linux splice simple test

gistfile1.c

/*
 * No license provided.
 */
#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

// gcc ./testsplice.c -o ./testsplice.out

int zcopy(int dstfd, int srcfd, loff_t offset, size_t size)
{
    int filedes[2];
    int ret;
    size_t to_write = size;

    ret = pipe(filedes);
    if (ret < 0)
        goto out;
    if (to_write == (size_t) -1) {
        struct stat buf;
        fstat(srcfd, &buf);
        to_write = size = buf.st_size;
    }

    while (to_write > 0) {
        ret = splice(srcfd, &offset, filedes[1], NULL, to_write, SPLICE_F_MORE | SPLICE_F_MOVE);
        if (ret < 0)
            goto pipe;
        else if (ret == 0)
            break;
        else
            to_write -= ret;
    }
    to_write = size - to_write;

    while (to_write > 0) {
        ret = splice(filedes[0], NULL, dstfd, NULL, to_write, SPLICE_F_MORE | SPLICE_F_MOVE);
        if (ret < 0)
            goto pipe;
        else
            to_write -= ret;
    }

pipe:
    close(filedes[0]);
    close(filedes[1]);

out:
    if (ret < 0) {
        perror("Something wrong");
        return -1;
    }
    return 0;
}


int main()
{
    int dstfd, srcfd;

    srcfd = open("./src.txt", O_RDONLY, 0);
    if (srcfd == -1) {
        perror("Failed to open");
        exit(EXIT_FAILURE);
    }

    dstfd = open("./dest.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (dstfd == -1) {
        perror("Failed to create");
        exit(EXIT_FAILURE);
    }

    zcopy(dstfd, srcfd, 0, 1024);

    dstfd = open("./dest2.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (dstfd == -1) {
        perror("Failed to create");
        exit(EXIT_FAILURE);
    }

    zcopy(dstfd, srcfd, 0, -1);

    return 0;
}