I/O vector helpers (Avi Kivity)

In general, it is not possible to predict the size of of an I/O vector since
a contiguous guest region may map to a disconiguous host region.  Add some
helpers to manage I/O vector growth.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6396 c046a42c-6fe2-441c-8c8c-71466251a162

cutils.c

@@ -101,3 +101,50 @@ int qemu_fls(int i)
 {
     return 32 - clz32(i);
 }
+
+/* io vectors */
+
+void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
+{
+    qiov->iov = qemu_malloc(alloc_hint * sizeof(struct iovec));
+    qiov->niov = 0;
+    qiov->nalloc = alloc_hint;
+}
+
+void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
+{
+    if (qiov->niov == qiov->nalloc) {
+        qiov->nalloc = 2 * qiov->nalloc + 1;
+        qiov->iov = qemu_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
+    }
+    qiov->iov[qiov->niov].iov_base = base;
+    qiov->iov[qiov->niov].iov_len = len;
+    ++qiov->niov;
+}
+
+void qemu_iovec_destroy(QEMUIOVector *qiov)
+{
+    qemu_free(qiov->iov);
+}
+
+void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf)
+{
+    uint8_t *p = (uint8_t *)buf;
+    int i;
+
+    for (i = 0; i < qiov->niov; ++i) {
+        memcpy(p, qiov->iov[i].iov_base, qiov->iov[i].iov_len);
+        p += qiov->iov[i].iov_len;
+    }
+}
+
+void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf)
+{
+    const uint8_t *p = (const uint8_t *)buf;
+    int i;
+
+    for (i = 0; i < qiov->niov; ++i) {
+        memcpy(qiov->iov[i].iov_base, p, qiov->iov[i].iov_len);
+        p += qiov->iov[i].iov_len;
+    }
+}

qemu-common.h

@@ -191,6 +191,18 @@ int cpu_load(QEMUFile *f, void *opaque, int version_id);
 /* Force QEMU to stop what it's doing and service IO */
 void qemu_service_io(void);
 
+typedef struct QEMUIOVector {
+    struct iovec *iov;
+    int niov;
+    int nalloc;
+} QEMUIOVector;
+
+void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
+void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
+void qemu_iovec_destroy(QEMUIOVector *qiov);
+void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf);
+void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf);
+
 #endif /* dyngen-exec.h hack */
 
 #endif