//
// Copyright 2016 Garrett D'Amore <garrett@damore.org>
//
// This software is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

#ifndef CORE_PLATFORM_H
#define CORE_PLATFORM_H

// We require some standard C header files.  The only one of these that might
// be problematic is <stdint.h>, which is required for C99.  Older versions
// of the Windows compilers might not have this.  However, latest versions of
// MS Studio have a functional <stdint.h>.  If this impacts you, just upgrade
// your tool chain.
#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>

// These are the APIs that a platform must implement to support nng.

// A word about fork-safety: This library is *NOT* fork safe, in that
// functions may not be called in the child process without an intervening
// exec().  The library attempts to detect this situation, and crashes the
// process with an error message if it encounters it.  (See nn_platform_init
// below.)
//
// Additionally, some file descriptors may leak across fork even to
// child processes.  We make every reasonable effort to ensure that this
// does not occur, but on some platforms there are unavoidable race
// conditions between file creation and marking the file close-on-exec.
//
// Forkers should use posix_spawn() if possible, and as much as possible
// arrange for file close on exec by posix_spawn, or close the descriptors
// they do not need in the child.  (Note that posix_spawn() does *NOT*
// arrange for pthread_atfork() handlers to be called on some platforms.)

// nni_plat_abort crashes the system; it should do whatever is appropriate
// for abnormal programs on the platform, such as calling abort().
extern void nni_plat_abort(void);

// nni_plat_println is used to emit debug messages.  Typically this is used
// during core debugging, or to emit panic messages.  Message content will
// not contain newlines, but the output will add them.
extern void nni_plat_println(const char *);

// nni_alloc allocates memory.  In most cases this can just be malloc().
// However, you may provide a different allocator, for example it is
// possible to use a slab allocator or somesuch.  It is permissible for this
// to return NULL if memory cannot be allocated.
extern void *nni_alloc(size_t);

// nni_free frees memory allocated with nni_alloc. It takes a size because
// some allocators do not track size, or can operate more efficiently if
// the size is provided with the free call.  Examples of this are slab
// allocators like this found in Solaris/illumos (see libumem or kmem).
// This routine does nothing if supplied with a NULL pointer and zero size.
// Most implementations can just call free() here.
extern void nni_free(void *, size_t);

typedef struct nni_mutex *	nni_mutex_t;
typedef struct nni_cond *	nni_cond_t;

// Mutex handling.
extern int nni_mutex_create(nni_mutex_t *);

extern void nni_mutex_destroy(nni_mutex_t);
extern void nni_mutex_enter(nni_mutex_t);
extern void nni_mutex_exit(nni_mutex_t);
extern int nni_mutex_tryenter(nni_mutex_t);

extern int nni_cond_create(nni_cond_t *, nni_mutex_t);
extern void nni_cond_destroy(nni_cond_t);

// nni_cond_broadcast wakes all waiters on the condition.  This should be
// called with the lock held.
extern void nni_cond_broadcast(nni_cond_t);

// nni_cond_signal wakes a signal waiter.
extern void nni_cond_signal(nni_cond_t);

// nni_cond_wait waits for a wake up on the condition variable.  The
// associated lock is atomically released and reacquired upon wake up.
// Callers can be spuriously woken.  The associated lock must be held.
extern void nni_cond_wait(nni_cond_t);

// nni_cond_timedwait waits for a wakeup on the condition variable, just
// as with nni_condwait, but it will also wake after the given number of
// microseconds has passed.  (This is a relative timed wait.)  Early
// wakeups are permitted, and the caller must take care to double check any
// conditions.  The return value is 0 on success, or an error code, which
// can be NNG_ETIMEDOUT.  Note that it is permissible to wait for longer
// than the timeout based on the resolution of your system clock.
extern int nni_cond_timedwait(nni_cond_t, uint64_t);

typedef struct nni_thread * nni_thread_t;

// nni_thread_creates a thread that runs the given function. The thread
// receives a single argument.
extern int nni_thread_create(nni_thread_t *, void (*fn)(void *), void *);

// nni_thread_reap waits for the thread to exit, and then releases any
// resources associated with the thread.  After this returns, it
// is an error to reference the thread in any further way.
extern void nni_thread_reap(nni_thread_t);

// nn_clock returns a number of microseconds since some arbitrary time
// in the past.  The values returned by nni_clock may be used with
// nni_cond_timedwait.
extern uint64_t nni_clock(void);

// nni_usleep sleeps for the specified number of microseconds (at least).
extern void nni_usleep(uint64_t);

// nni_platform_init is called to allow the platform the chance to
// do any necessary initialization.  This routine MUST be idempotent,
// and threadsafe, and will be called before any other API calls, and
// may be called at any point thereafter.  It is permitted to return
// an error if some critical failure inializing the platform occurs,
// but once this succeeds, all future calls must succeed as well, unless
// nni_plat_fini has been called.
//
// The function argument should be called if the platform has not initialized
// (i.e. exactly once please), and its result passed back to the caller.
//
extern int nni_plat_init(int (*)(void));

// nni_platform_fini is called to clean up resources.  It is intended to
// be called as the last thing executed in the library, and no other functions
// will be called until nni_platform_init is called.
extern void nni_plat_fini(void);

// Actual platforms we support.
#if defined(PLATFORM_POSIX)
#include "platform/posix/posix_impl.h"
#else
#error "unknown platform"
#endif

#endif // CORE_PLATFORM_H