+/* Process line for macros. The line is in big_buffer starting at offset len.
+Expand big_buffer if needed. Handle definitions of new macros, and
+imacro expansions, rewriting the line in thw buffer.
+
+Arguments:
+ len Offset in buffer of start of line
+ newlen Pointer to offset of end of line, updated on return
+ macro_found Pointer to return that a macro was expanded
+
+Return: pointer to first nonblank char in line
+*/
+
+uschar *
+macros_expand(int len, int * newlen, BOOL * macro_found)
+{
+uschar * ss = big_buffer + len;
+uschar * s;
+macro_item * m;
+
+/* Find the true start of the physical line - leading spaces are always
+ignored. */
+
+while (isspace(*ss)) ss++;
+
+/* Process the physical line for macros. If this is the start of the logical
+line, skip over initial text at the start of the line if it starts with an
+upper case character followed by a sequence of name characters and an equals
+sign, because that is the definition of a new macro, and we don't do
+replacement therein. */
+
+s = ss;
+if (len == 0 && isupper(*s))
+ {
+ while (isalnum(*s) || *s == '_') s++;
+ while (isspace(*s)) s++;
+ if (*s != '=') s = ss; /* Not a macro definition */
+ }
+
+/* Skip leading chars which cannot start a macro name, to avoid multiple
+pointless rescans in Ustrstr calls. */
+
+while (*s && !isupper(*s) && *s != '_') s++;
+
+/* For each defined macro, scan the line (from after XXX= if present),
+replacing all occurrences of the macro. */
+
+*macro_found = FALSE;
+for (m = macros; m; m = m->next)
+ {
+ uschar * p, *pp;
+ uschar * t = s;
+
+ while ((p = Ustrstr(t, m->name)) != NULL)
+ {
+ int moveby;
+
+/* fprintf(stderr, "%s: matched '%s' in '%s'\n", __FUNCTION__, m->name, ss); */
+ /* Expand the buffer if necessary */
+
+ while (*newlen - m->namelen + m->replen + 1 > big_buffer_size)
+ {
+ int newsize = big_buffer_size + BIG_BUFFER_SIZE;
+ uschar *newbuffer = store_malloc(newsize);
+ memcpy(newbuffer, big_buffer, *newlen + 1);
+ p = newbuffer + (p - big_buffer);
+ s = newbuffer + (s - big_buffer);
+ ss = newbuffer + (ss - big_buffer);
+ t = newbuffer + (t - big_buffer);
+ big_buffer_size = newsize;
+ store_free(big_buffer);
+ big_buffer = newbuffer;
+ }
+
+ /* Shuffle the remaining characters up or down in the buffer before
+ copying in the replacement text. Don't rescan the replacement for this
+ same macro. */
+
+ pp = p + m->namelen;
+ if ((moveby = m->replen - m->namelen) != 0)
+ {
+ memmove(p + m->replen, pp, (big_buffer + *newlen) - pp + 1);
+ *newlen += moveby;
+ }
+ Ustrncpy(p, m->replacement, m->replen);
+ t = p + m->replen;
+ while (*t && !isupper(*t) && *t != '_') t++;
+ *macro_found = TRUE;
+ }
+ }
+
+/* An empty macro replacement at the start of a line could mean that ss no
+longer points to the first non-blank character. */
+
+while (isspace(*ss)) ss++;
+return ss;
+}
+