util: add fixed-size stack

util/stack.c

@@ -0,0 +1,71 @@
+
+#include "stack.h"
+#include "../runtime/stdio.h"
+#include <memory.h>
+
+
+void stack_InitBuffered(stack *s, void *buffer, uintptr_t size) {
+	s->data = buffer;
+	s->size = size;
+	s->top  = buffer + size;
+}
+
+void stack_PushByte(stack *s, const uint8_t b) {
+	if (s->top <= s->data) {
+		io_Printf("stack_PushByte: full[%llu bytes], discarding byte 0x%x\n", s->size, b);
+		return;
+	}
+	*(uint8_t *)--s->top = b;
+}
+
+uint8_t stack_PopByte(stack *s) {
+	if (s->top == s->data + s->size) {
+		io_WriteConsoleASCII("stack_PopByte: popping an empty stack\n");
+		return 0;
+	}
+	return *(uint8_t *)s->top++;
+}
+
+void stack_Push(stack *s, const void *buffer, uintptr_t size) {
+	if (stack_Space(s) < size) {
+		io_Printf("stack_Push: insufficient space (%d/%d bytes, want %d bytes)\n", stack_Size(s), s->size, size);
+		return;
+	}
+	s->top -= size;
+	memcpy(s->top, buffer, size);
+}
+
+uintptr_t stack_Pop(stack *s, void *buffer, uintptr_t size) {
+	if (stack_Size(s) < size)
+		return 0;
+	memcpy(buffer, s->top, size);
+	s->top += size;
+	return size;
+}
+
+uint8_t stack_TopByte(stack *s) {
+	if (stack_Empty(s)) {
+		io_WriteConsoleASCII("stack_TopByte: called on an empty stack\n");
+		return 0;
+	}
+	return *(uint8_t *)s->top;
+}
+
+uintptr_t stack_Top(stack *s, void *buffer, uintptr_t size) {
+	if (stack_Size(s) < size)
+		return 0;
+	memcpy(buffer, s->top, size);
+	return size;
+}
+
+bool stack_Empty(stack *s) {
+	return s->top == s->data + s->size;
+}
+
+uintptr_t stack_Size(stack *s) {
+	return s->data + s->size - s->top;
+}
+
+uintptr_t stack_Space(stack *s) {
+	return s->top - s->data;
+}

util/stack.h

@@ -0,0 +1,52 @@
+#pragma once
+
+#include "../main.h"
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+typedef struct {
+	void *    data; // the data buffer
+	uintptr_t size; // size of data buffer
+	void *    top;  // top of the stack, the stack grows downward (from data+size to data)
+} stack;
+
+// initialize a stack with a existing buffer
+void stack_InitBuffered(stack *s, void *buffer, uintptr_t size);
+
+// pushes one byte to the stack, discarding if full
+void stack_PushByte(stack *s, const uint8_t b);
+
+// pops one byte from the top of the stack, returning it
+uint8_t stack_PopByte(stack *s);
+
+// pushes Size bytes to the stack, none written if there is not space for all the bytes
+void stack_Push(stack *s, const void *buffer, uintptr_t size);
+
+// pops Size bytes from the stack, none popped if there are no enough data
+// returns the number of bytes popped (either Size or 0)
+uintptr_t stack_Pop(stack *s, void *buffer, uintptr_t size);
+
+// return the byte at the top of the stack
+uint8_t stack_TopByte(stack *s);
+
+// copy the bytes at the top of the stack
+// returns the number of bytes copied
+uintptr_t stack_Top(stack *s, void *buffer, uintptr_t size);
+
+// tells if the stack is empty
+bool stack_Empty(stack *s);
+
+// returns the number of bytes in the stack
+uintptr_t stack_Size(stack *s);
+
+// returns the empty space left in the stack
+uintptr_t stack_Space(stack *s);
+
+
+#ifdef __cplusplus
+}
+#endif