Re: [Boost-users] [asio] multiple simultaneous async_read calls

Subject: Re: [Boost-users] [asio] multiple simultaneous async_read calls
From: bbxiong (bbxiong.xiao_at_[hidden])
Date: 2014-08-07 22:31:16

Hello, jason,
  from asio doc:
async_read will invoke handler one condition is true:
1. the supplied buffers are full.
2. an error occurred.

so if there is no socket error, async_read will return len1 bytes.

My question is, can we make simultaneous async_read calls on one socket,
will they interfere each other?

Thanks!

2014-08-08 10:17 GMT+08:00 Jason Roehm <jasonr_at_[hidden]>:

>
> On 08/07/2014 09:54 PM, bbxiong wrote:
>
>> Hello, all,
>>
>> If i write some code like this:
>> boost::asio::async_read(socket_, bosot::asio::buffer(buffer1_.data(),
>> len1, handler1);
>> boost::asio::async_read(socket_, boost::asio::buffer(buffer2_.data(),
>> len2, handler2);
>>
>> Will asio guarantee len1 bytes received by the first async_read, then
>> schedule async_read2?
>>
>> or the result is undefined(like several bytes filled into buffer1, then
>> next several bytes into buffer, then next several bytes into buffer1)?
>>
>
> I don't believe you're guaranteed that you will get `len1` bytes from the
> first read; it could be shorter. If you want to ensure that you get exactly
> that size in the first read, you should use the `transfer_exactly`
> completion condition:
>
> http://www.boost.org/doc/libs/1_56_0/doc/html/boost_asio/
> reference/transfer_exactly.html
>
> Jason
>
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