path: root/lib/libalpm/delta.c

/*
 *  delta.c
 *
 *  Copyright (c) 2006-2011 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 "config.h"

#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->childptr = 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 == -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) {
      alpm_graph_t *v_c = v->childptr->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->childptr = (v->childptr)->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 * MAX_DELTA_RATIO);
}

/** @} */

/** 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 line the string to parse
 * @return A pointer to the new alpm_delta_t object
 */
/* TODO this does not really belong here, but in a parsing lib */
alpm_delta_t *_alpm_delta_parse(char *line)
{
  alpm_delta_t *delta;
  char *tmp;
  const int num_matches = 6;
  size_t len;
  regex_t reg;
  regmatch_t pmatch[num_matches];

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

  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(tmp, &line[pmatch[1].rm_so], len, return NULL);

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

  len = pmatch[3].rm_eo - pmatch[3].rm_so;
  STRNDUP(tmp, &line[pmatch[3].rm_so], len, return NULL);
  delta->delta_size = _alpm_strtoofft(tmp);

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

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

  return delta;
}

void _alpm_delta_free(alpm_delta_t *delta)
{
  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, return NULL);
  STRDUP(newdelta->delta_md5, delta->delta_md5, return NULL);
  STRDUP(newdelta->from, delta->from, return NULL);
  STRDUP(newdelta->to, delta->to, return NULL);
  newdelta->delta_size = delta->delta_size;
  newdelta->download_size = delta->download_size;

  return newdelta;
}

/* vim: set ts=2 sw=2 noet: */