/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (C) 2009 Gabor Kovesdan <gabor@FreeBSD.org>
 * Copyright (C) 2012 Oleg Moskalenko <mom040267@gmail.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/queue.h>

#include <err.h>
#include <fcntl.h>
#if defined(SORT_THREADS)
#include <pthread.h>
#endif
#include <semaphore.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>
#include <wctype.h>

#include "coll.h"
#include "file.h"
#include "radixsort.h"

unsigned long long free_memory = 1000000;
unsigned long long available_free_memory = 1000000;

bool use_mmap;

const char *tmpdir = "/var/tmp";
const char *compress_program;

size_t max_open_files = 16;

/*
 * File reader structure
 */
struct file_reader
{
        FILE                    *file;
        char                    *fname;
        char                    *buffer;
        unsigned char           *mmapaddr;
        unsigned char           *mmapptr;
        size_t                   bsz;
        size_t                   mmapsize;
        int                      fd;
        char                     elsymb;
};

/*
 * Structure to be used in file merge process.
 */
struct file_header
{
        struct file_reader              *fr;
        struct sort_list_item           *si; /* current top line */
        size_t                           file_pos;
};

/*
 * List elements of "cleanable" files list.
 */
struct CLEANABLE_FILE
{
        char                            *fn;
        LIST_ENTRY(CLEANABLE_FILE)       files;
};

/*
 * List header of "cleanable" files list.
 */
static LIST_HEAD(CLEANABLE_FILES,CLEANABLE_FILE) tmp_files;

/*
 * Semaphore to protect the tmp file list.
 * We use semaphore here because it is signal-safe, according to POSIX.
 * And semaphore does not require pthread library.
 */
static sem_t tmp_files_sem;

static void mt_sort(struct sort_list *list,
    int (*sort_func)(void *, size_t, size_t,
    int (*)(const void *, const void *)), const char* fn);

/*
 * Init tmp files list
 */
void
init_tmp_files(void)
{

        LIST_INIT(&tmp_files);
        sem_init(&tmp_files_sem, 0, 1);
}

/*
 * Save name of a tmp file for signal cleanup
 */
void
tmp_file_atexit(const char *tmp_file)
{

        if (tmp_file) {
                sem_wait(&tmp_files_sem);
                struct CLEANABLE_FILE *item =
                    sort_malloc(sizeof(struct CLEANABLE_FILE));
                item->fn = sort_strdup(tmp_file);
                LIST_INSERT_HEAD(&tmp_files, item, files);
                sem_post(&tmp_files_sem);
        }
}

/*
 * Clear tmp files
 */
void
clear_tmp_files(void)
{
        struct CLEANABLE_FILE *item;

        sem_wait(&tmp_files_sem);
        LIST_FOREACH(item,&tmp_files,files) {
                if ((item) && (item->fn))
                        unlink(item->fn);
        }
        sem_post(&tmp_files_sem);
}

/*
 * Check whether a file is a temporary file
 */
static bool
file_is_tmp(const char* fn)
{
        struct CLEANABLE_FILE *item;
        bool ret = false;

        if (fn) {
                sem_wait(&tmp_files_sem);
                LIST_FOREACH(item,&tmp_files,files) {
                        if ((item) && (item->fn))
                                if (strcmp(item->fn, fn) == 0) {
                                        ret = true;
                                        break;
                                }
                }
                sem_post(&tmp_files_sem);
        }

        return (ret);
}

/*
 * Generate new temporary file name
 */
char *
new_tmp_file_name(void)
{
        char *ret;
        int fd;

        if (asprintf(&ret, "%s/.bsdsort.XXXXXXXXXX", tmpdir) == -1)
                err(2, "asprintf()");
        if ((fd = mkstemp(ret)) == -1)
                err(2, "mkstemp()");
        close(fd);

        tmp_file_atexit(ret);
        return (ret);
}

/*
 * Initialize file list
 */
void
file_list_init(struct file_list *fl, bool tmp)
{

        if (fl) {
                memset(fl, 0, sizeof(*fl));
                fl->tmp = tmp;
        }
}

/*
 * Add a file name to the list
 */
void
file_list_add(struct file_list *fl, const char *fn, bool allocate)
{

        if (fl && fn) {
                if (fl->count >= fl->sz || (fl->fns == NULL)) {
                        fl->sz = (fl->sz) * 2 + 1;
                        fl->fns = sort_realloc(fl->fns, fl->sz *
                            sizeof(char *));
                }
                fl->fns[fl->count] = allocate ? sort_strdup(fn) : fn;
                fl->count += 1;
        }
}

/*
 * Populate file list from array of file names
 */
void
file_list_populate(struct file_list *fl, int argc, char **argv, bool allocate)
{

        if (fl && argv) {
                int i;

                for (i = 0; i < argc; i++)
                        file_list_add(fl, argv[i], allocate);
        }
}

/*
 * Clean file list data and delete the files,
 * if this is a list of temporary files
 */
void
file_list_clean(struct file_list *fl)
{

        if (fl) {
                if (fl->fns) {
                        size_t i;

                        for (i = 0; i < fl->count; i++) {
                                if (fl->fns[i]) {
                                        if (fl->tmp)
                                                unlink(fl->fns[i]);
                                        sort_free(fl->fns[i]);
                                        fl->fns[i] = 0;
                                }
                        }
                        sort_free(fl->fns);
                        fl->fns = NULL;
                }
                fl->sz = 0;
                fl->count = 0;
                fl->tmp = false;
        }
}

/*
 * Init sort list
 */
void
sort_list_init(struct sort_list *l)
{

        if (l) {
                memset(l, 0, sizeof(*l));
                l->memsize = sizeof(struct sort_list);
        }
}

/*
 * Add string to sort list
 */
void
sort_list_add(struct sort_list *l, struct bwstring *str)
{

        if (l && str) {
                size_t indx = l->count;

                if ((l->list == NULL) || (indx >= l->size)) {
                        size_t newsize = (l->size + 1) + 1024;

                        l->list = sort_realloc(l->list,
                            sizeof(struct sort_list_item*) * newsize);
                        l->memsize += (newsize - l->size) *
                            sizeof(struct sort_list_item*);
                        l->size = newsize;
                }
                l->list[indx] = sort_list_item_alloc();
                sort_list_item_set(l->list[indx], str);
                l->memsize += sort_list_item_size(l->list[indx]);
                l->count += 1;
        }
}

/*
 * Clean sort list data
 */
void
sort_list_clean(struct sort_list *l)
{

        if (l) {
                if (l->list) {
                        size_t i;

                        for (i = 0; i < l->count; i++) {
                                struct sort_list_item *item;

                                item = l->list[i];

                                if (item) {
                                        sort_list_item_clean(item);
                                        sort_free(item);
                                        l->list[i] = NULL;
                                }
                        }
                        sort_free(l->list);
                        l->list = NULL;
                }
                l->count = 0;
                l->size = 0;
                l->memsize = sizeof(struct sort_list);
        }
}

/*
 * Write sort list to file
 */
void
sort_list_dump(struct sort_list *l, const char *fn)
{

        if (l && fn) {
                FILE *f;

                f = openfile(fn, "w");
                if (f == NULL)
                        err(2, NULL);

                if (l->list) {
                        size_t i;
                        if (!(sort_opts_vals.uflag)) {
                                for (i = 0; i < l->count; ++i)
                                        bwsfwrite(l->list[i]->str, f,
                                            sort_opts_vals.zflag);
                        } else {
                                struct sort_list_item *last_printed_item = NULL;
                                struct sort_list_item *item;
                                for (i = 0; i < l->count; ++i) {
                                        item = l->list[i];
                                        if ((last_printed_item == NULL) ||
                                            list_coll(&last_printed_item, &item)) {
                                                bwsfwrite(item->str, f, sort_opts_vals.zflag);
                                                last_printed_item = item;
                                        }
                                }
                        }
                }

                closefile(f, fn);
        }
}

/*
 * Checks if the given file is sorted.  Stops at the first disorder,
 * prints the disordered line and returns 1.
 */
int
check(const char *fn)
{
        struct bwstring *s1, *s2, *s1disorder, *s2disorder;
        struct file_reader *fr;
        struct keys_array *ka1, *ka2;
        int res;
        size_t pos, posdisorder;

        s1 = s2 = s1disorder = s2disorder = NULL;
        ka1 = ka2 = NULL;

        fr = file_reader_init(fn);

        res = 0;
        pos = 1;
        posdisorder = 1;

        if (fr == NULL) {
                err(2, NULL);
                goto end;
        }

        s1 = file_reader_readline(fr);
        if (s1 == NULL)
                goto end;

        ka1 = keys_array_alloc();
        preproc(s1, ka1);

        s2 = file_reader_readline(fr);
        if (s2 == NULL)
                goto end;

        ka2 = keys_array_alloc();
        preproc(s2, ka2);

        for (;;) {

                if (debug_sort) {
                        bwsprintf(stdout, s2, "s1=<", ">");
                        bwsprintf(stdout, s1, "s2=<", ">");
                }
                int cmp = key_coll(ka2, ka1, 0);
                if (debug_sort)
                        printf("; cmp1=%d", cmp);

                if (!cmp && sort_opts_vals.complex_sort &&
                    !(sort_opts_vals.uflag) && !(sort_opts_vals.sflag)) {
                        cmp = top_level_str_coll(s2, s1);
                        if (debug_sort)
                                printf("; cmp2=%d", cmp);
                }
                if (debug_sort)
                        printf("\n");

                if ((sort_opts_vals.uflag && (cmp <= 0)) || (cmp < 0)) {
                        if (!(sort_opts_vals.csilentflag)) {
                                s2disorder = bwsdup(s2);
                                posdisorder = pos;
                                if (debug_sort)
                                        s1disorder = bwsdup(s1);
                        }
                        res = 1;
                        goto end;
                }

                pos++;

                clean_keys_array(s1, ka1);
                sort_free(ka1);
                ka1 = ka2;
                ka2 = NULL;

                bwsfree(s1);
                s1 = s2;

                s2 = file_reader_readline(fr);
                if (s2 == NULL)
                        goto end;

                ka2 = keys_array_alloc();
                preproc(s2, ka2);
        }

end:
        if (ka1) {
                clean_keys_array(s1, ka1);
                sort_free(ka1);
        }

        if (s1)
                bwsfree(s1);

        if (ka2) {
                clean_keys_array(s2, ka2);
                sort_free(ka2);
        }

        if (s2)
                bwsfree(s2);

        if ((fn == NULL) || (*fn == 0) || (strcmp(fn, "-") == 0)) {
                for (;;) {
                        s2 = file_reader_readline(fr);
                        if (s2 == NULL)
                                break;
                        bwsfree(s2);
                }
        }

        file_reader_free(fr);

        if (s2disorder) {
                bws_disorder_warnx(s2disorder, fn, posdisorder);
                if (s1disorder) {
                        bws_disorder_warnx(s1disorder, fn, posdisorder);
                        if (s1disorder != s2disorder)
                                bwsfree(s1disorder);
                }
                bwsfree(s2disorder);
                s1disorder = NULL;
                s2disorder = NULL;
        }

        if (res)
                exit(res);

        return (0);
}

/*
 * Opens a file.  If the given filename is "-", stdout will be
 * opened.
 */
FILE *
openfile(const char *fn, const char *mode)
{
        FILE *file;

        if (strcmp(fn, "-") == 0)
                return ((mode && mode[0] == 'r') ? stdin : stdout);

        mode_t orig_file_mask = 0;
        int is_tmp = file_is_tmp(fn);

        if (is_tmp && (mode[0] == 'w'))
                orig_file_mask = umask(S_IWGRP | S_IWOTH |
                    S_IRGRP | S_IROTH);

        if (is_tmp && (compress_program != NULL)) {
                int r;
                char *cmd;

                fflush(stdout);

                if (mode[0] == 'r')
                        r = asprintf(&cmd, "cat %s | %s -d",
                            fn, compress_program);
                else if (mode[0] == 'w')
                        r = asprintf(&cmd, "%s > %s",
                            compress_program, fn);
                else
                        err(2, "%s", getstr(7));

                if (r == -1)
                        err(2, "aspritnf()");

                if ((file = popen(cmd, mode)) == NULL)
                        err(2, NULL);
                free(cmd);
        } else
                if ((file = fopen(fn, mode)) == NULL)
                        err(2, NULL);

        if (is_tmp && (mode[0] == 'w'))
                umask(orig_file_mask);

        return (file);
}

/*
 * Close file
 */
void
closefile(FILE *f, const char *fn)
{
        if (f == NULL || f == stdin)
                return;
        if (f == stdout) {
                fflush(f);
                return;
        }
        if (file_is_tmp(fn) && compress_program != NULL) {
                if(pclose(f)<0)
                        err(2,NULL);
        } else
                fclose(f);
}

/*
 * Reads a file into the internal buffer.
 */
struct file_reader *
file_reader_init(const char *fsrc)
{
        struct file_reader *ret;

        if (fsrc == NULL)
                fsrc = "-";

        ret = sort_calloc(1, sizeof(struct file_reader));

        ret->elsymb = sort_opts_vals.zflag ? '\0' : '\n';
        ret->fname = sort_strdup(fsrc);

        if (strcmp(fsrc, "-") && (compress_program == NULL) && use_mmap) {

                do {
                        struct stat stat_buf;
                        void *addr;
                        size_t sz = 0;
                        int fd, flags;

                        flags = MAP_NOCORE | MAP_NOSYNC;

                        fd = open(fsrc, O_RDONLY);
                        if (fd < 0)
                                err(2, NULL);

                        if (fstat(fd, &stat_buf) < 0) {
                                close(fd);
                                break;
                        }

                        sz = stat_buf.st_size;

#if defined(MAP_PREFAULT_READ)
                        flags |= MAP_PREFAULT_READ;
#endif

                        addr = mmap(NULL, sz, PROT_READ, flags, fd, 0);
                        if (addr == MAP_FAILED) {
                                close(fd);
                                break;
                        }

                        ret->fd = fd;
                        ret->mmapaddr = addr;
                        ret->mmapsize = sz;
                        ret->mmapptr = ret->mmapaddr;

                } while (0);
        }

        if (ret->mmapaddr == NULL) {
                ret->file = openfile(fsrc, "r");
                if (ret->file == NULL)
                        err(2, NULL);
        }

        return (ret);
}

struct bwstring *
file_reader_readline(struct file_reader *fr)
{
        struct bwstring *ret = NULL;

        if (fr->mmapaddr) {
                unsigned char *mmapend;

                mmapend = fr->mmapaddr + fr->mmapsize;
                if (fr->mmapptr >= mmapend)
                        return (NULL);
                else {
                        unsigned char *strend;
                        size_t sz;

                        sz = mmapend - fr->mmapptr;
                        strend = memchr(fr->mmapptr, fr->elsymb, sz);

                        if (strend == NULL) {
                                ret = bwscsbdup(fr->mmapptr, sz);
                                fr->mmapptr = mmapend;
                        } else {
                                ret = bwscsbdup(fr->mmapptr, strend -
                                    fr->mmapptr);
                                fr->mmapptr = strend + 1;
                        }
                }
        } else {
                ssize_t len;

                len = getdelim(&fr->buffer, &fr->bsz, fr->elsymb, fr->file);
                if (len < 0) {
                        if (!feof(fr->file))
                                err(2, NULL);
                        return (NULL);
                }
                if (len > 0 && fr->buffer[len - 1] == fr->elsymb)
                        len--;
                ret = bwscsbdup(fr->buffer, len);
        }

        return (ret);
}

static void
file_reader_clean(struct file_reader *fr)
{

        if (fr == NULL)
                return;

        if (fr->mmapaddr)
                munmap(fr->mmapaddr, fr->mmapsize);
        if (fr->fd)
                close(fr->fd);

        free(fr->buffer);
        closefile(fr->file, fr->fname);
        free(fr->fname);
        memset(fr, 0, sizeof(struct file_reader));
}

void
file_reader_free(struct file_reader *fr)
{

        if (fr == NULL)
                return;
        file_reader_clean(fr);
        free(fr);
}

int
procfile(const char *fsrc, struct sort_list *list, struct file_list *fl)
{
        struct file_reader *fr;

        fr = file_reader_init(fsrc);
        if (fr == NULL)
                err(2, NULL);

        /* file browse cycle */
        for (;;) {
                struct bwstring *bws;

                bws = file_reader_readline(fr);

                if (bws == NULL)
                        break;

                sort_list_add(list, bws);

                if (list->memsize >= available_free_memory) {
                        char *fn;

                        fn = new_tmp_file_name();
                        sort_list_to_file(list, fn);
                        file_list_add(fl, fn, false);
                        sort_list_clean(list);
                }
        }

        file_reader_free(fr);

        return (0);
}

/*
 * Compare file headers. Files with EOF always go to the end of the list.
 */
static int
file_header_cmp(struct file_header *f1, struct file_header *f2)
{

        if (f1 == f2)
                return (0);
        else {
                if (f1->fr == NULL) {
                        return ((f2->fr == NULL) ? 0 : +1);
                } else if (f2->fr == NULL)
                        return (-1);
                else {
                        int ret;

                        ret = list_coll(&(f1->si), &(f2->si));
                        if (!ret)
                                return ((f1->file_pos < f2->file_pos) ? -1 : +1);
                        return (ret);
                }
        }
}

/*
 * Allocate and init file header structure
 */
static void
file_header_init(struct file_header **fh, const char *fn, size_t file_pos)
{

        if (fh && fn) {
                struct bwstring *line;

                *fh = sort_malloc(sizeof(struct file_header));
                (*fh)->file_pos = file_pos;
                (*fh)->fr = file_reader_init(fn);
                if ((*fh)->fr == NULL) {
                        perror(fn);
                        err(2, "%s", getstr(8));
                }
                line = file_reader_readline((*fh)->fr);
                if (line == NULL) {
                        file_reader_free((*fh)->fr);
                        (*fh)->fr = NULL;
                        (*fh)->si = NULL;
                } else {
                        (*fh)->si = sort_list_item_alloc();
                        sort_list_item_set((*fh)->si, line);
                }
        }
}

/*
 * Close file
 */
static void
file_header_close(struct file_header **fh)
{

        if (fh && *fh) {
                file_reader_free((*fh)->fr);
                (*fh)->fr = NULL;
                if ((*fh)->si) {
                        sort_list_item_clean((*fh)->si);
                        sort_free((*fh)->si);
                        (*fh)->si = NULL;
                }
                sort_free(*fh);
                *fh = NULL;
        }
}

/*
 * Swap two array elements
 */
static void
file_header_swap(struct file_header **fh, size_t i1, size_t i2)
{
        struct file_header *tmp;

        tmp = fh[i1];
        fh[i1] = fh[i2];
        fh[i2] = tmp;
}

/* heap algorithm ==>> */

/*
 * See heap sort algorithm
 * "Raises" last element to its right place
 */
static void
file_header_heap_swim(struct file_header **fh, size_t indx)
{

        if (indx > 0) {
                size_t parent_index;

                parent_index = (indx - 1) >> 1;

                if (file_header_cmp(fh[indx], fh[parent_index]) < 0) {
                        /* swap child and parent and continue */
                        file_header_swap(fh, indx, parent_index);
                        file_header_heap_swim(fh, parent_index);
                }
        }
}

/*
 * Sink the top element to its correct position
 */
static void
file_header_heap_sink(struct file_header **fh, size_t indx, size_t size)
{
        size_t left_child_index;
        size_t right_child_index;

        left_child_index = indx + indx + 1;
        right_child_index = left_child_index + 1;

        if (left_child_index < size) {
                size_t min_child_index;

                min_child_index = left_child_index;

                if ((right_child_index < size) &&
                    (file_header_cmp(fh[left_child_index],
                    fh[right_child_index]) > 0))
                        min_child_index = right_child_index;
                if (file_header_cmp(fh[indx], fh[min_child_index]) > 0) {
                        file_header_swap(fh, indx, min_child_index);
                        file_header_heap_sink(fh, min_child_index, size);
                }
        }
}

/* <<== heap algorithm */

/*
 * Adds element to the "left" end
 */
static void
file_header_list_rearrange_from_header(struct file_header **fh, size_t size)
{

        file_header_heap_sink(fh, 0, size);
}

/*
 * Adds element to the "right" end
 */
static void
file_header_list_push(struct file_header *f, struct file_header **fh, size_t size)
{

        fh[size++] = f;
        file_header_heap_swim(fh, size - 1);
}

struct last_printed
{
        struct bwstring *str;
};

/*
 * Prints the current line of the file
 */
static void
file_header_print(struct file_header *fh, FILE *f_out, struct last_printed *lp)
{

        if (fh && fh->fr && f_out && fh->si && fh->si->str) {
                if (sort_opts_vals.uflag) {
                        if ((lp->str == NULL) || (str_list_coll(lp->str, &(fh->si)))) {
                                bwsfwrite(fh->si->str, f_out, sort_opts_vals.zflag);
                                if (lp->str)
                                        bwsfree(lp->str);
                                lp->str = bwsdup(fh->si->str);
                        }
                } else
                        bwsfwrite(fh->si->str, f_out, sort_opts_vals.zflag);
        }
}

/*
 * Read next line
 */
static void
file_header_read_next(struct file_header *fh)
{

        if (fh && fh->fr) {
                struct bwstring *tmp;

                tmp = file_reader_readline(fh->fr);
                if (tmp == NULL) {
                        file_reader_free(fh->fr);
                        fh->fr = NULL;
                        if (fh->si) {
                                sort_list_item_clean(fh->si);
                                sort_free(fh->si);
                                fh->si = NULL;
                        }
                } else {
                        if (fh->si == NULL)
                                fh->si = sort_list_item_alloc();
                        sort_list_item_set(fh->si, tmp);
                }
        }
}

/*
 * Merge array of "files headers"
 */
static void
file_headers_merge(size_t fnum, struct file_header **fh, FILE *f_out)
{
        struct last_printed lp;
        size_t i;

        memset(&lp, 0, sizeof(lp));

        /*
         * construct the initial sort structure
         */
        for (i = 0; i < fnum; i++)
                file_header_list_push(fh[i], fh, i);

        while (fh[0]->fr) { /* unfinished files are always in front */
                /* output the smallest line: */
                file_header_print(fh[0], f_out, &lp);
                /* read a new line, if possible: */
                file_header_read_next(fh[0]);
                /* re-arrange the list: */
                file_header_list_rearrange_from_header(fh, fnum);
        }

        if (lp.str)
                bwsfree(lp.str);
}

/*
 * Merges the given files into the output file, which can be
 * stdout.
 */
static void
merge_files_array(size_t argc, const char **argv, const char *fn_out)
{

        if (argv && fn_out) {
                struct file_header **fh;
                FILE *f_out;
                size_t i;

                f_out = openfile(fn_out, "w");

                if (f_out == NULL)
                        err(2, NULL);

                fh = sort_malloc((argc + 1) * sizeof(struct file_header *));

                for (i = 0; i < argc; i++)
                        file_header_init(fh + i, argv[i], (size_t) i);

                file_headers_merge(argc, fh, f_out);

                for (i = 0; i < argc; i++)
                        file_header_close(fh + i);

                sort_free(fh);

                closefile(f_out, fn_out);
        }
}

/*
 * Shrinks the file list until its size smaller than max number of opened files
 */
static int
shrink_file_list(struct file_list *fl)
{

        if ((fl == NULL) || (size_t) (fl->count) < max_open_files)
                return (0);
        else {
                struct file_list new_fl;
                size_t indx = 0;

                file_list_init(&new_fl, true);
                while (indx < fl->count) {
                        char *fnew;
                        size_t num;

                        num = fl->count - indx;
                        fnew = new_tmp_file_name();

                        if ((size_t) num >= max_open_files)
                                num = max_open_files - 1;
                        merge_files_array(num, fl->fns + indx, fnew);
                        if (fl->tmp) {
                                size_t i;

                                for (i = 0; i < num; i++)
                                        unlink(fl->fns[indx + i]);
                        }
                        file_list_add(&new_fl, fnew, false);
                        indx += num;
                }
                fl->tmp = false; /* already taken care of */
                file_list_clean(fl);

                fl->count = new_fl.count;
                fl->fns = new_fl.fns;
                fl->sz = new_fl.sz;
                fl->tmp = new_fl.tmp;

                return (1);
        }
}

/*
 * Merge list of files
 */
void
merge_files(struct file_list *fl, const char *fn_out)
{

        if (fl && fn_out) {
                while (shrink_file_list(fl));

                merge_files_array(fl->count, fl->fns, fn_out);
        }
}

static const char *
get_sort_method_name(int sm)
{

        if (sm == SORT_MERGESORT)
                return "mergesort";
        else if (sort_opts_vals.sort_method == SORT_RADIXSORT)
                return "radixsort";
        else if (sort_opts_vals.sort_method == SORT_HEAPSORT)
                return "heapsort";
        else
                return "quicksort";
}

/*
 * Wrapper for qsort
 */
static int sort_qsort(void *list, size_t count, size_t elem_size,
    int (*cmp_func)(const void *, const void *))
{

        qsort(list, count, elem_size, cmp_func);
        return (0);
}

/*
 * Sort list of lines and writes it to the file
 */
void
sort_list_to_file(struct sort_list *list, const char *outfile)
{
        struct sort_mods *sm = &(keys[0].sm);

        if (!(sm->Mflag) && !(sm->Rflag) && !(sm->Vflag) &&
            !(sm->gflag) && !(sm->hflag) && !(sm->nflag)) {
                if ((sort_opts_vals.sort_method == SORT_DEFAULT) && byte_sort)
                        sort_opts_vals.sort_method = SORT_RADIXSORT;

        } else if (sort_opts_vals.sort_method == SORT_RADIXSORT)
                err(2, "%s", getstr(9));

        /*
         * to handle stable sort and the unique cases in the
         * right order, we need stable basic algorithm
         */
        if (sort_opts_vals.sflag) {
                switch (sort_opts_vals.sort_method){
                case SORT_MERGESORT:
                        break;
                case SORT_RADIXSORT:
                        break;
                case SORT_DEFAULT:
                        sort_opts_vals.sort_method = SORT_MERGESORT;
                        break;
                default:
                        errx(2, "%s", getstr(10));
                }
        }

        if (sort_opts_vals.sort_method == SORT_DEFAULT)
                sort_opts_vals.sort_method = DEFAULT_SORT_ALGORITHM;

        if (debug_sort)
                printf("sort_method=%s\n",
                    get_sort_method_name(sort_opts_vals.sort_method));

        switch (sort_opts_vals.sort_method){
        case SORT_RADIXSORT:
                rxsort(list->list, list->count);
                sort_list_dump(list, outfile);
                break;
        case SORT_MERGESORT:
                mt_sort(list, mergesort, outfile);
                break;
        case SORT_HEAPSORT:
                mt_sort(list, heapsort, outfile);
                break;
        case SORT_QSORT:
                mt_sort(list, sort_qsort, outfile);
                break;
        default:
                mt_sort(list, DEFAULT_SORT_FUNC, outfile);
                break;
        }
}

/******************* MT SORT ************************/

#if defined(SORT_THREADS)
/* semaphore to count threads */
static sem_t mtsem;

/* current system sort function */
static int (*g_sort_func)(void *, size_t, size_t,
    int(*)(const void *, const void *));

/*
 * Sort cycle thread (in multi-threaded mode)
 */
static void*
mt_sort_thread(void* arg)
{
        struct sort_list *list = arg;

        g_sort_func(list->list, list->count, sizeof(struct sort_list_item *),
            (int(*)(const void *, const void *)) list_coll);

        sem_post(&mtsem);

        return (arg);
}

/*
 * Compare sub-lists. Empty sub-lists always go to the end of the list.
 */
static int
sub_list_cmp(struct sort_list *l1, struct sort_list *l2)
{

        if (l1 == l2)
                return (0);
        else {
                if (l1->count == 0) {
                        return ((l2->count == 0) ? 0 : +1);
                } else if (l2->count == 0) {
                        return (-1);
                } else {
                        int ret;

                        ret = list_coll(&(l1->list[0]), &(l2->list[0]));
                        if (!ret)
                                return ((l1->sub_list_pos < l2->sub_list_pos) ?
                                    -1 : +1);
                        return (ret);
                }
        }
}

/*
 * Swap two array elements
 */
static void
sub_list_swap(struct sort_list **sl, size_t i1, size_t i2)
{
        struct sort_list *tmp;

        tmp = sl[i1];
        sl[i1] = sl[i2];
        sl[i2] = tmp;
}

/* heap algorithm ==>> */

/*
 * See heap sort algorithm
 * "Raises" last element to its right place
 */
static void
sub_list_swim(struct sort_list **sl, size_t indx)
{

        if (indx > 0) {
                size_t parent_index;

                parent_index = (indx - 1) >> 1;

                if (sub_list_cmp(sl[indx], sl[parent_index]) < 0) {
                        /* swap child and parent and continue */
                        sub_list_swap(sl, indx, parent_index);
                        sub_list_swim(sl, parent_index);
                }
        }
}

/*
 * Sink the top element to its correct position
 */
static void
sub_list_sink(struct sort_list **sl, size_t indx, size_t size)
{
        size_t left_child_index;
        size_t right_child_index;

        left_child_index = indx + indx + 1;
        right_child_index = left_child_index + 1;

        if (left_child_index < size) {
                size_t min_child_index;

                min_child_index = left_child_index;

                if ((right_child_index < size) &&
                    (sub_list_cmp(sl[left_child_index],
                    sl[right_child_index]) > 0))
                        min_child_index = right_child_index;
                if (sub_list_cmp(sl[indx], sl[min_child_index]) > 0) {
                        sub_list_swap(sl, indx, min_child_index);
                        sub_list_sink(sl, min_child_index, size);
                }
        }
}

/* <<== heap algorithm */

/*
 * Adds element to the "right" end
 */
static void
sub_list_push(struct sort_list *s, struct sort_list **sl, size_t size)
{

        sl[size++] = s;
        sub_list_swim(sl, size - 1);
}

struct last_printed_item
{
        struct sort_list_item *item;
};

/*
 * Prints the current line of the file
 */
static void
sub_list_header_print(struct sort_list *sl, FILE *f_out,
    struct last_printed_item *lp)
{

        if (sl && sl->count && f_out && sl->list[0]->str) {
                if (sort_opts_vals.uflag) {
                        if ((lp->item == NULL) || (list_coll(&(lp->item),
                            &(sl->list[0])))) {
                                bwsfwrite(sl->list[0]->str, f_out,
                                    sort_opts_vals.zflag);
                                lp->item = sl->list[0];
                        }
                } else
                        bwsfwrite(sl->list[0]->str, f_out,
                            sort_opts_vals.zflag);
        }
}

/*
 * Read next line
 */
static void
sub_list_next(struct sort_list *sl)
{

        if (sl && sl->count) {
                sl->list += 1;
                sl->count -= 1;
        }
}

/*
 * Merge sub-lists to a file
 */
static void
merge_sub_lists(struct sort_list **sl, size_t n, FILE* f_out)
{
        struct last_printed_item lp;
        size_t i;

        memset(&lp,0,sizeof(lp));

        /* construct the initial list: */
        for (i = 0; i < n; i++)
                sub_list_push(sl[i], sl, i);

        while (sl[0]->count) { /* unfinished lists are always in front */
                /* output the smallest line: */
                sub_list_header_print(sl[0], f_out, &lp);
                /* move to a new line, if possible: */
                sub_list_next(sl[0]);
                /* re-arrange the list: */
                sub_list_sink(sl, 0, n);
        }
}

/*
 * Merge sub-lists to a file
 */
static void
merge_list_parts(struct sort_list **parts, size_t n, const char *fn)
{
        FILE* f_out;

        f_out = openfile(fn,"w");

        merge_sub_lists(parts, n, f_out);

        closefile(f_out, fn);
}

#endif /* defined(SORT_THREADS) */
/*
 * Multi-threaded sort algorithm "driver"
 */
static void
mt_sort(struct sort_list *list,
    int(*sort_func)(void *, size_t, size_t, int(*)(const void *, const void *)),
    const char* fn)
{
#if defined(SORT_THREADS)
        if (nthreads < 2 || list->count < MT_SORT_THRESHOLD) {
                size_t nthreads_save = nthreads;
                nthreads = 1;
#endif
                /* if single thread or small data, do simple sort */
                sort_func(list->list, list->count,
                    sizeof(struct sort_list_item *),
                    (int(*)(const void *, const void *)) list_coll);
                sort_list_dump(list, fn);
#if defined(SORT_THREADS)
                nthreads = nthreads_save;
        } else {
                /* multi-threaded sort */
                struct sort_list **parts;
                size_t avgsize, cstart, i;

                /* array of sub-lists */
                parts = sort_malloc(sizeof(struct sort_list*) * nthreads);
                cstart = 0;
                avgsize = list->count / nthreads;

                /* set global system sort function */
                g_sort_func = sort_func;

                /* set sublists */
                for (i = 0; i < nthreads; ++i) {
                        size_t sz = 0;

                        parts[i] = sort_malloc(sizeof(struct sort_list));
                        parts[i]->list = list->list + cstart;
                        parts[i]->memsize = 0;
                        parts[i]->sub_list_pos = i;

                        sz = (i == nthreads - 1) ? list->count - cstart :
                            avgsize;

                        parts[i]->count = sz;

                        parts[i]->size = parts[i]->count;

                        cstart += sz;
                }

                /* init threads counting semaphore */
                sem_init(&mtsem, 0, 0);

                /* start threads */
                for (i = 0; i < nthreads; ++i) {
                        pthread_t pth;
                        pthread_attr_t attr;

                        pthread_attr_init(&attr);
                        pthread_attr_setdetachstate(&attr, PTHREAD_DETACHED);

                        for (;;) {
                                int res = pthread_create(&pth, &attr,
                                    mt_sort_thread, parts[i]);

                                if (res >= 0)
                                        break;
                                if (errno == EAGAIN) {
                                        pthread_yield();
                                        continue;
                                }
                                err(2, NULL);
                        }

                        pthread_attr_destroy(&attr);
                }

                /* wait for threads completion */
                for (i = 0; i < nthreads; ++i) {
                        sem_wait(&mtsem);
                }
                /* destroy the semaphore - we do not need it anymore */
                sem_destroy(&mtsem);

                /* merge sorted sub-lists to the file */
                merge_list_parts(parts, nthreads, fn);

                /* free sub-lists data */
                for (i = 0; i < nthreads; ++i) {
                        sort_free(parts[i]);
                }
                sort_free(parts);
        }
#endif /* defined(SORT_THREADS) */
}