Buffer.cpp

#include <muduo/Buffer.h>
#include <muduo/base/SocketOps.h>
using namespace muduo;

const size_t Buffer::kCheapPrepend;
const size_t Buffer::kInitialSize;

ssize_t Buffer::ReadFd(int fd, int* savedErrno) {
    // saved an ioctl()/FIONREAD call to tell how much to read
    char extrabuf[65536];
    struct iovec vec[2];
    const size_t writable = WriteableBytes();
    vec[0].iov_base = Begin() + writerIndex_;
    vec[0].iov_len = writable;
    vec[1].iov_base = extrabuf;
    vec[1].iov_len = sizeof extrabuf;
    // when there is enough space in this buffer, don't read into extrabuf.
    // when extrabuf is used, we read 128k-1 bytes at most.
    const int iovcnt = (writable < sizeof extrabuf) ? 2 : 1;
    const ssize_t n = sockets::readv(fd, vec, iovcnt);
    if (n < 0) {
        *savedErrno = errno;
    } else if (static_cast<size_t>(n) <= writable) {
        writerIndex_ += n;
    } else {
        writerIndex_ = buffer_.size();
        Append(extrabuf, n - writable);
    }
    return n;
}