Index: src/include/port.h
===================================================================
RCS file: /cvsroot/pgsql-server/src/include/port.h,v
retrieving revision 1.27
diff -c -c -r1.27 port.h
*** src/include/port.h	30 Apr 2004 17:52:07 -0000	1.27
--- src/include/port.h	4 May 2004 17:07:30 -0000
***************
*** 26,31 ****
--- 26,32 ----
  extern char *last_path_separator(const char *filename);
  extern void canonicalize_path(char *path);
  extern char *get_progname(char *argv0);
+ extern char *relative_path(const char *src, const char *dst, const char *target);
  
  /* Portable delay handling */
  extern void pg_usleep(long microsec);
Index: src/port/path.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/port/path.c,v
retrieving revision 1.5
diff -c -c -r1.5 path.c
*** src/port/path.c	9 Mar 2004 04:49:02 -0000	1.5
--- src/port/path.c	4 May 2004 17:07:31 -0000
***************
*** 13,21 ****
--- 13,31 ----
   *-------------------------------------------------------------------------
   */
  
+ #ifndef FRONTEND
+ #include "postgres.h"
+ #else
  #include "c.h"
+ #endif
  #include <ctype.h>
  
+ #ifndef WIN32
+ #define ISSEP(c)	((c) == '/')
+ #else
+ #define ISSEP(c)	((c) == '/' || (c) == '\\')
+ #endif
+ 
  /*
   *	is_absolute_path
   */
***************
*** 33,39 ****
  }
  
  
- 
  /*
   *	first_path_separator
   */
--- 43,48 ----
***************
*** 120,123 ****
--- 129,241 ----
  		return argv0;
  	else
  		return last_path_separator(argv0) + 1;
+ }
+ 
+ 
+ /*
+  *	relative_path
+  *
+  *	Determine the relative path for getting from 'src' to 'dst' and
+  *	map that change from 'target' to a new directory.
+  */
+ char *
+ relative_path(const char *src, const char *dst, const char *target)
+ {
+ 	const char *dst_slash = NULL;
+ 	char	*ret;
+ 	int		dirs_up;
+ 	
+ #ifdef WIN32
+ 	if (isalpha(*src) && src[1] == ':' &&
+ 		isalpha(*dst) && dst[1] == ':')
+ 	{
+ 		if (toupper(*src) != toupper(*src))
+ 			return NULL;	/* no relative path, can't cross drive letters */
+ 	}
+ 
+ 	/* Move past drive letters */
+ 	if (isalpha(*src) && src[1] == ':')
+ 		src += 2;
+ 	if (isalpha(*dst) && dst[1] == ':')
+ 		src += 2;
+ #endif
+ 
+ 	/* If we don't have two absolute paths, give up */
+ 	if (!is_absolute_path(src) ||
+ 		!is_absolute_path(dst))
+ 		return NULL;
+ 
+ 	dst_slash = dst;
+ 
+ 	while (1)
+ 	{
+ 		/* Move past adjacent slashes like //, and trailing ones */
+ 		while (ISSEP(*src) && (ISSEP(src[1]) || !src[1]))
+ 			src++;
+ 		while (ISSEP(*dst) && (ISSEP(dst[1]) || !dst[1]))
+ 			dst++;
+ 
+ 		/* Paths are done or not equal? */
+ 		if (!*src || !*dst)
+ 			break;
+ #ifndef WIN32
+ 		if (*src != *dst)
+ 			break;
+ #else
+ 		/* Win32 filesystem is case insensitive */
+ 		if (toupper(*src) != toupper(*dst) &&
+ 			(!ISSEP(*src) || !ISSEP(*dst)))	/* '/' == '\\' */
+ 			break;
+ #endif
+ 		if (ISSEP(*dst))
+ 			dst_slash = dst;
+ 
+ 		src++;
+ 		dst++;
+ 	}
+ 
+ 	/* Did the last part of the path match? */
+ 	dirs_up = ((*src == '\0' || ISSEP(*src)) &&
+ 			   (*dst == '\0' || ISSEP(*dst))) ? 0 : 1;
+ 
+ 	/* How many directories do we have to move up? */
+ 	while (*src)
+ 	{
+ 		if (ISSEP(*src))
+ 		{
+ 			while (ISSEP(*src))
+ 				src++;
+ 			if (*src != '\0')	/* skip trailing slash */
+ 				dirs_up++;
+ 		}
+ 		else
+ 			src++;
+ 	}
+ 		
+ #ifndef FRONTEND
+ 	ret = palloc(strlen(target) + strlen(dst) + 1);
+ #else
+ 	ret = malloc(strlen(target) + strlen(dst) + 1);
+ #endif
+ 
+ 	strcpy(ret, target);
+ 
+ 	/* Trim off trailing slash from target */
+ 	if (strlen(ret) > 0 && ISSEP(ret[strlen(ret)-1]))
+ 		dirs_up++;
+ 		
+ 	while (dirs_up--)
+ 		if (last_path_separator(ret) != NULL)
+ 			*last_path_separator(ret) = '\0';	/* trim off directory */
+ 		else
+ 			return NULL;
+ 
+ 	/* Add dst to trimmed target */
+ 	strcat(ret, dst_slash);
+ 	
+ 	/* Trim off trailing slash from result */
+ 	if (strlen(ret) > 0 && ISSEP(ret[strlen(ret)-1]))
+ 		*last_path_separator(ret) = '\0';	/* trim off slash */
+ 
+ 	return ret;
  }