6dea2ec25eb2e896aef0d7669c68b81f4d75b104
jcasper
  Fri Jan 8 16:07:06 2016 -0800
Updating relative path calculation to support root-level resource paths beginning with //

diff --git src/lib/filePath.c src/lib/filePath.c
index 68fe762..62b2030 100644
--- src/lib/filePath.c
+++ src/lib/filePath.c
@@ -1,175 +1,193 @@
 /* filePath - stuff to handle file name parsing. */
 
 /* Copyright (C) 2011 The Regents of the University of California 
  * See README in this or parent directory for licensing information. */
 
 #include "common.h"
 #include "filePath.h"
 
 
 void undosPath(char *path)
 /* Convert '\' to '/' in path. */
 {
 subChar(path, '\\', '/');
 }
 
 void splitPath(char *path, char dir[PATH_LEN], char name[FILENAME_LEN],
 	       char extension[FILEEXT_LEN])
 /* Split a full path into components.  The dir component will include the
  * trailing / if any.  The extension component will include the starting
  * . if any.   Pass in NULL for dir, name, or extension if you don't care about
  * that part. */
 {
 char *dirStart, *nameStart, *extStart, *extEnd;
 int dirSize, nameSize, extSize;
 
 undosPath(path);
 dirStart = path;
 nameStart = strrchr(path,'/');
 if (nameStart == NULL)
     nameStart = path;
 else
     nameStart += 1;
 extStart = strrchr(nameStart, '.');
 if (extStart == NULL)
     extStart = nameStart + strlen(nameStart);
 extEnd = extStart + strlen(extStart);
 if ((dirSize = (nameStart - dirStart)) >= PATH_LEN)
     errAbort("Directory too long in %s", path);
 if ((nameSize = (extStart - nameStart)) >= FILENAME_LEN)
     errAbort("Name too long in %s", path);
 if ((extSize = (extEnd - extStart)) >= FILEEXT_LEN)
     errAbort("Extension too long in %s", path);
 if (dir != NULL)
     {
     memcpy(dir, dirStart, dirSize);
     dir[dirSize] = 0;
     }
 if (name != NULL)
     {
     memcpy(name, nameStart, nameSize);
     name[nameSize] = 0;
     }
 if (extension != NULL)
     {
     memcpy(extension, extStart, extSize);
     extension[extSize] = 0;
     }
 }
 
 static char *findSlashBefore(char *start, char *e)
 /* Return first slash before s (but not before start) */
 {
 while (--e >= start)
     {
     if (*e == '/')
          return e;
     }
 return start;
 }
 
 char *expandRelativePath(char *baseDir, char *relPath)
 /* Expand relative path to more absolute one. */
 {
 if (relPath[0] == '/')
    // hey, it's absolute actually... 
    return cloneString(relPath);
 
 char *e = baseDir + strlen(baseDir);
 int slashCount;
 char *rel = relPath;
 char *result;
 int size, baseSize;
 undosPath(baseDir);
 undosPath(relPath);
 slashCount = countChars(baseDir, '/');
 if (baseDir[0] == 0)
     slashCount = -1;
 while (startsWith("../", rel))
     {
     if (slashCount < 0)
         {
 	warn("More ..'s in \"%s\" than directories in \"%s\"", relPath, baseDir);
 	return NULL;
 	}
     else if (slashCount == 0)
         e = baseDir;
     else
         e = findSlashBefore(baseDir, e);
     slashCount -= 1;
     rel += 3;
     }
 baseSize = e - baseDir;
 size = strlen(rel) + 1;
 if (baseSize > 0)
     size += baseSize + 1;
 if (baseSize > 0)
     {
     result = needMem(size);
     memcpy(result, baseDir, baseSize);
     result[baseSize] = '/';
     strcpy(result + baseSize + 1, rel);
     }
 else
     result = cloneString(rel);
 return result;
 }
 
 char *pathRelativeToFile(char *baseFile, char *relPath)
 /* Given a base file name and a path relative to that, return
  * relative path interpreted as if it were seen from the
  * same directory holding the baseFile.  
  *   An example of using this would be in processing include
  * files.  In this case the baseFile would be the current
  * source file, and the relPath would be from the include
  * statement.  The returned result could then be used to
  * open the include file. */
 {
 char dir[PATH_LEN];
 splitPath(baseFile, dir, NULL, NULL);
 int dirLen = strlen(dir);
 if (dirLen > 0 && dir[dirLen-1] == '/')
      dir[dirLen-1] = 0;
 return expandRelativePath(dir, relPath);
 }
 
 char *makeRelativePath(char *from, char *to)
 /* Calculate a relative path from one absolute directory/file to another.
- * Assumptions: both from and to are absolute paths beginning at "/", and
- * may be as small as only "/".  Filenames are okay, but all directory
- * names must end with a "/" to distinguish them from files.
+ * Assumptions: both from and to are canonicalized absolute paths beginning
+ * at "/" or "//".  Filenames are okay, but all directory names must end with
+ * a "/" to distinguish them from files.
  * e.g., /test/dir/ is a directory, but /test/dir is a file.
  */
 {
 int i, j, toCount, fromCount;
 char fromDir[PATH_LEN];
 char toDir[PATH_LEN], toFile[FILENAME_LEN], toExt[FILEEXT_LEN];
 char relPath [PATH_LEN] = "";
 char *fromDirList[PATH_LEN], *toDirList[PATH_LEN];
+boolean fromStartsDoubleSlash = FALSE, toStartsDoubleSlash = FALSE;
+
+if (startsWith("//", from) && from[2] != '/')
+    {
+    fromStartsDoubleSlash = TRUE;
+    from[1] = '_'; // prevent initial // from being misinterpreted
+    }
+if (startsWith("//", to) && to[2] != '/')
+    {
+    toStartsDoubleSlash = TRUE;
+    to[1] = '_'; // prevent initial // from being misinterpreted
+    }
 
 splitPath(from, fromDir, NULL, NULL);
 splitPath(to, toDir, toFile, toExt);
 
 fromCount = chopByChar(fromDir, '/', fromDirList, ArraySize(fromDirList));
 toCount   = chopByChar(toDir,   '/', toDirList,   ArraySize(toDirList));
 
-for (i=1; i < min(fromCount, toCount); i++)
+if (fromStartsDoubleSlash == TRUE)
+    fromDirList[1][0] = '/';
+if (toStartsDoubleSlash == TRUE)
+    toDirList[1][0] = '/';
+    
+
+for (i=1; i < min(fromCount-1, toCount-1); i++)
     {
     if (!sameString(fromDirList[i], toDirList[i]))
         break;
     }
 for (j=i; j < fromCount-1; j++)
     {
     safecat(relPath, sizeof relPath, "../");
     }
 for (j=i; j < toCount-1; j++)
     {
     safecat(relPath, sizeof relPath, toDirList[j]);
     safecat(relPath, sizeof relPath, "/");
     }
 
 safecat(relPath, sizeof relPath, toFile);
 safecat(relPath, sizeof relPath, toExt);
 
 return cloneString(relPath);
 }