delta.c

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/*
 *  delta.c
 *
 *  Copyright (c) 2007 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 "config.h"

#include <stdlib.h>
#include <string.h>

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

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

const char SYMEXPORT *alpm_delta_get_from(pmdelta_t *delta)
{
    ALPM_LOG_FUNC;

    /* Sanity checks */
    ASSERT(delta != NULL, return(NULL));

    return(delta->from);
}

const char SYMEXPORT *alpm_delta_get_to(pmdelta_t *delta)
{
    ALPM_LOG_FUNC;

    /* Sanity checks */
    ASSERT(delta != NULL, return(NULL));

    return(delta->to);
}

unsigned long SYMEXPORT alpm_delta_get_size(pmdelta_t *delta)
{
    ALPM_LOG_FUNC;

    /* Sanity checks */
    ASSERT(delta != NULL, return(-1));

    return(delta->size);
}

const char SYMEXPORT *alpm_delta_get_filename(pmdelta_t *delta)
{
    ALPM_LOG_FUNC;

    /* Sanity checks */
    ASSERT(delta != NULL, return(NULL));

    return(delta->filename);
}

const char SYMEXPORT *alpm_delta_get_md5sum(pmdelta_t *delta)
{
    ALPM_LOG_FUNC;

    /* Sanity checks */
    ASSERT(delta != NULL, return(NULL));

    return(delta->md5sum);
}

/** @} */

/** Calculates the combined size of a list of delta files.
 *
 * @param deltas the list of pmdelta_t * objects
 *
 * @return the combined size
 */
unsigned long _alpm_delta_path_size(alpm_list_t *deltas)
{
    unsigned long sum = 0;
    alpm_list_t *dlts = deltas;

    while(dlts) {
        pmdelta_t *d = (pmdelta_t *)alpm_list_getdata(dlts);
        sum += d->size;

        dlts = alpm_list_next(dlts);
    }

    return(sum);
}

/** Calculates the combined size of a list of delta files that are not
 * in the cache.
 *
 * @param deltas the list of pmdelta_t * objects
 *
 * @return the combined size
 */
unsigned long _alpm_delta_path_size_uncached(alpm_list_t *deltas)
{
    unsigned long sum = 0;
    alpm_list_t *dlts = deltas;

    while(dlts) {
        pmdelta_t *d = (pmdelta_t *)alpm_list_getdata(dlts);
        char *fname = _alpm_filecache_find(d->filename);

        if(!fname) {
            sum += d->size;
        }

        FREE(fname);

        dlts = alpm_list_next(dlts);
    }

    return(sum);
}

/** 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.
 *
 * The algorithm is based on Dijkstra's shortest path algorithm.
 *
 * @param deltas the list of pmdelta_t * objects that a package has
 * @param from the version to start from
 * @param to the version to end at
 * @param path the current path
 *
 * @return the list of pmdelta_t * objects that has the smallest size.
 * NULL (the empty list) is returned if there is no path between the
 * versions.
 */
static alpm_list_t *shortest_delta_path(alpm_list_t *deltas,
        const char *from, const char *to, alpm_list_t *path)
{
    alpm_list_t *d;
    alpm_list_t *shortest = NULL;

    /* Found the 'to' version, this is a good path so return it. */
    if(strcmp(from, to) == 0) {
        return(path);
    }

    for(d = deltas; d; d = alpm_list_next(d)) {
        pmdelta_t *v = alpm_list_getdata(d);

        /* If this vertex has already been visited in the path, go to the
         * next vertex. */
        if(alpm_list_find_ptr(path, v)) {
            continue;
        }

        /* Once we find a vertex that starts at the 'from' version,
         * recursively find the shortest path using the 'to' version of this
         * current vertex as the 'from' version in the function call. */
        if(strcmp(v->from, from) == 0) {
            alpm_list_t *newpath = alpm_list_copy(path);
            newpath = alpm_list_add(newpath, v);
            newpath = shortest_delta_path(deltas, v->to, to, newpath);

            if(newpath != NULL) {
                /* The path returned works, now use it unless there is already a
                 * shorter path found. */
                if(shortest == NULL) {
                    shortest = newpath;
                } else if(_alpm_delta_path_size(shortest) > _alpm_delta_path_size(newpath)) {
                    alpm_list_free(shortest);
                    shortest = newpath;
                } else {
                    alpm_list_free(newpath);
                }
            }
        }
    }

    alpm_list_free(path);

    return(shortest);
}

/** 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 deltas the list of pmdelta_t * objects that a package has
 * @param from the version to start from
 * @param to the version to end at
 *
 * @return the list of pmdelta_t * objects that has the smallest size.
 * NULL (the empty list) is returned if there is no path between the
 * versions.
 */
alpm_list_t *_alpm_shortest_delta_path(alpm_list_t *deltas, const char *from,
        const char *to)
{
    alpm_list_t *path = NULL;

    path = shortest_delta_path(deltas, from, to, path);

    return(path);
}

/** Parses the string representation of a pmdelta_t object.
 *
 * This function assumes that the string is in the correct format.
 *
 * @param line the string to parse
 *
 * @return A pointer to the new pmdelta_t object
 */
pmdelta_t *_alpm_delta_parse(char *line)
{
    pmdelta_t *delta;
    char *tmp = line, *tmp2;

    CALLOC(delta, 1, sizeof(pmdelta_t), RET_ERR(PM_ERR_MEMORY, NULL));

    tmp2 = tmp;
    tmp = strchr(tmp, ' ');
    *(tmp++) = '\0';
    strncpy(delta->from, tmp2, DLT_VERSION_LEN);

    tmp2 = tmp;
    tmp = strchr(tmp, ' ');
    *(tmp++) = '\0';
    strncpy(delta->to, tmp2, DLT_VERSION_LEN);

    tmp2 = tmp;
    tmp = strchr(tmp, ' ');
    *(tmp++) = '\0';
    delta->size = atol(tmp2);

    tmp2 = tmp;
    tmp = strchr(tmp, ' ');
    *(tmp++) = '\0';
    strncpy(delta->filename, tmp2, DLT_FILENAME_LEN);

    strncpy(delta->md5sum, tmp, DLT_MD5SUM_LEN);

    return(delta);
}

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