/*

 * read.c - read the blkid cache from disk, to avoid scanning all devices

 *

 * Copyright (C) 2001, 2003 Theodore Y. Ts'o

 * Copyright (C) 2001 Andreas Dilger

 *

 * %Begin-Header%

 * This file may be redistributed under the terms of the

 * GNU Lesser General Public License.

 * %End-Header%

 */

#include <stdio.h>

#include <ctype.h>

#include <string.h>

#include <time.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <unistd.h>

#ifdef HAVE_ERRNO_H

#include <errno.h>

#endif

#include "blkidP.h"

#ifdef HAVE_STDLIB_H

# ifndef _XOPEN_SOURCE

#  define _XOPEN_SOURCE 600 /* for inclusion of strtoull */

# endif

# include <stdlib.h>

#endif

/*

 * File format:

 *

 *  <device [<NAME="value"> ...]>device_name</device>

 *

 *  The following tags are required for each entry:

 *  <ID="id"> unique (within this file) ID number of this device

 *  <TIME="sec.usec"> (time_t and suseconds_t) time this entry was last

 *                   read from disk

 *  <TYPE="type"> (detected) type of filesystem/data for this partition

 *

 *  The following tags may be present, depending on the device contents

 *  <LABEL="label"> (user supplied) label (volume name, etc)

 *  <UUID="uuid"> (generated) universally unique identifier (serial no)

 */

static char *skip_over_blank(char *cp)

{

  while (*cp && isspace(*cp))

    cp++;

  return cp;

}

static char *skip_over_word(char *cp)

{

  char ch;

  while ((ch = *cp)) {

    /* If we see a backslash, skip the next character */

    if (ch == '\\') {

      cp++;

      if (*cp == '\0')

        break;

      cp++;

      continue;

    }

    if (isspace(ch) || ch == '<' || ch == '>')

      break;

    cp++;

  }

  return cp;

}

static char *strip_line(char *line)

{

  char  *p;

  line = skip_over_blank(line);

  p = line + strlen(line) - 1;

  while (*line) {

    if (isspace(*p))

      *p-- = '\0';

    else

      break;

  }

  return line;

}

#if 0

static char *parse_word(char **buf)

{

  char *word, *next;

  word = *buf;

  if (*word == '\0')

    return NULL;

  word = skip_over_blank(word);

  next = skip_over_word(word);

  if (*next) {

    char *end = next - 1;

    if (*end == '"' || *end == '\'')

      *end = '\0';

    *next++ = '\0';

  }

  *buf = next;

  if (*word == '"' || *word == '\'')

    word++;

  return word;

}

#endif

/*

 * Start parsing a new line from the cache.

 *

 * line starts with "<device" return 1 -> continue parsing line

 * line starts with "<foo", empty, or # return 0 -> skip line

 * line starts with other, return -BLKID_ERR_CACHE -> error

 */

static int parse_start(char **cp)

{

  char *p;

  p = strip_line(*cp);

  /* Skip comment or blank lines.  We can't just NUL the first '#' char,

   * in case it is inside quotes, or escaped.

   */

  if (*p == '\0' || *p == '#')

    return 0;

  if (!strncmp(p, "<device", 7)) {

    DBG(READ, ul_debug("found device header: %8s", p));

    p += 7;

    *cp = p;

    return 1;

  }

  if (*p == '<')

    return 0;

  return -BLKID_ERR_CACHE;

}

/* Consume the remaining XML on the line (cosmetic only) */

static int parse_end(char **cp)

{

  *cp = skip_over_blank(*cp);

  if (!strncmp(*cp, "</device>", 9)) {

    DBG(READ, ul_debug("found device trailer %9s", *cp));

    *cp += 9;

    return 0;

  }

  return -BLKID_ERR_CACHE;

}

/*

 * Allocate a new device struct with device name filled in.  Will handle

 * finding the device on lines of the form:

 * <device foo=bar>devname</device>

 * <device>devname<foo>bar</foo></device>

 */

static int parse_dev(blkid_cache cache, blkid_dev *dev, char **cp)

{

  char *start, *tmp, *end, *name;

  int ret;

  if ((ret = parse_start(cp)) <= 0)

    return ret;

  start = tmp = strchr(*cp, '>');

  if (!start) {

    DBG(READ, ul_debug("blkid: short line parsing dev: %s", *cp));

    return -BLKID_ERR_CACHE;

  }

  start = skip_over_blank(start + 1);

  end = skip_over_word(start);

  DBG(READ, ul_debug("device should be %*s",

             (int)(end - start), start));

  if (**cp == '>')

    *cp = end;

  else

    (*cp)++;

  *tmp = '\0';

  if (!(tmp = strrchr(end, '<')) || parse_end(&tmp) < 0) {

    DBG(READ, ul_debug("blkid: missing </device> ending: %s", end));

  } else if (tmp)

    *tmp = '\0';

  if (end - start <= 1) {

    DBG(READ, ul_debug("blkid: empty device name: %s", *cp));

    return -BLKID_ERR_CACHE;

  }

  name = strndup(start, end - start);

  if (name == NULL)

    return -BLKID_ERR_MEM;

  DBG(READ, ul_debug("found dev %s", name));

  if (!(*dev = blkid_get_dev(cache, name, BLKID_DEV_CREATE))) {

    free(name);

    return -BLKID_ERR_MEM;

  }

  free(name);

  return 1;

}

/*

 * Extract a tag of the form NAME="value" from the line.

 */

static int parse_token(char **name, char **value, char **cp)

{

  char *end;

  if (!name || !value || !cp)

    return -BLKID_ERR_PARAM;

  if (!(*value = strchr(*cp, '=')))

    return 0;

  **value = '\0';

  *name = strip_line(*cp);

  *value = skip_over_blank(*value + 1);

  if (**value == '"') {

    char *p = end = *value + 1;

    /* convert 'foo\"bar'  to 'foo"bar' */

    while (*p) {

      if (*p == '\\') {

        p++;

        *end = *p;

      } else {

        *end = *p;

        if (*p == '"')

          break;

      }

      p++;

      end++;

    }

    if (*end != '"') {

      DBG(READ, ul_debug("unbalanced quotes at: %s", *value));

      *cp = *value;

      return -BLKID_ERR_CACHE;

    }

    (*value)++;

    *end = '\0';

    end = ++p;

  } else {

    end = skip_over_word(*value);

    if (*end) {

      *end = '\0';

      end++;

    }

  }

  *cp = end;

  return 1;

}

/*

 * Extract a tag from the line.

 *

 * Return 1 if a valid tag was found.

 * Return 0 if no tag found.

 * Return -ve error code.

 */

static int parse_tag(blkid_cache cache, blkid_dev dev, char **cp)

{

  char *name = NULL;

  char *value = NULL;

  int ret;

  if (!cache || !dev)

    return -BLKID_ERR_PARAM;

  if ((ret = parse_token(&name, &value, cp)) <= 0)

    return ret;

  DBG(READ, ul_debug("tag: %s=\"%s\"", name, value));

  errno = 0;

  /* Some tags are stored directly in the device struct */

  if (!strcmp(name, "DEVNO")) {

    dev->bid_devno = strtoull(value, NULL, 0);

    if (errno)

      return -errno;

  } else if (!strcmp(name, "PRI")) {

    dev->bid_pri = strtol(value, NULL, 0);

    if (errno)

      return -errno;

  } else if (!strcmp(name, "TIME")) {

    char *end = NULL;

    dev->bid_time = strtoull(value, &end, 0);

    if (errno == 0 && end && *end == '.')

      dev->bid_utime = strtoull(end + 1, NULL, 0);

    if (errno)

      return -errno;

  } else

    ret = blkid_set_tag(dev, name, value, strlen(value));

  return ret < 0 ? ret : 1;

}

/*

 * Parse a single line of data, and return a newly allocated dev struct.

 * Add the new device to the cache struct, if one was read.

 *

 * Lines are of the form <device [TAG="value" ...]>/dev/foo</device>

 *

 * Returns -ve value on error.

 * Returns 0 otherwise.

 * If a valid device was read, *dev_p is non-NULL, otherwise it is NULL

 * (e.g. comment lines, unknown XML content, etc).

 */

static int blkid_parse_line(blkid_cache cache, blkid_dev *dev_p, char *cp)

{

  blkid_dev dev;

  int ret;

  if (!cache || !dev_p)

    return -BLKID_ERR_PARAM;

  *dev_p = NULL;

  DBG(READ, ul_debug("line: %s", cp));

  if ((ret = parse_dev(cache, dev_p, &cp)) <= 0)

    return ret;

  dev = *dev_p;

  while ((ret = parse_tag(cache, dev, &cp)) > 0) {

    ;

  }

  if (dev->bid_type == NULL) {

    DBG(READ, ul_debug("blkid: device %s has no TYPE",dev->bid_name));

    blkid_free_dev(dev);

    goto done;

  }

done:

  return ret;

}

/*

 * Parse the specified filename, and return the data in the supplied or

 * a newly allocated cache struct.  If the file doesn't exist, return a

 * new empty cache struct.

 */

void blkid_read_cache(blkid_cache cache)

{

  FILE *file;

  char buf[4096];

  int fd, lineno = 0;

  struct stat st;

  /*

   * If the file doesn't exist, then we just return an empty

   * struct so that the cache can be populated.

   */

  if ((fd = open(cache->bic_filename, O_RDONLY|O_CLOEXEC)) < 0)

    return;

  if (fstat(fd, &st) < 0)

    goto errout;

  if ((st.st_mtime == cache->bic_ftime) ||

      (cache->bic_flags & BLKID_BIC_FL_CHANGED)) {

    DBG(CACHE, ul_debug("skipping re-read of %s",

          cache->bic_filename));

    goto errout;

  }

  DBG(CACHE, ul_debug("reading cache file %s",

        cache->bic_filename));

  file = fdopen(fd, "r" UL_CLOEXECSTR);

  if (!file)

    goto errout;

  while (fgets(buf, sizeof(buf), file)) {

    blkid_dev dev;

    unsigned int end;

    lineno++;

    if (buf[0] == 0)

      continue;

    end = strlen(buf) - 1;

    /* Continue reading next line if it ends with a backslash */

    while (end < (sizeof(buf) - 2) && buf[end] == '\\' &&

           fgets(buf + end, sizeof(buf) - end, file)) {

      end = strlen(buf) - 1;

      lineno++;

    }

    if (blkid_parse_line(cache, &dev, buf) < 0) {

      DBG(READ, ul_debug("blkid: bad format on line %d", lineno));

      continue;

    }

  }

  fclose(file);

  /*

   * Initially we do not need to write out the cache file.

   */

  cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;

  cache->bic_ftime = st.st_mtime;

  return;

errout:

  close(fd);

}

#ifdef TEST_PROGRAM

int main(int argc, char**argv)

{

  blkid_cache cache = NULL;

  int ret;

  blkid_init_debug(BLKID_DEBUG_ALL);

  if (argc > 2) {

    fprintf(stderr, "Usage: %s [filename]\n"

      "Test parsing of the cache (filename)\n", argv[0]);

    exit(1);

  }

  if ((ret = blkid_get_cache(&cache, argv[1])) < 0)

    fprintf(stderr, "error %d reading cache file %s\n", ret,

      argv[1] ? argv[1] : blkid_get_cache_filename(NULL));

  blkid_put_cache(cache);

  return ret;

}

#endif