[RFC PATCH v1 09/26] migration/qemu-file: add utility methods for working with seekable channels

[Fabiano Rosas]

From: Nikolay Borisov <nborisov@suse.com>

Add utility methods that will be needed when implementing 'fixed-ram'
migration capability.

qemu_file_is_seekable
qemu_put_buffer_at
qemu_get_buffer_at
qemu_set_offset
qemu_get_offset

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
fixed total_transferred accounting

restructured to use qio_channel_file_preadv instead of the _full
variant
---
 include/migration/qemu-file-types.h |  2 +
 migration/qemu-file.c               | 80 +++++++++++++++++++++++++++++
 migration/qemu-file.h               |  4 ++
 3 files changed, 86 insertions(+)

diff --git a/include/migration/qemu-file-types.h 
b/include/migration/qemu-file-types.h
index 2867e3da84..eb0325ee86 100644
--- a/include/migration/qemu-file-types.h
+++ b/include/migration/qemu-file-types.h
@@ -50,6 +50,8 @@ unsigned int qemu_get_be16(QEMUFile *f);
 unsigned int qemu_get_be32(QEMUFile *f);
 uint64_t qemu_get_be64(QEMUFile *f);
 
+bool qemu_file_is_seekable(QEMUFile *f);
+
 static inline void qemu_put_be64s(QEMUFile *f, const uint64_t *pv)
 {
     qemu_put_be64(f, *pv);
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 102ab3b439..a1f7dbb3d9 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -30,6 +30,7 @@
 #include "qemu-file.h"
 #include "trace.h"
 #include "qapi/error.h"
+#include "io/channel-file.h"
 
 #define IO_BUF_SIZE 32768
 #define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64)
@@ -281,6 +282,10 @@ static void qemu_iovec_release_ram(QEMUFile *f)
     memset(f->may_free, 0, sizeof(f->may_free));
 }
 
+bool qemu_file_is_seekable(QEMUFile *f)
+{
+    return qio_channel_has_feature(f->ioc, QIO_CHANNEL_FEATURE_SEEKABLE);
+}
 
 /**
  * Flushes QEMUFile buffer
@@ -559,6 +564,81 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, 
size_t size)
     }
 }
 
+void qemu_put_buffer_at(QEMUFile *f, const uint8_t *buf, size_t buflen, off_t 
pos)
+{
+    Error *err = NULL;
+
+    if (f->last_error) {
+        return;
+    }
+
+    qemu_fflush(f);
+    qio_channel_pwritev(f->ioc, (char *)buf, buflen, pos, &err);
+
+    if (err) {
+        qemu_file_set_error_obj(f, -EIO, err);
+    } else {
+        f->total_transferred += buflen;
+    }
+
+    return;
+}
+
+
+size_t qemu_get_buffer_at(QEMUFile *f, const uint8_t *buf, size_t buflen, 
off_t pos)
+{
+    Error *err = NULL;
+    ssize_t ret;
+
+    if (f->last_error) {
+        return 0;
+    }
+
+    ret = qio_channel_preadv(f->ioc, (char *)buf, buflen, pos, &err);
+    if (ret == -1 || err) {
+        goto error;
+    }
+
+    return (size_t)ret;
+
+ error:
+    qemu_file_set_error_obj(f, -EIO, err);
+    return 0;
+}
+
+void qemu_set_offset(QEMUFile *f, off_t off, int whence)
+{
+    Error *err = NULL;
+    off_t ret;
+
+    qemu_fflush(f);
+
+    if (!qemu_file_is_writable(f)) {
+        f->buf_index = 0;
+        f->buf_size = 0;
+    }
+
+    ret = qio_channel_io_seek(f->ioc, off, whence, &err);
+    if (ret == (off_t)-1) {
+        qemu_file_set_error_obj(f, -EIO, err);
+    }
+}
+
+off_t qemu_get_offset(QEMUFile *f)
+{
+    Error *err = NULL;
+    off_t ret;
+
+    qemu_fflush(f);
+
+    ret = qio_channel_io_seek(f->ioc, 0, SEEK_CUR, &err);
+    if (ret == (off_t)-1) {
+        qemu_file_set_error_obj(f, -EIO, err);
+    }
+    return ret;
+}
+
+
 void qemu_put_byte(QEMUFile *f, int v)
 {
     if (f->last_error) {
diff --git a/migration/qemu-file.h b/migration/qemu-file.h
index 9d0155a2a1..350273b441 100644
--- a/migration/qemu-file.h
+++ b/migration/qemu-file.h
@@ -149,6 +149,10 @@ QEMUFile *qemu_file_get_return_path(QEMUFile *f);
 void qemu_fflush(QEMUFile *f);
 void qemu_file_set_blocking(QEMUFile *f, bool block);
 int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size);
+void qemu_set_offset(QEMUFile *f, off_t off, int whence);
+off_t qemu_get_offset(QEMUFile *f);
+void qemu_put_buffer_at(QEMUFile *f, const uint8_t *buf, size_t buflen, off_t 
pos);
+size_t qemu_get_buffer_at(QEMUFile *f, const uint8_t *buf, size_t buflen, 
off_t pos);
 
 void ram_control_before_iterate(QEMUFile *f, uint64_t flags);
 void ram_control_after_iterate(QEMUFile *f, uint64_t flags);
-- 
2.35.3