initial interpreter, base and stack

base.h

@@ -0,0 +1,20 @@
+#ifndef bci_base_h__
+#define bci_base_h__
+#include <inttypes.h>
+#include "stack.h"
+
+#define BCI_CORE_NUM_REG 40
+
+// Note that void * state will later be casted to
+// machine_state_t.
+typedef char (* bci_core_method_t)(uint8_t small_arg
+				, void * state);
+
+
+#define BCI_CORE_RESULT_RESERVED_BITS    0b11000000
+#define BCI_CORE_RESULT_APPLICATION_BITS 0b00111111
+
+#define BCI_CORE_SMALL_ARG_MASK 0b0000000000111111
+#define BCI_CORE_OPCODE_MASK    0b1111111111000000
+
+#endif

interpreter/interpreter.c

@@ -0,0 +1,145 @@
+#include <stdlib.h>
+
+#include "interpreter.h"
+
+
+
+machine_state_t machine_state_t_new( void * cache_function_data
+				, size_t cache_size
+				, size_t (* cache_block)(uint16_t * cache
+							, uint16_t offset
+							, size_t cache_size
+							, void * cache_function_data)
+				, dispatch_tree_t method_dispatcher)
+{
+	machine_state_t state = malloc(sizeof(struct machine_state_s));
+	if(!state)
+	{
+		return NULL;
+	}
+	uint16_t * cache = calloc(sizeof(uint16_t), cache_size);
+	if(!cache)
+	{
+		free(state);
+		return NULL;
+	}
+
+	state->cache = cache;
+	state->cache_block = cache_block;
+	state->cache_size = cache_size;
+	state->cache_loaded = 0;
+	state->cache_function_data = cache_function_data;
+
+	state->program_counter = 0;
+	state->status_reg = 0;
+	state->shutdown_reg = 0;
+	int i;
+	for(i = 0; i < BCI_CORE_NUM_REG; i++)
+	{
+		state->data_reg[BCI_CORE_NUM_REG] = 0;
+	}
+	state->stack = NULL;
+
+	state->method_dispatcher = method_dispatcher;
+
+	return state;
+}
+
+void machine_state_t_del(machine_state_t state)
+{
+	free(state->cache);
+	dispatch_tree_t_del(state->method_dispatcher);
+	free(state);
+}
+
+
+char update_cache(machine_state_t state)
+{
+	// Calculate a clever offset for caching.
+	uint16_t cache_offset = state->program_counter;
+	if((cache_offset + state->cache_size)
+		> state->program_size)
+	{
+		if(state->program_size < state->cache_size)
+		{
+			cache_offset = 0;
+		}
+		else
+		{
+			cache_offset = state->program_size - state->cache_size;
+		}
+	}
+	size_t cached = state->cache_block(state->cache
+					, cache_offset
+					, state->cache_size
+					, state->cache_function_data);
+
+	if(cached != state->cache_size)
+	{
+		return 1;
+	}
+	return 0;
+}
+
+char machine_state_t_exec_cycle(machine_state_t state)
+{
+	uint16_t opcode, arg;
+
+	// This would be bad.
+	if(state->program_counter >= state->program_size)
+	{
+		return 0b01000000 | 1; 
+	}
+	
+	// Calculate the in-cache offset of the program counter.
+	int32_t offset = state->program_counter - state->cache_offset;
+
+	// Check if we need to update the cache.
+	if( offset < 0
+		|| !(state->cache_loaded)
+		// Note: 
+		// +1 for cache starting with 0
+		// +1 for the argument
+		|| (offset + 2) > state->cache_size)
+	{
+		if(update_cache(state))
+		{
+			return 0b01000000 | 2;
+		}
+		// Re-calculate the in-cache offset
+		offset = state->program_counter - state->cache_offset;
+	}
+
+	// Check if the argument is cached.
+	if(offset + 2 > state->cache_size)
+	{
+		// Because we have cached the program memory above
+		// there is no way that we can include the argument
+		// now. There is something wrong.
+		return 0b01000000 | 3;
+	}
+
+	opcode = state->cache[offset];
+	arg = state->cache[offset + 1];
+
+	bci_core_method_t method = dispatch_tree_t_dispatch(
+					state->method_dispatcher
+					, opcode & BCI_CORE_OPCODE_MASK);
+	if(!method)
+	{
+		return 0b10000000 | 1;
+	}
+
+	return BCI_CORE_RESULT_APPLICATION_BITS 
+		& method(arg
+			, opcode & BCI_CORE_SMALL_ARG_MASK
+			, state);
+
+}
+
+
+char machine_state_t_default_afterexec(machine_state_t state, uint8_t argc)
+{
+	state->program_counter += 1 + argc;
+	return 0;
+}

interpreter/interpreter.h

@@ -0,0 +1,79 @@
+#ifndef bci_interpreter_h__
+#define bci_interpreter_h__
+
+#include <stddef.h>
+#include "base.h"
+#include "method_dispatcher.h"
+#include "stack.h"
+
+typedef machine_state_s
+{
+	// The size of the program in 16-bit words
+	uint16_t program_size; 
+	void * cache_function_data;
+
+	size_t cache_size;
+	uint16_t cache_offset;
+	uint16_t * cache;
+	size_t (* cache_block)(uint16_t * cache
+				, uint16_t offset
+				, size_t cache_size
+				, void * cache_function_data);
+	char cache_loaded;
+
+	uint16_t program_counter;
+	uint16_t status_reg;
+	// Any non-zero value in this register will
+	// break the program execution.
+	uint16_t shutdown_reg;
+	uint16_t data_reg[BCI_CORE_NUM_REG];
+	bci_stack_t stack;
+
+
+	dispatch_tree_t method_dispatcher;
+
+} * machine_state_t;
+
+machine_state_t machine_state_t_new( void * cache_function_data
+				, size_t cache_size
+				, size_t (* cache_block)(uint16_t * cache
+							, uint16_t offset
+							, size_t cache_size
+							, void * cache_function_data)
+				, dispatch_tree_t method_dispatcher);
+
+void machine_state_t_del(machine_state_t state);
+
+/*
+ * This function essentially executes one cycle of the machine execution.
+ * It will fetch the opcode and argument, dispatch the method and execute it.
+ *
+ * Also this will update the cache if needed.
+ *
+ * Possible return codes:
+ *
+ * - 0bxyXXXXXX
+ *   Error while executing the cycle.
+ *   - 0b01XXXXXX
+ *     Error in the internal memory management (i.e. program counter out
+ *     of bounds)
+ *     - 0b01000000 | 1: program_counter > program_size
+ *     - 0b01000000 | 2: failed to cache new data
+ *     - 0b01000000 | 3: argument is out of program bounds
+ *
+ *   - 0b10XXXXXX
+ *     Error while dispatching the method
+ *     - 0b10000000 | 1: unknown opcode
+ *
+ * - 0b00XXXXXX
+ *   XXXXXX is the return value of the bci_core_method_t method.
+ * */
+char machine_state_t_exec_cycle(machine_state_t state);
+
+/*
+ * Do the default updates on the machine state.
+ * This will be basically increasing the program counter.
+ * */
+char machine_state_t_default_afterexec(machine_state_t state, uint8_t argc);
+
+#endif

stack.c

@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include "stack.h"
+
+char bci_stack_t_push(bci_stack_t * stack, uint16_t value)
+{
+	bci_stack_t node = malloc(sizeof(struct bci_stack_s));
+	if(!node)
+	{
+		return 1;
+	}
+	node->next = *stack;
+	node->value = value;
+	stack = &node;
+	return 0;
+}
+char bci_stack_t_pop(bci_stack_t * stack, uint16_t * result)
+{
+	if(!*stack)
+	{
+		return 1;
+	}
+	*result = (*stack)->value;
+	*stack = (*stack)->next;
+	return 0;
+}
+

stack.h

@@ -0,0 +1,14 @@
+#ifndef bci_stack_h__
+#define bci_stack_h__
+
+#include <inttypes.h>
+
+typedef struct bci_stack_s
+{
+	struct bci_stack_s * next;
+	uint16_t value;
+} * bci_stack_t;
+
+char bci_stack_t_push(bci_stack_t * stack, uint16_t value);
+char bci_stack_t_pop(bci_stack_t * stack, uint16_t * result);
+#endif