Function sys_pread64

components/lwp/lwp_syscall.c:10489–10535

* @brief Read data from a file descriptor at a specific offset. * * This function reads data from a file descriptor `fd` into the buffer `buf`, starting from the * specified byte `offset`. Unlike a regular `read` call, `sys_pread64` allows the file pointer to * remain unchanged after the read, as the operation directly accesses the file at the provided * offset. * * @param[in] fd The f

 *       reads from arbitrary positions without affecting the current file pointer.
 */
ssize_t sys_pread64(int fd, void *buf, int size, size_t offset)
#ifdef RT_USING_DFS_V2
{
    ssize_t pread(int fd, void *buf, size_t len, size_t offset);
#ifdef ARCH_MM_MMU
    ssize_t ret = -1;
    void *kmem = RT_NULL;

    if (!size)
    {
        return -EINVAL;
    }

    if (!lwp_user_accessable((void *)buf, size))
    {
        return -EFAULT;
    }
    kmem = kmem_get(size);
    if (!kmem)
    {
        return -ENOMEM;
    }

    ret = pread(fd, kmem, size, offset);
    if (ret > 0)
    {
        lwp_put_to_user(buf, kmem, ret);
    }

    if (ret < 0)
    {
        ret = GET_ERRNO();
    }

    kmem_put(kmem);

    return ret;
#else
    if (!lwp_user_accessable((void *)buf, size))
    {
        return -EFAULT;
    }

    ssize_t ret = pread(fd, kmem, size, offset);
    return (ret < 0 ? GET_ERRNO() : ret);
#endif
}
#else
{
    ssize_t ret = -ENOSYS;