X-Git-Url: http://winboard.nl/cgi-bin?a=blobdiff_plain;f=book.c;h=6b1198df8d7cde1b316206bc9b2e314a9a6b13c2;hb=6e49be9af735766630fd7b2fdb646127b126c873;hp=e42b9c6e5099e0a3560bcd28b384e2d26dca88fc;hpb=09d925e8732793829e2a2a2abe582a46343e3fd2;p=xboard.git

diff --git a/book.c b/book.c
index e42b9c6..6b1198d 100644
--- a/book.c
+++ b/book.c
@@ -676,8 +676,10 @@ void SaveToBook(char *text)
     if(count != currentCount) {
 	do {
 	    for(i=0; i<len1; i++) buf2[i] = buf1[i]; len2 = len1;
-	    fseek(f, readpos, SEEK_SET);
-	    readpos += len1 = fread(buf1, 1, 4096, f);
+	    if(readpos > writepos) {
+		fseek(f, readpos, SEEK_SET);
+		readpos += len1 = fread(buf1, 1, 4096, f);
+	    } else len1 = 0; // wrote already past old EOF
 	    fseek(f, writepos, SEEK_SET);
 	    fwrite(buf2, 1, len2, f);
 	    writepos += len2;