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/* Copyright (C) 2023 Aryadev Chavali
* You may distribute and modify this code under the terms of the
* GPLv2 license. You should have received a copy of the GPLv2
* license with this file. If not, please write to:
* aryadev@aryadevchavali.com.
* Created: 2023-10-15
* Author: Aryadev Chavali
* Description: Entrypoint to program
*/
#include <stdio.h>
#include <string.h>
#include "./base.h"
#include "./inst.h"
#define VM_BYTE_REGISTERS 8
#define VM_WORD_REGISTERS 8
#define VM_FLOAT_REGISTERS 8
typedef struct
{
struct Registers
{
byte b[VM_BYTE_REGISTERS];
word w[VM_WORD_REGISTERS];
f64 f[VM_FLOAT_REGISTERS];
} registers;
struct Stack
{
byte *data;
word ptr, max;
} stack;
struct Program
{
inst_t *instructions;
word ptr, max;
} program;
} vm_t;
void vm_load_program(vm_t *vm, inst_t *instructions, size_t size)
{
vm->program.instructions = instructions;
vm->program.max = size;
vm->program.ptr = 0;
}
void vm_load_stack(vm_t *vm, byte *bytes, size_t size)
{
vm->stack.data = bytes;
vm->stack.max = size;
vm->stack.ptr = 0;
}
void vm_push_byte(vm_t *vm, data_t b)
{
if (vm->stack.ptr >= vm->stack.max)
// TODO: Error STACK_OVERFLOW
return;
vm->stack.data[vm->stack.ptr++] = b.as_byte;
}
void vm_push_word(vm_t *vm, data_t w)
{
if (vm->stack.ptr + WORD_SIZE >= vm->stack.max)
// TODO: Error STACK_OVERFLOW
return;
// By default store in big endian
for (size_t i = 64; i > 0; i -= 8)
{
const word mask = ((word)0b11111111) << (i - 8);
byte b = (w.as_word & mask) >> (i - 8);
vm_push_byte(vm, DBYTE(b));
}
}
void vm_push_float(vm_t *vm, data_t f)
{
if (vm->stack.ptr + FLOAT_SIZE >= vm->stack.max)
// TODO: Error STACK_OVERFLOW
return;
// TODO: Make this machine independent (encode IEEE754 floats
// yourself?)
memcpy(vm->stack.data + vm->stack.ptr, &f.as_float, FLOAT_SIZE);
vm->stack.ptr += FLOAT_SIZE;
}
void vm_mov_byte(vm_t *vm, data_t b, word reg)
{
if (reg >= VM_BYTE_REGISTERS)
// TODO: Error (reg is not a valid byte register)
return;
vm->registers.b[reg] = b.as_byte;
}
void vm_mov_word(vm_t *vm, data_t w, word reg)
{
if (reg >= VM_WORD_REGISTERS)
// TODO: Error (reg is not a valid byte register)
return;
vm->registers.w[reg] = w.as_word;
}
void vm_mov_float(vm_t *vm, data_t f, word reg)
{
if (reg >= VM_FLOAT_REGISTERS)
// TODO: Error (reg is not a valid byte register)
return;
vm->registers.f[reg] = f.as_float;
}
data_t vm_pop_byte(vm_t *vm)
{
if (vm->stack.ptr == 0)
// TODO: Error STACK_UNDERFLOW
return DBYTE(0);
return DBYTE(vm->stack.data[--vm->stack.ptr]);
}
data_t vm_pop_word(vm_t *vm)
{
if (vm->stack.ptr < WORD_SIZE)
// TODO: Error STACK_UNDERFLOW
return DWORD(0);
word w = 0;
for (size_t i = 0; i < WORD_SIZE; ++i)
{
data_t b = vm_pop_byte(vm);
w = w | ((word)(b.as_byte) << (i * 8));
}
return DWORD(w);
}
data_t vm_pop_float(vm_t *vm)
{
if (vm->stack.ptr < FLOAT_SIZE)
// TODO: Error STACK_UNDERFLOW
return DFLOAT(0);
f64 f = 0;
// TODO: Make this machine independent (encode IEEE754 floats
// yourself?)
memcpy(&f, vm->stack.data + vm->stack.ptr - FLOAT_SIZE, FLOAT_SIZE);
vm->stack.ptr -= FLOAT_SIZE;
return DFLOAT(f);
}
typedef void (*push_f)(vm_t *, data_t);
typedef void (*mov_f)(vm_t *, data_t, word);
static const push_f PUSH_ROUTINES[] = {
[OP_PUSH_BYTE] = vm_push_byte,
[OP_PUSH_WORD] = vm_push_word,
[OP_PUSH_FLOAT] = vm_push_float,
};
static const mov_f MOV_ROUTINES[] = {
[OP_MOV_BYTE] = vm_mov_byte,
[OP_MOV_WORD] = vm_mov_word,
[OP_MOV_FLOAT] = vm_mov_float,
};
void vm_execute(vm_t *vm)
{
struct Program *prog = &vm->program;
if (prog->ptr >= prog->max)
// TODO: Error (Went past end of program)
return;
inst_t instruction = prog->instructions[prog->ptr];
if (OPCODE_IS_PUSH(instruction.opcode))
{
PUSH_ROUTINES[instruction.opcode](vm, instruction.operand);
prog->ptr++;
}
else if (OPCODE_IS_MOV(instruction.opcode))
{
MOV_ROUTINES[instruction.opcode](vm, instruction.operand, instruction.reg);
prog->ptr++;
}
else
{
// TODO: Error (Unknown opcode)
return;
}
}
#define ARR_SIZE(xs) (sizeof(xs) / sizeof(xs[0]))
int main(void)
{
byte stack_data[256];
vm_t vm = {0};
vm_load_stack(&vm, stack_data, ARR_SIZE(stack_data));
return 0;
}
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