retroforth/vm/nga-c-no-libc/retro.c
crc f1d8d866d8 vm/nga-c-no-libc: update sources and work on openbsd support (now builds, but does not run}
FossilOrigin-Name: 3df16411b8c768560c08602d7d88b7bc0dffffb636a099966477623a725075e8
2019-12-20 19:04:13 +00:00

658 lines
16 KiB
C

/* RETRO -------------------------------------------------------------
A personal, minimalistic forth
Copyright (c) 2016 - 2019 Charles Childers
This is the `repl`, a basic interactive interface for RETRO. It is
intended to be simple and very minimalistic, providing the minimal
I/O and additions needed to support a basic RETRO system. For a much
larger system, see `rre`.
I'll include commentary throughout the source, so read on.
---------------------------------------------------------------------*/
int getchar(void);
int putchar(int c);
int r_strlen(char *str) {
const char *s;
for (s = str; *s; ++s);
return(s - str);
}
int r_strcmp(const char *s1, const char *s2) {
while (*s1 == *s2++)
if (*s1++ == '\0')
return (0);
return (*(const unsigned char *)s1 - *(const unsigned char *)(s2 - 1));
}
/*---------------------------------------------------------------------
First, a few constants relating to the image format and memory
layout. If you modify the kernel (Rx.md), these will need to be
altered to match your memory layout.
---------------------------------------------------------------------*/
#define TIB 1025
#define D_OFFSET_LINK 0
#define D_OFFSET_XT 1
#define D_OFFSET_CLASS 2
#define D_OFFSET_NAME 3
/*---------------------------------------------------------------------
Next we get into some things that relate to the Nga virtual machine
that RETRO runs on.
---------------------------------------------------------------------*/
#define CELL long /* Cell size (32 bit, signed integer */
#define IMAGE_SIZE 524288 * 8 /* Amount of RAM. 4MiB by default. */
#define ADDRESSES 1024 /* Depth of address stack */
#define STACK_DEPTH 128 /* Depth of data stack */
CELL sp, rp, ip; /* Data, address, instruction pointers */
CELL data[STACK_DEPTH]; /* The data stack */
CELL address[ADDRESSES]; /* The address stack */
CELL memory[IMAGE_SIZE + 1]; /* The memory for the image */
#define TOS data[sp] /* Shortcut for top item on stack */
#define NOS data[sp-1] /* Shortcut for second item on stack */
#define TORS address[rp] /* Shortcut for top item on address stack */
#define NUM_DEVICES 1
typedef void (*Handler)(void);
Handler IO_deviceHandlers[NUM_DEVICES + 1];
Handler IO_queryHandlers[NUM_DEVICES + 1];
#include "image.c"
/*---------------------------------------------------------------------
Moving forward, a few variables. These are updated to point to the
latest values in the image.
---------------------------------------------------------------------*/
CELL Dictionary;
CELL NotFound;
CELL interpret;
/*---------------------------------------------------------------------
Function prototypes.
---------------------------------------------------------------------*/
CELL stack_pop();
void stack_push(CELL value);
int string_inject(char *str, int buffer);
char *string_extract(int at);
int d_link(CELL dt);
int d_xt(CELL dt);
int d_class(CELL dt);
int d_name(CELL dt);
int d_lookup(CELL Dictionary, char *name);
CELL d_xt_for(char *Name, CELL Dictionary);
void update_rx();
void execute(int cell);
void evaluate(char *s);
int not_eol(int ch);
void read_token(char *token_buffer, int echo);
CELL ngaLoadImage(char *imageFile);
void ngaPrepare();
void ngaProcessOpcode(CELL opcode);
void ngaProcessPackedOpcodes(CELL opcode);
int ngaValidatePackedOpcodes(CELL opcode);
/*---------------------------------------------------------------------
Here's an output helper. I define a wrapper over `write` to avoid
using `printf()`.
---------------------------------------------------------------------*/
void retro_puts(char *s) {
while (*s) putchar(*s++);
}
/*---------------------------------------------------------------------
Now to the fun stuff: interfacing with the virtual machine. There are
a things I like to have here:
- push a value to the stack
- pop a value off the stack
- extract a string from the image
- inject a string into the image.
- lookup dictionary headers and access dictionary fields
---------------------------------------------------------------------*/
/*---------------------------------------------------------------------
Stack push/pop is easy. I could avoid these, but it aids in keeping
the code readable, so it's worth the slight overhead.
---------------------------------------------------------------------*/
CELL stack_pop() {
sp--;
return data[sp + 1];
}
void stack_push(CELL value) {
sp++;
data[sp] = value;
}
/*---------------------------------------------------------------------
Strings are next. RETRO uses C-style NULL terminated strings. So I
can easily inject or extract a string. Injection iterates over the
string, copying it into the image. This also takes care to ensure
that the NULL terminator is added.
---------------------------------------------------------------------*/
int string_inject(char *str, int buffer) {
int i = 0;
while (*str) {
memory[buffer + i] = (CELL)*str++;
memory[buffer + i + 1] = 0;
i++;
}
return buffer;
}
/*---------------------------------------------------------------------
Extracting a string is similar, but I have to iterate over the VM
memory instead of a C string and copy the charaters into a buffer.
This uses a static buffer (`string_data`) as I prefer to avoid using
`malloc()`.
---------------------------------------------------------------------*/
char string_data[1025];
char *string_extract(int at) {
CELL starting = at;
CELL i = 0;
while(memory[starting] && i < 1024)
string_data[i++] = (char)memory[starting++];
string_data[i] = 0;
return (char *)string_data;
}
/*---------------------------------------------------------------------
Continuing along, I now define functions to access the dictionary.
RETRO's dictionary is a linked list. Each entry is setup like:
0000 Link to previous entry (NULL if this is the root entry)
0001 Pointer to definition start
0002 Pointer to class handler
0003 Start of a NULL terminated string with the word name
First, functions to access each field. The offsets were defineed at
the start of the file.
---------------------------------------------------------------------*/
int d_link(CELL dt) {
return dt + D_OFFSET_LINK;
}
int d_xt(CELL dt) {
return dt + D_OFFSET_XT;
}
int d_class(CELL dt) {
return dt + D_OFFSET_CLASS;
}
int d_name(CELL dt) {
return dt + D_OFFSET_NAME;
}
/*---------------------------------------------------------------------
Next, a more complext word. This will walk through the entries to
find one with a name that matches the specified name. This is *slow*,
but works ok unless you have a really large dictionary. (I've not
run into issues with this in practice).
---------------------------------------------------------------------*/
int d_lookup(CELL Dictionary, char *name) {
CELL dt = 0;
CELL i = Dictionary;
char *dname;
while (memory[i] != 0 && i != 0) {
dname = string_extract(d_name(i));
if (r_strcmp(dname, name) == 0) {
dt = i;
i = 0;
} else {
i = memory[i];
}
}
return dt;
}
/*---------------------------------------------------------------------
My last dictionary related word returns the `xt` pointer for a word.
This is used to help keep various important bits up to date.
---------------------------------------------------------------------*/
CELL d_xt_for(char *Name, CELL Dictionary) {
return memory[d_xt(d_lookup(Dictionary, Name))];
}
/*---------------------------------------------------------------------
This interface tracks a few words and variables in the image. These
are:
Dictionary - the latest dictionary header
NotFound - called when a word is not found
interpret - the heart of the interpreter/compiler
I have to call this periodically, as the Dictionary will change as
new words are defined, and the user might write a new error handler
or interpreter.
---------------------------------------------------------------------*/
void update_rx() {
Dictionary = memory[2];
NotFound = d_xt_for("err:notfound", Dictionary);
interpret = d_xt_for("interpret", Dictionary);
}
/*---------------------------------------------------------------------
This is an implementation of the generic output device. It's set to
write output to the standard display.
---------------------------------------------------------------------*/
void generic_output() {
putchar(stack_pop());
}
void generic_output_query() {
stack_push(0);
stack_push(0);
}
/*---------------------------------------------------------------------
With these out of the way, I implement `execute`, which takes an
address and runs the code at it. This has a couple of interesting
bits.
Nga uses packed instruction bundles, with up to four instructions per
bundle. Since RETRO requires an additional instruction to handle
displaying a character, I define the handler for that here.
This will also exit if the address stack depth is zero (meaning that
the word being run, and it's dependencies) are finished.
---------------------------------------------------------------------*/
void execute(int cell) {
CELL opcode;
rp = 1;
ip = cell;
while (ip < IMAGE_SIZE) {
if (ip == NotFound) {
retro_puts(string_extract(TIB));
retro_puts(" ?\n");
}
opcode = memory[ip];
if (ngaValidatePackedOpcodes(opcode) != 0) {
ngaProcessPackedOpcodes(opcode);
} else {
retro_puts("Invalid instruction!\n");
retro_puts("System halted.\n");
while(1);
}
ip++;
if (rp == 0)
ip = IMAGE_SIZE;
}
}
/*---------------------------------------------------------------------
RETRO's `interpret` word expects a token on the stack. This next
function copies a token to the `TIB` (text input buffer) and then
calls `interpret` to process it.
---------------------------------------------------------------------*/
void evaluate(char *s) {
if (r_strlen(s) == 0) return;
update_rx();
string_inject(s, TIB);
stack_push(TIB);
execute(interpret);
}
/*---------------------------------------------------------------------
`read_token` reads a token from the specified file. It will stop on
a whitespace or newline. It also tries to handle backspaces, though
the success of this depends on how your terminal is configured.
---------------------------------------------------------------------*/
int not_eol(int ch) {
return (ch != (char)10) && (ch != (char)13) && (ch != (char)32) && (ch != 0);
}
void read_token(char *token_buffer, int echo) {
int ch = getchar();
if (echo != 0)
putchar(ch);
int count = 0;
while (not_eol(ch))
{
if ((ch == 8 || ch == 127) && count > 0) {
count--;
if (echo != 0) {
putchar(8);
putchar(32);
putchar(8);
}
} else {
token_buffer[count++] = ch;
}
ch = getchar();
if (echo != 0)
putchar(ch);
}
token_buffer[count] = '\0';
}
/*---------------------------------------------------------------------
The `main()` routine. This sets up the Nga VM, loads the image, and
enters a loop.
The loop:
- reads input
- otherwise, pass to `evaluate()` to run
---------------------------------------------------------------------*/
int main(int argc, char **argv) {
char input[1024];
IO_deviceHandlers[0] = generic_output;
IO_queryHandlers[0] = generic_output_query;
ngaPrepare();
for (CELL i = 0; i < ngaImageCells; i++)
memory[i] = ngaImage[i];
update_rx();
retro_puts("RETRO Listener (c) 2016-2019, Charles Childers\n\n");
while(1) {
Dictionary = memory[2];
read_token(input, 0);
evaluate(input);
}
return 0;
}
/* Nga ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Copyright (c) 2008 - 2019, Charles Childers
Copyright (c) 2009 - 2010, Luke Parrish
Copyright (c) 2010, Marc Simpson
Copyright (c) 2010, Jay Skeer
Copyright (c) 2011, Kenneth Keating
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
enum vm_opcode {
VM_NOP, VM_LIT, VM_DUP, VM_DROP, VM_SWAP, VM_PUSH, VM_POP,
VM_JUMP, VM_CALL, VM_CCALL, VM_RETURN, VM_EQ, VM_NEQ, VM_LT,
VM_GT, VM_FETCH, VM_STORE, VM_ADD, VM_SUB, VM_MUL, VM_DIVMOD,
VM_AND, VM_OR, VM_XOR, VM_SHIFT, VM_ZRET, VM_HALT, VM_IE,
VM_IQ, VM_II
};
#define NUM_OPS VM_II + 1
#ifndef NUM_DEVICES
#define NUM_DEVICES 0
#endif
CELL ngaLoadImage(char *imageFile) {
CELL i;
for (i = 0; i < ngaImageCells; i++)
memory[i] = ngaImage[i];
return i;
}
void ngaPrepare() {
ip = sp = rp = 0;
for (ip = 0; ip < IMAGE_SIZE; ip++)
memory[ip] = VM_NOP;
for (ip = 0; ip < STACK_DEPTH; ip++)
data[ip] = 0;
for (ip = 0; ip < ADDRESSES; ip++)
address[ip] = 0;
}
void inst_nop() {
}
void inst_lit() {
sp++;
ip++;
TOS = memory[ip];
}
void inst_dup() {
sp++;
data[sp] = NOS;
}
void inst_drop() {
data[sp] = 0;
if (--sp < 0)
ip = IMAGE_SIZE;
}
void inst_swap() {
CELL a;
a = TOS;
TOS = NOS;
NOS = a;
}
void inst_push() {
rp++;
TORS = TOS;
inst_drop();
}
void inst_pop() {
sp++;
TOS = TORS;
rp--;
}
void inst_jump() {
ip = TOS - 1;
inst_drop();
}
void inst_call() {
rp++;
TORS = ip;
ip = TOS - 1;
inst_drop();
}
void inst_ccall() {
CELL a, b;
a = TOS; inst_drop(); /* False */
b = TOS; inst_drop(); /* Flag */
if (b != 0) {
rp++;
TORS = ip;
ip = a - 1;
}
}
void inst_return() {
ip = TORS;
rp--;
}
void inst_eq() {
NOS = (NOS == TOS) ? -1 : 0;
inst_drop();
}
void inst_neq() {
NOS = (NOS != TOS) ? -1 : 0;
inst_drop();
}
void inst_lt() {
NOS = (NOS < TOS) ? -1 : 0;
inst_drop();
}
void inst_gt() {
NOS = (NOS > TOS) ? -1 : 0;
inst_drop();
}
void inst_fetch() {
switch (TOS) {
case -1: TOS = sp - 1; break;
case -2: TOS = rp; break;
case -3: TOS = IMAGE_SIZE; break;
default: TOS = memory[TOS]; break;
}
}
void inst_store() {
if (TOS <= IMAGE_SIZE && TOS >= 0) {
memory[TOS] = NOS;
inst_drop();
inst_drop();
} else {
ip = IMAGE_SIZE;
}
}
void inst_add() {
NOS += TOS;
inst_drop();
}
void inst_sub() {
NOS -= TOS;
inst_drop();
}
void inst_mul() {
NOS *= TOS;
inst_drop();
}
void inst_divmod() {
CELL a, b;
a = TOS;
b = NOS;
TOS = b / a;
NOS = b % a;
}
void inst_and() {
NOS = TOS & NOS;
inst_drop();
}
void inst_or() {
NOS = TOS | NOS;
inst_drop();
}
void inst_xor() {
NOS = TOS ^ NOS;
inst_drop();
}
void inst_shift() {
CELL y = TOS;
CELL x = NOS;
if (TOS < 0)
NOS = NOS << (TOS * -1);
else {
if (x < 0 && y > 0)
NOS = x >> y | ~(~0U >> y);
else
NOS = x >> y;
}
inst_drop();
}
void inst_zret() {
if (TOS == 0) {
inst_drop();
ip = TORS;
rp--;
}
}
void inst_halt() {
ip = IMAGE_SIZE;
}
void inst_ie() {
sp++;
TOS = NUM_DEVICES;
}
void inst_iq() {
CELL Device = TOS;
inst_drop();
IO_queryHandlers[Device]();
}
void inst_ii() {
CELL Device = TOS;
inst_drop();
IO_deviceHandlers[Device]();
}
Handler instructions[NUM_OPS] = {
inst_nop, inst_lit, inst_dup, inst_drop, inst_swap, inst_push, inst_pop,
inst_jump, inst_call, inst_ccall, inst_return, inst_eq, inst_neq, inst_lt,
inst_gt, inst_fetch, inst_store, inst_add, inst_sub, inst_mul, inst_divmod,
inst_and, inst_or, inst_xor, inst_shift, inst_zret, inst_halt, inst_ie,
inst_iq, inst_ii
};
void ngaProcessOpcode(CELL opcode) {
if (opcode != 0)
instructions[opcode]();
}
int ngaValidatePackedOpcodes(CELL opcode) {
CELL raw = opcode;
CELL current;
int valid = -1;
int i;
for (i = 0; i < 4; i++) {
current = raw & 0xFF;
if (!(current >= 0 && current <= 29))
valid = 0;
raw = raw >> 8;
}
return valid;
}
void ngaProcessPackedOpcodes(CELL opcode) {
CELL raw = opcode;
int i;
for (i = 0; i < 4; i++) {
ngaProcessOpcode(raw & 0xFF);
raw = raw >> 8;
}
}