text: /**
   * @file
   * OS abstraction layer
   */
  
  /*
   * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without modification,
   * are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice,
   *    this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   * 3. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
   * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
   * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
   * OF SUCH DAMAGE.
   *
   * This file is part of the lwIP TCP/IP stack.
   *
   * Author: Adam Dunkels <adam@sics.se>
   */
  
  #ifndef LWIP_HDR_SYS_H
  #define LWIP_HDR_SYS_H
  
  #include "lwip/opt.h"
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #if NO_SYS
  
  /* For a totally minimal and standalone system, we provide null
     definitions of the sys_ functions. */
  typedef u8_t sys_sem_t;
  typedef u8_t sys_mutex_t;
  typedef u8_t sys_mbox_t;
  
  #define sys_sem_new(s, c) ERR_OK
  #define sys_sem_signal(s)
  #define sys_sem_wait(s)
  #define sys_arch_sem_wait(s,t)
  #define sys_sem_free(s)
  #define sys_sem_valid(s) 0
  #define sys_sem_valid_val(s) 0
  #define sys_sem_set_invalid(s)
  #define sys_sem_set_invalid_val(s)
  #define sys_mutex_new(mu) ERR_OK
  #define sys_mutex_lock(mu)
  #define sys_mutex_unlock(mu)
  #define sys_mutex_free(mu)
  #define sys_mutex_valid(mu) 0
  #define sys_mutex_set_invalid(mu)
  #define sys_mbox_new(m, s) ERR_OK
  #define sys_mbox_fetch(m,d)
  #define sys_mbox_tryfetch(m,d)
  #define sys_mbox_post(m,d)
  #define sys_mbox_trypost(m,d)
  #define sys_mbox_free(m)
  #define sys_mbox_valid(m)
  #define sys_mbox_valid_val(m)
  #define sys_mbox_set_invalid(m)
  #define sys_mbox_set_invalid_val(m)
  
  #define sys_thread_new(n,t,a,s,p)
  
  #define sys_msleep(t)
  
  #else /* NO_SYS */
  
  /** Return code for timeouts from sys_arch_mbox_fetch and sys_arch_sem_wait */
  #define SYS_ARCH_TIMEOUT 0xffffffffUL
  
  /** sys_mbox_tryfetch() returns SYS_MBOX_EMPTY if appropriate.
   * For now we use the same magic value, but we allow this to change in future.
   */
  #define SYS_MBOX_EMPTY SYS_ARCH_TIMEOUT
  
  #include "lwip/err.h"
  #include "arch/sys_arch.h"
  
  /** Function prototype for thread functions */
  typedef void (*lwip_thread_fn)(void *arg);
  
  /* Function prototypes for functions to be implemented by platform ports
     (in sys_arch.c) */
  
  /* Mutex functions: */
  
  /** Define LWIP_COMPAT_MUTEX if the port has no mutexes and binary semaphores
      should be used instead */
  #ifndef LWIP_COMPAT_MUTEX
  #define LWIP_COMPAT_MUTEX 0
  #endif
  
  #if LWIP_COMPAT_MUTEX
  /* for old ports that don't have mutexes: define them to binary semaphores */
  #define sys_mutex_t                   sys_sem_t
  #define sys_mutex_new(mutex)          sys_sem_new(mutex, 1)
  #define sys_mutex_lock(mutex)         sys_sem_wait(mutex)
  #define sys_mutex_unlock(mutex)       sys_sem_signal(mutex)
  #define sys_mutex_free(mutex)         sys_sem_free(mutex)
  #define sys_mutex_valid(mutex)        sys_sem_valid(mutex)
  #define sys_mutex_set_invalid(mutex)  sys_sem_set_invalid(mutex)
  
  #else /* LWIP_COMPAT_MUTEX */
  
  /**
   * @ingroup sys_mutex
   * Create a new mutex.
   * Note that mutexes are expected to not be taken recursively by the lwIP code,
   * so both implementation types (recursive or non-recursive) should work.
   * The mutex is allocated to the memory that 'mutex'
   * points to (which can be both a pointer or the actual OS structure).
   * If the mutex has been created, ERR_OK should be returned. Returning any
   * other error will provide a hint what went wrong, but except for assertions,
   * no real error handling is implemented.
   * 
   * @param mutex pointer to the mutex to create
   * @return ERR_OK if successful, another err_t otherwise
   */
  err_t sys_mutex_new(sys_mutex_t *mutex);
  /**
   * @ingroup sys_mutex
   * Blocks the thread until the mutex can be grabbed.
   * @param mutex the mutex to lock
   */
  void sys_mutex_lock(sys_mutex_t *mutex);
  /**
   * @ingroup sys_mutex
   * Releases the mutex previously locked through 'sys_mutex_lock()'.
   * @param mutex the mutex to unlock
   */
  void sys_mutex_unlock(sys_mutex_t *mutex);
  /**
   * @ingroup sys_mutex
   * Deallocates a mutex.
   * @param mutex the mutex to delete
   */
  void sys_mutex_free(sys_mutex_t *mutex);
  #ifndef sys_mutex_valid
  /**
   * @ingroup sys_mutex
   * Returns 1 if the mutes is valid, 0 if it is not valid.
   * When using pointers, a simple way is to check the pointer for != NULL.
   * When directly using OS structures, implementing this may be more complex.
   * This may also be a define, in which case the function is not prototyped.
   */
  int sys_mutex_valid(sys_mutex_t *mutex);
  #endif
  #ifndef sys_mutex_set_invalid
  /**
   * @ingroup sys_mutex
   * Invalidate a mutex so that sys_mutex_valid() returns 0.
   * ATTENTION: This does NOT mean that the mutex shall be deallocated:
   * sys_mutex_free() is always called before calling this function!
   * This may also be a define, in which case the function is not prototyped.
   */
  void sys_mutex_set_invalid(sys_mutex_t *mutex);
  #endif
  #endif /* LWIP_COMPAT_MUTEX */
  
  /* Semaphore functions: */
  
  /**
   * @ingroup sys_sem
   * Create a new semaphore
   * Creates a new semaphore. The semaphore is allocated to the memory that 'sem'
   * points to (which can be both a pointer or the actual OS structure).
   * The "count" argument specifies the initial state of the semaphore (which is
   * either 0 or 1).
   * If the semaphore has been created, ERR_OK should be returned. Returning any
   * other error will provide a hint what went wrong, but except for assertions,
   * no real error handling is implemented.
   *
   * @param sem pointer to the semaphore to create
   * @param count initial count of the semaphore
   * @return ERR_OK if successful, another err_t otherwise
   */
  err_t sys_sem_new(sys_sem_t *sem, u8_t count);
  /**
   * @ingroup sys_sem
   * Signals a semaphore
   * @param sem the semaphore to signal
   */
  void sys_sem_signal(sys_sem_t *sem);
  /**
   * @ingroup sys_sem
   *  Blocks the thread while waiting for the semaphore to be signaled. If the
   * "timeout" argument is non-zero, the thread should only be blocked for the
   * specified time (measured in milliseconds). If the "timeout" argument is zero,
   * the thread should be blocked until the semaphore is signalled.
   * 
   * The return value is SYS_ARCH_TIMEOUT if the semaphore wasn't signaled within
   * the specified time or any other value if it was signaled (with or without
   * waiting).
   * Notice that lwIP implements a function with a similar name,
   * sys_sem_wait(), that uses the sys_arch_sem_wait() function.
   * 
   * @param sem the semaphore to wait for
   * @param timeout timeout in milliseconds to wait (0 = wait forever)
   * @return SYS_ARCH_TIMEOUT on timeout, any other value on success
   */
  u32_t sys_arch_sem_wait(sys_sem_t *sem, u32_t timeout);
  /**
   * @ingroup sys_sem
   * Deallocates a semaphore.
   * @param sem semaphore to delete
   */
  void sys_sem_free(sys_sem_t *sem);
  /** Wait for a semaphore - forever/no timeout */
  #define sys_sem_wait(sem)                  sys_arch_sem_wait(sem, 0)
  #ifndef sys_sem_valid
  /**
   * @ingroup sys_sem
   * Returns 1 if the semaphore is valid, 0 if it is not valid.
   * When using pointers, a simple way is to check the pointer for != NULL.
   * When directly using OS structures, implementing this may be more complex.
   * This may also be a define, in which case the function is not prototyped.
   */
  int sys_sem_valid(sys_sem_t *sem);
  #endif
  #ifndef sys_sem_set_invalid
  /**
   * @ingroup sys_sem
   * Invalidate a semaphore so that sys_sem_valid() returns 0.
   * ATTENTION: This does NOT mean that the semaphore shall be deallocated:
   * sys_sem_free() is always called before calling this function!
   * This may also be a define, in which case the function is not prototyped.
   */
  void sys_sem_set_invalid(sys_sem_t *sem);
  #endif
  #ifndef sys_sem_valid_val
  /**
   * Same as sys_sem_valid() but taking a value, not a pointer
   */
  #define sys_sem_valid_val(sem)       sys_sem_valid(&(sem))
  #endif
  #ifndef sys_sem_set_invalid_val
  /**
   * Same as sys_sem_set_invalid() but taking a value, not a pointer
   */
  #define sys_sem_set_invalid_val(sem) sys_sem_set_invalid(&(sem))
  #endif
  
  #ifndef sys_msleep
  /**
   * @ingroup sys_misc
   * Sleep for specified number of ms
   */
  void sys_msleep(u32_t ms); /* only has a (close to) 1 ms resolution. */
  #endif
  
  /* Mailbox functions. */
  
  /**
   * @ingroup sys_mbox
   * Creates an empty mailbox for maximum "size" elements. Elements stored
   * in mailboxes are pointers. You have to define macros "_MBOX_SIZE"
   * in your lwipopts.h, or ignore this parameter in your implementation
   * and use a default size.
   * If the mailbox has been created, ERR_OK should be returned. Returning any
   * other error will provide a hint what went wrong, but except for assertions,
   * no real error handling is implemented.
   * 
   * @param mbox pointer to the mbox to create
   * @param size (minimum) number of messages in this mbox
   * @return ERR_OK if successful, another err_t otherwise
   */
  err_t sys_mbox_new(sys_mbox_t *mbox, int size);
  /**
   * @ingroup sys_mbox
   * Post a message to an mbox - may not fail
   * -> blocks if full, only to be used from tasks NOT from ISR!
   * 
   * @param mbox mbox to posts the message
   * @param msg message to post (ATTENTION: can be NULL)
   */
  void sys_mbox_post(sys_mbox_t *mbox, void *msg);
  /**
   * @ingroup sys_mbox
   * Try to post a message to an mbox - may fail if full.
   * Can be used from ISR (if the sys arch layer allows this).
   * Returns ERR_MEM if it is full, else, ERR_OK if the "msg" is posted.
   * 
   * @param mbox mbox to posts the message
   * @param msg message to post (ATTENTION: can be NULL)
   */
  err_t sys_mbox_trypost(sys_mbox_t *mbox, void *msg);
  /**
   * @ingroup sys_mbox
   * Try to post a message to an mbox - may fail if full.
   * To be be used from ISR.
   * Returns ERR_MEM if it is full, else, ERR_OK if the "msg" is posted.
   * 
   * @param mbox mbox to posts the message
   * @param msg message to post (ATTENTION: can be NULL)
   */
  err_t sys_mbox_trypost_fromisr(sys_mbox_t *mbox, void *msg);
  /**
   * @ingroup sys_mbox
   * Blocks the thread until a message arrives in the mailbox, but does
   * not block the thread longer than "timeout" milliseconds (similar to
   * the sys_arch_sem_wait() function). If "timeout" is 0, the thread should
   * be blocked until a message arrives. The "msg" argument is a result
   * parameter that is set by the function (i.e., by doing "*msg =
   * ptr"). The "msg" parameter maybe NULL to indicate that the message
   * should be dropped.
   * The return values are the same as for the sys_arch_sem_wait() function:
   * SYS_ARCH_TIMEOUT if there was a timeout, any other value if a messages
   * is received.
   * 
   * Note that a function with a similar name, sys_mbox_fetch(), is
   * implemented by lwIP. 
   * 
   * @param mbox mbox to get a message from
   * @param msg pointer where the message is stored
   * @param timeout maximum time (in milliseconds) to wait for a message (0 = wait forever)
   * @return SYS_ARCH_TIMEOUT on timeout, any other value if a message has been received
   */
  u32_t sys_arch_mbox_fetch(sys_mbox_t *mbox, void **msg, u32_t timeout);
  /* Allow port to override with a macro, e.g. special timeout for sys_arch_mbox_fetch() */
  #ifndef sys_arch_mbox_tryfetch
  /**
   * @ingroup sys_mbox
   * This is similar to sys_arch_mbox_fetch, however if a message is not
   * present in the mailbox, it immediately returns with the code
   * SYS_MBOX_EMPTY. On success 0 is returned.
   * To allow for efficient implementations, this can be defined as a
   * function-like macro in sys_arch.h instead of a normal function. For
   * example, a naive implementation could be:
   * \#define sys_arch_mbox_tryfetch(mbox,msg) sys_arch_mbox_fetch(mbox,msg,1)
   * although this would introduce unnecessary delays.
   * 
   * @param mbox mbox to get a message from
   * @param msg pointer where the message is stored
   * @return 0 (milliseconds) if a message has been received
   *         or SYS_MBOX_EMPTY if the mailbox is empty
   */
  u32_t sys_arch_mbox_tryfetch(sys_mbox_t *mbox, void **msg);
  #endif
  /**
   * For now, we map straight to sys_arch implementation.
   */
  #define sys_mbox_tryfetch(mbox, msg) sys_arch_mbox_tryfetch(mbox, msg)
  /**
   * @ingroup sys_mbox
   * Deallocates a mailbox. If there are messages still present in the
   * mailbox when the mailbox is deallocated, it is an indication of a
   * programming error in lwIP and the developer should be notified.
   * 
   * @param mbox mbox to delete
   */
  void sys_mbox_free(sys_mbox_t *mbox);
  #define sys_mbox_fetch(mbox, msg) sys_arch_mbox_fetch(mbox, msg, 0)
  #ifndef sys_mbox_valid
  /**
   * @ingroup sys_mbox
   * Returns 1 if the mailbox is valid, 0 if it is not valid.
   * When using pointers, a simple way is to check the pointer for != NULL.
   * When directly using OS structures, implementing this may be more complex.
   * This may also be a define, in which case the function is not prototyped.
   */
  int sys_mbox_valid(sys_mbox_t *mbox);
  #endif
  #ifndef sys_mbox_set_invalid
  /**
   * @ingroup sys_mbox
   * Invalidate a mailbox so that sys_mbox_valid() returns 0.
   * ATTENTION: This does NOT mean that the mailbox shall be deallocated:
   * sys_mbox_free() is always called before calling this function!
   * This may also be a define, in which case the function is not prototyped.
   */
  void sys_mbox_set_invalid(sys_mbox_t *mbox);
  #endif
  #ifndef sys_mbox_valid_val
  /**
   * Same as sys_mbox_valid() but taking a value, not a pointer
   */
  #define sys_mbox_valid_val(mbox)       sys_mbox_valid(&(mbox))
  #endif
  #ifndef sys_mbox_set_invalid_val
  /**
   * Same as sys_mbox_set_invalid() but taking a value, not a pointer
   */
  #define sys_mbox_set_invalid_val(mbox) sys_mbox_set_invalid(&(mbox))
  #endif
  
  
  /**
   * @ingroup sys_misc
   * The only thread function:
   * Starts a new thread named "name" with priority "prio" that will begin its
   * execution in the function "thread()". The "arg" argument will be passed as an
   * argument to the thread() function. The stack size to used for this thread is
   * the "stacksize" parameter. The id of the new thread is returned. Both the id
   * and the priority are system dependent.
   * ATTENTION: although this function returns a value, it MUST NOT FAIL (ports have to assert this!)
   * 
   * @param name human-readable name for the thread (used for debugging purposes)
   * @param thread thread-function
   * @param arg parameter passed to 'thread'
   * @param stacksize stack size in bytes for the new thread (may be ignored by ports)
   * @param prio priority of the new thread (may be ignored by ports) */
  sys_thread_t sys_thread_new(const char *name, lwip_thread_fn thread, void *arg, int stacksize, int prio);
  
  #endif /* NO_SYS */
  
  /**
   * @ingroup sys_misc
   * sys_init() must be called before anything else.
   * Initialize the sys_arch layer.
   */
  void sys_init(void);
  
  #ifndef sys_jiffies
  /**
   * Ticks/jiffies since power up.
   */
  u32_t sys_jiffies(void);
  #endif
  
  /**
   * @ingroup sys_time
   * Returns the current time in milliseconds,
   * may be the same as sys_jiffies or at least based on it.
   * Don't care for wraparound, this is only used for time diffs.
   * Not implementing this function means you cannot use some modules (e.g. TCP
   * timestamps, internal timeouts for NO_SYS==1).
   */
  u32_t sys_now(void);
  
  /* Critical Region Protection */
  /* These functions must be implemented in the sys_arch.c file.
     In some implementations they can provide a more light-weight protection
     mechanism than using semaphores. Otherwise semaphores can be used for
     implementation */
  #ifndef SYS_ARCH_PROTECT
  /** SYS_LIGHTWEIGHT_PROT
   * define SYS_LIGHTWEIGHT_PROT in lwipopts.h if you want inter-task protection
   * for certain critical regions during buffer allocation, deallocation and memory
   * allocation and deallocation.
   */
  #if SYS_LIGHTWEIGHT_PROT
  
  /**
   * @ingroup sys_prot
   * SYS_ARCH_DECL_PROTECT
   * declare a protection variable. This macro will default to defining a variable of
   * type sys_prot_t. If a particular port needs a different implementation, then
   * this macro may be defined in sys_arch.h.
   */
  #define SYS_ARCH_DECL_PROTECT(lev) sys_prot_t lev
  /**
   * @ingroup sys_prot
   * SYS_ARCH_PROTECT
   * Perform a "fast" protect. This could be implemented by
   * disabling interrupts for an embedded system or by using a semaphore or
   * mutex. The implementation should allow calling SYS_ARCH_PROTECT when
   * already protected. The old protection level is returned in the variable
   * "lev". This macro will default to calling the sys_arch_protect() function
   * which should be implemented in sys_arch.c. If a particular port needs a
   * different implementation, then this macro may be defined in sys_arch.h
   */
  #define SYS_ARCH_PROTECT(lev) lev = sys_arch_protect()
  /**
   * @ingroup sys_prot
   * SYS_ARCH_UNPROTECT
   * Perform a "fast" set of the protection level to "lev". This could be
   * implemented by setting the interrupt level to "lev" within the MACRO or by
   * using a semaphore or mutex.  This macro will default to calling the
   * sys_arch_unprotect() function which should be implemented in
   * sys_arch.c. If a particular port needs a different implementation, then
   * this macro may be defined in sys_arch.h
   */
  #define SYS_ARCH_UNPROTECT(lev) sys_arch_unprotect(lev)
  sys_prot_t sys_arch_protect(void);
  void sys_arch_unprotect(sys_prot_t pval);
  
  #else
  
  #define SYS_ARCH_DECL_PROTECT(lev)
  #define SYS_ARCH_PROTECT(lev)
  #define SYS_ARCH_UNPROTECT(lev)
  
  #endif /* SYS_LIGHTWEIGHT_PROT */
  
  #endif /* SYS_ARCH_PROTECT */
  
  /*
   * Macros to set/get and increase/decrease variables in a thread-safe way.
   * Use these for accessing variable that are used from more than one thread.
   */
  
  #ifndef SYS_ARCH_INC
  #define SYS_ARCH_INC(var, val) do { \
                                  SYS_ARCH_DECL_PROTECT(old_level); \
                                  SYS_ARCH_PROTECT(old_level); \
                                  var += val; \
                                  SYS_ARCH_UNPROTECT(old_level); \
                                } while(0)
  #endif /* SYS_ARCH_INC */
  
  #ifndef SYS_ARCH_DEC
  #define SYS_ARCH_DEC(var, val) do { \
                                  SYS_ARCH_DECL_PROTECT(old_level); \
                                  SYS_ARCH_PROTECT(old_level); \
                                  var -= val; \
                                  SYS_ARCH_UNPROTECT(old_level); \
                                } while(0)
  #endif /* SYS_ARCH_DEC */
  
  #ifndef SYS_ARCH_GET
  #define SYS_ARCH_GET(var, ret) do { \
                                  SYS_ARCH_DECL_PROTECT(old_level); \
                                  SYS_ARCH_PROTECT(old_level); \
                                  ret = var; \
                                  SYS_ARCH_UNPROTECT(old_level); \
                                } while(0)
  #endif /* SYS_ARCH_GET */
  
  #ifndef SYS_ARCH_SET
  #define SYS_ARCH_SET(var, val) do { \
                                  SYS_ARCH_DECL_PROTECT(old_level); \
                                  SYS_ARCH_PROTECT(old_level); \
                                  var = val; \
                                  SYS_ARCH_UNPROTECT(old_level); \
                                } while(0)
  #endif /* SYS_ARCH_SET */
  
  #ifndef SYS_ARCH_LOCKED
  #define SYS_ARCH_LOCKED(code) do { \
                                  SYS_ARCH_DECL_PROTECT(old_level); \
                                  SYS_ARCH_PROTECT(old_level); \
                                  code; \
                                  SYS_ARCH_UNPROTECT(old_level); \
                                } while(0)
  #endif /* SYS_ARCH_LOCKED */
  
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* LWIP_HDR_SYS_H */
  