Merge lp:~gaul/percona-data-recovery-tool-for-innodb/innochecksum-write-page-only-once into lp:percona-data-recovery-tool-for-innodb

[Andrew Gaul]

=== modified file 'innochecksum.c'
--- innochecksum.c	2012-08-07 20:36:41 +0000
+++ innochecksum.c	2012-08-10 00:00:29 +0000
@@ -172,6 +172,8 @@
   lastt= 0;
   while (!feof(f))
   {
+    int modified = 0;
+
     fgetpos(f, &pos);
     bytes= fread(p, 1, UNIV_PAGE_SIZE, f);
     if (!bytes && feof(f)) return 0;
@@ -195,15 +197,7 @@
 	buf_lsn = mach_read_from_4((uchar*)&fixed_lsn);
 	memcpy(p + FIL_PAGE_LSN + 4, &buf_lsn, sizeof(buf_lsn));
 	memcpy(p + UNIV_PAGE_SIZE - FIL_PAGE_END_LSN_OLD_CHKSUM + 4, &buf_lsn, sizeof(buf_lsn));
-	// move to beginning of the page
-	if(0 != fsetpos(f, &pos)){
-      		perror("couldn't set a position to the start of the page");
-		return 1;
-		}
-	if(1 != fwrite(p, UNIV_PAGE_SIZE, 1, f)){
-      		perror("couldn't update the page");
-		return 1;
-		}
+        modified = 1;
       	}
       else{
       	return 1;
@@ -224,15 +218,7 @@
 	// rewite recorded checksum with calculated one
 	fixed_chksum = mach_read_from_4((uchar*)&csum);
 	memcpy(p + FIL_PAGE_SPACE_OR_CHKSUM, &fixed_chksum, sizeof(fixed_chksum));
-	// move to beginning of the page
-	if(0 != fsetpos(f, &pos)){
-      		perror("couldn't set a position to the start of the page");
-		return 1;
-		}
-	if(1 != fwrite(p, UNIV_PAGE_SIZE, 1, f)){
-      		perror("couldn't update the page");
-		return 1;
-		}
+        modified = 1;
       	}
       else{
       	return 1;
@@ -253,21 +239,25 @@
 	// rewite recorded checksum with calculated one
 	fixed_chksum = mach_read_from_4((uchar*)&oldcsum);
 	memcpy(p + UNIV_PAGE_SIZE - FIL_PAGE_END_LSN_OLD_CHKSUM, &fixed_chksum, sizeof(fixed_chksum));
-	// move to the beginning of the page
-	if(0 != fsetpos(f, &pos)){
-      		perror("couldn't set a position to the start of the page");
-		return 1;
-		}
-	if(1 != fwrite(p, UNIV_PAGE_SIZE, 1, f)){
-      		perror("couldn't update the page");
-		return 1;
-		}
+        modified = 1;
       	}
       else{
       	return 1;
       	}
     }
 
+    if (modified) {
+      // move to the beginning of the page
+      if(0 != fsetpos(f, &pos)) {
+        perror("couldn't set a position to the start of the page");
+        return 1;
+      }
+      if(1 != fwrite(p, UNIV_PAGE_SIZE, 1, f)) {
+        perror("couldn't update the page");
+        return 1;
+      }
+    }
+
     /* end if this was the last page we were supposed to check */
     if (use_end_page && (ct >= end_page))
       return 0;