atomic.hpp

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               : "memory", "cc");                   // clobbered   
   return prev;
}

//! Atomically increment an apr_uint32_t by 1
//! "mem": pointer to the object
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_inc32(volatile boost::uint32_t *mem)
{  return atomic_add32(mem, 1);  }

//! Atomically decrement an boost::uint32_t by 1
//! "mem": pointer to the atomic value
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_dec32(volatile boost::uint32_t *mem)
{  return atomic_add32(mem, boost::uint32_t(-1u));  }

//! Atomically read an boost::uint32_t from memory
inline boost::uint32_t atomic_read32(volatile boost::uint32_t *mem)
{  return *mem;   }

//! Atomically set an boost::uint32_t in memory
//! "mem": pointer to the object
//! "param": val value that the object will assume
inline void atomic_write32(volatile boost::uint32_t *mem, boost::uint32_t val)
{  *mem = val; }

}  //namespace detail{
}  //namespace interprocess{
}  //namespace boost{

#elif defined(__GNUC__) && ( __GNUC__ * 100 + __GNUC_MINOR__ >= 401 )

namespace boost {
namespace interprocess {
namespace detail{

//! Atomically add 'val' to an boost::uint32_t
//! "mem": pointer to the object
//! "val": amount to add
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_add32
   (volatile boost::uint32_t *mem, boost::uint32_t val)
{  return __sync_fetch_and_add(const_cast<boost::uint32_t *>(mem), val);   }

//! Atomically increment an apr_uint32_t by 1
//! "mem": pointer to the object
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_inc32(volatile boost::uint32_t *mem)
{  return atomic_add32(mem, 1);  }

//! Atomically decrement an boost::uint32_t by 1
//! "mem": pointer to the atomic value
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_dec32(volatile boost::uint32_t *mem)
{  return atomic_add32(mem, (boost::uint32_t)-1);   }

//! Atomically read an boost::uint32_t from memory
inline boost::uint32_t atomic_read32(volatile boost::uint32_t *mem)
{  return *mem;   }

//! Compare an boost::uint32_t's value with "cmp".
//! If they are the same swap the value with "with"
//! "mem": pointer to the value
//! "with" what to swap it with
//! "cmp": the value to compare it to
//! Returns the old value of *mem
inline boost::uint32_t atomic_cas32
   (volatile boost::uint32_t *mem, boost::uint32_t with, boost::uint32_t cmp)
{  return __sync_val_compare_and_swap(const_cast<boost::uint32_t *>(mem), with, cmp);   }

//! Atomically set an boost::uint32_t in memory
//! "mem": pointer to the object
//! "param": val value that the object will assume
inline void atomic_write32(volatile boost::uint32_t *mem, boost::uint32_t val)
{  *mem = val; }

}  //namespace detail{
}  //namespace interprocess{
}  //namespace boost{

#elif (defined(sun) || defined(__sun))

#include <atomic.h>

namespace boost{
namespace interprocess{
namespace detail{

//! Atomically add 'val' to an boost::uint32_t
//! "mem": pointer to the object
//! "val": amount to add
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_add32(volatile boost::uint32_t *mem, boost::uint32_t val)
{   return atomic_add_32_nv(reinterpret_cast<volatile ::uint32_t*>(mem), (int32_t)val) - val;   }

//! Compare an boost::uint32_t's value with "cmp".
//! If they are the same swap the value with "with"
//! "mem": pointer to the value
//! "with" what to swap it with
//! "cmp": the value to compare it to
//! Returns the old value of *mem
inline boost::uint32_t atomic_cas32
   (volatile boost::uint32_t *mem, boost::uint32_t with, boost::uint32_t cmp)
{  return atomic_cas_32(reinterpret_cast<volatile ::uint32_t*>(mem), cmp, with);  }

//! Atomically increment an apr_uint32_t by 1
//! "mem": pointer to the object
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_inc32(volatile boost::uint32_t *mem)
{  return atomic_add_32_nv(reinterpret_cast<volatile ::uint32_t*>(mem), 1) - 1; }

//! Atomically decrement an boost::uint32_t by 1
//! "mem": pointer to the atomic value
//! Returns the old value pointed to by mem
inline boost::uint32_t atomic_dec32(volatile boost::uint32_t *mem)
{  return atomic_add_32_nv(reinterpret_cast<volatile ::uint32_t*>(mem), (boost::uint32_t)-1) + 1; }

//! Atomically read an boost::uint32_t from memory
inline boost::uint32_t atomic_read32(volatile boost::uint32_t *mem)
{  return *mem;   }

//! Atomically set an boost::uint32_t in memory
//! "mem": pointer to the object
//! "param": val value that the object will assume
inline void atomic_write32(volatile boost::uint32_t *mem, boost::uint32_t val)
{  *mem = val; }

}  //namespace detail{
}  //namespace interprocess{
}  //namespace boost{

#elif defined(__osf__) && defined(__DECCXX)

#include <machine/builtins.h>
#include <c_asm.h>

namespace boost{
namespace interprocess{
namespace detail{

//! Atomically decrement a uint32_t by 1
//! "mem": pointer to the atomic value
//! Returns the old value pointed to by mem
//! Acquire, memory barrier after decrement.
inline boost::uint32_t atomic_dec32(volatile boost::uint32_t *mem)
{  boost::uint32_t old_val = __ATOMIC_DECREMENT_LONG(mem); __MB(); return old_val; }

//! Atomically increment a uint32_t by 1
//! "mem": pointer to the object
//! Returns the old value pointed to by mem
//! Release, memory barrier before increment.
inline boost::uint32_t atomic_inc32(volatile boost::uint32_t *mem)
{  __MB(); return __ATOMIC_INCREMENT_LONG(mem); }

// Rational for the implementation of the atomic read and write functions.
//
// 1. The Alpha Architecture Handbook requires that access to a byte,
// an aligned word, an aligned longword, or an aligned quadword is
// atomic. (See 'Alpha Architecture Handbook', version 4, chapter 5.2.2.)
//
// 2. The CXX User's Guide states that volatile quantities are accessed
// with single assembler instructions, and that a compilation error
// occurs when declaring a quantity as volatile which is not properly
// aligned.

//! Atomically read an boost::uint32_t from memory
//! Acquire, memory barrier after load.
inline boost::uint32_t atomic_read32(volatile boost::uint32_t *mem)
{  boost::uint32_t old_val = *mem; __MB(); return old_val;  }

//! Atomically set an boost::uint32_t in memory
//! "mem": pointer to the object
//! "param": val value that the object will assume
//! Release, memory barrier before store.
inline void atomic_write32(volatile boost::uint32_t *mem, boost::uint32_t val)
{  __MB(); *mem = val; }

//! Compare an boost::uint32_t's value with "cmp".
//! If they are the same swap the value with "with"
//! "mem": pointer to the value
//! "with" what to swap it with
//! "cmp": the value to compare it to
//! Returns the old value of *mem
//! Memory barrier between load and store.
inline boost::uint32_t atomic_cas32(
  volatile boost::uint32_t *mem, boost::uint32_t with, boost::uint32_t cmp)
{
  // Note:
  //
  // Branch prediction prefers backward branches, and the Alpha Architecture
  // Handbook explicitely states that the loop should not be implemented like
  // it is below. (See chapter 4.2.5.) Therefore the code should probably look
  // like this:
  //
  // return asm(
  //   "10: ldl_l %v0,(%a0) ;"
  //   "    cmpeq %v0,%a2,%t0 ;"
  //   "    beq %t0,20f ;"
  //   "    mb ;"
  //   "    mov %a1,%t0 ;"
  //   "    stl_c %t0,(%a0) ;"
  //   "    beq %t0,30f ;"
  //   "20: ret ;"
  //   "30: br 10b;",
  //   mem, with, cmp);
  //
  // But as the compiler always transforms this into the form where a backward
  // branch is taken on failure, we can as well implement it in the straight
  // forward form, as this is what it will end up in anyway.

  return asm(
    "10: ldl_l %v0,(%a0) ;"    // load prev value from mem and lock mem
    "    cmpeq %v0,%a2,%t0 ;"  // compare with given value
    "    beq %t0,20f ;"        // if not equal, we're done
    "    mb ;"                 // memory barrier
    "    mov %a1,%t0 ;"        // load new value into scratch register
    "    stl_c %t0,(%a0) ;"    // store new value to locked mem (overwriting scratch)
    "    beq %t0,10b ;"        // store failed because lock has been stolen, retry
    "20: ",
    mem, with, cmp);
}

}  //namespace detail{
}  //namespace interprocess{
}  //namespace boost{

#else

#error No atomic operations implemented for this platform, sorry!

#endif

#include <boost/interprocess/detail/config_end.hpp>

#endif   //BOOST_INTERPROCESS_DETAIL_ATOMIC_HPP