【Boost】boost库asio详解7——boost::asio::buffer用法

【Boost】boost库asio详解7——boost::asio::buffer用法

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1. asio::buffer常用的构造方法

asio::buffer有多种的构造方法，而且buffer大小是自动管理的

1.1 字符数组

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char d1[128];

size_t bytes_transferred = socket.receive(boost::asio::buffer(d1));

1.2 字符向量

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std::vector<char> d2(128);

size_t bytes_transferred = socket.receive(boost::asio::buffer(d2));

1.3 boost的数组

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boost::array<char, 128> d3;

size_t bytes_transferred = sock.receive(boost::asio::buffer(d3));

1.4 字符串

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string str = "hello world";

bytes_transferred = socket.send(boost::asio::buffer(str));

2. asio::buffer的常用方法

2.1 转换方法

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boost::asio::mutable_buffer b1 =boost::asio::buffer(str)；

unsigned char* p1 = boost::asio::buffer_cast<unsigned char*>(b1);

2.2 获取大小

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std::size_t s1 = boost::asio::buffer_size(b1);

3. asio::buffer的读写问题

注意的是boost::asio::const_buffer是只读的buffer,
而boost::asio::mutable_buffer则可写。

读写buffer也是有讲究的

3.1 与transfer_all()结合

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boost::array<char, 128> buf;

boost::system::error_code ec;

std::size_t n = boost::asio::read(

socket,

boost::asio::buffer(buf),

boost::asio::transfer_all(),

ec);

if (ec)

{

// An error occurred.

}

else

{

// n == 128

}

boost::asio::transfer_all()能够使buffer中的所有数据都传送完毕。即读满buffer为止。

3.2 与transfer_at_least()结合

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std::size_t n = boost::asio::read(

socket,

boost::asio::buffer(buf),

boost::asio::transfer_at_least(64),

ec);

意义即读满64字节为止。返回。

当然还有最常用的bytes_transferred，这个例子就很多了。