text: /*
   * Copyright (c) 2001-2012 Marc Alexander Lehmann <schmorp@schmorp.de>
   *
   * Redistribution and use in source and binary forms, with or without modifica-
   * tion, 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.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
   * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
   * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
   * CIAL, 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 OTH-
   * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * Alternatively, the contents of this file may be used under the terms of
   * the GNU General Public License ("GPL") version 2 or any later version,
   * in which case the provisions of the GPL are applicable instead of
   * the above. If you wish to allow the use of your version of this file
   * only under the terms of the GPL and not to allow others to use your
   * version of this file under the BSD license, indicate your decision
   * by deleting the provisions above and replace them with the notice
   * and other provisions required by the GPL. If you do not delete the
   * provisions above, a recipient may use your version of this file under
   * either the BSD or the GPL.
   *
   * This library is modelled strictly after Ralf S. Engelschalls article at
   * http://www.gnu.org/software/pth/rse-pmt.ps. So most of the credit must
   * go to Ralf S. Engelschall <rse@engelschall.com>.
   *
   * This coroutine library is very much stripped down. You should either
   * build your own process abstraction using it or - better - just use GNU
   * Portable Threads, http://www.gnu.org/software/pth/.
   *
   */
  
  /*
   * 2006-10-26 Include stddef.h on OS X to work around one of its bugs.
   *            Reported by Michael_G_Schwern.
   * 2006-11-26 Use _setjmp instead of setjmp on GNU/Linux.
   * 2007-04-27 Set unwind frame info if gcc 3+ and ELF is detected.
   *            Use _setjmp instead of setjmp on _XOPEN_SOURCE >= 600.
   * 2007-05-02 Add assembly versions for x86 and amd64 (to avoid reliance
   *            on SIGUSR2 and sigaltstack in Crossfire).
   * 2008-01-21 Disable CFI usage on anything but GNU/Linux.
   * 2008-03-02 Switched to 2-clause BSD license with GPL exception.
   * 2008-04-04 New (but highly unrecommended) pthreads backend.
   * 2008-04-24 Reinstate CORO_LOSER (had wrong stack adjustments).
   * 2008-10-30 Support assembly method on x86 with and without frame pointer.
   * 2008-11-03 Use a global asm statement for CORO_ASM, idea by pippijn.
   * 2008-11-05 Hopefully fix misaligned stacks with CORO_ASM/SETJMP.
   * 2008-11-07 rbp wasn't saved in CORO_ASM on x86_64.
   *            introduce coro_destroy, which is a nop except for pthreads.
   *            speed up CORO_PTHREAD. Do no longer leak threads either.
   *            coro_create now allows one to create source coro_contexts.
   *            do not rely on makecontext passing a void * correctly.
   *            try harder to get _setjmp/_longjmp.
   *            major code cleanup/restructuring.
   * 2008-11-10 the .cfi hacks are no longer needed.
   * 2008-11-16 work around a freebsd pthread bug.
   * 2008-11-19 define coro_*jmp symbols for easier porting.
   * 2009-06-23 tentative win32-backend support for mingw32 (Yasuhiro Matsumoto).
   * 2010-12-03 tentative support for uclibc (which lacks all sorts of things).
   * 2011-05-30 set initial callee-saved-registers to zero with CORO_ASM.
   *            use .cfi_undefined rip on linux-amd64 for better backtraces.
   * 2011-06-08 maybe properly implement weird windows amd64 calling conventions.
   * 2011-07-03 rely on __GCC_HAVE_DWARF2_CFI_ASM for cfi detection.
   * 2011-08-08 cygwin trashes stacks, use pthreads with double stack on cygwin.
   * 2012-12-04 reduce misprediction penalty for x86/amd64 assembly switcher.
   * 2012-12-05 experimental fiber backend (allocates stack twice).
   * 2012-12-07 API version 3 - add coro_stack_alloc/coro_stack_free.
   * 2012-12-21 valgrind stack registering was broken.
   */
  
  #ifndef CORO_H
  #define CORO_H
  
  #if __cplusplus
  extern "C" {
  #endif
  
  /*
   * This library consists of only three files
   * coro.h, coro.c and LICENSE (and optionally README)
   *
   * It implements what is known as coroutines, in a hopefully
   * portable way.
   *
   * All compiletime symbols must be defined both when including coro.h
   * (using libcoro) as well as when compiling coro.c (the implementation).
   *
   * You can manually specify which flavour you want. If you don't define
   * any of these, libcoro tries to choose a safe and fast default:
   *
   * -DCORO_UCONTEXT
   *
   *    This flavour uses SUSv2's get/set/swap/makecontext functions that
   *    unfortunately only some unices support, and is quite slow.
   *
   * -DCORO_SJLJ
   *
   *    This flavour uses SUSv2's setjmp/longjmp and sigaltstack functions to
   *    do it's job. Coroutine creation is much slower than UCONTEXT, but
   *    context switching is a bit cheaper. It should work on almost all unices.
   *
   * -DCORO_LINUX
   *
   *    CORO_SJLJ variant.
   *    Old GNU/Linux systems (<= glibc-2.1) only work with this implementation
   *    (it is very fast and therefore recommended over other methods, but
   *    doesn't work with anything newer).
   *
   * -DCORO_LOSER
   *
   *    CORO_SJLJ variant.
   *    Microsoft's highly proprietary platform doesn't support sigaltstack, and
   *    this selects a suitable workaround for this platform. It might not work
   *    with your compiler though - it has only been tested with MSVC 6.
   *
   * -DCORO_FIBER
   *
   *    Slower, but probably more portable variant for the Microsoft operating
   *    system, using fibers. Ignores the passed stack and allocates it internally.
   *    Also, due to bugs in cygwin, this does not work with cygwin.
   *
   * -DCORO_IRIX
   *
   *    CORO_SJLJ variant.
   *    For SGI's version of Microsoft's NT ;)
   *
   * -DCORO_ASM
   *
   *    Hand coded assembly, known to work only on a few architectures/ABI:
   *    GCC + x86/IA32 and amd64/x86_64 + GNU/Linux and a few BSDs. Fastest choice,
   *    if it works.
   *
   * -DCORO_PTHREAD
   *
   *    Use the pthread API. You have to provide <pthread.h> and -lpthread.
   *    This is likely the slowest backend, and it also does not support fork(),
   *    so avoid it at all costs.
   *
   * If you define neither of these symbols, coro.h will try to autodetect
   * the best/safest model. To help with the autodetection, you should check
   * (e.g. using autoconf) and define the following symbols: HAVE_UCONTEXT_H
   * / HAVE_SETJMP_H / HAVE_SIGALTSTACK.
   */
  
  /*
   * Changes when the API changes incompatibly.
   * This is ONLY the API version - there is no ABI compatibility between releases.
   *
   * Changes in API version 2:
   * replaced bogus -DCORO_LOOSE with grammatically more correct -DCORO_LOSER
   * Changes in API version 3:
   * introduced stack management (CORO_STACKALLOC)
   */
  #define CORO_VERSION 3
  
  #include <stddef.h>
  
  /*
   * This is the type for the initialization function of a new coroutine.
   */
  typedef void (*coro_func)(void *);
  
  /*
   * A coroutine state is saved in the following structure. Treat it as an
   * opaque type. errno and sigmask might be saved, but don't rely on it,
   * implement your own switching primitive if you need that.
   */
  typedef struct coro_context coro_context;
  
  /*
   * This function creates a new coroutine. Apart from a pointer to an
   * uninitialised coro_context, it expects a pointer to the entry function
   * and the single pointer value that is given to it as argument.
   *
   * Allocating/deallocating the stack is your own responsibility.
   *
   * As a special case, if coro, arg, sptr and ssze are all zero,
   * then an "empty" coro_context will be created that is suitable
   * as an initial source for coro_transfer.
   *
   * This function is not reentrant, but putting a mutex around it
   * will work.
   */
  void coro_create (coro_context *ctx, /* an uninitialised coro_context */
                    coro_func coro,    /* the coroutine code to be executed */
                    void *arg,         /* a single pointer passed to the coro */
                    void *sptr,        /* start of stack area */
                    size_t ssze);      /* size of stack area in bytes */
  
  /*
   * The following prototype defines the coroutine switching function. It is
   * sometimes implemented as a macro, so watch out.
   *
   * This function is thread-safe and reentrant.
   */
  #if 0
  void coro_transfer (coro_context *prev, coro_context *next);
  #endif
  
  /*
   * The following prototype defines the coroutine destroy function. It
   * is sometimes implemented as a macro, so watch out. It also serves no
   * purpose unless you want to use the CORO_PTHREAD backend, where it is
   * used to clean up the thread. You are responsible for freeing the stack
   * and the context itself.
   *
   * This function is thread-safe and reentrant.
   */
  #if 0
  void coro_destroy (coro_context *ctx);
  #endif
  
  /*****************************************************************************/
  /* optional stack management                                                 */
  /*****************************************************************************/
  /*
   * You can disable all of the stack management functions by
   * defining CORO_STACKALLOC to 0. Otherwise, they are enabled by default.
   *
   * If stack management is enabled, you can influence the implementation via these
   * symbols:
   *
   * -DCORO_USE_VALGRIND
   *
   *    If defined, then libcoro will include valgrind/valgrind.h and register
   *    and unregister stacks with valgrind.
   *
   * -DCORO_GUARDPAGES=n
   *
   *    libcoro will try to use the specified number of guard pages to protect against
   *    stack overflow. If n is 0, then the feature will be disabled. If it isn't
   *    defined, then libcoro will choose a suitable default. If guardpages are not
   *    supported on the platform, then the feature will be silently disabled.
   */
  #ifndef CORO_STACKALLOC
  # define CORO_STACKALLOC 1
  #endif
  
  #if CORO_STACKALLOC
  
  /*
   * The only allowed operations on these struct members is to read the
   * "sptr" and "ssze" members to pass it to coro_create, to read the "sptr"
   * member to see if it is false, in which case the stack isn't allocated,
   * and to set the "sptr" member to 0, to indicate to coro_stack_free to
   * not actually do anything.
   */
  
  struct coro_stack
  {
    void *sptr;
    size_t ssze;
  #if CORO_USE_VALGRIND
    int valgrind_id;
  #endif
  };
  
  /*
   * Try to allocate a stack of at least the given size and return true if
   * successful, or false otherwise.
   *
   * The size is *NOT* specified in bytes, but in units of sizeof (void *),
   * i.e. the stack is typically 4(8) times larger on 32 bit(64 bit) platforms
   * then the size passed in.
   *
   * If size is 0, then a "suitable" stack size is chosen (usually 1-2MB).
   */
  int coro_stack_alloc (struct coro_stack *stack, unsigned int size);
  
  /*
   * Free the stack allocated by coro_stack_alloc again. It is safe to
   * call this function on the coro_stack structure even if coro_stack_alloc
   * failed.
   */
  void coro_stack_free (struct coro_stack *stack);
  
  #endif
  
  /*
   * That was it. No other user-serviceable parts below here.
   */
  
  /*****************************************************************************/
  
  #if !defined CORO_LOSER      && !defined CORO_UCONTEXT \
      && !defined CORO_SJLJ    && !defined CORO_LINUX \
      && !defined CORO_IRIX    && !defined CORO_ASM \
      && !defined CORO_PTHREAD && !defined CORO_FIBER
  # if defined WINDOWS && (defined __i386 || (__x86_64 || defined _M_IX86 || defined _M_AMD64))
  #  define CORO_ASM 1
  # elif defined WINDOWS || defined _WIN32
  #  define CORO_LOSER 1 /* you don't win with windoze */
  # elif __linux && (__i386 || (__x86_64 && !__ILP32))
  #  define CORO_ASM 1
  # elif defined HAVE_UCONTEXT_H
  #  define CORO_UCONTEXT 1
  # elif defined HAVE_SETJMP_H && defined HAVE_SIGALTSTACK
  #  define CORO_SJLJ 1
  # else
  # error unknown or unsupported architecture
  # endif
  #endif
  
  /*****************************************************************************/
  
  #if CORO_UCONTEXT
  
  # include <ucontext.h>
  
  struct coro_context
  {
    ucontext_t uc;
  };
  
  # define coro_transfer(p,n) swapcontext (&((p)->uc), &((n)->uc))
  # define coro_destroy(ctx) (void *)(ctx)
  
  #elif CORO_SJLJ || CORO_LOSER || CORO_LINUX || CORO_IRIX
  
  # if defined(CORO_LINUX) && !defined(_GNU_SOURCE)
  #  define _GNU_SOURCE /* for glibc */
  # endif
  
  # if !CORO_LOSER
  #  include <unistd.h>
  # endif
  
  /* solaris is hopelessly borked, it expands _XOPEN_UNIX to nothing */
  # if __sun
  #  undef _XOPEN_UNIX
  #  define _XOPEN_UNIX 1
  # endif
  
  # include <setjmp.h>
  
  # if _XOPEN_UNIX > 0 || defined (_setjmp)
  #  define coro_jmp_buf      jmp_buf
  #  define coro_setjmp(env)  _setjmp (env)
  #  define coro_longjmp(env) _longjmp ((env), 1)
  # elif CORO_LOSER
  #  define coro_jmp_buf      jmp_buf
  #  define coro_setjmp(env)  setjmp (env)
  #  define coro_longjmp(env) longjmp ((env), 1)
  # else
  #  define coro_jmp_buf      sigjmp_buf
  #  define coro_setjmp(env)  sigsetjmp (env, 0)
  #  define coro_longjmp(env) siglongjmp ((env), 1)
  # endif
  
  struct coro_context
  {
    coro_jmp_buf env;
  };
  
  # define coro_transfer(p,n) do { if (!coro_setjmp ((p)->env)) coro_longjmp ((n)->env); } while (0)
  # define coro_destroy(ctx) (void *)(ctx)
  
  #elif CORO_ASM
  
  struct coro_context
  {
    void **sp; /* must be at offset 0 */
  };
  
  void __attribute__ ((__noinline__, __regparm__(2)))
  coro_transfer (coro_context *prev, coro_context *next);
  
  # define coro_destroy(ctx) (void *)(ctx)
  
  #elif CORO_PTHREAD
  
  # include <pthread.h>
  
  extern pthread_mutex_t coro_mutex;
  
  struct coro_context
  {
    pthread_cond_t cv;
    pthread_t id;
  };
  
  void coro_transfer (coro_context *prev, coro_context *next);
  void coro_destroy (coro_context *ctx);
  
  #elif CORO_FIBER
  
  struct coro_context
  {
    void *fiber;
    /* only used for initialisation */
    coro_func coro;
    void *arg;
  };
  
  void coro_transfer (coro_context *prev, coro_context *next);
  void coro_destroy (coro_context *ctx);
  
  #endif
  
  #if __cplusplus
  }
  #endif
  
  #endif
  
  