source: MondoRescue/branches/stable/mindi-busybox/e2fsprogs/blkid/read.c@ 1014

/*
 * 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>
#include <errno.h>

#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

#include <stdlib.h>

#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", 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)))
        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", dev->bid_devno);
    printf("  dev: TIME=\"%lu\"\n", 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