path: root/lib/libalpm/delta.c

/*
 *  delta.c
 *
 *  Copyright (c) 2006-2017 Pacman Development Team <pacman-dev@archlinux.org>
 *  Copyright (c) 2007-2006 by Judd Vinet <jvinet@zeroflux.org>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <string.h>
#include <stdint.h> /* intmax_t */
#include <limits.h>
#include <sys/types.h>
#include <regex.h>

/* libalpm */
#include "delta.h"
#include "alpm_list.h"
#include "util.h"
#include "log.h"
#include "graph.h"

static alpm_list_t *graph_init(alpm_list_t *deltas, int reverse)
{
        alpm_list_t *i, *j;
        alpm_list_t *vertices = NULL;
        /* create the vertices */
        for(i = deltas; i; i = i->next) {
                alpm_graph_t *v = _alpm_graph_new();
                if(!v) {
                        alpm_list_free(vertices);
                        return NULL;
                }
                alpm_delta_t *vdelta = i->data;
                vdelta->download_size = vdelta->delta_size;
                v->weight = LONG_MAX;
                v->data = vdelta;
                vertices = alpm_list_add(vertices, v);
        }

        /* compute the edges */
        for(i = vertices; i; i = i->next) {
                alpm_graph_t *v_i = i->data;
                alpm_delta_t *d_i = v_i->data;
                /* loop a second time so we make all possible comparisons */
                for(j = vertices; j; j = j->next) {
                        alpm_graph_t *v_j = j->data;
                        alpm_delta_t *d_j = v_j->data;
                        /* We want to create a delta tree like the following:
                         *          1_to_2
                         *            |
                         * 1_to_3   2_to_3
                         *   \        /
                         *     3_to_4
                         * If J 'from' is equal to I 'to', then J is a child of I.
                         * */
                        if((!reverse && strcmp(d_j->from, d_i->to) == 0) ||
                                        (reverse && strcmp(d_j->to, d_i->from) == 0)) {
                                v_i->children = alpm_list_add(v_i->children, v_j);
                        }
                }
                v_i->iterator = v_i->children;
        }
        return vertices;
}

static void graph_init_size(alpm_handle_t *handle, alpm_list_t *vertices)
{
        alpm_list_t *i;

        for(i = vertices; i; i = i->next) {
                char *fpath, *md5sum;
                alpm_graph_t *v = i->data;
                alpm_delta_t *vdelta = v->data;

                /* determine whether the delta file already exists */
                fpath = _alpm_filecache_find(handle, vdelta->delta);
                if(fpath) {
                        md5sum = alpm_compute_md5sum(fpath);
                        if(md5sum && strcmp(md5sum, vdelta->delta_md5) == 0) {
                                vdelta->download_size = 0;
                        }
                        FREE(md5sum);
                        FREE(fpath);
                } else {
                        char *fnamepart;
                        CALLOC(fnamepart, strlen(vdelta->delta) + 6, sizeof(char), return);
                        sprintf(fnamepart, "%s.part", vdelta->delta);
                        fpath = _alpm_filecache_find(handle, fnamepart);
                        if(fpath) {
                                struct stat st;
                                if(stat(fpath, &st) == 0) {
                                        vdelta->download_size = vdelta->delta_size - st.st_size;
                                        vdelta->download_size = vdelta->download_size < 0 ? 0 : vdelta->download_size;
                                }
                                FREE(fpath);
                        }
                        FREE(fnamepart);
                }

                /* determine whether a base 'from' file exists */
                fpath = _alpm_filecache_find(handle, vdelta->from);
                if(fpath) {
                        v->weight = vdelta->download_size;
                }
                FREE(fpath);
        }
}


static void dijkstra(alpm_list_t *vertices)
{
        alpm_list_t *i;
        alpm_graph_t *v;
        while(1) {
                v = NULL;
                /* find the smallest vertice not visited yet */
                for(i = vertices; i; i = i->next) {
                        alpm_graph_t *v_i = i->data;

                        if(v_i->state == ALPM_GRAPH_STATE_PROCESSING) {
                                continue;
                        }

                        if(v == NULL || v_i->weight < v->weight) {
                                v = v_i;
                        }
                }
                if(v == NULL || v->weight == LONG_MAX) {
                        break;
                }

                v->state = ALPM_GRAPH_STATE_PROCESSING;

                v->iterator = v->children;
                while(v->iterator) {
                        alpm_graph_t *v_c = v->iterator->data;
                        alpm_delta_t *d_c = v_c->data;
                        if(v_c->weight > v->weight + d_c->download_size) {
                                v_c->weight = v->weight + d_c->download_size;
                                v_c->parent = v;
                        }

                        v->iterator = (v->iterator)->next;

                }
        }
}

static off_t shortest_path(alpm_list_t *vertices, const char *to, alpm_list_t **path)
{
        alpm_list_t *i;
        alpm_graph_t *v = NULL;
        off_t bestsize = 0;
        alpm_list_t *rpath = NULL;

        for(i = vertices; i; i = i->next) {
                alpm_graph_t *v_i = i->data;
                alpm_delta_t *d_i = v_i->data;

                if(strcmp(d_i->to, to) == 0) {
                        if(v == NULL || v_i->weight < v->weight) {
                                v = v_i;
                                bestsize = v->weight;
                        }
                }
        }

        while(v != NULL) {
                alpm_delta_t *vdelta = v->data;
                rpath = alpm_list_add(rpath, vdelta);
                v = v->parent;
        }
        *path = alpm_list_reverse(rpath);
        alpm_list_free(rpath);

        return bestsize;
}

/** Calculates the shortest path from one version to another.
 * The shortest path is defined as the path with the smallest combined
 * size, not the length of the path.
 * @param handle the context handle
 * @param deltas the list of alpm_delta_t * objects that a file has
 * @param to the file to start the search at
 * @param path the pointer to a list location where alpm_delta_t * objects that
 * have the smallest size are placed. NULL is set if there is no path
 * possible with the files available.
 * @return the size of the path stored, or LONG_MAX if path is unfindable
 */
off_t _alpm_shortest_delta_path(alpm_handle_t *handle, alpm_list_t *deltas,
                const char *to, alpm_list_t **path)
{
        alpm_list_t *bestpath = NULL;
        alpm_list_t *vertices;
        off_t bestsize = LONG_MAX;

        if(deltas == NULL) {
                *path = NULL;
                return bestsize;
        }

        _alpm_log(handle, ALPM_LOG_DEBUG, "started delta shortest-path search for '%s'\n", to);

        vertices = graph_init(deltas, 0);
        graph_init_size(handle, vertices);
        dijkstra(vertices);
        bestsize = shortest_path(vertices, to, &bestpath);

        _alpm_log(handle, ALPM_LOG_DEBUG, "delta shortest-path search complete : '%jd'\n", (intmax_t)bestsize);

        alpm_list_free_inner(vertices, _alpm_graph_free);
        alpm_list_free(vertices);

        *path = bestpath;
        return bestsize;
}

static alpm_list_t *find_unused(alpm_list_t *deltas, const char *to, off_t quota)
{
        alpm_list_t *unused = NULL;
        alpm_list_t *vertices;
        alpm_list_t *i;
        vertices = graph_init(deltas, 1);

        for(i = vertices; i; i = i->next) {
                alpm_graph_t *v = i->data;
                alpm_delta_t *vdelta = v->data;
                if(strcmp(vdelta->to, to) == 0)
                {
                        v->weight = vdelta->download_size;
                }
        }
        dijkstra(vertices);
        for(i = vertices; i; i = i->next) {
                alpm_graph_t *v = i->data;
                alpm_delta_t *vdelta = v->data;
                if(v->weight > quota) {
                        unused = alpm_list_add(unused, vdelta->delta);
                }
        }
        alpm_list_free_inner(vertices, _alpm_graph_free);
        alpm_list_free(vertices);
        return unused;
}

/** \addtogroup alpm_deltas Delta Functions
 * @brief Functions to manipulate libalpm deltas
 * @{
 */

alpm_list_t SYMEXPORT *alpm_pkg_unused_deltas(alpm_pkg_t *pkg)
{
        ASSERT(pkg != NULL, return NULL);
        return find_unused(pkg->deltas, pkg->filename,
                        pkg->size * pkg->handle->deltaratio);
}

/** @} */

#define NUM_MATCHES 6

/** Parses the string representation of a alpm_delta_t object.
 * This function assumes that the string is in the correct format.
 * This format is as follows:
 * $deltafile $deltamd5 $deltasize $oldfile $newfile
 * @param handle the context handle
 * @param line the string to parse
 * @return A pointer to the new alpm_delta_t object
 */
alpm_delta_t *_alpm_delta_parse(alpm_handle_t *handle, const char *line)
{
        alpm_delta_t *delta;
        size_t len;
        regmatch_t pmatch[NUM_MATCHES];
        char filesize[32];

        /* this is so we only have to compile the pattern once */
        if(!handle->delta_regex_compiled) {
                /* $deltafile $deltamd5 $deltasize $oldfile $newfile*/
                regcomp(&handle->delta_regex,
                                "^([^[:space:]]+) ([[:xdigit:]]{32}) ([[:digit:]]+)"
                                " ([^[:space:]]+) ([^[:space:]]+)$",
                                REG_EXTENDED | REG_NEWLINE);
                handle->delta_regex_compiled = 1;
        }

        if(regexec(&handle->delta_regex, line, NUM_MATCHES, pmatch, 0) != 0) {
                /* delta line is invalid, return NULL */
                return NULL;
        }

        CALLOC(delta, 1, sizeof(alpm_delta_t), return NULL);

        /* start at index 1 -- match 0 is the entire match */
        len = pmatch[1].rm_eo - pmatch[1].rm_so;
        STRNDUP(delta->delta, &line[pmatch[1].rm_so], len, goto error);

        len = pmatch[2].rm_eo - pmatch[2].rm_so;
        STRNDUP(delta->delta_md5, &line[pmatch[2].rm_so], len, goto error);

        len = pmatch[3].rm_eo - pmatch[3].rm_so;
        if(len < sizeof(filesize)) {
                strncpy(filesize, &line[pmatch[3].rm_so], len);
                filesize[len] = '\0';
                delta->delta_size = _alpm_strtoofft(filesize);
        }

        len = pmatch[4].rm_eo - pmatch[4].rm_so;
        STRNDUP(delta->from, &line[pmatch[4].rm_so], len, goto error);

        len = pmatch[5].rm_eo - pmatch[5].rm_so;
        STRNDUP(delta->to, &line[pmatch[5].rm_so], len, goto error);

        return delta;

error:
        _alpm_delta_free(delta);
        return NULL;
}

#undef NUM_MATCHES

void _alpm_delta_free(alpm_delta_t *delta)
{
        ASSERT(delta != NULL, return);
        FREE(delta->delta);
        FREE(delta->delta_md5);
        FREE(delta->from);
        FREE(delta->to);
        FREE(delta);
}

alpm_delta_t *_alpm_delta_dup(const alpm_delta_t *delta)
{
        alpm_delta_t *newdelta;
        CALLOC(newdelta, 1, sizeof(alpm_delta_t), return NULL);
        STRDUP(newdelta->delta, delta->delta, goto error);
        STRDUP(newdelta->delta_md5, delta->delta_md5, goto error);
        STRDUP(newdelta->from, delta->from, goto error);
        STRDUP(newdelta->to, delta->to, goto error);
        newdelta->delta_size = delta->delta_size;
        newdelta->download_size = delta->download_size;

        return newdelta;

error:
        _alpm_delta_free(newdelta);
        return NULL;
}

/* vim: set noet: */