[Qemu-devel] [PATCH 3/7] cutils: qemu_iovec_copy and qemu_iovec_memset

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

From: Kevin Wolf <kwolf@redhat.com>

This adds two functions that work on QEMUIOVectors and will be used by the next
qcow2 patches.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
Kevin already has this queued up for mainline.  QED uses qemu_iovec_memset().

 cutils.c      |   50 +++++++++++++++++++++++++++++++++++++++++---------
 qemu-common.h |    3 +++
 2 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/cutils.c b/cutils.c
index 76f7501..de00472 100644
--- a/cutils.c
+++ b/cutils.c
@@ -168,30 +168,50 @@ void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 }
 
 /*
- * Copies iovecs from src to the end dst until src is completely copied or the
- * total size of the copied iovec reaches size. The size of the last copied
- * iovec is changed in order to fit the specified total size if it isn't a
- * perfect fit already.
+ * Copies iovecs from src to the end of dst. It starts copying after skipping
+ * the given number of bytes in src and copies until src is completely copied
+ * or the total size of the copied iovec reaches size.The size of the last
+ * copied iovec is changed in order to fit the specified total size if it isn't
+ * a perfect fit already.
  */
-void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size)
+void qemu_iovec_copy(QEMUIOVector *dst, QEMUIOVector *src, uint64_t skip,
+    size_t size)
 {
     int i;
     size_t done;
+    void *iov_base;
+    uint64_t iov_len;
 
     assert(dst->nalloc != -1);
 
     done = 0;
     for (i = 0; (i < src->niov) && (done != size); i++) {
-        if (done + src->iov[i].iov_len > size) {
-            qemu_iovec_add(dst, src->iov[i].iov_base, size - done);
+        if (skip >= src->iov[i].iov_len) {
+            /* Skip the whole iov */
+            skip -= src->iov[i].iov_len;
+            continue;
+        } else {
+            /* Skip only part (or nothing) of the iov */
+            iov_base = (uint8_t*) src->iov[i].iov_base + skip;
+            iov_len = src->iov[i].iov_len - skip;
+            skip = 0;
+        }
+
+        if (done + iov_len > size) {
+            qemu_iovec_add(dst, iov_base, size - done);
             break;
         } else {
-            qemu_iovec_add(dst, src->iov[i].iov_base, src->iov[i].iov_len);
+            qemu_iovec_add(dst, iov_base, iov_len);
         }
-        done += src->iov[i].iov_len;
+        done += iov_len;
     }
 }
 
+void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size)
+{
+    qemu_iovec_copy(dst, src, 0, size);
+}
+
 void qemu_iovec_destroy(QEMUIOVector *qiov)
 {
     assert(qiov->nalloc != -1);
@@ -234,6 +254,18 @@ void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count)
     }
 }
 
+void qemu_iovec_memset(QEMUIOVector *qiov, int c, size_t count)
+{
+    size_t n;
+    int i;
+
+    for (i = 0; i < qiov->niov && count; ++i) {
+        n = MIN(count, qiov->iov[i].iov_len);
+        memset(qiov->iov[i].iov_base, c, n);
+        count -= n;
+    }
+}
+
 #ifndef _WIN32
 /* Sets a specific flag */
 int fcntl_setfl(int fd, int flag)
diff --git a/qemu-common.h b/qemu-common.h
index e0900b8..0404817 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -280,11 +280,14 @@ typedef struct 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_copy(QEMUIOVector *dst, QEMUIOVector *src, uint64_t skip,
+    size_t size);
 void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size);
 void qemu_iovec_destroy(QEMUIOVector *qiov);
 void qemu_iovec_reset(QEMUIOVector *qiov);
 void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf);
 void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count);
+void qemu_iovec_memset(QEMUIOVector *qiov, int c, size_t count);
 
 struct Monitor;
 typedef struct Monitor Monitor;
-- 
1.7.1