[Dotgnu-pnet-commits] CVS: pnet/image image.h,1.18,1.19 pecoff_writer.c,1.9,1.10 writer.c,1.9,1.10

[Rhys Weatherley <address@hidden>]

Update of /cvsroot/dotgnu-pnet/pnet/image
In directory subversions:/tmp/cvs-serv28307/image

Modified Files:
        image.h pecoff_writer.c writer.c 
Log Message:


Implement a caching mechanism for back-patching to smooth out
filesystem performance, particular on NFS-mounted filesystems.


Index: image.h
===================================================================
RCS file: /cvsroot/dotgnu-pnet/pnet/image/image.h,v
retrieving revision 1.18
retrieving revision 1.19
diff -C2 -r1.18 -r1.19
*** image.h     7 Feb 2003 11:31:30 -0000       1.18
--- image.h     8 Feb 2003 04:24:29 -0000       1.19
***************
*** 351,354 ****
--- 351,360 ----
        int                             writeFailed;    /* The write failed at 
some point */
  
+       /* Back-patch cache */
+       int                             backpatching;   /* Non-zero if last 
write was back-patch */
+       unsigned long   backpatchSeek;  /* Seek position of back-patch cache */
+       unsigned long   backpatchLen;   /* Length of back-patch cache */
+       unsigned char  *backpatchBuf;   /* Buffer containing back-patch data */
+ 
  };
  

Index: pecoff_writer.c
===================================================================
RCS file: /cvsroot/dotgnu-pnet/pnet/image/pecoff_writer.c,v
retrieving revision 1.9
retrieving revision 1.10
diff -C2 -r1.9 -r1.10
*** pecoff_writer.c     26 Nov 2002 05:04:46 -0000      1.9
--- pecoff_writer.c     8 Feb 2003 04:24:29 -0000       1.10
***************
*** 27,30 ****
--- 27,58 ----
  
  /*
+  * Flush the back-patch cache if necessary.
+  */
+ static void FlushBackPatchCache(ILWriter *writer)
+ {
+       if(writer->backpatching)
+       {
+               /* Seek to the beginning of the back-patch area */
+               if(fseek(writer->stream, writer->backpatchSeek, 0) < 0)
+               {
+                       writer->writeFailed = 1;
+                       return;
+               }
+ 
+               /* Write the modified contents of the back-patch buffer */
+               if(fwrite(writer->backpatchBuf, 1, 
(unsigned)(writer->backpatchLen),
+                                 writer->stream) != 
(unsigned)(writer->backpatchLen))
+               {
+                       writer->writeFailed = 1;
+                       return;
+               }
+ 
+               /* Record the new seek position and exit the back-patching mode 
*/
+               writer->currSeek = writer->backpatchSeek + writer->backpatchLen;
+               writer->backpatching = 0;
+       }
+ }
+ 
+ /*
   * Write a block of data to an output image.
   */
***************
*** 38,41 ****
--- 66,72 ----
        if(writer->seekable)
        {
+               /* Flush the back-patching cache, if present */
+               FlushBackPatchCache(writer);
+ 
                /* This is a seekable stream, so write directly to it */
                if(writer->offset != writer->currSeek)
***************
*** 110,113 ****
--- 141,149 ----
                }
        }
+       else
+       {
+               /* Flush the back-patching cache */
+               FlushBackPatchCache(writer);
+       }
  }
  
***************
*** 141,144 ****
--- 177,224 ----
        if(writer->seekable)
        {
+               /* Can we add the bytes to the current back-patch cache? */
+               if(writer->backpatching && posn >= writer->backpatchSeek &&
+                  (posn + size) <= (writer->backpatchSeek + 
writer->backpatchLen))
+               {
+                       ILMemCpy(writer->backpatchBuf +
+                                        (unsigned)(posn - 
writer->backpatchSeek), buffer, size);
+                       return;
+               }
+ 
+               /* Flush the current back-patch cache contents */
+               FlushBackPatchCache(writer);
+ 
+               /* Only do caching for small values (usually 32-bit quantities) 
*/
+               if(size <= 4 && writer->backpatchBuf)
+               {
+                       /* Align the back-patch cache for better filesystem 
performance */
+                       writer->backpatchSeek = posn & ~511;
+                       writer->backpatchLen = writer->offset - 
writer->backpatchSeek;
+                       if(writer->backpatchLen > IL_WRITE_BUFFER_SIZE)
+                       {
+                               writer->backpatchLen = IL_WRITE_BUFFER_SIZE;
+                       }
+ 
+                       /* Read the block to be patched into memory */
+                       if(fseek(writer->stream, writer->backpatchSeek, 0) < 0)
+                       {
+                               writer->writeFailed = 1;
+                               return;
+                       }
+                       if(fread(writer->backpatchBuf, 1, 
(unsigned)(writer->backpatchLen),
+                                        writer->stream) != 
(unsigned)(writer->backpatchLen))
+                       {
+                               writer->writeFailed = 1;
+                               return;
+                       }
+                       writer->currSeek = writer->backpatchSeek + 
writer->backpatchLen;
+ 
+                       /* Patch the required bytes and return */
+                       ILMemCpy(writer->backpatchBuf +
+                                        (unsigned)(posn - 
writer->backpatchSeek), buffer, size);
+                       writer->backpatching = 1;
+                       return;
+               }
+ 
                /* Seek back in the file and write the change */
                if(posn != writer->currSeek)

Index: writer.c
===================================================================
RCS file: /cvsroot/dotgnu-pnet/pnet/image/writer.c,v
retrieving revision 1.9
retrieving revision 1.10
diff -C2 -r1.9 -r1.10
*** writer.c    7 Jan 2003 11:57:18 -0000       1.9
--- writer.c    8 Feb 2003 04:24:29 -0000       1.10
***************
*** 119,122 ****
--- 119,126 ----
        writer->maxDebugTokens = 0;
        writer->debugHash = 0;
+       writer->backpatching = 0;
+       writer->backpatchSeek = 0;
+       writer->backpatchLen = 0;
+       writer->backpatchBuf = 0;
  
        /* Initialize buffer lists */
***************
*** 132,135 ****
--- 136,147 ----
        writer->lastFixup = 0;
  
+       /* Allocate the back-patching buffer.  If we run out of
+          memory, then disable the back-patch cache */
+       if(seekable)
+       {
+               writer->backpatchBuf = (unsigned char *)ILMalloc
+                       (IL_WRITE_BUFFER_SIZE);
+       }
+ 
        /* Write the headers to the output stream */
        if(flags & IL_WRITEFLAG_JVM_MODE)
***************
*** 623,626 ****
--- 635,644 ----
        {
                ILHashDestroy(writer->debugHash);
+       }
+ 
+       /* Free the back-patch buffer */
+       if(writer->backpatchBuf)
+       {
+               ILFree(writer->backpatchBuf);
        }