dot.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ctype.h>
#include <mach.h>
#define Extern extern
#include "acid.h"

Type*
srch(Type *t, char *s)
{
	Type *f;

	f = 0;
	while(t) {
		if(strcmp(t->tag->name, s) == 0) {
			if(f == 0 || t->depth < f->depth)
				f = t;
		}
		t = t->next;
	}
	return f;
}

void
odot(Node *n, Node *r)
{
	char *s;
	Type *t;
	Node res;
	uvlong addr;

	s = n->sym->name;
	if(s == 0)
		fatal("dodot: no tag");

	expr(n->left, &res);
	if(res.comt == 0)
		error("no type specified for (expr).%s", s);

	if(res.type != TINT)
		error("pointer must be integer for (expr).%s", s);

	t = srch(res.comt, s);
	if(t == 0)
		error("no tag for (expr).%s", s);

	/* Propagate types */
	if(t->type) 
		r->comt = t->type->lt;
	
	addr = res.ival+t->offset;
	if(t->fmt == 'a') {
		r->op = OCONST;
		r->fmt = 'a';
		r->type = TINT;
		r->ival = addr;
	}
	else 
		indir(cormap, addr, t->fmt, r);

}

static Type **tail;
static Lsym *base;

void
buildtype(Node *m, int d)
{
	Type *t;

	if(m == ZN)
		return;

	switch(m->op) {
	case OLIST:
		buildtype(m->left, d);		
		buildtype(m->right, d);
		break;

	case OCTRUCT:
		buildtype(m->left, d+1);
		break;
	default:
		t = malloc(sizeof(Type));
		t->next = 0;
		t->depth = d;
		t->tag = m->sym;
		t->base = base;
		t->offset = m->ival;
		if(m->left) {
			t->type = m->left->sym;
			t->fmt = 'a';			
		}
		else {
			t->type = 0;
			if(m->right)
				t->type = m->right->sym;
			t->fmt = m->fmt;
		}

		*tail = t;
		tail = &t->next;
	}			
}

void
defcomplex(Node *tn, Node *m)
{
	tail = &tn->sym->lt;
	base = tn->sym;
	buildtype(m, 0);
}

void
decl(Node *n)
{
	Node *l;
	Value *v;
	Frtype *f;
	Lsym *type;

	type = n->sym;
	if(type->lt == 0)
		error("%s is not a complex type", type->name);

	l = n->left;
	if(l->op == ONAME) {
		v = l->sym->v;
		v->comt = type->lt;
		v->fmt = 'a';
		return;
	}

	/*
	 * Frame declaration
	 */
	for(f = l->sym->local; f; f = f->next) {
		if(f->var == l->left->sym) {
			f->type = n->sym->lt;
			return;
		}
	}
	f = malloc(sizeof(Frtype));
	if(f == 0)
		fatal("out of memory");

	f->type = type->lt;

	f->var = l->left->sym;
	f->next = l->sym->local;
	l->sym->local = f;
}