- djm@cvs.openbsd.org 2010/01/30 02:54:53

[openssh.git] / buffer.c

diff --git a/buffer.c b/buffer.c
index 08682e0f125bd17b03ce4a940ce8a92c1bf883b4..e02e1e35c9947dce9937655cff72db2d00efa9a6 100644 (file)
--- 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
@@ -13,10 +14,20 @@
 
 #include "includes.h"
 
+#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
@@ -65,6 +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
@@ -92,29 +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