1 files changed, 170 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/strat.c b/reference/C/CONTRIB/SNIP/strat.c
new file mode 100755
index 0000000..fb00d5b
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/strat.c
@@ -0,0 +1,170 @@
+/*
+**  strat.c  10-5-91  Robert Mashlan, public domain
+**
+**   Interface functions to DOS 3.0+ set allocation strategy
+**   and get allocation strategy functions via int 21h,
+**   function 58h.
+**
+**   By setting the dos allocation strategy to LAST_FIT_LOW
+**   before using DOS the set handle count function int 21h,
+**   function 67h, DOS will allocate memory for the extended
+**   file handle table at the end of free memory instead of
+**   after the last heap allocation, with the benefit of
+**   allowing the heap manager make further contiguous
+**   allocations from the operating system.
+**
+*/
+
+#include <stdlib.h>
+#include <dos.h>
+#include "strat.h"
+
+/*
+**   Gets dos memory allocation strategy via function 0x58.
+**   Returns  allocation strategy, else returns -1 and sets
+**   _doserrno on error.
+*/
+
+int get_alloc_strat(void)
+{
+      union REGS r;
+
+      r.x.ax = 0x5800;              /* DOS "get allocation strategy" */
+      int86(0x21,&r,&r);
+      if (r.x.cflag)                /* error? */
+      {
+            _doserrno = r.x.ax;     /* save error code */
+            return -1;
+      }
+      else  return r.x.ax;
+}
+
+/*
+**   Sets DOS memory allocation strategy
+**   returns allocation strategy on success,
+**   else returns -1 and sets _doserrno on error
+*/
+
+int set_alloc_strat( int strat )
+{
+      union REGS r;
+
+      r.x.ax = 0x5801;              /* DOS "set allocation strategy" */
+      r.x.bx = strat;
+      int86(0x21,&r,&r);
+      if (r.x.cflag)                /* error? */
+      {
+            _doserrno = r.x.ax;     /* save error code */
+            return -1;
+      }
+      _doserrno = 0;
+      return strat;
+}
+
+/*
+**   Uses dos function 67h to increase open file handle count.
+**   Returns -1 and sets _doserrno on error, 0 otherwise.
+*/
+
+int set_handle_count( unsigned nhandles )
+{
+      union REGS r;
+
+      r.x.ax = 0x6700;
+      r.x.bx = nhandles;
+      int86(0x21,&r,&r);
+      if(r.x.cflag)
+      {
+            _doserrno = r.x.ax;
+            return -1;
+      }
+      _doserrno = 0;
+      return 0;
+}
+
+#ifdef DEMO
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <io.h>
+#include <fcntl.h>
+
+/*
+**  returns maximum number of files that can be open
+*/
+
+int handle_count(void)
+{
+      int handles[500];
+      int i, result;
+
+      /* try allocating as many file handles as possible */
+
+      for (i = 0; i < 500; i++)
+      {
+            if( (handles[i]=open("NUL",O_WRONLY)) == -1 )
+                  break;
+      }
+      result = i;
+
+      /* close all files opened */
+
+      for (i--; i >= 0; i--)
+            close(handles[i]);
+      return result;
+}
+
+
+/*
+**   Memory test, returns number of kilobytes that
+**   can be allocated before failure.
+*/
+
+int memtest(void)
+{
+      static void *mem[1024];
+      int i,result;
+
+      /* try allocating as many 1K blocks as possible */
+
+      for(i=0;i<1024;i++)
+      {
+            if( (mem[i]=malloc(1024)) == NULL )
+                  break;
+      }
+      result = i;                               /* save result */
+
+      /* free memory allocated */
+
+      for(i--; i >= 0; i--)
+            free(mem[i]);
+      return result;
+}
+
+#define checkdoserror(f) \
+   ((f==-1)?printf("%s failed, doserror = %#02x\n",#f,_doserrno):(void)0)
+
+int main(void)
+{
+      int strat;
+
+      /* do pre-test diagnostics */
+
+      printf("allocated %d Kbytes before failure\n",memtest());
+      printf("opened %d files\n",handle_count());
+
+      strat = get_alloc_strat();  /* save current allocation strategy */
+      checkdoserror(set_alloc_strat(LAST_FIT_LOW));
+      puts("setting handle count to 50, with changed allocation strategy");
+      checkdoserror(set_handle_count(50));
+      checkdoserror(set_alloc_strat(strat)); /* restore strategy */
+
+      /* do post-test diagnostics */
+
+      printf("allocated %d Kbytes before failure\n",memtest());
+      printf("opened %d files\n",handle_count());
+
+      return 0;
+}
+
+#endif