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read.c

/*
 * 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>
#if HAVE_ERRNO_H
#include <errno.h>
#endif

#include "blkidP.h"
#include "uuid/uuid.h"

#ifdef HAVE_STRTOULL
#define __USE_ISOC9X
#define STRTOULL strtoull /* defined in stdlib.h if you try hard enough */
#else
/* FIXME: need to support real strtoull here */
#define STRTOULL strtoul
#endif

#if HAVE_STDLIB_H
#include <stdlib.h>
#endif

#ifdef TEST_PROGRAM
#define blkid_debug_dump_dev(dev)   (debug_dump_dev(dev))
static void debug_dump_dev(blkid_dev dev);
#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="time">     (ascii time_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(DEBUG_READ, printf("found device header: %8s\n", 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(DEBUG_READ, printf("found device trailer %9s\n", *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(DEBUG_READ,
                printf("blkid: short line parsing dev: %s\n", *cp));
            return -BLKID_ERR_CACHE;
      }
      start = skip_over_blank(start + 1);
      end = skip_over_word(start);

      DBG(DEBUG_READ, printf("device should be %*s\n",
                         (int)(end - start), start));

      if (**cp == '>')
            *cp = end;
      else
            (*cp)++;

      *tmp = '\0';

      if (!(tmp = strrchr(end, '<')) || parse_end(&tmp) < 0) {
            DBG(DEBUG_READ,
                printf("blkid: missing </device> ending: %s\n", end));
      } else if (tmp)
            *tmp = '\0';

      if (end - start <= 1) {
            DBG(DEBUG_READ, printf("blkid: empty device name: %s\n", *cp));
            return -BLKID_ERR_CACHE;
      }

      name = blkid_strndup(start, end-start);
      if (name == NULL)
            return -BLKID_ERR_MEM;

      DBG(DEBUG_READ, printf("found dev %s\n", 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 == '"') {
            end = strchr(*value + 1, '"');
            if (!end) {
                  DBG(DEBUG_READ,
                      printf("unbalanced quotes at: %s\n", *value));
                  *cp = *value;
                  return -BLKID_ERR_CACHE;
            }
            (*value)++;
            *end = '\0';
            end++;
      } else {
            end = skip_over_word(*value);
            if (*end) {
                  *end = '\0';
                  end++;
            }
      }
      *cp = end;

      return 1;
}

/*
 * Extract a tag of the form <NAME>value</NAME> from the line.
 */
/*
static int parse_xml(char **name, char **value, char **cp)
{
      char *end;

      if (!name || !value || !cp)
            return -BLKID_ERR_PARAM;

      *name = strip_line(*cp);

      if ((*name)[0] != '<' || (*name)[1] == '/')
            return 0;

      FIXME: finish this.
}
*/

/*
 * 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;
      char *value;
      int ret;

      if (!cache || !dev)
            return -BLKID_ERR_PARAM;

      if ((ret = parse_token(&name, &value, cp)) <= 0 /* &&
          (ret = parse_xml(&name, &value, cp)) <= 0 */)
            return ret;

      /* Some tags are stored directly in the device struct */
      if (!strcmp(name, "DEVNO")) 
            dev->bid_devno = STRTOULL(value, 0, 0);
      else if (!strcmp(name, "PRI"))
            dev->bid_pri = strtol(value, 0, 0);
      else if (!strcmp(name, "TIME"))
            /* FIXME: need to parse a long long eventually */
            dev->bid_time = strtol(value, 0, 0);
      else
            ret = blkid_set_tag(dev, name, value, strlen(value));

      DBG(DEBUG_READ, printf("    tag: %s=\"%s\"\n", name, 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(DEBUG_READ, printf("line: %s\n", 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(DEBUG_READ,
                printf("blkid: device %s has no TYPE\n",dev->bid_name));
            blkid_free_dev(dev);
      }

      DBG(DEBUG_READ, blkid_debug_dump_dev(dev));

      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 (!cache)
            return;

      /*
       * 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)) < 0)
            return;
      if (fstat(fd, &st) < 0)
            goto errout;
      if ((st.st_mtime == cache->bic_ftime) ||
          (cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
            DBG(DEBUG_CACHE, printf("skipping re-read of %s\n",
                              cache->bic_filename));
            goto errout;
      }
      
      DBG(DEBUG_CACHE, printf("reading cache file %s\n",
                        cache->bic_filename));

      file = fdopen(fd, "r");
      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 (buf[end] == '\\' && end < sizeof(buf) - 2 &&
                   fgets(buf + end, sizeof(buf) - end, file)) {
                  end = strlen(buf) - 1;
                  lineno++;
            }

            if (blkid_parse_line(cache, &dev, buf) < 0) {
                  DBG(DEBUG_READ,
                      printf("blkid: bad format on line %d\n", 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);
      return;
}

#ifdef TEST_PROGRAM
static void debug_dump_dev(blkid_dev dev)
{
      struct list_head *p;

      if (!dev) {
            printf("  dev: NULL\n");
            return;
      }

      printf("  dev: name = %s\n", dev->bid_name);
      printf("  dev: DEVNO=\"0x%0llx\"\n", (long long)dev->bid_devno);
      printf("  dev: TIME=\"%lld\"\n", (long long)dev->bid_time);
      printf("  dev: PRI=\"%d\"\n", dev->bid_pri);
      printf("  dev: flags = 0x%08X\n", dev->bid_flags);

      list_for_each(p, &dev->bid_tags) {
            blkid_tag tag = list_entry(p, struct blkid_struct_tag, bit_tags);
            if (tag)
                  printf("    tag: %s=\"%s\"\n", tag->bit_name, 
                         tag->bit_val);
            else
                  printf("    tag: NULL\n");
      }
      printf("\n");
}

int main(int argc, char**argv)
{
      blkid_cache cache = NULL;
      int ret;

      blkid_debug_mask = 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_CACHE_FILE);

      blkid_put_cache(cache);

      return ret;
}
#endif

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