source: trunk/server/lib/util/util.c

/* 
   Unix SMB/CIFS implementation.
   Samba utility functions
   Copyright (C) Andrew Tridgell 1992-1998
   Copyright (C) Jeremy Allison 2001-2002
   Copyright (C) Simo Sorce 2001
   Copyright (C) Jim McDonough (jmcd@us.ibm.com)  2003.
   Copyright (C) James J Myers 2003
   
   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 3 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 "includes.h"
#include "system/network.h"
#include "system/filesys.h"
#include "system/locale.h"
#include "system/shmem.h"

#undef malloc
#undef strcasecmp
#undef strncasecmp
#undef strdup
#undef realloc

#if defined(UID_WRAPPER)
#if !defined(UID_WRAPPER_REPLACE) && !defined(UID_WRAPPER_NOT_REPLACE)
#define UID_WRAPPER_REPLACE
#include "../uid_wrapper/uid_wrapper.h"
#endif
#else
#define uwrap_enabled() 0
#endif

/**
 * @file
 * @brief Misc utility functions
 */

/**
 Find a suitable temporary directory. The result should be copied immediately
 as it may be overwritten by a subsequent call.
**/
_PUBLIC_ const char *tmpdir(void)
{
        char *p;
        if ((p = getenv("TMPDIR")))
                return p;
        return "/tmp";
}


/**
 Check if a file exists - call vfs_file_exist for samba files.
**/
_PUBLIC_ bool file_exist(const char *fname)
{
        struct stat st;

        if (stat(fname, &st) != 0) {
                return false;
        }

        return ((S_ISREG(st.st_mode)) || (S_ISFIFO(st.st_mode)));
}

/**
 Check a files mod time.
**/

_PUBLIC_ time_t file_modtime(const char *fname)
{
        struct stat st;
  
        if (stat(fname,&st) != 0) 
                return(0);

        return(st.st_mtime);
}

/**
 Check if a directory exists.
**/

_PUBLIC_ bool directory_exist(const char *dname)
{
        struct stat st;
        bool ret;

        if (stat(dname,&st) != 0) {
                return false;
        }

        ret = S_ISDIR(st.st_mode);
        if(!ret)
                errno = ENOTDIR;
        return ret;
}

/**
 * Try to create the specified directory if it didn't exist.
 *
 * @retval true if the directory already existed and has the right permissions 
 * or was successfully created.
 */
_PUBLIC_ bool directory_create_or_exist(const char *dname, uid_t uid, 
                               mode_t dir_perms)
{
        mode_t old_umask;
        struct stat st;
      
        old_umask = umask(0);
        if (lstat(dname, &st) == -1) {
                if (errno == ENOENT) {
                        /* Create directory */
                        if (mkdir(dname, dir_perms) == -1) {
                                DEBUG(0, ("error creating directory "
                                          "%s: %s\n", dname, 
                                          strerror(errno)));
                                umask(old_umask);
                                return false;
                        }
                } else {
                        DEBUG(0, ("lstat failed on directory %s: %s\n",
                                  dname, strerror(errno)));
                        umask(old_umask);
                        return false;
                }
        } else {
                /* Check ownership and permission on existing directory */
                if (!S_ISDIR(st.st_mode)) {
                        DEBUG(0, ("directory %s isn't a directory\n",
                                dname));
                        umask(old_umask);
                        return false;
                }
                if (st.st_uid != uid && !uwrap_enabled()) {
                        DEBUG(0, ("invalid ownership on directory "
                                  "%s\n", dname));
                        umask(old_umask);
                        return false;
                }
                if ((st.st_mode & 0777) != dir_perms) {
                        DEBUG(0, ("invalid permissions on directory "
                                  "%s\n", dname));
                        umask(old_umask);
                        return false;
                }
        }
        return true;
}       


/**
 Sleep for a specified number of milliseconds.
**/

_PUBLIC_ void smb_msleep(unsigned int t)
{
#if defined(HAVE_NANOSLEEP)
        struct timespec ts;
        int ret;

        ts.tv_sec = t/1000;
        ts.tv_nsec = 1000000*(t%1000);

        do {
                errno = 0;
                ret = nanosleep(&ts, &ts);
        } while (ret < 0 && errno == EINTR && (ts.tv_sec > 0 || ts.tv_nsec > 0));
#else
        unsigned int tdiff=0;
        struct timeval tval,t1,t2;
        fd_set fds;

        GetTimeOfDay(&t1);
        t2 = t1;

        while (tdiff < t) {
                tval.tv_sec = (t-tdiff)/1000;
                tval.tv_usec = 1000*((t-tdiff)%1000);

                /* Never wait for more than 1 sec. */
                if (tval.tv_sec > 1) {
                        tval.tv_sec = 1;
                        tval.tv_usec = 0;
                }

                FD_ZERO(&fds);
                errno = 0;
                select(0,&fds,NULL,NULL,&tval);

                GetTimeOfDay(&t2);
                if (t2.tv_sec < t1.tv_sec) {
                        /* Someone adjusted time... */
                        t1 = t2;
                }

                tdiff = usec_time_diff(&t2,&t1)/1000;
        }
#endif
}

/**
 Get my own name, return in talloc'ed storage.
**/

_PUBLIC_ char *get_myname(TALLOC_CTX *ctx)
{
        char *p;
        char hostname[HOST_NAME_MAX];

        /* get my host name */
        if (gethostname(hostname, sizeof(hostname)) == -1) {
                DEBUG(0,("gethostname failed\n"));
                return NULL;
        }

        /* Ensure null termination. */
        hostname[sizeof(hostname)-1] = '\0';

        /* split off any parts after an initial . */
        p = strchr_m(hostname, '.');
        if (p) {
                *p = 0;
        }

        return talloc_strdup(ctx, hostname);
}

/**
 Check if a process exists. Does this work on all unixes?
**/

_PUBLIC_ bool process_exists_by_pid(pid_t pid)
{
        /* Doing kill with a non-positive pid causes messages to be
         * sent to places we don't want. */
        SMB_ASSERT(pid > 0);
        return(kill(pid,0) == 0 || errno != ESRCH);
}

/**
 Simple routine to do POSIX file locking. Cruft in NFS and 64->32 bit mapping
 is dealt with in posix.c
**/

_PUBLIC_ bool fcntl_lock(int fd, int op, off_t offset, off_t count, int type)
{
        struct flock lock;
        int ret;

        DEBUG(8,("fcntl_lock %d %d %.0f %.0f %d\n",fd,op,(double)offset,(double)count,type));

        lock.l_type = type;
        lock.l_whence = SEEK_SET;
        lock.l_start = offset;
        lock.l_len = count;
        lock.l_pid = 0;

        ret = fcntl(fd,op,&lock);

        if (ret == -1 && errno != 0)
                DEBUG(3,("fcntl_lock: fcntl lock gave errno %d (%s)\n",errno,strerror(errno)));

        /* a lock query */
        if (op == F_GETLK) {
                if ((ret != -1) &&
                                (lock.l_type != F_UNLCK) && 
                                (lock.l_pid != 0) && 
                                (lock.l_pid != getpid())) {
                        DEBUG(3,("fcntl_lock: fd %d is locked by pid %d\n",fd,(int)lock.l_pid));
                        return true;
                }

                /* it must be not locked or locked by me */
                return false;
        }

        /* a lock set or unset */
        if (ret == -1) {
                DEBUG(3,("fcntl_lock: lock failed at offset %.0f count %.0f op %d type %d (%s)\n",
                        (double)offset,(double)count,op,type,strerror(errno)));
                return false;
        }

        /* everything went OK */
        DEBUG(8,("fcntl_lock: Lock call successful\n"));

        return true;
}

static void debugadd_cb(const char *buf, void *private_data)
{
        int *plevel = (int *)private_data;
        DEBUGADD(*plevel, ("%s", buf));
}

void print_asc_cb(const uint8_t *buf, int len,
                  void (*cb)(const char *buf, void *private_data),
                  void *private_data)
{
        int i;
        char s[2];
        s[1] = 0;

        for (i=0; i<len; i++) {
                s[0] = isprint(buf[i]) ? buf[i] : '.';
                cb(s, private_data);
        }
}

void print_asc(int level, const uint8_t *buf,int len)
{
        print_asc_cb(buf, len, debugadd_cb, &level);
}

/**
 * Write dump of binary data to a callback
 */
void dump_data_cb(const uint8_t *buf, int len,
                  bool omit_zero_bytes,
                  void (*cb)(const char *buf, void *private_data),
                  void *private_data)
{
        int i=0;
        static const uint8_t empty[16] = { 0, };
        bool skipped = false;
        char tmp[16];

        if (len<=0) return;

        for (i=0;i<len;) {

                if (i%16 == 0) {
                        if ((omit_zero_bytes == true) &&
                            (i > 0) &&
                            (len > i+16) &&
                            (memcmp(&buf[i], &empty, 16) == 0))
                        {
                                i +=16;
                                continue;
                        }

                        if (i<len)  {
                                snprintf(tmp, sizeof(tmp), "[%04X] ", i);
                                cb(tmp, private_data);
                        }
                }

                snprintf(tmp, sizeof(tmp), "%02X ", (int)buf[i]);
                cb(tmp, private_data);
                i++;
                if (i%8 == 0) {
                        cb("  ", private_data);
                }
                if (i%16 == 0) {

                        print_asc_cb(&buf[i-16], 8, cb, private_data);
                        cb(" ", private_data);
                        print_asc_cb(&buf[i-8], 8, cb, private_data);
                        cb("\n", private_data);

                        if ((omit_zero_bytes == true) &&
                            (len > i+16) &&
                            (memcmp(&buf[i], &empty, 16) == 0)) {
                                if (!skipped) {
                                        cb("skipping zero buffer bytes\n",
                                           private_data);
                                        skipped = true;
                                }
                        }
                }
        }

        if (i%16) {
                int n;
                n = 16 - (i%16);
                cb(" ", private_data);
                if (n>8) {
                        cb(" ", private_data);
                }
                while (n--) {
                        cb("   ", private_data);
                }
                n = MIN(8,i%16);
                print_asc_cb(&buf[i-(i%16)], n, cb, private_data);
                cb(" ", private_data);
                n = (i%16) - n;
                if (n>0) {
                        print_asc_cb(&buf[i-n], n, cb, private_data);
                }
                cb("\n", private_data);
        }

}

/**
 * Write dump of binary data to the log file.
 *
 * The data is only written if the log level is at least level.
 */
_PUBLIC_ void dump_data(int level, const uint8_t *buf, int len)
{
        if (!DEBUGLVL(level)) {
                return;
        }
        dump_data_cb(buf, len, false, debugadd_cb, &level);
}

/**
 * Write dump of binary data to the log file.
 *
 * The data is only written if the log level is at least level.
 * 16 zero bytes in a row are omitted
 */
_PUBLIC_ void dump_data_skip_zeros(int level, const uint8_t *buf, int len)
{
        if (!DEBUGLVL(level)) {
                return;
        }
        dump_data_cb(buf, len, true, debugadd_cb, &level);
}


/**
 malloc that aborts with smb_panic on fail or zero size.
**/

_PUBLIC_ void *smb_xmalloc(size_t size)
{
        void *p;
        if (size == 0)
                smb_panic("smb_xmalloc: called with zero size.\n");
        if ((p = malloc(size)) == NULL)
                smb_panic("smb_xmalloc: malloc fail.\n");
        return p;
}

/**
 Memdup with smb_panic on fail.
**/

_PUBLIC_ void *smb_xmemdup(const void *p, size_t size)
{
        void *p2;
        p2 = smb_xmalloc(size);
        memcpy(p2, p, size);
        return p2;
}

/**
 strdup that aborts on malloc fail.
**/

char *smb_xstrdup(const char *s)
{
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strdup
#undef strdup
#endif
#endif

#ifndef HAVE_STRDUP
#define strdup rep_strdup
#endif

        char *s1 = strdup(s);
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strdup
#undef strdup
#endif
#define strdup(s) __ERROR_DONT_USE_STRDUP_DIRECTLY
#endif
        if (!s1) {
                smb_panic("smb_xstrdup: malloc failed");
        }
        return s1;

}

/**
 strndup that aborts on malloc fail.
**/

char *smb_xstrndup(const char *s, size_t n)
{
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strndup
#undef strndup
#endif
#endif

#if (defined(BROKEN_STRNDUP) || !defined(HAVE_STRNDUP))
#undef HAVE_STRNDUP
#define strndup rep_strndup
#endif

        char *s1 = strndup(s, n);
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef strndup
#undef strndup
#endif
#define strndup(s,n) __ERROR_DONT_USE_STRNDUP_DIRECTLY
#endif
        if (!s1) {
                smb_panic("smb_xstrndup: malloc failed");
        }
        return s1;
}



/**
 Like strdup but for memory.
**/

_PUBLIC_ void *memdup(const void *p, size_t size)
{
        void *p2;
        if (size == 0)
                return NULL;
        p2 = malloc(size);
        if (!p2)
                return NULL;
        memcpy(p2, p, size);
        return p2;
}

/**
 * Write a password to the log file.
 *
 * @note Only actually does something if DEBUG_PASSWORD was defined during 
 * compile-time.
 */
_PUBLIC_ void dump_data_pw(const char *msg, const uint8_t * data, size_t len)
{
#ifdef DEBUG_PASSWORD
        DEBUG(11, ("%s", msg));
        if (data != NULL && len > 0)
        {
                dump_data(11, data, len);
        }
#endif
}


/**
 * see if a range of memory is all zero. A NULL pointer is considered
 * to be all zero 
 */
_PUBLIC_ bool all_zero(const uint8_t *ptr, size_t size)
{
        int i;
        if (!ptr) return true;
        for (i=0;i<size;i++) {
                if (ptr[i]) return false;
        }
        return true;
}

/**
  realloc an array, checking for integer overflow in the array size
*/
_PUBLIC_ void *realloc_array(void *ptr, size_t el_size, unsigned count, bool free_on_fail)
{
#define MAX_MALLOC_SIZE 0x7fffffff
        if (count == 0 ||
            count >= MAX_MALLOC_SIZE/el_size) {
                if (free_on_fail)
                        SAFE_FREE(ptr);
                return NULL;
        }
        if (!ptr) {
                return malloc(el_size * count);
        }
        return realloc(ptr, el_size * count);
}

/****************************************************************************
 Type-safe malloc.
****************************************************************************/

void *malloc_array(size_t el_size, unsigned int count)
{
        return realloc_array(NULL, el_size, count, false);
}

/**
 Trim the specified elements off the front and back of a string.
**/
_PUBLIC_ bool trim_string(char *s, const char *front, const char *back)
{
        bool ret = false;
        size_t front_len;
        size_t back_len;
        size_t len;

        /* Ignore null or empty strings. */
        if (!s || (s[0] == '\0'))
                return false;

        front_len       = front? strlen(front) : 0;
        back_len        = back? strlen(back) : 0;

        len = strlen(s);

        if (front_len) {
                while (len && strncmp(s, front, front_len)==0) {
                        /* Must use memmove here as src & dest can
                         * easily overlap. Found by valgrind. JRA. */
                        memmove(s, s+front_len, (len-front_len)+1);
                        len -= front_len;
                        ret=true;
                }
        }
        
        if (back_len) {
                while ((len >= back_len) && strncmp(s+len-back_len,back,back_len)==0) {
                        s[len-back_len]='\0';
                        len -= back_len;
                        ret=true;
                }
        }
        return ret;
}

/**
 Find the number of 'c' chars in a string
**/
_PUBLIC_ _PURE_ size_t count_chars(const char *s, char c)
{
        size_t count = 0;

        while (*s) {
                if (*s == c) count++;
                s ++;
        }

        return count;
}

/**
 Routine to get hex characters and turn them into a 16 byte array.
 the array can be variable length, and any non-hex-numeric
 characters are skipped.  "0xnn" or "0Xnn" is specially catered
 for.

 valid examples: "0A5D15"; "0x15, 0x49, 0xa2"; "59\ta9\te3\n"


**/
_PUBLIC_ size_t strhex_to_str(char *p, size_t p_len, const char *strhex, size_t strhex_len)
{
        size_t i = 0;
        size_t num_chars = 0;
        uint8_t   lonybble, hinybble;
        const char     *hexchars = "0123456789ABCDEF";
        char           *p1 = NULL, *p2 = NULL;

        /* skip leading 0x prefix */
        if (strncasecmp(strhex, "0x", 2) == 0) {
                i += 2; /* skip two chars */
        }

        for (; i < strhex_len && strhex[i] != 0; i++) {
                if (!(p1 = strchr(hexchars, toupper((unsigned char)strhex[i]))))
                        break;

                i++; /* next hex digit */

                if (!(p2 = strchr(hexchars, toupper((unsigned char)strhex[i]))))
                        break;

                /* get the two nybbles */
                hinybble = PTR_DIFF(p1, hexchars);
                lonybble = PTR_DIFF(p2, hexchars);

                if (num_chars >= p_len) {
                        break;
                }

                p[num_chars] = (hinybble << 4) | lonybble;
                num_chars++;

                p1 = NULL;
                p2 = NULL;
        }
        return num_chars;
}

/** 
 * Parse a hex string and return a data blob. 
 */
_PUBLIC_ _PURE_ DATA_BLOB strhex_to_data_blob(TALLOC_CTX *mem_ctx, const char *strhex) 
{
        DATA_BLOB ret_blob = data_blob_talloc(mem_ctx, NULL, strlen(strhex)/2+1);

        ret_blob.length = strhex_to_str((char *)ret_blob.data, ret_blob.length,
                                        strhex,
                                        strlen(strhex));

        return ret_blob;
}


/**
 * Routine to print a buffer as HEX digits, into an allocated string.
 */
_PUBLIC_ void hex_encode(const unsigned char *buff_in, size_t len, char **out_hex_buffer)
{
        int i;
        char *hex_buffer;

        *out_hex_buffer = malloc_array_p(char, (len*2)+1);
        hex_buffer = *out_hex_buffer;

        for (i = 0; i < len; i++)
                slprintf(&hex_buffer[i*2], 3, "%02X", buff_in[i]);
}

/**
 * talloc version of hex_encode()
 */
_PUBLIC_ char *hex_encode_talloc(TALLOC_CTX *mem_ctx, const unsigned char *buff_in, size_t len)
{
        int i;
        char *hex_buffer;

        hex_buffer = talloc_array(mem_ctx, char, (len*2)+1);
        if (!hex_buffer) {
                return NULL;
        }

        for (i = 0; i < len; i++)
                slprintf(&hex_buffer[i*2], 3, "%02X", buff_in[i]);

        talloc_set_name_const(hex_buffer, hex_buffer);
        return hex_buffer;
}

/**
  varient of strcmp() that handles NULL ptrs
**/
_PUBLIC_ int strcmp_safe(const char *s1, const char *s2)
{
        if (s1 == s2) {
                return 0;
        }
        if (s1 == NULL || s2 == NULL) {
                return s1?-1:1;
        }
        return strcmp(s1, s2);
}


/**
return the number of bytes occupied by a buffer in ASCII format
the result includes the null termination
limited by 'n' bytes
**/
_PUBLIC_ size_t ascii_len_n(const char *src, size_t n)
{
        size_t len;

        len = strnlen(src, n);
        if (len+1 <= n) {
                len += 1;
        }

        return len;
}

/**
 Set a boolean variable from the text value stored in the passed string.
 Returns true in success, false if the passed string does not correctly 
 represent a boolean.
**/

_PUBLIC_ bool set_boolean(const char *boolean_string, bool *boolean)
{
        if (strwicmp(boolean_string, "yes") == 0 ||
            strwicmp(boolean_string, "true") == 0 ||
            strwicmp(boolean_string, "on") == 0 ||
            strwicmp(boolean_string, "1") == 0) {
                *boolean = true;
                return true;
        } else if (strwicmp(boolean_string, "no") == 0 ||
                   strwicmp(boolean_string, "false") == 0 ||
                   strwicmp(boolean_string, "off") == 0 ||
                   strwicmp(boolean_string, "0") == 0) {
                *boolean = false;
                return true;
        }
        return false;
}

/**
return the number of bytes occupied by a buffer in CH_UTF16 format
the result includes the null termination
**/
_PUBLIC_ size_t utf16_len(const void *buf)
{
        size_t len;

        for (len = 0; SVAL(buf,len); len += 2) ;

        return len + 2;
}

/**
return the number of bytes occupied by a buffer in CH_UTF16 format
the result includes the null termination
limited by 'n' bytes
**/
_PUBLIC_ size_t utf16_len_n(const void *src, size_t n)
{
        size_t len;

        for (len = 0; (len+2 < n) && SVAL(src, len); len += 2) ;

        if (len+2 <= n) {
                len += 2;
        }

        return len;
}

/**
 * @file
 * @brief String utilities.
 **/

static bool next_token_internal_talloc(TALLOC_CTX *ctx,
                                const char **ptr,
                                char **pp_buff,
                                const char *sep,
                                bool ltrim)
{
        const char *s;
        const char *saved_s;
        char *pbuf;
        bool quoted;
        size_t len=1;

        *pp_buff = NULL;
        if (!ptr) {
                return(false);
        }

        s = *ptr;

        /* default to simple separators */
        if (!sep) {
                sep = " \t\n\r";
        }

        /* find the first non sep char, if left-trimming is requested */
        if (ltrim) {
                while (*s && strchr_m(sep,*s)) {
                        s++;
                }
        }

        /* nothing left? */
        if (!*s) {
                return false;
        }

        /* When restarting we need to go from here. */
        saved_s = s;

        /* Work out the length needed. */
        for (quoted = false; *s &&
                        (quoted || !strchr_m(sep,*s)); s++) {
                if (*s == '\"') {
                        quoted = !quoted;
                } else {
                        len++;
                }
        }

        /* We started with len = 1 so we have space for the nul. */
        *pp_buff = talloc_array(ctx, char, len);
        if (!*pp_buff) {
                return false;
        }

        /* copy over the token */
        pbuf = *pp_buff;
        s = saved_s;
        for (quoted = false; *s &&
                        (quoted || !strchr_m(sep,*s)); s++) {
                if ( *s == '\"' ) {
                        quoted = !quoted;
                } else {
                        *pbuf++ = *s;
                }
        }

        *ptr = (*s) ? s+1 : s;
        *pbuf = 0;

        return true;
}

bool next_token_talloc(TALLOC_CTX *ctx,
                        const char **ptr,
                        char **pp_buff,
                        const char *sep)
{
        return next_token_internal_talloc(ctx, ptr, pp_buff, sep, true);
}

/*
 * Get the next token from a string, return false if none found.  Handles
 * double-quotes.  This version does not trim leading separator characters
 * before looking for a token.
 */

bool next_token_no_ltrim_talloc(TALLOC_CTX *ctx,
                        const char **ptr,
                        char **pp_buff,
                        const char *sep)
{
        return next_token_internal_talloc(ctx, ptr, pp_buff, sep, false);
}

/**
 * Get the next token from a string, return False if none found.
 * Handles double-quotes.
 *
 * Based on a routine by GJC@VILLAGE.COM.
 * Extensively modified by Andrew.Tridgell@anu.edu.au
 **/
_PUBLIC_ bool next_token(const char **ptr,char *buff, const char *sep, size_t bufsize)
{
        const char *s;
        bool quoted;
        size_t len=1;

        if (!ptr)
                return false;

        s = *ptr;

        /* default to simple separators */
        if (!sep)
                sep = " \t\n\r";

        /* find the first non sep char */
        while (*s && strchr_m(sep,*s))
                s++;

        /* nothing left? */
        if (!*s)
                return false;

        /* copy over the token */
        for (quoted = false; len < bufsize && *s && (quoted || !strchr_m(sep,*s)); s++) {
                if (*s == '\"') {
                        quoted = !quoted;
                } else {
                        len++;
                        *buff++ = *s;
                }
        }

        *ptr = (*s) ? s+1 : s;
        *buff = 0;

        return true;
}

struct anonymous_shared_header {
        union {
                size_t length;
                uint8_t pad[16];
        } u;
};

/* Map a shared memory buffer of at least nelem counters. */
void *anonymous_shared_allocate(size_t orig_bufsz)
{
        void *ptr;
        void *buf;
        size_t pagesz = getpagesize();
        size_t pagecnt;
        size_t bufsz = orig_bufsz;
        struct anonymous_shared_header *hdr;

        bufsz += sizeof(*hdr);

        /* round up to full pages */
        pagecnt = bufsz / pagesz;
        if (bufsz % pagesz) {
                pagecnt += 1;
        }
        bufsz = pagesz * pagecnt;

        if (orig_bufsz >= bufsz) {
                /* integer wrap */
                errno = ENOMEM;
                return NULL;
        }

#ifdef MAP_ANON
        /* BSD */
        buf = mmap(NULL, bufsz, PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED,
                        -1 /* fd */, 0 /* offset */);
#else
        buf = mmap(NULL, bufsz, PROT_READ|PROT_WRITE, MAP_FILE|MAP_SHARED,
                        open("/dev/zero", O_RDWR), 0 /* offset */);
#endif

        if (buf == MAP_FAILED) {
                return NULL;
        }

        hdr = (struct anonymous_shared_header *)buf;
        hdr->u.length = bufsz;

        ptr = (void *)(&hdr[1]);

        return ptr;
}

void anonymous_shared_free(void *ptr)
{
        struct anonymous_shared_header *hdr;

        if (ptr == NULL) {
                return;
        }

        hdr = (struct anonymous_shared_header *)ptr;

        hdr--;

        munmap(hdr, hdr->u.length);
}

#ifdef DEVELOPER
/* used when you want a debugger started at a particular point in the
   code. Mostly useful in code that runs as a child process, where
   normal gdb attach is harder to organise.
*/
void samba_start_debugger(void)
{
        char *cmd = NULL;
        if (asprintf(&cmd, "xterm -e \"gdb --pid %u\"&", getpid()) == -1) {
                return;
        }
        if (system(cmd) == -1) {
                free(cmd);
                return;
        }
        free(cmd);
        sleep(2);
}
#endif