--- /dev/null
+/* $Id$ */
+
+/* _PDCLIB_allocpages( int const )
+
+ This file is part of the Public Domain C Library (PDCLib).
+ Permission is granted to use, modify, and / or redistribute at will.
+*/
+
+/* This is an example implementation of _PDCLIB_allocpages() (declared in
+ _PDCLIB_config.h), fit for use with POSIX kernels.
+*/
+
+#include <stdint.h>
+#include <stddef.h>
+
+void * sbrk( intptr_t );
+
+#ifndef _PDCLIB_GLUE_H
+#define _PDCLIB_GLUE_H _PDCLIB_GLUE_H
+#include <_PDCLIB_glue.h>
+#endif
+
+static void * membreak = NULL;
+
+void * _PDCLIB_allocpages( int const n )
+{
+ if ( membreak == NULL )
+ {
+ /* first call, make sure end-of-heap is page-aligned */
+ intptr_t unaligned = 0;
+ membreak = sbrk( 0 );
+ unaligned = _PDCLIB_PAGESIZE - (intptr_t)membreak % _PDCLIB_PAGESIZE;
+ if ( unaligned < _PDCLIB_PAGESIZE )
+ {
+ /* end-of-heap not page-aligned - adjust */
+ if ( sbrk( unaligned ) != membreak )
+ {
+ /* error */
+ return NULL;
+ }
+ membreak = (char *)membreak + unaligned;
+ }
+ }
+ /* increasing or decreasing heap - standard operation */
+ void * oldbreak = membreak;
+ membreak = (void *)( (char *)membreak + ( n * _PDCLIB_PAGESIZE ) );
+ if ( sbrk( (char*)membreak - (char*)oldbreak ) == membreak )
+ {
+ /* successful */
+ return oldbreak;
+ }
+ else
+ {
+ /* out of memory */
+ membreak = oldbreak;
+ return NULL;
+ }
+}
+
+#ifdef TEST
+#include <_PDCLIB_test.h>
+
+int main( void )
+{
+ char * startbreak = sbrk( 0 );
+ TESTCASE( _PDCLIB_allocpages( 0 ) );
+ TESTCASE( ( (char *)sbrk( 0 ) - startbreak ) <= _PDCLIB_PAGESIZE );
+ startbreak = sbrk( 0 );
+ TESTCASE( _PDCLIB_allocpages( 1 ) );
+ TESTCASE( sbrk( 0 ) == startbreak + ( 1 * _PDCLIB_PAGESIZE ) );
+ TESTCASE( _PDCLIB_allocpages( 5 ) );
+ TESTCASE( sbrk( 0 ) == startbreak + ( 6 * _PDCLIB_PAGESIZE ) );
+ TESTCASE( _PDCLIB_allocpages( -3 ) );
+ TESTCASE( sbrk( 0 ) == startbreak + ( 3 * _PDCLIB_PAGESIZE ) );
+}
+
+#endif