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Add qemu_get_buffer_in_place to avoid copies some of the time

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qemu_get_buffer always copies the data it reads to a users buffer,
however in many cases the file buffer inside qemu_file could be given
back to the caller, avoiding the copy.  This isn't always possible
depending on the size and alignment of the data.

Thus 'qemu_get_buffer_in_place' either copies the data to a supplied
buffer or updates a pointer to the internal buffer if convenient.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2015-11-05 18:10:35 +00:00 • committed by Juan Quintela
parent 42e2aa5637
commit 9504fb510c
2 changed files with 39 additions and 0 deletions
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2
include/migration/qemu-file.h
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@ -163,9 +163,11 @@ void qemu_put_be32(QEMUFile *f, unsigned int v);
void qemu_put_be64(QEMUFile *f, uint64_t v);
size_t qemu_peek_buffer(QEMUFile *f, uint8_t **buf, size_t size, size_t offset);
size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t size);
size_t qemu_get_buffer_in_place(QEMUFile *f, uint8_t **buf, size_t size);
ssize_t qemu_put_compression_data(QEMUFile *f, const uint8_t *p, size_t size,
int level);
int qemu_put_qemu_file(QEMUFile *f_des, QEMUFile *f_src);
/*
* Note that you can only peek continuous bytes from where the current pointer
* is; you aren't guaranteed to be able to peak to +n bytes unless you've