[Qemu-devel] [PATCH RFC v3 09/27] QEMUSizedBuffer: Introduce two help functions for qsb

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

Introduce two new QEMUSizedBuffer APIs which will be used by COLO to buffer
VM state:
One is qsb_put_buffer(), which put the content of a given QEMUSizedBuffer
into QEMUFile, this is used to send buffered VM state to secondary.
Another is qsb_fill_buffer(), read 'size' bytes of data from the file into
qsb, this is used to get VM state from socket into a buffer.

Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
---
 include/migration/qemu-file.h |  3 ++-
 migration/qemu-file-buf.c     | 57 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index a923cec..07039e2 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -141,7 +141,8 @@ ssize_t qsb_get_buffer(const QEMUSizedBuffer *, off_t start, size_t count,
                        uint8_t *buf);
 ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *buf,
                      off_t pos, size_t count);
-
+void qsb_put_buffer(QEMUFile *f, QEMUSizedBuffer *qsb, int size);
+int qsb_fill_buffer(QEMUSizedBuffer *qsb, QEMUFile *f, int size);
 
 /*
  * For use on files opened with qemu_bufopen
diff --git a/migration/qemu-file-buf.c b/migration/qemu-file-buf.c
index e97e0bd..78170bc 100644
--- a/migration/qemu-file-buf.c
+++ b/migration/qemu-file-buf.c
@@ -392,6 +392,63 @@ QEMUSizedBuffer *qsb_clone(const QEMUSizedBuffer *qsb)
     return out;
 }
 
+/**
+ * Put the content of a given QEMUSizedBuffer into QEMUFile.
+ *
+ * @f: A QEMUFile
+ * @qsb: A QEMUSizedBuffer
+ * @size: size of content to write
+ */
+void qsb_put_buffer(QEMUFile *f, QEMUSizedBuffer *qsb, int size)
+{
+    int i, l;
+
+    for (i = 0; i < qsb->n_iov && size > 0; i++) {
+        l = MIN(qsb->iov[i].iov_len, size);
+        qemu_put_buffer(f, qsb->iov[i].iov_base, l);
+        size -= l;
+    }
+}
+
+/*
+ * Read 'size' bytes of data from the file into qsb.
+ * always fill from pos 0 and used after qsb_create().
+ *
+ * It will return size bytes unless there was an error, in which case it will
+ * return as many as it managed to read (assuming blocking fd's which
+ * all current QEMUFile are)
+ */
+int qsb_fill_buffer(QEMUSizedBuffer *qsb, QEMUFile *f, int size)
+{
+    ssize_t rc = qsb_grow(qsb, size);
+    int pending = size, i;
+    qsb->used = 0;
+    uint8_t *buf = NULL;
+
+    if (rc < 0) {
+        return rc;
+    }
+
+    for (i = 0; i < qsb->n_iov && pending > 0; i++) {
+        int doneone = 0;
+        /* read until iov full */
+        while (doneone < qsb->iov[i].iov_len && pending > 0) {
+            int readone = 0;
+            buf = qsb->iov[i].iov_base;
+            readone = qemu_get_buffer(f, buf,
+                                MIN(qsb->iov[i].iov_len - doneone, pending));
+            if (readone == 0) {
+                return qsb->used;
+            }
+            buf += readone;
+            doneone += readone;
+            pending -= readone;
+            qsb->used += readone;
+        }
+    }
+    return qsb->used;
+}
+
 typedef struct QEMUBuffer {
     QEMUSizedBuffer *qsb;
     QEMUFile *file;
-- 
1.7.12.4