51 lines
902 B
C
51 lines
902 B
C
#include <cpm.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <unistd.h>
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#define OUT_OF_MEMORY (void*)(-1) /* sbrk returns this on failure */
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#define STACK_BUFFER 128 /* number of bytes to leave for stack */
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extern char _end[1];
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int brk(void* newend)
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{
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/* We determine the amount of free memory by looking at the address of the
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* BDOS vector at 0x0006. */
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char* memtop = (char*) ((*(unsigned char*)0x0007)<<8);
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char* p = newend;
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if ((p >= memtop) ||
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(p < _end))
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return -1;
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cpm_ram = p;
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return 0;
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}
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void* sbrk(int increment)
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{
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char* old;
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char* new;
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if (increment == 0)
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return cpm_ram;
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old = cpm_ram;
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new = old + increment;
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if ((increment > 0) && (new <= old))
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goto out_of_memory;
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else if ((increment < 0) && (new >= old))
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goto out_of_memory;
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if (brk(new) < 0)
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goto out_of_memory;
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return old;
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out_of_memory:
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errno = ENOMEM;
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return OUT_OF_MEMORY;
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}
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