tests/unistd/pipe.c

/*
 * Copyright 2017 The Emscripten Authors.  All rights reserved.
 * Emscripten is available under two separate licenses, the MIT license and the
 * University of Illinois/NCSA Open Source License.  Both these licenses can be
 * found in the LICENSE file.
 */

#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <poll.h>
#include <errno.h>
#include <assert.h>
#include <string.h>
#include <stdio.h>

unsigned char buf[1 << 16];

#define FALSE 0
#define TRUE 1

// This test program relies on the simplest read/write behavior when
// all the data can be read/written in one call.

void test_write(int fd1, unsigned char *ch, int size)
{
    memset(buf, 0, sizeof buf);
    for(int i = 0; i < size; ++i)
        buf[i] = (*ch)++;
    assert(write(fd1, buf, size) == size);
}

void test_read(int fd0, unsigned char *ch, int size)
{
    memset(buf, 0, sizeof buf);
    assert(read(fd0, buf, size) == size);
    for(int i = 0; i < sizeof buf; ++i)
    {
        unsigned char correct_ch = (i < size) ? (*ch)++ : 0;
        assert(buf[i] == correct_ch);
    }
}

void test_poll(int *fd, int data_available)
{
    struct pollfd pfds[2];
    memset(pfds, 0, sizeof pfds);
    pfds[0].fd = fd[0];
    pfds[0].events = POLLIN | POLLOUT;
    pfds[1].fd = fd[1];
    pfds[1].events = POLLIN | POLLOUT;

    int ret = poll(pfds, 2, 0);
    if(data_available)
    {
        assert(ret == 2);
        assert(pfds[0].revents == POLLIN);
    }
    else
    {
        assert(ret == 1);
        assert(pfds[0].revents == 0);
    }
    assert(pfds[1].revents == POLLOUT);
}

int main()
{
    int fd[2];
    unsigned char wchar = 0;
    unsigned char rchar = 0;

    assert(pipe(fd) == 0);

    // Test that pipe is not seekable

    memset(buf, 0, sizeof buf);
    assert(write(fd[1], buf, 128) == 128);
    assert(lseek(fd[0], 0, SEEK_CUR) == -1);
    assert(errno == ESPIPE);
    assert(lseek(fd[1], 0, SEEK_CUR) == -1);
    assert(errno == ESPIPE);
    assert(read(fd[0], buf, sizeof buf) == 128);

    // Now pipe is empty
    // Test interleaved writing and reading of different buffer sizes

    for(int i = 1; i < 200; ++i) // write about 40 Kb of data
    {
        test_write(fd[1], &wchar, i + 2);
        test_poll(fd, TRUE);
        test_read (fd[0], &rchar, i);
        test_poll(fd, TRUE);
        test_write(fd[1], &wchar, i + 1);
        test_poll(fd, TRUE);
        test_read (fd[0], &rchar, i + 3);
        test_poll(fd, FALSE);
    }

    // Test reading when there is less data available than the read buffer size

    assert(write(fd[1], buf, 10) == 10);
    assert(read(fd[0], buf, sizeof buf) == 10);

    // Write total of 1 Mb of data in small chunks
    // The pipe should not overflow

    int bytes_to_write = 1 << 20;
    while(bytes_to_write > 0)
    {
        test_write(fd[1], &wchar, sizeof buf);
        test_read (fd[0], &rchar, sizeof buf);
        bytes_to_write -= sizeof buf;
    }

    // Write large chunks of data (supposed to be larger than one internal buffer)
    test_write(fd[1], &wchar, 123);
    test_write(fd[1], &wchar, (1 << 15) + 321);
    test_write(fd[1], &wchar, 456);
    test_read(fd[0], &rchar, 456);
    test_read(fd[0], &rchar, (1 << 15) + 123);
    test_read(fd[0], &rchar, 321);


    // Test non-blocking read from empty pipe

    assert(fcntl(fd[0], F_SETFL, O_NONBLOCK) == 0);
    assert(read(fd[0], buf, sizeof buf) == -1);
    assert(errno == EAGAIN);

    // Normal operations still work in non-blocking mode

    test_poll(fd, FALSE);
    test_write(fd[1], &wchar, 10);
    test_poll(fd, TRUE);
    test_read (fd[0], &rchar, 10);
    test_poll(fd, FALSE);

    puts("success");

    return 0;
}