path: root/lib/libalpm/delta.c

/*
 *  delta.c
 *
 *  Copyright (c) 2007-2008 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>
#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"

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

const char SYMEXPORT *alpm_delta_get_from(pmdelta_t *delta)
{
  ASSERT(delta != NULL, return(NULL));
  return(delta->from);
}

const char SYMEXPORT *alpm_delta_get_from_md5sum(pmdelta_t *delta)
{
  ASSERT(delta != NULL, return(NULL));
  return(delta->from_md5);
}

const char SYMEXPORT *alpm_delta_get_to(pmdelta_t *delta)
{
  ASSERT(delta != NULL, return(NULL));
  return(delta->to);
}

const char SYMEXPORT *alpm_delta_get_to_md5sum(pmdelta_t *delta)
{
  ASSERT(delta != NULL, return(NULL));
  return(delta->to_md5);
}

const char SYMEXPORT *alpm_delta_get_filename(pmdelta_t *delta)
{
  ASSERT(delta != NULL, return(NULL));
  return(delta->delta);
}

const char SYMEXPORT *alpm_delta_get_md5sum(pmdelta_t *delta)
{
  ASSERT(delta != NULL, return(NULL));
  return(delta->delta_md5);
}

off_t SYMEXPORT alpm_delta_get_size(pmdelta_t *delta)
{
  ASSERT(delta != NULL, return(-1));
  return(delta->delta_size);
}

/** @} */

static alpm_list_t *delta_graph_init(alpm_list_t *deltas)
{
  alpm_list_t *i, *j;
  alpm_list_t *vertices = NULL;
  /* create the vertices */
  for(i = deltas; i; i = i->next) {
    char *fpath, *md5sum;
    pmgraph_t *v = _alpm_graph_new();
    pmdelta_t *vdelta = i->data;
    vdelta->download_size = vdelta->delta_size;
    v->weight = LONG_MAX;

    /* determine whether the delta file already exists */
    fpath = _alpm_filecache_find(vdelta->delta);
    md5sum = alpm_compute_md5sum(fpath);
    if(fpath && md5sum && strcmp(md5sum, vdelta->delta_md5) == 0) {
      vdelta->download_size = 0;
    }
    FREE(fpath);
    FREE(md5sum);

    /* determine whether a base 'from' file exists */
    fpath = _alpm_filecache_find(vdelta->from);
    md5sum = alpm_compute_md5sum(fpath);
    if(fpath && md5sum && strcmp(md5sum, vdelta->from_md5) == 0) {
      v->weight = vdelta->download_size;
    }
    FREE(fpath);
    FREE(md5sum);

    v->data = vdelta;
    vertices = alpm_list_add(vertices, v);
  }

  /* compute the edges */
  for(i = vertices; i; i = i->next) {
    pmgraph_t *v_i = i->data;
    pmdelta_t *d_i = v_i->data;
    /* loop a second time so we make all possible comparisons */
    for(j = vertices; j; j = j->next) {
      pmgraph_t *v_j = j->data;
      pmdelta_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(strcmp(d_j->from, d_i->to) == 0
          && strcmp(d_j->from_md5, d_i->to_md5) == 0) {
        v_i->children = alpm_list_add(v_i->children, v_j);
      }
    }
    v_i->childptr = v_i->children;
  }
  return(vertices);
}

static off_t delta_vert(alpm_list_t *vertices,
    const char *to, const char *to_md5, alpm_list_t **path) {
  alpm_list_t *i;
  pmgraph_t *v;
  while(1) {
    v = NULL;
    /* find the smallest vertice not visited yet */
    for(i = vertices; i; i = i->next) {
      pmgraph_t *v_i = i->data;

      if(v_i->state == -1) {
        continue;
      }

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

    v->state = -1;

    v->childptr = v->children;
    while(v->childptr) {
      pmgraph_t *v_c = v->childptr->data;
      pmdelta_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->childptr = (v->childptr)->next;

    }
  }

  v = NULL;
  off_t bestsize = 0;

  for(i = vertices; i; i = i->next) {
    pmgraph_t *v_i = i->data;
    pmdelta_t *d_i = v_i->data;

    if(strcmp(d_i->to, to) == 0
        || strcmp(d_i->to_md5, to_md5) == 0) {
      if(v == NULL || v_i->weight < v->weight) {
        v = v_i;
        bestsize = v->weight;
      }
    }
  }

  alpm_list_t *rpath = NULL;
  while(v != NULL) {
    pmdelta_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 deltas the list of pmdelta_t * objects that a file has
 * @param to the file to start the search at
 * @param to_md5 the md5sum of the above named file
 * @param path the pointer to a list location where pmdelta_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_list_t *deltas,
    const char *to, const char *to_md5, alpm_list_t **path)
{
  alpm_list_t *bestpath = NULL;
  alpm_list_t *vertices;
  off_t bestsize = LONG_MAX;

  ALPM_LOG_FUNC;

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

  _alpm_log(PM_LOG_DEBUG, "started delta shortest-path search\n");

  vertices = delta_graph_init(deltas);

  bestsize = delta_vert(vertices, to, to_md5, &bestpath);

  _alpm_log(PM_LOG_DEBUG, "delta shortest-path search complete\n");

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

  *path = bestpath;
  return(bestsize);
}

/** Parses the string representation of a pmdelta_t object.
 * This function assumes that the string is in the correct format.
 * This format is as follows:
 * $oldfile $oldmd5 $newfile $newmd5 $deltafile $deltamd5 $deltasize
 * @param line the string to parse
 * @return A pointer to the new pmdelta_t object
 */
/* TODO this does not really belong here, but in a parsing lib */
pmdelta_t *_alpm_delta_parse(char *line)
{
  pmdelta_t *delta;
  char *tmp = line, *tmp2;
  regex_t reg;

  regcomp(&reg,
      "^[^[:space:]]* [[:xdigit:]]{32}"
      " [^[:space:]]* [[:xdigit:]]{32}"
      " [^[:space:]]* [[:xdigit:]]{32} [[:digit:]]*$",
      REG_EXTENDED | REG_NOSUB | REG_NEWLINE);
  if(regexec(&reg, line, 0, 0, 0) != 0) {
    /* delta line is invalid, return NULL */
    regfree(&reg);
    return(NULL);
  }
  regfree(&reg);

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

  tmp2 = tmp;
  tmp = strchr(tmp, ' ');
  *(tmp++) = '\0';
  STRDUP(delta->from, tmp2, RET_ERR(PM_ERR_MEMORY, NULL));

  tmp2 = tmp;
  tmp = strchr(tmp, ' ');
  *(tmp++) = '\0';
  STRDUP(delta->from_md5, tmp2, RET_ERR(PM_ERR_MEMORY, NULL));

  tmp2 = tmp;
  tmp = strchr(tmp, ' ');
  *(tmp++) = '\0';
  STRDUP(delta->to, tmp2, RET_ERR(PM_ERR_MEMORY, NULL));

  tmp2 = tmp;
  tmp = strchr(tmp, ' ');
  *(tmp++) = '\0';
  STRDUP(delta->to_md5, tmp2, RET_ERR(PM_ERR_MEMORY, NULL));

  tmp2 = tmp;
  tmp = strchr(tmp, ' ');
  *(tmp++) = '\0';
  STRDUP(delta->delta, tmp2, RET_ERR(PM_ERR_MEMORY, NULL));

  tmp2 = tmp;
  tmp = strchr(tmp, ' ');
  *(tmp++) = '\0';
  STRDUP(delta->delta_md5, tmp2, RET_ERR(PM_ERR_MEMORY, NULL));

  delta->delta_size = atol(tmp);

  return(delta);
}

void _alpm_delta_free(pmdelta_t *delta)
{
  FREE(delta->from);
  FREE(delta->from_md5);
  FREE(delta->to);
  FREE(delta->to_md5);
  FREE(delta->delta);
  FREE(delta->delta_md5);
  FREE(delta);
}

/* vim: set ts=2 sw=2 noet: */