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/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2011-2013, University of Amsterdam
VU University Amsterdam
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.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"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
COPYRIGHT OWNER OR CONTRIBUTORS 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.
*/
#ifndef BUFFER_H_INCLUDED
#define BUFFER_H_INCLUDED
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Triples are buffered in an array. This is used by transactions for
committing, etc. The data is allocated using PL_malloc_uncollectable()
to make sure that discarded triples are not really removed by GC,
notably before their changes can be broadcasted.
FIXME: Check that all triple buffers are allocated either on the stack
or in memory that is scanned by BDWGC. The ones for transactions are
stored on the C-stack.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
#define TFAST_SIZE 64
typedef struct triple_buffer
{ triple **base;
triple **top;
triple **max;
triple *fast[TFAST_SIZE];
} triple_buffer;
static inline void
init_triple_buffer(triple_buffer *b)
{ b->base = b->top = b->fast;
b->max = b->top + TFAST_SIZE;
}
static inline int
is_empty_buffer(triple_buffer *b)
{ return b->top == b->base;
}
static inline int
buffer_triple(triple_buffer *b, triple *t)
{ if ( b->top < b->max )
{ *b->top++ = t;
} else
{ if ( b->base == b->fast )
{ triple **tmp = PL_malloc_uncollectable(TFAST_SIZE*2*sizeof(triple*));
if ( tmp )
{ memcpy(tmp, b->base, (char*)b->top - (char*)b->base);
b->base = tmp;
b->max = b->base + TFAST_SIZE*2;
b->top = b->base + TFAST_SIZE;
*b->top++ = t;
} else
return FALSE;
} else
{ size_t size = (b->max - b->base);
triple **tmp = PL_malloc_uncollectable(size*2*sizeof(triple*));
assert(b->top == b->max);
if ( tmp )
{ memcpy(tmp, b->base, (char*)b->top - (char*)b->base);
PL_free(b->base);
b->base = tmp;
b->top = b->base + size;
b->max = b->base + size*2;
*b->top++ = t;
} else
return FALSE;
}
}
return TRUE;
}
static inline void
free_triple_buffer(triple_buffer *b)
{ if ( b->base && b->base != b->fast )
PL_free(b->base);
}
#endif /*BUFFER_H_INCLUDED*/
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