fish-shell/common.c

/** \file common.c
	
Various functions, mostly string utilities, that are used by most
parts of fish.
*/
#include <stdlib.h>
#include <termios.h>
#include <wchar.h>
#include <string.h>
#include <stdio.h>
#include <dirent.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <wctype.h>
#include <errno.h>
#include <limits.h>
#include <stdarg.h>		
#include <signal.h>		
#include <locale.h>
#include <time.h>
#include <sys/time.h>
#include <fcntl.h>

#if HAVE_NCURSES_H
#include <ncurses.h>
#else
#include <curses.h>
#endif

#if HAVE_TERMIO_H
#include <termio.h>
#endif

#include <term.h>


#include "config.h"
#include "util.h"
#include "wutil.h"
#include "common.h"
#include "expand.h"
#include "proc.h"
#include "wildcard.h"
#include "parser.h"

/**
   Error message to show on string convertion error
*/
#define STR2WCS_MSG "fish: Invalid multibyte sequence \'"

/**
   The maximum number of minor errors to report. Further errors will be omitted.
*/
#define ERROR_MAX_COUNT 1

/**
   The number of microseconds to wait between polls when attempting to acquire 
   a lockfile
*/
#define LOCKPOLLINTERVAL 10

struct termios shell_modes;      

/**
   Number of error encountered. This is reset after each command, and
   used to limit the number of error messages on commands with many
   string convertion problems.
*/
static int error_count=0;

int error_max=1;

wchar_t ellipsis_char;

static int c1=0, c2=0, c3=0, c4=0, c5;

char *profile=0;

wchar_t *program_name;

int debug_level=1;


static int block_count=0;

void common_destroy()
{
	debug( 3, L"Calls: wcsdupcat %d, wcsdupcat2 %d, wcsndup %d, str2wcs %d, wcs2str %d", c1, c2, c3, c4, c5 );
}



wchar_t **list_to_char_arr( array_list_t *l )
{
	wchar_t ** res = malloc( sizeof(wchar_t *)*(al_get_count( l )+1) );
	int i;
	if( res == 0 )
	{
		die_mem();
	}
	for( i=0; i<al_get_count( l ); i++ )
		res[i] = (wchar_t *)al_get(l,i);
	res[i]='\0';
	return res;	
}

void block()
{
	block_count++;
	if( block_count == 1 )
	{
		sigset_t chldset; 
		sigemptyset( &chldset );
		sigaddset( &chldset, SIGCHLD );
		sigprocmask(SIG_BLOCK, &chldset, 0);
	}
}


void unblock()
{
	block_count--;
	if( block_count == 0 )
	{
		sigset_t chldset; 
		sigemptyset( &chldset );
		sigaddset( &chldset, SIGCHLD );
		sigprocmask(SIG_UNBLOCK, &chldset, 0);
	}
}



int fgetws2( wchar_t **b, int *len, FILE *f )
{
	int i=0;
	wint_t c;
	
	wchar_t *buff = *b;

	/*
	  This is a kludge: We block SIGCHLD while reading, since I can't
	  get getwc to perform reliably when signals are flying. Even when
	  watching for EINTR errors, bytes are lost. 
	*/

	block();

	while( 1 )
	{
		/* Reallocate the buffer if necessary */
		if( i+1 >= *len )
		{
			int new_len = maxi( 128, (*len)*2);
			buff = realloc( buff, sizeof(wchar_t)*new_len );
			if( buff == 0 )
			{
				die_mem();
			}
			else
			{
				*len = new_len;
				*b = buff;
			}			
		}
		
		errno=0;		
		
		c = getwc( f );
		
		if( errno == EILSEQ )
		{

			getc( f );
			continue;
		}
	
//fwprintf( stderr, L"b\n" );
		
		switch( c )
		{
			/* End of line */ 
			case WEOF:
			case L'\n':
			case L'\0':
				buff[i]=L'\0';
				unblock();

				return i;				
				/* Ignore carriage returns */
			case L'\r':
				break;
				
			default:
				buff[i++]=c;
				break;
		}		


	}
	unblock();

}


/**
   Wrapper for wcsfilecmp
*/
static int completion_cmp( const void *a, const void *b )
{
	wchar_t *c= *((wchar_t **)a);
	wchar_t *d= *((wchar_t **)b);
	return wcsfilecmp( c, d );
}

void sort_list( array_list_t *comp )
{
	qsort( comp->arr, 
		   al_get_count( comp ),
		   sizeof( void*),
		   &completion_cmp );
}

wchar_t *str2wcs( const char *in )
{
	c4++;
	
	wchar_t *res;
	
	res = malloc( sizeof(wchar_t)*(strlen(in)+1) );
	
	if( !res )
	{
		die_mem();
		
	}
	
	if( (size_t)-1 == mbstowcs( res, in, sizeof(wchar_t)*(strlen(in)) +1) )
	{
		error_count++;
		if( error_count <=error_max )
		{
			fflush( stderr );			
			write( 2,
				   STR2WCS_MSG,
				   strlen(STR2WCS_MSG) );
			write( 2,
				   in,
				   strlen(in ));
			write( 2, 
				   "\'\n",
				   2 );
		}
		
		free(res);
		return 0;
	}	
	
	return res;
	
}

void error_reset()
{
	error_count=0;
}

char *wcs2str( const wchar_t *in )
{
	c5++;
	
	char *res = malloc( MAX_UTF8_BYTES*wcslen(in)+1 );
	if( res == 0 )
	{
		die_mem();
	}

	wcstombs( res, 
			  in,
			  MAX_UTF8_BYTES*wcslen(in)+1 );

	res = realloc( res, strlen( res )+1 );

	return res;
}

char **wcsv2strv( const wchar_t **in )
{
	int count =0;
	int i;

	while( in[count] != 0 )
		count++;
	char **res = malloc( sizeof( char *)*(count+1));
	if( res == 0 )
	{
		die_mem();
		
	}

	for( i=0; i<count; i++ )
	{
		res[i]=wcs2str(in[i]);
	}
	res[count]=0;
	return res;

}

wchar_t *wcsdupcat( const wchar_t *a, const wchar_t *b )
{
	c1++;
	
	return wcsdupcat2( a, b, 0 );
}

wchar_t *wcsdupcat2( const wchar_t *a, ... )
{
	c2++;
	
	int len=wcslen(a);
	int pos;
	va_list va, va2;
	wchar_t *arg;

	va_start( va, a );
	va_copy( va2, va );
	while( (arg=va_arg(va, wchar_t *) )!= 0 ) 
	{
		len += wcslen( arg );
	}
	va_end( va );

	wchar_t *res = malloc( sizeof(wchar_t)*(len +1 ));
	if( res == 0 )
		return 0;

	wcscpy( res, a );
	pos = wcslen(a);
	while( (arg=va_arg(va2, wchar_t *) )!= 0 ) 
	{
		wcscpy( res+pos, arg );
		pos += wcslen(arg);
	}
	va_end( va2 );
	return res;	

}


wchar_t **strv2wcsv( const char **in )
{
	int count =0;
	int i;

	while( in[count] != 0 )
		count++;
	wchar_t **res = malloc( sizeof( wchar_t *)*(count+1));
	if( res == 0 )
	{
		die_mem();
	}

	for( i=0; i<count; i++ )
	{
		res[i]=str2wcs(in[i]);
	}
	res[count]=0;
	return res;

}



wchar_t *wcsndup( const wchar_t *in, int c )
{
	c3++;
	
	wchar_t *res = malloc( sizeof(wchar_t)*(c+1) );
	if( res == 0 )
	{
		die_mem();
	}
	wcsncpy( res, in, c );
	res[c] = L'\0';	
	return res;	
}

long convert_digit( wchar_t d, int base )
{
	long res=-1;
	if( (d <= L'9') && (d >= L'0') )
	{
		res = d - L'0';
	}
	else if( (d <= L'z') && (d >= L'a') )
	{
		res = d + 10 - L'a';		
	}
	else if( (d <= L'Z') && (d >= L'A') )
	{
		res = d + 10 - L'A';		
	}
	if( res >= base )
	{
		res = -1;
	}
	
	return res;
}


long wcstol(const wchar_t *nptr, 
			wchar_t **endptr,
			int base)
{
	long long res=0;
	int is_set=0;
	if( base > 36 )
	{
		errno = EINVAL;
		return 0;
	}

	while( 1 )
	{
		long nxt = convert_digit( *nptr, base );
		if( endptr != 0 )
			*endptr = (wchar_t *)nptr;
		if( nxt < 0 )
		{
			if( !is_set )
			{
				errno = EINVAL;
			}
			return res;			
		}
		res = (res*base)+nxt;
		is_set = 1;
		if( res > LONG_MAX )
		{
			errno = ERANGE;
			return LONG_MAX;
		}
		if( res < LONG_MIN )
		{
			errno = ERANGE;
			return LONG_MIN;
		}
		nptr++;
	}
}

/*$OpenBSD: strlcat.c,v 1.11 2003/06/17 21:56:24 millert Exp $*/

/*
 * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/**
   Appends src to string dst of size siz (unlike wcsncat, siz is the
   full size of dst, not space left).  At most siz-1 characters will be
   copied.  Always NUL terminates (unless siz <= wcslen(dst)).  Returns
   wcslen(src) + MIN(siz, wcslen(initial dst)).  If retval >= siz,
   truncation occurred.

   This is the OpenBSD strlcat function, modified for wide characters,
   and renamed to reflect this change.

*/
size_t
wcslcat(wchar_t *dst, const wchar_t *src, size_t siz)
{
	
	register wchar_t *d = dst;
	register const wchar_t *s = src;
	register size_t n = siz;	
	size_t dlen;

	/* Find the end of dst and adjust bytes left but don't go past end */
	while (n-- != 0 && *d != '\0')
		d++;
	
	dlen = d - dst;
	n = siz - dlen;	

	if (n == 0)
		return(dlen + wcslen(s));

	while (*s != '\0') 
	{
		if (n != 1) 
		{
			*d++ = *s;
			n--;
		}
		s++;
	}
	*d = '\0';

	return(dlen + (s - src));
	/* count does not include NUL */
}

/*$OpenBSD: strlcpy.c,v 1.8 2003/06/17 21:56:24 millert Exp $*/

/*
 * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/**
   Copy src to string dst of size siz.  At most siz-1 characters will
   be copied.  Always NUL terminates (unless siz == 0).  Returns
   wcslen(src); if retval >= siz, truncation occurred.

   This is the OpenBSD strlcpy function, modified for wide characters,
   and renamed to reflect this change. 
*/
size_t
wcslcpy(wchar_t *dst, const wchar_t *src, size_t siz)
{
	register wchar_t *d = dst;
	register const wchar_t *s = src;
	register size_t n = siz;
	
	/* Copy as many bytes as will fit */
	if (n != 0 && --n != 0) 
	{		
		do 
		{			
			if ((*d++ = *s++) == 0)
				break;
		}
		while (--n != 0);
	}

	/* Not enough room in dst, add NUL and traverse rest of src */
	if (n == 0) 
	{		
		if (siz != 0)
			*d = '\0';
		/* NUL-terminate dst */
		while (*s++)
			;
	}
	return(s - src - 1);
	/* count does not include NUL */
}

wchar_t *wcsdup( const wchar_t *in )
{
	wchar_t *out = malloc( sizeof( wchar_t)*(wcslen(in)+1));
	if( out == 0 )
	{
		die_mem();
		
	}
	wcscpy( out, in );
	return out;
	
}

int wcscasecmp( const wchar_t *a, const wchar_t *b )
{
	if( *a == 0 )
	{
		return (*b==0)?0:-1;
	}
	else if( *b == 0 )
	{
		return 1;
	}
	int diff = towlower(*a)-towlower(*b);
	if( diff != 0 )
		return diff;
	else
		return wcscasecmp( a+1,b+1);
}

int wcsvarname( wchar_t *str )
{
	while( *str )
	{
		if( (!iswalnum(*str)) && (*str != L'_' ) )
		{
			return 0;
		}
		str++;
	}
	return 1;
	
	
}

#if !HAVE_WCWIDTH
/**
   Return the number of columns used by a character. 

   In locales without a native wcwidth, Unicode is probably so broken
   that it isn't worth trying to implement a real wcwidth. This
   wcwidth assumes any printing character takes up one column.
*/
int wcwidth( wchar_t c )
{
	if( c < 32 )
		return 0;
	if ( c == 127 )
		return 0;
	return 1;
}
#endif

/** 
	The glibc version of wcswidth seems to hang on some strings. fish uses this replacement.
*/
int my_wcswidth( const wchar_t *c )
{
	int res=0;
	while( *c )
	{
		int w = wcwidth( *c++ );
		if( w < 0 )
			w = 1;
		if( w > 2 )
			w=1;
		
		res += w;		
	}
	return res;
}

wchar_t *quote_end( const wchar_t *in )
{
	int level=1;
	int offset = (*in != L'\"');

	in++;
	
	while(1)
	{
/*		fwprintf( stderr, L"Check %c\n", *tok->buff );*/
		switch( *in )
		{
			case L'\\':
				in++;
				if( *in == L'\0' )
				{
					return 0;
				}
				break;
			case L'\"':
			case L'\'':
				if( (((level+offset) % 2)?L'\"':L'\'') == *in )
				{
					level--;
				}
				else
				{
					level++;
				}
				
				break;
		}
		if( (*in == L'\0') ||(level==0))
			break;
		
		in++;
	}
	return level?0:(wchar_t *)in;
	
}


void fish_setlocale(int category, const wchar_t *locale)
{
	char *lang = wcs2str( locale );
	setlocale(category,lang);
	free( lang );
	/*
	  Use ellipsis if on known unicode system, otherwise use $
	*/
	if( wcslen( locale ) )
	{
		ellipsis_char = wcsstr( locale, L".UTF")?L'\u2026':L'$';	
	}
	else
	{
		char *lang = getenv( "LANG" );
		if( lang )
			ellipsis_char = strstr( lang, ".UTF")?L'\u2026':L'$';	
		else
			ellipsis_char = L'$';
	}
}

int contains_str( const wchar_t *a, ... )
{
	wchar_t *arg;
	va_list va;
	int res = 0;
	
	va_start( va, a );
	while( (arg=va_arg(va, wchar_t *) )!= 0 ) 
	{
		if( wcscmp( a,arg) == 0 )
		{
			res=1;
			break;
		}
		
	}
	va_end( va );
	return res;	
}

int read_blocked(int fd, void *buf, size_t count)
{
	int res;	
	sigset_t chldset, oldset; 

	sigemptyset( &chldset );
	sigaddset( &chldset, SIGCHLD );
	sigprocmask(SIG_BLOCK, &chldset, &oldset);
	res = read( fd, buf, count );
	sigprocmask( SIG_SETMASK, &oldset, 0 );
	return res;	
}

int writeb( tputs_arg_t b )
{
	write( 1, &b, 1 );
//	putc( b, stdout );
	return 0;
}

void die_mem()
{
	/*
	  int *foo=0;	
	  *foo = 6;
	  */	
	debug( 0, L"Out of memory, shutting down fish." );
	exit(1);
}

void debug( int level, wchar_t *msg, ... )
{
	va_list va;

	if( level > debug_level )
		return;

	va_start( va, msg );
	
	fwprintf( stderr, L"%ls: ", program_name );
	vfwprintf( stderr, msg, va );
	va_end( va );	
	fwprintf( stderr, L"\n" );
}

wchar_t *escape( wchar_t *in, 
				 int escape_all )
{
	wchar_t *killme=in;	
	wchar_t *out = malloc( sizeof(wchar_t)*(wcslen(in)*4 + 1));
	if( out != 0 )
	{
		wchar_t *pos=out;
		while( *in != 0 )
		{
			switch( *in )
			{
				case L'\t':
					*(pos++) = L'\\';
					*(pos++) = L't';					
					break;
					
				case L'\n':
					*(pos++) = L'\\';
					*(pos++) = L'n';					
					break;
					
				case L'\b':
					*(pos++) = L'\\';
					*(pos++) = L'b';					
					break;
					
				case L'\r':
					*(pos++) = L'\\';
					*(pos++) = L'r';					
					break;
					
				case L'\e':
					*(pos++) = L'\\';
					*(pos++) = L'e';					
					break;
					
				case L'\\':
				case L'&':
				case L'$':
				case L' ':
				case L'#':
				case L'^':
				case L'<':
				case L'>':
				case L'@':
				case L'(':
				case L')':
				case L'{':
				case L'}':
				case L'?':
				case L'*':
				case L'|':
				case L';':
				case L':':
				case L'\'':
				case L'\"':
					if( escape_all )
						*pos++ = L'\\';
					*pos++ = *in;
					break;
					
				default:
					if( *in < 32 )
					{
						int tmp = (*in)%16;
						*pos++ = L'\\';
						*pos++ = L'x';
						*pos++ = ((*in>15)? L'1' : L'0');
						*pos++ = tmp > 9? L'a'+(tmp-10):L'0'+tmp;
					}
					else
						*pos++ = *in;
					break;
			}
			in++;
		}
		*pos = 0;
		free(killme);		
	}

	return out;
}


wchar_t *unescape( wchar_t * in, int escape_special )
{
	int in_pos, out_pos, len = wcslen( in );
	int c;
	int bracket_count=0;
	wchar_t prev=0;	

	for( in_pos=0, out_pos=0; in_pos<len; prev=in[out_pos], out_pos++, in_pos++ )
	{
		c = in[in_pos];
		if( c == L'\\' )
		{
			switch( in[++in_pos] )
			{
				case L'\0':
					error( SYNTAX_ERROR, L"Unexpected end of string", -1 );
					return in;
					
					break;

				case L'n':
					in[out_pos]=L'\n';
					break;

				case L'r':
					in[out_pos]=L'\r';
					break;

				case L't':
					in[out_pos]=L'\t';
					break;

				case L'b':
					in[out_pos]=L'\b';
					break;

				case L'e':
					in[out_pos]=L'\e';
					break;

				case L'u':
				case L'U':
				case L'x':
				case L'o':
				{
					int i;
					wchar_t res=0;
					int chars=2;
					int base=16;
					
					switch( in[in_pos] )
					{
						case L'u':
							base=16;
							chars=4;
							break;
							
						case L'U':
							base=16;
							chars=8;
							break;
							
						case L'x':
							base=16;
							chars=2;
							break;
							
						case L'o':
							base=8;
							chars=3;
							break;
							
					}
					
					for( i=0; i<chars; i++ )
					{
						int d = convert_digit( in[++in_pos],base);
						if( d < 0 )
						{
							in_pos--;
							break;
						}
						
						res=(res*base)|d;
						
					}
					
					in[out_pos] = res;
					
					break;
				}

				default:
					in[out_pos]=in[in_pos];
					break;
			}
		}
		else 
		{
			switch( in[in_pos]){
				case L'~':
					if( escape_special && (in_pos == 0) )
						in[out_pos]=HOME_DIRECTORY;
					else
						in[out_pos] = L'~';
					break;
				case L'%':
					if( escape_special && (in_pos == 0) )
						in[out_pos]=PROCESS_EXPAND;
					else
						in[out_pos]=in[in_pos];						
					break;
				case L'*':
					if( escape_special )
					{
						if( out_pos > 0 && in[out_pos-1]==ANY_STRING )
						{
							out_pos--;
							in[out_pos] = ANY_STRING_RECURSIVE;
						}
						else
							in[out_pos]=ANY_STRING;
					}
					else
						in[out_pos]=in[in_pos];						
					break;
				case L'?':
					if( escape_special )
						in[out_pos]=ANY_CHAR;
					else
						in[out_pos]=in[in_pos];						
					break;					
				case L'$':
					if( escape_special )
						in[out_pos]=VARIABLE_EXPAND;
					else
						in[out_pos]=in[in_pos];											
					break;					
				case L'{':
					if( escape_special )
					{
						bracket_count++;
						in[out_pos]=BRACKET_BEGIN;
					}
					else
						in[out_pos]=in[in_pos];						
					break;					
				case L'}':
					if( escape_special )
					{
						bracket_count--;
						in[out_pos]=BRACKET_END;
					}
					else
						in[out_pos]=in[in_pos];						
					break;					

				case L',':
					if( escape_special && bracket_count && prev!=BRACKET_SEP)
					{
						in[out_pos]=BRACKET_SEP;
					}
					else
						in[out_pos]=in[in_pos];						
					break;					

				case L'\'':
				case L'\"':
				{
					wchar_t *end = quote_end( &in[in_pos] );
					int len;
					
					if( end == 0 )
					{
						error( SYNTAX_ERROR, L"Unexpected end of string", -1 );
						return in;
					}
					
					len = end- &in[in_pos]-1;					

					if( escape_special)
						in[out_pos++]=INTERNAL_SEPARATOR;

					memmove( &in[out_pos], &in[in_pos+1], sizeof(wchar_t)*(len) );
					in_pos += len+1;
					out_pos += len-1;

					if( escape_special)
						in[++out_pos]=INTERNAL_SEPARATOR;

					break;
				}
				default:
					in[out_pos] = in[in_pos];
					break;
			}
		}		
	}
	in[out_pos]=L'\0';
	return in;	
}

/**
   Convert a pid_t to a decimal string representation.
   The str parameter must contain sufficient space.
   The conservatively approximate maximum number of characters a pid_t will 
   represent is given by: (int)(3.1 * sizeof(pid_t) + CHAR_BIT + 1)
   Returns the length of the string
*/
static int pidtostr( pid_t pid, char *str )
{
	int len, i = 0;
	int dig;

	/* Store digits in reverse order into string */
	while( pid != 0 )
	{
		dig = pid % 10;
		str[i] = '0' + dig;
		pid = ( pid - dig ) / 10;
		i++;
	}
	len = i;
	/* Reverse digits */
	i /= 2;
	while( i )
	{
		i--;
		dig = str[i];
		str[i] = str[len -  1 - i];
		str[len - 1 - i] = dig;
	}
	return len;
}

/**
   Create a copy of str adding this process's decimalised pid
   The memory returned should be freed using free()
*/
static char *dup_str_with_pid( const char *str )
{
	int pidlen, len = strlen( str );
	/*
	   allocate enough extra space for max size of pid when converted to a 
	   string; 3.1 ~= log(10)2
	*/
	char *newstr = malloc( len + 1 + 
			(int)(3.1 * sizeof(pid_t) * CHAR_BIT + 1) );
	
	if ( newstr == NULL )
	{
		return newstr;
	}
	memcpy( newstr, str, len );
	pidlen = pidtostr( getpid(), newstr + len );
	newstr[len + pidlen] = '\0';
	return newstr;
}

/**
   Attempt to acquire a lock based on a lockfile, waiting LOCKPOLLINTERVAL 
   nanoseconds between polls and timing out after timeout seconds, 
   thereafter forcibly attempting to obtain the lock.
   Returns 1 on success, 0 on failure.
   A temporary file based on adding the pid to the lockfile name is used, so 
   be aware that such a file will be deleted if it already exists.
   To remove the lock the lockfile must be unlinked.
*/
int acquire_lock_file( const char *lockfile, const int timeout, int force )
{
	int fd, timed_out = 0;
	int ret = 0; /* early exit returns failure */
	struct timespec pollint;
	struct timeval start, end;
	double elapsed;
	struct stat statbuf;

	/*
	  (Re)create a unique file and check that it has one only link.
	  The check would be subject to a race if the filename were not unique.
	*/
	char *linkfile = dup_str_with_pid( lockfile );
	if( linkfile == NULL )
	{
		goto done;
	}
	(void)unlink( linkfile );
	if( ( fd = open( linkfile, O_CREAT|O_RDONLY ) ) == -1 )
	{
		goto done;
	}
	close( fd );
	if( stat( linkfile, &statbuf ) != 0 || statbuf.st_nlink != 1 )
	{
		goto done;
	}

	if( gettimeofday( &start, NULL ) != 0 )
	{
		goto done;
	}
	end = start;
	pollint.tv_sec = 0;
	pollint.tv_nsec = LOCKPOLLINTERVAL * 1000000;
	do 
	{
		/*
		  Try to create a hard link to the unique file from the 
		  lockfile.  This will only succeed if the lockfile does not 
		  already exist.  It is guaranteed to provide race-free 
		  semantics over NFS which the alternative of calling 
		  open(O_EXCL|O_CREAT) on the lockfile is not.  The lock 
		  succeeds if the call to link returns 0 or the link count on 
		  the unique file increases to 2.
		*/
		if( link( linkfile, lockfile ) == 0 ||
		    ( stat( linkfile, &statbuf ) == 0 && 
				statbuf.st_nlink == 2 ) )
		{
			/* Successful lock */
			ret = 1;
			break;
		}
		elapsed = end.tv_sec + end.tv_usec/1000000.0 - 
			( start.tv_sec + start.tv_usec/1000000.0 );
		/* 
		  The check for elapsed < 0 is to deal with the unlikely event 
		  that after the loop is entered the system time is set forward
		  past the loop's end time.  This would otherwise result in a 
		  (practically) infinite loop.
		*/
		if( timed_out || elapsed >= timeout || elapsed < 0 )
		{
			if ( timed_out == 0 && force )
			{
				/*
				  Timed out and force was specified - attempt to
				  remove stale lock and try a final time
				*/
				(void)unlink( lockfile );
				timed_out = 1;
				continue;
			}
			else
			{
				/*
				  Timed out and final try was unsuccessful or 
				  force was not specified
				*/
				break;
			}
		}
		nanosleep( &pollint, NULL );
	} while( gettimeofday( &end, NULL ) == 0 );
done:
	/* The linkfile is not needed once the lockfile has been created */
	(void)unlink( linkfile );
	free( linkfile );
	return ret;
}