fix ${EXTEN:X} where X < 0 (bug #3572)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/v1-0@5051 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/pbx.c b/pbx.c
index 09f173e1ea0d3ae130ba2c2e5514ac34e3df77f5..f0dad5b8f7ffa75ae7fe490b9e63679405ed4cdc 100755 (executable)
--- a/pbx.c
+++ b/pbx.c
@@ -817,6 +817,9 @@ static struct ast_exten *pbx_find_extension(struct ast_channel *chan, char *cont
        return NULL;
 }
 
+/*--- pbx_retrieve_variable: Support for Asterisk built-in variables and
+      functions in the dialplan
+  ---*/
 static void pbx_substitute_variables_temp(struct ast_channel *c, const char *var, char **ret, char *workspace, int workspacelen)
 {
        char *first,*second;
@@ -832,7 +835,7 @@ static void pbx_substitute_variables_temp(struct ast_channel *c, const char *var
                headp=&c->varshead;
        *ret=NULL;
        /* Now we have the variable name on cp3 */
-       if (!strncasecmp(var,"LEN(",4)) {
+       if (!strncasecmp(var,"LEN(",4)) {       /* ${LEN(<string>)} */
                int len=strlen(var);
                int len_len=4;
                if (strrchr(var,')')) {
@@ -845,37 +848,45 @@ static void pbx_substitute_variables_temp(struct ast_channel *c, const char *var
                        /* length is zero */
                        *ret = "0";
                }
-       } else if ((first=strchr(var,':'))) {
+       } else if ((first=strchr(var,':'))) {   /* : Remove characters counting from end or start of string */
                strncpy(tmpvar, var, sizeof(tmpvar) - 1);
                first = strchr(tmpvar, ':');
                if (!first)
                        first = tmpvar + strlen(tmpvar);
                *first='\0';
                pbx_substitute_variables_temp(c,tmpvar,ret,workspace,workspacelen - 1);
-               if (!(*ret)) return;
-               offset=atoi(first+1);
-               if ((second=strchr(first+1,':'))) {
+               if (!(*ret)) 
+                       return;
+               offset=atoi(first+1);   /* The number of characters, 
+                                          positive: remove # of chars from start
+                                          negative: keep # of chars from end */
+                                               
+               if ((second=strchr(first+1,':'))) {     
                        *second='\0';
-                       offset2=atoi(second+1);
-               } else
-                       offset2=strlen(*ret)-offset;
-               if (abs(offset)>strlen(*ret)) {
-                       if (offset>=0) 
+                       offset2 = atoi(second+1);               /* Number of chars to copy */
+               } else if (offset >= 0) {
+                       offset2 = strlen(*ret)-offset;  /* Rest of string */
+               } else {
+                       offset2 = abs(offset);
+               }
+
+               if (abs(offset) > strlen(*ret)) {       /* Offset beyond string */
+                       if (offset >= 0) 
                                offset=strlen(*ret);
                        else 
                                offset=-strlen(*ret);
                }
-               if ((offset<0 && offset2>-offset) || (offset>=0 && offset+offset2>strlen(*ret))) {
-                       if (offset>=0) 
+               if ((offset < 0 && offset2 > -offset) || (offset >= 0 && offset+offset2 > strlen(*ret))) {
+                       if (offset >= 0) 
                                offset2=strlen(*ret)-offset;
                        else 
                                offset2=strlen(*ret)+offset;
                }
-               if (offset>=0)
-                       *ret+=offset;
+               if (offset >= 0)
+                       *ret += offset;
                else
-                       *ret+=strlen(*ret)+offset;
-               (*ret)[offset2] = '\0';
+                       *ret += strlen(*ret)+offset;
+                       (*ret)[offset2] = '\0';         /* Cut at offset2 position */
        } else if (c && !strcmp(var, "CALLERIDNUM")) {
                if (c->callerid)
                        strncpy(workspace, c->callerid, workspacelen - 1);