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+ hostip.c explained
+ ==================
+
+ The main COMPILE-TIME DEFINES to keep in mind when reading the host*.c
+ source file are these:
+
+ CURLRES_IPV6 - this host has getaddrinfo() and family, and thus we use
+ that. The host may not be able to resolve IPv6, but we don't really have to
+ take that into account. Hosts that aren't IPv6-enabled have CURLRES_IPV4
+ defined.
+
+ CURLRES_ARES - is defined if libcurl is built to use c-ares for asynchronous
+ name resolves. It cannot have ENABLE_IPV6 defined at the same time, as c-ares
+ has no ipv6 support. This can be Windows or *nix.
+
+ CURLRES_THREADED - is defined if libcurl is built to run under (native)
+ Windows, and then the name resolve will be done in a new thread, and the
+ supported asynch API will be the same as for ares-builds.
+
+ If any of the two previous are defined, CURLRES_ASYNCH is defined too. If
+ libcurl is not built to use an asynchronous resolver, CURLRES_SYNCH is
+ defined.
+
+ The host*.c sources files are split up like this:
+
+ hostip.c   - method-independent resolver functions and utility functions
+ hostasyn.c - functions for asynchronous name resolves
+ hostsyn.c  - functions for synchronous name resolves
+ hostares.c - functions for ares-using name resolves
+ hostthre.c - functions for threaded name resolves
+ hostip4.c  - ipv4-specific functions
+ hostip6.c  - ipv6-specific functions
+
+ The hostip.h is the single united header file for all this. It defines the
+ CURLRES_* defines based on the config*.h and setup.h defines.