56 lines
2.1 KiB
C
56 lines
2.1 KiB
C
#include <stdint.h>
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#include <stdbool.h>
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#define SP_ADDR 0xffff
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#define RS_ADDR 0xff00
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#define SYSVARS RS_ADDR-0xb0
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#define MEMSIZE 0x10000
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typedef uint8_t byte;
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typedef uint16_t word;
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// Native words in this C Forth VMs are indexed in an array. The word in memory
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// is the typical 0x00 to indicate native, followed by an index byte. The
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// Execute routine will then know which native word to execute.
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typedef void (*NativeWord) ();
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typedef byte (*IORD) ();
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typedef void (*IOWR) (byte data);
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typedef struct {
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byte mem[MEMSIZE];
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word SP; // parameter Stack Pointer
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word RS; // Return Stack pointer
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word IP; // Interpreter Pointer
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// A list of native words' code. This is filled in VM_init() by calls to
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// native(). The order is very important because we refer to these elements
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// by index. For example, "0x42 CODE FOO" in Forth creates the native word
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// FOO which, when executed, will call the code at index 0x42 in this array.
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NativeWord nativew[0x100];
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byte nativew_count;
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// Array of 0x100 function pointers to IO read and write routines. Leave to
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// NULL when IO port is unhandled.
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IORD iord[0x100];
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IOWR iowr[0x100];
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// Used for keeping track of max RS and min SP during the lifetime of the
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// program. Useful for debugging.
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word maxRS;
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word minSP;
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bool running;
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// Whether we're in stack underflow situation. Alters the behavior of some
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// core action, notably popping. Doesn't stay set for more than a single
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// execute cycle. The goal is to avoid over-popping in native words that
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// pop more than once and thus corrupt memory.
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bool uflw;
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// Same as uflw, but for stack overflow. However, we behave differently with
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// oflw than with uflw. We can't prevent push() and pushRS() because it
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// would prevent us from calling (oflw). Instead, we clear both stacks on
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// oflw conditions, which gives us the room to maneuver.
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bool oflw;
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} VM;
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VM* VM_init(char *bin_path, char *blkfs_path);
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void VM_deinit();
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bool VM_steps(int n);
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void VM_memdump();
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void VM_debugstr(char *s);
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void VM_printdbg();
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