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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <20140321143919.GA8476@work-vm> (David Alan Gilbert's message of
	"Fri, 21 Mar 2014 14:39:19 +0000")
References: <1395320327-16613-1-git-send-email-dgilbert@redhat.com>
	<871txvit1p.fsf@elfo.mitica> <20140321143919.GA8476@work-vm>
Date: Fri, 21 Mar 2014 17:05:07 +0100
Message-ID: <87r45vh70s.fsf@elfo.mitica>
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Subject: Re: [Qemu-devel] [PATCH 1/1] Make qemu_peek_buffer loop until it
	gets it's data
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To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: qemu-devel@nongnu.org

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
>> > +    while (index >= f->buf_size) {
>> > +        int received = qemu_fill_buffer(f);
>> > +
>> > +        if (received <= 0) {
>> 
>> here, I don't know really what to do.  We just need one character, so
>> the 1st call to qemu_fill_buffer() gives it to us, or we are already on
>> problems.  i.e. no need of the while() loop.
>
> The problem is that peek_byte takes an offset, so while qemu_fill_buffer
> will get us a byte, we actually need it to get us all the bytes upto the
> offset, and that's not guaranteed from one call.

that is not a problem.

We never got a "hole" on the things that we ask for.  We ask for the
"next byte", or the "next bytes", so in qemu_peek_byte() we are
guaranteed (with current users) that we would only have to read a single
byte.

I.e. qemu_peek_{buffer,byte}(....,offset, size) means that we have
"already" peek until offset, and now we want size more bytes.

Later, Juan.