Function sys_read

components/lwp/lwp_syscall.c:423–468

* @brief Reads data from a file descriptor into a buffer. * * This system call reads up to `nbyte` bytes of data from the file descriptor * specified by `fd` into the buffer pointed to by `buf`. * * @param fd The file descriptor to read from. This should be a valid file * descriptor obtained through system calls like `open()` or `socket()`. * @param buf A pointer to the buffer whe

 *          of bytes, as failing to do so may result in undefined behavior.
 */
ssize_t sys_read(int fd, void *buf, size_t nbyte)
{
#ifdef ARCH_MM_MMU
    void *kmem = RT_NULL;
    ssize_t ret = -1;

    if (!nbyte)
    {
        return -EINVAL;
    }

    if (!lwp_user_accessable((void *)buf, nbyte))
    {
        return -EFAULT;
    }

    kmem = kmem_get(nbyte);
    if (!kmem)
    {
        return -ENOMEM;
    }

    ret = read(fd, kmem, nbyte);
    if (ret > 0)
    {
        if (ret != lwp_put_to_user(buf, kmem, ret))
            return -EFAULT;
    }

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

    kmem_put(kmem);

    return ret;
#else
    if (!lwp_user_accessable((void *)buf, nbyte))
    {
        return -EFAULT;
    }
    ssize_t ret = read(fd, buf, nbyte);
    return (ret < 0 ? GET_ERRNO() : ret);
#endif
}

/**
 * @brief Writes data from a buffer to a file descriptor.