// SPDX-License-Identifier: GPL-2.0
#include <unistd.h>
#include <stdbool.h>
#include <errno.h>
#include <linux/kernel.h>
#include <internal/lib.h>

unsigned int page_size;

static ssize_t ion(bool is_read, int fd, void *buf, size_t n)
{
        void *buf_start = buf;
        size_t left = n;

        while (left) {
                /* buf must be treated as const if !is_read. */
                ssize_t ret = is_read ? read(fd, buf, left) :
                                        write(fd, buf, left);

                if (ret < 0 && errno == EINTR)
                        continue;
                if (ret <= 0)
                        return ret;

                left -= ret;
                buf  += ret;
        }

        BUG_ON((size_t)(buf - buf_start) != n);
        return n;
}

/*
 * Read exactly 'n' bytes or return an error.
 */
ssize_t readn(int fd, void *buf, size_t n)
{
        return ion(true, fd, buf, n);
}

ssize_t preadn(int fd, void *buf, size_t n, off_t offs)
{
        size_t left = n;

        while (left) {
                ssize_t ret = pread(fd, buf, left, offs);

                if (ret < 0 && errno == EINTR)
                        continue;
                if (ret <= 0)
                        return ret;

                left -= ret;
                buf  += ret;
                offs += ret;
        }

        return n;
}

/*
 * Write exactly 'n' bytes or return an error.
 */
ssize_t writen(int fd, const void *buf, size_t n)
{
        /* ion does not modify buf. */
        return ion(false, fd, (void *)buf, n);
}