diff --git a/renderdoc/os/os_specific.h b/renderdoc/os/os_specific.h
index 5e28d76ae..0452d1926 100644
--- a/renderdoc/os/os_specific.h
+++ b/renderdoc/os/os_specific.h
@@ -253,7 +253,8 @@ void GetExecutableFilename(string &selfName);
 
 uint64_t GetModifiedTimestamp(const string &filename);
 
-void Copy(const char *from, const char *to, bool allowOverwrite);
+bool Copy(const char *from, const char *to, bool allowOverwrite);
+bool Move(const char *from, const char *to, bool allowOverwrite);
 void Delete(const char *path);
 std::vector<PathEntry> GetFilesInDirectory(const char *path);
 
@@ -271,6 +272,10 @@ std::string getline(FILE *f);
 uint64_t ftell64(FILE *f);
 void fseek64(FILE *f, uint64_t offset, int origin);
 
+void ftruncateat(FILE *f, uint64_t length);
+
+bool fflush(FILE *f);
+
 bool feof(FILE *f);
 
 int fclose(FILE *f);
diff --git a/renderdoc/os/posix/posix_stringio.cpp b/renderdoc/os/posix/posix_stringio.cpp
index c216b1cb2..2d282fa44 100644
--- a/renderdoc/os/posix/posix_stringio.cpp
+++ b/renderdoc/os/posix/posix_stringio.cpp
@@ -255,17 +255,17 @@ uint64_t GetModifiedTimestamp(const string &filename)
   return 0;
 }
 
-void Copy(const char *from, const char *to, bool allowOverwrite)
+bool Copy(const char *from, const char *to, bool allowOverwrite)
 {
   if(from[0] == 0 || to[0] == 0)
-    return;
+    return false;
 
   FILE *ff = ::fopen(from, "r");
 
   if(!ff)
   {
     RDCERR("Can't open source file for copy '%s'", from);
-    return;
+    return false;
   }
 
   FILE *tf = ::fopen(to, "r");
@@ -275,7 +275,7 @@ void Copy(const char *from, const char *to, bool allowOverwrite)
     RDCERR("Destination file for non-overwriting copy '%s' already exists", from);
     ::fclose(ff);
     ::fclose(tf);
-    return;
+    return false;
   }
 
   if(tf)
@@ -287,6 +287,7 @@ void Copy(const char *from, const char *to, bool allowOverwrite)
   {
     ::fclose(ff);
     RDCERR("Can't open destination file for copy '%s'", to);
+    return false;
   }
 
   char buffer[BUFSIZ];
@@ -299,6 +300,19 @@ void Copy(const char *from, const char *to, bool allowOverwrite)
 
   ::fclose(ff);
   ::fclose(tf);
+
+  return true;
+}
+
+bool Move(const char *from, const char *to, bool allowOverwrite)
+{
+  if(exists(to))
+  {
+    if(!allowOverwrite)
+      return false;
+  }
+
+  return ::rename(from, to) == 0;
 }
 
 void Delete(const char *path)
@@ -434,6 +448,18 @@ bool feof(FILE *f)
   return ::feof(f) != 0;
 }
 
+void ftruncateat(FILE *f, uint64_t length)
+{
+  ::fflush(f);
+  int fd = ::fileno(f);
+  ::ftruncate(fd, (off_t)length);
+}
+
+bool fflush(FILE *f)
+{
+  return ::fflush(f) == 0;
+}
+
 int fclose(FILE *f)
 {
   return ::fclose(f);
diff --git a/renderdoc/os/win32/win32_stringio.cpp b/renderdoc/os/win32/win32_stringio.cpp
index 037db0d5d..5e45f29ea 100644
--- a/renderdoc/os/win32/win32_stringio.cpp
+++ b/renderdoc/os/win32/win32_stringio.cpp
@@ -23,6 +23,7 @@
  * THE SOFTWARE.
  ******************************************************************************/
 
+#include <io.h>
 #include <shlobj.h>
 #include <shlwapi.h>
 #include <stdio.h>
@@ -394,12 +395,28 @@ uint64_t GetModifiedTimestamp(const string &filename)
   return 0;
 }
 
-void Copy(const char *from, const char *to, bool allowOverwrite)
+bool Copy(const char *from, const char *to, bool allowOverwrite)
 {
   wstring wfrom = StringFormat::UTF82Wide(string(from));
   wstring wto = StringFormat::UTF82Wide(string(to));
 
-  ::CopyFileW(wfrom.c_str(), wto.c_str(), allowOverwrite == false);
+  return ::CopyFileW(wfrom.c_str(), wto.c_str(), allowOverwrite == false) != 0;
+}
+
+bool Move(const char *from, const char *to, bool allowOverwrite)
+{
+  wstring wfrom = StringFormat::UTF82Wide(string(from));
+  wstring wto = StringFormat::UTF82Wide(string(to));
+
+  if(exists(to))
+  {
+    if(allowOverwrite)
+      Delete(to);
+    else
+      return false;
+  }
+
+  return ::MoveFileW(wfrom.c_str(), wto.c_str()) != 0;
 }
 
 void Delete(const char *path)
@@ -591,6 +608,18 @@ bool feof(FILE *f)
   return ::feof(f) != 0;
 }
 
+void ftruncateat(FILE *f, uint64_t length)
+{
+  ::fflush(f);
+  int fd = ::_fileno(f);
+  ::_chsize_s(fd, (int64_t)length);
+}
+
+bool fflush(FILE *f)
+{
+  return ::fflush(f) == 0;
+}
+
 int fclose(FILE *f)
 {
   return ::fclose(f);
diff --git a/renderdoc/serialise/streamio.h b/renderdoc/serialise/streamio.h
index 6716f3f5c..13c73ee9a 100644
--- a/renderdoc/serialise/streamio.h
+++ b/renderdoc/serialise/streamio.h
@@ -401,7 +401,7 @@ public:
     if(m_Compressor)
       return m_Compressor->Finish();
     else if(m_File)
-      return fflush(m_File) == 0;
+      return FileIO::fflush(m_File);
     else if(m_Sock)
       return true;