Protecting Buffers against erratic seeks.

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/Buffer.cc b/lib/Buffer.cc
index 68ecb9e..473da62 100644
--- a/lib/Buffer.cc
+++ b/lib/Buffer.cc
@@ -181,9 +181,11 @@ bool Buffer::CanSeek() const {
 }
 
 off_t Buffer::seek(off_t off, int wheel) throw (GeneralException) {
+    size_t old_ptr;
     if (!seekable) {
         throw GeneralException("This buffer is a fifo, thus is not seekable");
     }
+    old_ptr = ptr;
     switch (wheel) {
     case SEEK_SET:
         ptr = off;
@@ -195,6 +197,10 @@ off_t Buffer::seek(off_t off, int wheel) throw (GeneralException) {
         ptr = realsiz + off;
         break;
     }
+    if (ptr < 0) {
+        ptr = old_ptr;
+        throw GeneralException("Can't seek a Buffer before its start.")
+    }
     operator[](ptr);
     return ptr;
 }