+                    break;
+            }
             return total;
         }
     }
diff --git a/src/std/io/file.d b/src/std/io/file.d
index 14aa65b..c602962 100644
--- a/src/std/io/file.d
+++ b/src/std/io/file.d
@@ -255,6 +255,17 @@ struct File
         assert(f.read(buf[$ / 2 .. $], buf[0 .. $ / 2]) == buf.length);
     }
 
+    @("partial reads")
+    unittest
+    {
+        auto f = File("LICENSE.txt");
+        ubyte[256] buf = void;
+        auto len = f.read(buf[$ / 2 .. $], buf[0 .. $ / 2]);
+        while (len == buf.length)
+            len = f.read(buf[$ / 2 .. $], buf[0 .. $ / 2]);
+        assert(len < buf.length);
+    }
+
     /**
        Write buffer content to file.