/*
 * Copyright 2002-2019 Intel Corporation.
 * 
 * This software is provided to you as Sample Source Code as defined in the accompanying
 * End User License Agreement for the Intel(R) Software Development Products ("Agreement")
 * section 1.L.
 * 
 * This software and the related documents are provided as is, with no express or implied
 * warranties, other than those that are expressly stated in the License.
 */

#ifdef NDEBUG
# undef NDEBUG
#endif
#include <assert.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>

void createFileWithRandomData(const char* filename, size_t desiredFileLength)
{
    size_t totalWritten = 0;
    int pgSize = getpagesize();
    char* pageBuf = malloc(pgSize);
    int outFd;
    outFd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, S_IRWXU | S_IRWXG);
    assert(outFd >= 0);
    while (totalWritten < desiredFileLength)
    {
        int i;
        int* p = (int*)pageBuf;
        for (i = 0; i < pgSize; i += sizeof(int), p++)
        {
            *p = random();
        }
        size_t thisTimeWriten = 0;
        while (thisTimeWriten < pgSize)
        {
            ssize_t writeCount = write(outFd, pageBuf + thisTimeWriten, pgSize - thisTimeWriten);
            assert(writeCount > 0 || (writeCount < 0 && errno == EINTR));
            if (writeCount > 0)
            {
                thisTimeWriten += writeCount;
            }
        }
        totalWritten += pgSize;
    }
    close(outFd);
    free(pageBuf);
}

void* readOnePage(int fd)
{
    size_t totalRead = 0;
    char* buf = malloc(getpagesize());
    while (totalRead < getpagesize())
    {
        ssize_t readCount = read(fd, buf + totalRead, getpagesize() - totalRead);
        assert(readCount > 0 || (readCount < 0 && errno == EINTR));
        if (readCount > 0)
        {
            totalRead += readCount;
        }
    }
    return (void*)buf;
}

int main(int argc, const char* argv[])
{
    const char* filename = argv[1];
    int fd, fd2;
    void *addr, *buf;
    if (argc != 2)
    {
        fprintf(stderr, "Usage %s <file-to-generate>\n", argv[0]);
        return 1;
    }

    createFileWithRandomData(filename, getpagesize() * 5);
    fd = open(filename, O_RDONLY);
    assert(fd >= 0);
    fd2 = dup(fd);

    addr = mmap(NULL, getpagesize(), PROT_READ, MAP_FILE | MAP_PRIVATE , fd2, 3 * getpagesize());
    assert(NULL != addr);

    lseek(fd, 3 * getpagesize(), SEEK_SET);
    buf = readOnePage(fd);

    assert(memcmp(buf, addr, getpagesize()) == 0);

    free(buf);

    return 0;
}