in parsetok.cstatic node * parsetok(struct tok_state *tok, grammar *g, int start, perrdetail *err_ret, int *flags) 函数step1 . parser_state * ps = PyParser_New(g, start);--g is static grammar _PyParser_Grammar = {6,dfas,{19, labels},256};--start is predefined macro #define Py_file_input 257 in Python.hin parser_state *PyParser_New(grammar *g, int start)step 1.1ps->p_grammar = p;ps->p_tree = PyNode_New(start), start defines the 'type' of node因为 node *PyNode_New(int type){node *n = (node *) PyObject_MALLOC(1 * sizeof(node));if (n == NULL)return NULL;n->n_type = type;n->n_str = NULL;n->n_lineno = 0;n->n_nchildren = 0;n->n_child = NULL;return n;}step1.2 s_reset(&ps->p_stack)其中static voids_reset(stack *s){s->s_top = &s->s_base[MAXSTACK];} 让stack的 s_top 指向s_base最后一个元素step1.3 s_push(&ps->p_stack, PyGrammar_FindDFA(g, start), ps->p_tree);其中dfa *PyGrammar_FindDFA(grammar *g, register int type){register dfa *d;#if 1/* Massive speed-up */d = &g->g_dfa[type - NT_OFFSET]; //type = 257 as predefined, #define NT_OFFSET 256//so d is one of static dfa dfas[81] member, dfas[1] in graminit.c//dfas[1]'s type is 257, assert(d->d_type == type);return d;#else#endif}而static ints_push(register stack *s, dfa *d, node *parent){register stackentry *top;top = --s->s_top;top->s_dfa = d;top->s_parent = parent;top->s_state = 0;return 0;}top指向前一个element, 赋值该element的s_dfa, s_parent参见parser.h typedef struct {int s_state;/* State in current DFA */dfa*s_dfa;/* Current DFA */struct _node*s_parent;/* Where to add next node */} stackentry;step 2. for 循环中step2.1 type = PyTokenizer_Get(tok, &a, &b); PyParser_AddToken(ps, (int)type, str, tok->lineno, col_offset, &(err_ret->expected))step2.1.1 /* Find out which label this token is */ilabel = classify(ps, type, str); //for example type=1, str="a"//it will search static label labels[168] , defined in graminit.c//and find the pair (1, NULL), return the index of the element in arraystep2.1.2 /* Loop until the token is shifted or an error occurred */for (;;) {/* Fetch the current dfa and state */register dfa *d = ps->p_stack.s_top->s_dfa;register state *s = &d->d_state[ps->p_stack.s_top->s_state];/* Check accelerator */if (s->s_lower <= ilabel && ilabel < s->s_upper) {register int x = s->s_accel[ilabel - s->s_lower];if (x != -1) {if (x & (1<<7)) {/* Push non-terminal */int nt = (x >> 8) + NT_OFFSET;int arrow = x & ((1<<7)-1);dfa *d1 = PyGrammar_FindDFA(ps->p_grammar, nt);if ((err = push(&ps->p_stack, nt, d1, =======>pusharrow, lineno, col_offset)) > 0) {D(printf(" MemError: push\n"));return err;}D(printf(" Push ...\n"));continue;}.....return E_OK;}}}这段的关键是push函数,static intpush(register stack *s, int type, dfa *d, int newstate, int lineno, int col_offset){int err;register node *n;n = s->s_top->s_parent;assert(!s_empty(s));err = PyNode_AddChild(n, type, (char *)NULL, lineno, col_offset);if (err)return err;s->s_top->s_state = newstate;return s_push(s, d, CHILD(n, NCH(n)-1));}它建立起了一个复杂的数据如图
