#ifndef XPC_STRING_H_
#define XPC_STRING_H_

#include <stddef.h>
#include <xpc/status.h>

#define XPC_STRING_NPOS ((size_t)-1)

#define XPC_STRING_IN(msg, offset, size)                                       \
	{                                                                      \
		.s_flags = XPC_STRING_F_IN | XPC_STRING_F_REMOTE,              \
		.s_origin = (msg),                                             \
		.s_offset = (offset),                                          \
		.s_len = (size),                                               \
	}
#define XPC_STRING_OUT(msg, offset, size)                                      \
	{                                                                      \
		.s_flags = XPC_STRING_F_OUT | XPC_STRING_F_REMOTE,             \
		.s_origin = (msg),                                             \
		.s_offset = (offset),                                          \
		.s_len = (size),                                               \
	}

struct xpc_msg;

typedef enum xpc_string_flags {
	/* the string can be read from */
	XPC_STRING_F_IN = 0x01u,
	/* the string can be written to */
	XPC_STRING_F_OUT = 0x02u,
	/* the string is backed by a buffer located in another address space.
	 * the string can only be accessed via xpc_string_read and/or
	 * xpc_string_write */
	XPC_STRING_F_REMOTE = 0x04u,
	/* free the buffer backing this string when the string is discarded.
	 * this is only used for out-strings. the buffer must have been
	 * allocated using xpc_context_alloc, as it will be freed via a call
	 * to xpc_context_free */
	XPC_STRING_F_FREE_ON_DISCARD = 0x08u,
} xpc_string_flags_t;

typedef struct xpc_string {
	xpc_string_flags_t s_flags;
	union {
		struct {
			/* only valid if F_OUT is set. specifies the maximum
			 * number of chars that can be written to s_buf,
			 * including the null terminator. */
			size_t s_max;
			/* only valid if F_OUT is set.
			 * if F_FREE_ON_DISCARD is set, must be either NULL or
			 * allocated via xpc_context_alloc */
			const char *s_buf;
		};

		struct {
			/* only valid if F_IN is set. offset of the string data
			 * within the associated message. used when reading
			 * string data from a message. */
			size_t s_offset;
		};
	};

	/* only valid if F_REMOTE is set.
	 * used to read/write string data from/to the sender's address space. */
	const struct xpc_msg *s_origin;

	/* valid for both F_IN and F_OUT strings.
	 * F_IN: specifies the length of the incoming string data.
	 * F_OUT: specifies how many characters from s_buf to send. */
	size_t s_len;
} xpc_string_t;

extern xpc_status_t xpc_string_read(
	const xpc_string_t *s,
	char *out,
	size_t max,
	size_t *nr_read);
extern xpc_status_t xpc_string_write(
	xpc_string_t *s,
	const char *in,
	size_t len,
	size_t *nr_written);

#endif