int rewritehost(&out,buf,len,&rules);
int rewritehost_addr(&out,buf,len,&rules);
int rewritehost_list(&out,buf,len,&rules);
stralloc rules;
stralloc out;
char *buf;
unsigned int len;
rewritehost_addr reads an address in the form user@host from buf of length len. It rewrites host according to instructions in rules, unless both user and host are empty, in which case it rewrites the address as the empty string. It puts the rewritten address into out. rewritehost_addr accepts user as a synonym for user@ with an empty host name.
rewritehost_list reads an address list from buf of length len, rewrites each address in the list according to instructions in rules, and puts the rewritten address list into out. The address list consists of \0-terminated chunks; a chunk is either an address preceded by a plus sign, or a comment preceded by a left parenthesis. rewritehost_list copies comments without change.
Each function returns 1 if it succeeds, 0 if it runs out of memory.