// SPDX-License-Identifier: GPL-2.0-only
/*
 * Manage printing of source lines
 * Copyright (c) 2017, Intel Corporation.
 * Author: Andi Kleen
 */
#include <linux/list.h>
#include <linux/zalloc.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
#include <string.h>
#include "srccode.h"
#include "debug.h"
#include <internal/lib.h> // page_size
#include "hashmap.h"

#define MAXSRCCACHE (32*1024*1024)
#define MAXSRCFILES     64
#define SRC_HTAB_SZ     64

struct srcfile {
        struct hlist_node hash_nd;
        struct list_head nd;
        char *fn;
        char **lines;
        char *map;
        unsigned numlines;
        size_t maplen;
};

static struct hlist_head srcfile_htab[SRC_HTAB_SZ];
static LIST_HEAD(srcfile_list);
static long map_total_sz;
static int num_srcfiles;

static int countlines(char *map, int maplen)
{
        int numl;
        char *end = map + maplen;
        char *p = map;

        if (maplen == 0)
                return 0;
        numl = 0;
        while (p < end && (p = memchr(p, '\n', end - p)) != NULL) {
                numl++;
                p++;
        }
        if (p < end)
                numl++;
        return numl;
}

static void fill_lines(char **lines, int maxline, char *map, int maplen)
{
        int l;
        char *end = map + maplen;
        char *p = map;

        if (maplen == 0 || maxline == 0)
                return;
        l = 0;
        lines[l++] = map;
        while (p < end && (p = memchr(p, '\n', end - p)) != NULL) {
                if (l >= maxline)
                        return;
                lines[l++] = ++p;
        }
        if (p < end)
                lines[l] = p;
}

static void free_srcfile(struct srcfile *sf)
{
        list_del_init(&sf->nd);
        hlist_del(&sf->hash_nd);
        map_total_sz -= sf->maplen;
        munmap(sf->map, sf->maplen);
        zfree(&sf->lines);
        zfree(&sf->fn);
        free(sf);
        num_srcfiles--;
}

static struct srcfile *find_srcfile(char *fn)
{
        struct stat st;
        struct srcfile *h;
        int fd;
        unsigned long sz;
        size_t hval = str_hash(fn) % SRC_HTAB_SZ;

        hlist_for_each_entry (h, &srcfile_htab[hval], hash_nd) {
                if (!strcmp(fn, h->fn)) {
                        /* Move to front */
                        list_move(&h->nd, &srcfile_list);
                        return h;
                }
        }

        /* Only prune if there is more than one entry */
        while ((num_srcfiles > MAXSRCFILES || map_total_sz > MAXSRCCACHE) &&
               srcfile_list.next != &srcfile_list) {
                assert(!list_empty(&srcfile_list));
                h = list_entry(srcfile_list.prev, struct srcfile, nd);
                free_srcfile(h);
        }

        fd = open(fn, O_RDONLY);
        if (fd < 0 || fstat(fd, &st) < 0) {
                pr_debug("cannot open source file %s\n", fn);
                return NULL;
        }

        h = malloc(sizeof(struct srcfile));
        if (!h)
                return NULL;

        h->fn = strdup(fn);
        if (!h->fn)
                goto out_h;

        h->maplen = st.st_size;
        sz = (h->maplen + page_size - 1) & ~(page_size - 1);
        h->map = mmap(NULL, sz, PROT_READ, MAP_SHARED, fd, 0);
        close(fd);
        if (h->map == (char *)-1) {
                pr_debug("cannot mmap source file %s\n", fn);
                goto out_fn;
        }
        h->numlines = countlines(h->map, h->maplen);
        h->lines = calloc(h->numlines, sizeof(char *));
        if (!h->lines)
                goto out_map;
        fill_lines(h->lines, h->numlines, h->map, h->maplen);
        list_add(&h->nd, &srcfile_list);
        hlist_add_head(&h->hash_nd, &srcfile_htab[hval]);
        map_total_sz += h->maplen;
        num_srcfiles++;
        return h;

out_map:
        munmap(h->map, sz);
out_fn:
        zfree(&h->fn);
out_h:
        free(h);
        return NULL;
}

/* Result is not 0 terminated */
char *find_sourceline(char *fn, unsigned line, int *lenp)
{
        char *l, *p;
        struct srcfile *sf = find_srcfile(fn);
        if (!sf)
                return NULL;
        line--;
        if (line >= sf->numlines)
                return NULL;
        l = sf->lines[line];
        if (!l)
                return NULL;
        p = memchr(l, '\n', sf->map + sf->maplen - l);
        *lenp = p - l;
        return l;
}