From 98f41fe4d29e344fe710bb85fcc906c1cecda795 Mon Sep 17 00:00:00 2001
From: Andrew Hanushevsky <abh@stanford.edu>
Date: Wed, 9 Oct 2019 07:50:41 -0700
Subject: [PATCH] [Server] Add default implementation for pgRead and pgWrite.

---
 src/XrdSfs/XrdSfsInterface.cc | 75 +++++++++++++++++++++++++++++++----
 src/XrdSfs/XrdSfsInterface.hh | 10 ++---
 2 files changed, 72 insertions(+), 13 deletions(-)

diff --git a/src/XrdSfs/XrdSfsInterface.cc b/src/XrdSfs/XrdSfsInterface.cc
index acf2a22e08a..a36d77a282a 100644
--- a/src/XrdSfs/XrdSfsInterface.cc
+++ b/src/XrdSfs/XrdSfsInterface.cc
@@ -27,9 +27,19 @@
 /* specific prior written permission of the institution or contributor.       */
 /******************************************************************************/
 
+#include "XrdOuc/XrdOucCRC.hh"
 #include "XrdSfs/XrdSfsAio.hh"
 #include "XrdSfs/XrdSfsInterface.hh"
 
+/******************************************************************************/
+/*                        S t a t i c   S y m b o l s                         */
+/******************************************************************************/
+  
+namespace
+{
+static const XrdSfsFileOffset pgSize = XrdSfsPageSize;
+}
+
 /******************************************************************************/
 /*                                p g R e a d                                 */
 /******************************************************************************/
@@ -39,10 +49,29 @@ XrdSfsXferSize XrdSfsFile::pgRead(XrdSfsFileOffset   offset,
                                   XrdSfsXferSize     rdlen,
                                   uint32_t          *csvec,
                                   bool               verify)
-{(void)offset; (void)buffer; (void)rdlen;
- (void)csvec;  (void)verify;
- error.setErrInfo(ENOTSUP, "Not supported.");
- return SFS_ERROR;
+{
+   XrdSfsXferSize bytes;
+
+// Make sure the offset is on a 4K boundary and the size if a multiple of
+// 4k as well (we use simple and for this).
+//
+   if ((offset & ~pgSize) || (rdlen & ~XrdSfsPageSize))
+      {error.setErrInfo(EINVAL,"Offset or readlen not a multiple of pagesize.");
+       return SFS_ERROR;
+      }
+
+// Read the data into the buffer
+//
+   bytes = read(offset, buffer, rdlen);
+
+// Calculate checksums if so wanted
+//
+   if (bytes > 0 && csvec)
+      XrdOucCRC::Calc32C((void *)buffer, rdlen, csvec, XrdSfsPageSize);
+
+// All done
+//
+   return bytes;
 }
 
 /******************************************************************************/
@@ -66,10 +95,40 @@ XrdSfsXferSize XrdSfsFile::pgWrite(XrdSfsFileOffset   offset,
                                    XrdSfsXferSize     wrlen,
                                    uint32_t          *csvec,
                                    bool               verify)
-{(void)offset; (void)buffer; (void)wrlen;
- (void)csvec;  (void)verify;
- error.setErrInfo(ENOTSUP, "Not supported.");
- return SFS_ERROR;
+{
+// Make sure the offset is on a 4K boundary
+//
+   if (offset & ~pgSize)
+      {error.setErrInfo(EINVAL,"Offset or readlen not a multiple of pagesize.");
+       return SFS_ERROR;
+      }
+
+// If a virtual end of file marker is set, make sure we are not trying to
+// write past it.
+//
+   if (pgwrEOF && (offset+wrlen) > pgwrEOF)
+      {error.setErrInfo(ESPIPE,"Attempt to write past virtual EOF.");
+       return SFS_ERROR;
+      }
+
+// If this is a short write then establish the virtual eof
+//
+   if (wrlen & ~XrdSfsPageSize) pgwrEOF = (offset + wrlen) & ~pgSize;
+
+// If we have a checksum vector and verify is on, make sure the data
+// in the buffer corresponds to he checksums.
+//
+   if (csvec && verify)
+      {int pgErr;
+       if (!XrdOucCRC::Ver32C((void *)buffer,wrlen,csvec,XrdSfsPageSize,pgErr))
+          {error.setErrInfo(EDOM,"Checksum error.");
+           return SFS_ERROR;
+          }
+      }
+
+// Now just return the result of a plain write
+//
+   return write(offset, buffer, wrlen);
 }
 
 /******************************************************************************/
diff --git a/src/XrdSfs/XrdSfsInterface.hh b/src/XrdSfs/XrdSfsInterface.hh
index 51ffad35797..b3f7d4fc62c 100644
--- a/src/XrdSfs/XrdSfsInterface.hh
+++ b/src/XrdSfs/XrdSfsInterface.hh
@@ -738,7 +738,7 @@ virtual void           setXio(XrdSfsXio *xioP) { (void)xioP; }
 
                        XrdSfsFile(const char *user=0, int MonID=0)
                                  : error(*(new XrdOucErrInfo(user, MonID)))
-                                 {lclEI = &error;}
+                                 {lclEI = &error; pgwrEOF = 0;}
 
 //-----------------------------------------------------------------------------
 //! Constructor for plugins that wrap another SFS plugin. This constructor
@@ -749,7 +749,7 @@ virtual void           setXio(XrdSfsXio *xioP) { (void)xioP; }
 //-----------------------------------------------------------------------------
 
                        XrdSfsFile(XrdSfsFile &wrapF)
-                                 : error(wrapF.error), lclEI(0) {}
+                                 : error(wrapF.error), lclEI(0), pgwrEOF(0) {}
 
 //-----------------------------------------------------------------------------
 //! Constructor for base plugins that predefined an error object. This is a
@@ -759,7 +759,7 @@ virtual void           setXio(XrdSfsXio *xioP) { (void)xioP; }
 //-----------------------------------------------------------------------------
 
                        XrdSfsFile(XrdOucErrInfo &eInfo)
-                                 : error(eInfo), lclEI(0) {}
+                                 : error(eInfo), lclEI(0), pgwrEOF(0) {}
 
 //-----------------------------------------------------------------------------
 //! Destructor
@@ -768,8 +768,8 @@ virtual void           setXio(XrdSfsXio *xioP) { (void)xioP; }
 virtual               ~XrdSfsFile() {if (lclEI) delete lclEI;}
 
 private:
-XrdOucErrInfo* lclEI;
-
+XrdOucErrInfo*   lclEI;
+XrdSfsFileOffset pgwrEOF;
 }; // class XrdSfsFile
 
 /******************************************************************************/