These functions are expected to be useful only to X protocol extension implementations built on XCB. They are declared in xcbext.h.

Care is required when calling these functions, as they generally do not have the type-safety properties of the public API functions.

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## `struct xcb_extension_t`

		struct xcb_extension_t {
			const char *name;         // the X name of this extension, stored as a null-terminated string
			int global_id;            // a small integer unique across all extensions in the current process
		};

## `xcb_protocol_request_t`

		typedef struct {
			size_t count;            // number of elements in the iovec array
			xcb_extension_t *ext;    // extension identifier, or null for the core protocol
			uint8_t opcode;          // major opcode of the request for the core protocol, or minor opcode for an extension
			uint8_t isvoid;          // zero if this request will return a reply; non-zero otherwise
		} xcb_protocol_request_t;

Values for a particular request that are always constant.

## `xcb_send_request`

(`xcb_out.c`)

		int
		xcb_send_request (xcb_connection *c,
						  int flags,                                // a combination of the flags `XCB_REQUEST_CHECKED`, `XCB_REQUEST_RAW`, and `XCB_REQUEST_DISCARD_REPLY`
						  unsigned int *sequence,
						  struct iovec *vector,
						  const xcb_protocol_request_t *request );

## `xcb_wait_for_reply`

(`xcb_in.c`)

		void *
		xcb_wait_for_reply (xcb_connection *c,
							unsigned int request,
							xcb_generic_error_t **e );

## `xcb_poll_for_reply`

(`xcb_in.c`)

		int
		xcb_poll_for_reply (xcb_connection *c,
							unsigned int request,
							void **reply,
							xcb_generic_error_t **e );

Returns: 1 if the reply was recieved (reply or error is filled in), 0 if the reply has not yet arrived.

## `xcb_popcount`

(`xcb_util.c`)

		int
		xcb_popcount (uint32_t mask);

Returns the number of bits in the binary representation of `mask` that are equal to 1. This is also called a "population count".