Re: [Qemu-devel] [PATCH v6] qemu-io: add pattern file for write command

[Max Reitz <mreitz@redhat.com>]

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On 27.06.19 17:26, Denis Plotnikov wrote:
> 
> 
> On 19.06.2019 13:09, Vladimir Sementsov-Ogievskiy wrote:
>> 10.06.2019 16:21, Denis Plotnikov wrote:
>>> The patch allows to provide a pattern file for write
>>> command. There was no similar ability before.
>>>
>>> Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
>>> ---
>>> v6:
>>>     * the pattern file is read once to reduce io
>>>
>>> v5:
>>>     * file name initiated with null to make compilers happy
>>>
>>> v4:
>>>     * missing signed-off clause added
>>>
>>> v3:
>>>     * missing file closing added
>>>     * exclusive flags processing changed
>>>     * buffer void* converted to char* to fix pointer arithmetics
>>>     * file reading error processing added
>>> ---
>>>    qemu-io-cmds.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++----
>>>    1 file changed, 82 insertions(+), 6 deletions(-)

[...]

>>> +    if (l < len) {
>>> +        char *file_buf = g_malloc(sizeof(char) * l);

Note that sizeof(char) is guaranteed to be 1.

(C1x standard, 6.5.3.4, paragraph 4.)

>>> +        memcpy(file_buf, buf, l);
>>
>> I see no reason to copy it, you can just use buf_origin pointer
>> instead.
> I use buf_origin to save the beginning pointer to return it from the 
> function avoiding later calculation of the beginning address since 
> pointer of the buf is changed in the loop.

The point is that you don’t need file_buf.  You can drop it, replace all
occurrences of file_buf by buf_origin, and probably use memmove instead
of memcpy.

Max


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