add qemu_iovec_init_external (Christoph Hellwig)

Allow to initialize a QEMUIOVector from an externally allocated iovec.
qiov->nalloc is initialized to -1 to indicate external storage for qiov->iov
and all functions dealing with memory management assert on the iovec beeing
an internally managed first.


Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6902 c046a42c-6fe2-441c-8c8c-71466251a162

cutils.c

@@ -23,6 +23,7 @@
  */
 #include "qemu-common.h"
 #include "host-utils.h"
+#include <assert.h>
 
 void pstrcpy(char *buf, int buf_size, const char *str)
 {
@@ -112,8 +113,22 @@ void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
     qiov->size = 0;
 }
 
+void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
+{
+    int i;
+
+    qiov->iov = iov;
+    qiov->niov = niov;
+    qiov->nalloc = -1;
+    qiov->size = 0;
+    for (i = 0; i < niov; i++)
+        qiov->size += iov[i].iov_len;
+}
+
 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 {
+    assert(qiov->nalloc != -1);
+
     if (qiov->niov == qiov->nalloc) {
         qiov->nalloc = 2 * qiov->nalloc + 1;
         qiov->iov = qemu_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
@@ -126,11 +141,15 @@ void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 
 void qemu_iovec_destroy(QEMUIOVector *qiov)
 {
+    assert(qiov->nalloc != -1);
+
     qemu_free(qiov->iov);
 }
 
 void qemu_iovec_reset(QEMUIOVector *qiov)
 {
+    assert(qiov->nalloc != -1);
+
     qiov->niov = 0;
     qiov->size = 0;
 }

qemu-common.h

@@ -194,6 +194,7 @@ typedef struct QEMUIOVector {
 } QEMUIOVector;
 
 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
+void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
 void qemu_iovec_destroy(QEMUIOVector *qiov);
 void qemu_iovec_reset(QEMUIOVector *qiov);