equi/equi.c

/*
 * Equi platform reference implementation
 *
 * Created in 2022 by Luxferre, released into public domain
 *
 * See equi.md file for the specification and manual
 *
 * @license Unlicense <https://unlicense.org>
 * @author Luxferre
 */

/* Standard includes */

#include <stdlib.h>
#include <stdio.h>

/* Definitions section */

#define ushort unsigned short /* basic 16-bit integer */
#define uchar unsigned char /* basic 8-bit integer */
#define WS sizeof(ushort) /* Equi word size in bytes */
#define CLT_ENTRY_LEN 6 /* Amount of significant compiled word characters */
#define CLT_ENTRY_SIZE (CLT_ENTRY_LEN + WS) /* Full size in bytes taken by one CLT entry */

/* Configuration section (constants overridable at compile-time) */

/* Main and return stack size in bytes */
#ifndef STACK_SIZE
#define STACK_SIZE 256
#endif

/* Literal stack size in bytes */
#ifndef LIT_STACK_SIZE
#define LIT_STACK_SIZE 32
#endif

/* GPD (general purpose data) area start address */
#ifndef GPD_AREA_START
#define GPD_AREA_START 0x2300
#endif

/* Command buffer start address */
#ifndef CMD_BUF_START
#define CMD_BUF_START 0x5000
#endif

/* Command buffer size in bytes */
#ifndef CMD_BUF_SIZE
#define CMD_BUF_SIZE 0x5700
#endif

/* Some necessary constants and offsets derived from the above values */
#define STACK_SIZE_WORDS (STACK_SIZE / WS) /* Main and return stack size in words */

#define MAIN_STACK_ADDR 0 /* Main stack address */
#define RETURN_STACK_ADDR STACK_SIZE /* Return stack address */
#define LIT_STACK_ADDR (RETURN_STACK_ADDR + STACK_SIZE) /* Literal stack address */
#define PC_ADDR (LIT_STACK_ADDR + LIT_STACK_SIZE) /* Program counter address */
#define CBP_ADDR (PC_ADDR + WS) /* Compilation buffer pointer location address */
#define CLTP_ADDR (CBP_ADDR + WS) /* Compilation lookup table pointer location address */
#define FLAGS_ADDR (CLTP_ADDR + WS) /* Flags register address */
#define GPD_START_LOC_ADDR (FLAGS_ADDR + 1) /* Location where GPD_AREA_START value is stored */
#define CMD_START_LOC_ADDR (GPD_START_LOC_ADDR + WS) /* Location where CMD_BUF_START value is stored */
#define CMD_SIZE_LOC_ADDR (CMD_START_LOC_ADDR + WS) /* Location where CMD_BUF_SIZE value is stored */
#define CLT_START (CMD_SIZE_LOC_ADDR + 213u) /* should be 0x300 by default */
#define CLT_SIZE (GPD_AREA_START - CLT_START) /* Compilation lookup table size in bytes */
#define CLT_ENTRIES_MAX (CLT_SIZE / CLT_ENTRY_SIZE) /* Maximum amount of entries in CLT, must be integer */
#define GPD_AREA_SIZE (CMD_BUF_START - GPD_AREA_START) /* GPD area size in bytes */

/*
 * Structures that describe Equi machine RAM using the above configuration
 */

struct EquiFlags {
  uchar II:1; /* instruction ignore mode */
  uchar CM:1; /* compilation mode */
  uchar IM:1; /* interpretation mode */
};

struct CLTEntry {
  uchar name[6]; /* compiled word name */
  ushort loc;    /* compiled word location */
};

struct EquiRAM { 
  ushort main_stack[STACK_SIZE_WORDS];
  ushort return_stack[STACK_SIZE_WORDS];
  uchar literal_stack[LIT_STACK_SIZE];
  ushort pc; /* program counter */
  ushort msp; /* main stack pointer */
  ushort rsp; /* return stack pointer */
  uchar lsp; /* literal stack pointer */
  ushort cbp; /* compilation buffer pointer */
  ushort cltp; /* compilation lookup table pointer */
  struct EquiFlags flags;
  ushort gpd_start;
  ushort cmd_start;
  ushort cmd_size;
  uchar reserved[206]; /* reserved space */
  struct CLTEntry clt[CLT_ENTRIES_MAX]; /* compilation lookup table */
  uchar gpd[GPD_AREA_SIZE];
  uchar cmdbuf[CMD_BUF_SIZE];
};


/*
 * Before running the main code, instantiate and initialize the machine RAM
 */

static struct EquiRAM ram = {
  .gpd_start = GPD_AREA_START,
  .cmd_start = CMD_BUF_START,
  .cmd_size = CMD_BUF_SIZE
};

/* Also create an alternative view of the same RAM area for direct offset-based access */
static uchar* flatram = (uchar *)&ram;

int main(int argc, char* argv[]) {

  /* */

  printf("0x%X", ram.cmd_size);

  return 0;
}