1 files changed, 55 insertions, 14 deletions

diff --git a/buffer.c b/buffer.c
index 487e08105..e02e1e35c 100644
--- a/buffer.c
+++ b/buffer.c
@@ -1,3 +1,4 @@
+/* $OpenBSD: buffer.c,v 1.31 2006/08/03 03:34:41 deraadt Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -12,12 +13,21 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: buffer.c,v 1.23 2005/03/14 11:46:56 markus Exp $");
+
+#include <sys/param.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
 
 #include "xmalloc.h"
 #include "buffer.h"
 #include "log.h"
 
+#define BUFFER_MAX_CHUNK        0x100000
+#define BUFFER_MAX_LEN          0xa00000
+#define BUFFER_ALLOCSZ          0x008000
+
 /* Initializes the buffer structure. */
 
 void
@@ -66,6 +76,23 @@ buffer_append(Buffer *buffer, const void *data, u_int len)
         memcpy(p, data, len);
 }
 
+static int
+buffer_compact(Buffer *buffer)
+{
+        /*
+         * If the buffer is quite empty, but all data is at the end, move the
+         * data to the beginning.
+         */
+        if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
+                memmove(buffer->buf, buffer->buf + buffer->offset,
+                        buffer->end - buffer->offset);
+                buffer->end -= buffer->offset;
+                buffer->offset = 0;
+                return (1);
+        }
+        return (0);
+}
+
 /*
  * Appends space to the buffer, expanding the buffer if necessary. This does
  * not actually copy the data into the buffer, but instead returns a pointer
@@ -93,29 +120,43 @@ restart:
                 buffer->end += len;
                 return p;
         }
-        /*
-         * If the buffer is quite empty, but all data is at the end, move the
-         * data to the beginning and retry.
-         */
-        if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
-                memmove(buffer->buf, buffer->buf + buffer->offset,
-                        buffer->end - buffer->offset);
-                buffer->end -= buffer->offset;
-                buffer->offset = 0;
+
+        /* Compact data back to the start of the buffer if necessary */
+        if (buffer_compact(buffer))
                 goto restart;
-        }
-        /* Increase the size of the buffer and retry. */
 
-        newlen = buffer->alloc + len + 32768;
+        /* Increase the size of the buffer and retry. */
+        newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
         if (newlen > BUFFER_MAX_LEN)
                 fatal("buffer_append_space: alloc %u not supported",
                     newlen);
-        buffer->buf = xrealloc(buffer->buf, newlen);
+        buffer->buf = xrealloc(buffer->buf, 1, newlen);
         buffer->alloc = newlen;
         goto restart;
         /* NOTREACHED */
 }
 
+/*
+ * Check whether an allocation of 'len' will fit in the buffer
+ * This must follow the same math as buffer_append_space
+ */
+int
+buffer_check_alloc(Buffer *buffer, u_int len)
+{
+        if (buffer->offset == buffer->end) {
+                buffer->offset = 0;
+                buffer->end = 0;
+        }
+ restart:
+        if (buffer->end + len < buffer->alloc)
+                return (1);
+        if (buffer_compact(buffer))
+                goto restart;
+        if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
+                return (1);
+        return (0);
+}
+
 /* Returns the number of bytes of data in the buffer. */
 
 u_int