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equi.c

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+/*
+ * 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 */
+  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[207]; /* 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;
+}