/*
* syn2:
* syn3
* syn3 | syn2
* syn3 ^ syn2
*/
static struct tnode *
syn2(char **p1, char **p2)
{
struct tnode *t;
int subcnt;
char **p;
subcnt = 0;
for (p = p1; p < p2; p++)
switch (**p) {
case LPARENTHESIS:
subcnt++;
continue;
case RPARENTHESIS:
subcnt--;
continue;
case VERTICALBAR:
case CARET:
if (subcnt == 0) {
if ((t = talloc()) == NULL)
return NULL;
t->ntype = TPIPE;
t->nleft = syn3(p1, p);
t->nright = syn2(p + 1, p2);
t->nflags = 0;
return t;
}
break;
}
return syn3(p1, p2);
}
/*
* syn2
* syn3
* syn3 | syn2
*
* syn2负责构建管道线节点，搜索管道线符号，
* 自顶向下生成左子树，递归生成右子树。
* p1指向token列表头部，p2指向token列表末尾的下一个。
*/
int *syn2(char **p1, char **p2)
{
char **p;
int l, *t;
l = 0;
for(p=p1; p!=p2; p++)
switch(**p) {
case '(':
l++;
continue; /* 此处等同于break */
case ')':
l--;
continue;
case '|':
case '^':
if(l == 0) { /* 没有圆括弧嵌套 */
t = tree(4);
t[DTYP] = TFIL; /* 建立管道线节点*/
t[DLEF] = (int)syn3(p1, p); /* 左边列表递进一层生成左子树节点*/
t[DRIT] = (int)syn2(p+1, p2); /* 右边递归生成右子树节点*/
t[DFLG] = 0; /* 标志位继承自上层节点*/
return(t);
}
}
return(syn3(p1, p2)); /* 没有找到管道线，所有列表递进一层，不需要判断嵌套是否归零*/
}
/*
* syn2
* syn3
* syn3 | syn2
* syn3 |& syn2
*/
static struct command *
syn2(struct wordent *p1, struct wordent *p2, int flags)
{
struct wordent *p, *pn;
struct command *t;
int f, l;
l = 0;
for (p = p1; p != p2; p = p->next)
switch (p->word[0]) {
case '(':
l++;
continue;
case ')':
l--;
continue;
case '|':
if (l != 0)
continue;
t = (struct command *)xcalloc(1, sizeof(*t));
f = flags | POUT;
pn = p->next;
if (pn != p2 && pn->word[0] == '&') {
f |= PERR;
t->t_dflg |= F_STDERR;
}
t->t_dtyp = NODE_PIPE;
t->t_dcar = syn3(p1, p, f);
if (pn != p2 && pn->word[0] == '&')
p = pn;
t->t_dcdr = syn2(p->next, p2, flags | PIN);
return (t);
}
return (syn3(p1, p2, flags));
}
