Lua 5.3.4 里的 lparser.c
我要先记录下在 lparser.h 的定义。
/*
** $Id: lparser.h,v 1.76 2015/12/30 18:16:13 roberto Exp $
** Lua Parser
** See Copyright Notice in lua.h
*/
#ifndef lparser_h
#define lparser_h
#include "llimits.h"
#include "lobject.h"
#include "lzio.h"
/*
** Expression and variable descriptor.
** Code generation for variables and expressions can be delayed to allow
** optimizations; An 'expdesc' structure describes a potentially-delayed
** variable/expression. It has a description of its "main" value plus a
** list of conditional jumps that can also produce its value (generated
** by short-circuit operators 'and'/'or').
*/
/* kinds of variables/expressions */
typedef enum {
VVOID, /* when 'expdesc' describes the last expression a list,
this kind means an empty list (so, no expression) */
VNIL, /* constant nil */
VTRUE, /* constant true */
VFALSE, /* constant false */
VK, /* constant in 'k'; info = index of constant in 'k' */
VKFLT, /* floating constant; nval = numerical float value */
VKINT, /* integer constant; nval = numerical integer value */
VNONRELOC, /* expression has its value in a fixed register;
info = result register */
VLOCAL, /* local variable; info = local register */
VUPVAL, /* upvalue variable; info = index of upvalue in 'upvalues' */
VINDEXED, /* indexed variable;
ind.vt = whether 't' is register or upvalue;
ind.t = table register or upvalue;
ind.idx = key's R/K index */
VJMP, /* expression is a test/comparison;
info = pc of corresponding jump instruction */
VRELOCABLE, /* expression can put result in any register;
info = instruction pc */
VCALL, /* expression is a function call; info = instruction pc */
VVARARG /* vararg expression; info = instruction pc */
} expkind;
#define vkisvar(k) (VLOCAL <= (k) && (k) <= VINDEXED)
#define vkisinreg(k) ((k) == VNONRELOC || (k) == VLOCAL)
typedef struct expdesc {
expkind k;
union {
lua_Integer ival; /* for VKINT */
lua_Number nval; /* for VKFLT */
int info; /* for generic use */
struct { /* for indexed variables (VINDEXED) */
short idx; /* index (R/K) */
lu_byte t; /* table (register or upvalue) */
lu_byte vt; /* whether 't' is register (VLOCAL) or upvalue (VUPVAL) */
} ind;
} u;
int t; /* patch list of 'exit when true' */
int f; /* patch list of 'exit when false' */
} expdesc;
/* description of active local variable */
typedef struct Vardesc {
short idx; /* variable index in stack */
} Vardesc;
/* description of pending goto statements and label statements */
typedef struct Labeldesc {
TString *name; /* label identifier */
int pc; /* position in code */
int line; /* line where it appeared */
lu_byte nactvar; /* local level where it appears in current block */
} Labeldesc;
/* list of labels or gotos */
typedef struct Labellist {
Labeldesc *arr; /* array */
int n; /* number of entries in use */
int size; /* array size */
} Labellist;
/* dynamic structures used by the parser */
typedef struct Dyndata {
struct { /* list of active local variables */
Vardesc *arr;
int n;
int size;
} actvar;
Labellist gt; /* list of pending gotos */
Labellist label; /* list of active labels */
} Dyndata;
/* control of blocks */
struct BlockCnt; /* defined in lparser.c */
/* state needed to generate code for a given function */
typedef struct FuncState {
Proto *f; /* current function header */
struct FuncState *prev; /* enclosing function */
struct LexState *ls; /* lexical state */
struct BlockCnt *bl; /* chain of current blocks */
int pc; /* next position to code (equivalent to 'ncode') */
int lasttarget; /* 'label' of last 'jump label' */
int jpc; /* list of pending jumps to 'pc' */
int nk; /* number of elements in 'k' */
int np; /* number of elements in 'p' */
int firstlocal; /* index of first local var (in Dyndata array) */
short nlocvars; /* number of elements in 'f->locvars' */
lu_byte nactvar; /* number of active local variables */
lu_byte nups; /* number of upvalues */
lu_byte freereg; /* first free register */
} FuncState;
LUAI_FUNC LClosure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
Dyndata *dyd, const char *name, int firstchar);
#endif我现在做的主要是从 REPL 输入来看 Lua 的 parser，但是实际上区别不大，因为 Lua 在读入的时候抽象了一个 Zio 的结构，这个结构会处理不同的读入。所以无论怎么调用，入口都在 luaY_parser 方法上。
LClosure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
Dyndata *dyd, const char *name, int firstchar) {
LexState lexstate;
FuncState funcstate;
LClosure *cl = luaF_newLclosure(L, 1); /* create main closure */
setclLvalue(L, L->top, cl); /* anchor it (to avoid being collected) */
luaD_inctop(L);
lexstate.h = luaH_new(L); /* create table for scanner */
sethvalue(L, L->top, lexstate.h); /* anchor it */
luaD_inctop(L);
funcstate.f = cl->p = luaF_newproto(L);
funcstate.f->source = luaS_new(L, name); /* create and anchor TString */
lua_assert(iswhite(funcstate.f)); /* do not need barrier here */
lexstate.buff = buff;
lexstate.dyd = dyd;
dyd->actvar.n = dyd->gt.n = dyd->label.n = 0;
luaX_setinput(L, &lexstate, z, funcstate.f->source, firstchar);
mainfunc(&lexstate, &funcstate);
lua_assert(!funcstate.prev && funcstate.nups == 1 && !lexstate.fs);
/* all scopes should be correctly finished */
lua_assert(dyd->actvar.n == 0 && dyd->gt.n == 0 && dyd->label.n == 0);
L->top--; /* remove scanner's table */
return cl; /* closure is on the stack, too */
}在这里，像 dyd 跟 buff 的初始化是在 ldo.c 里面的 luaD_protectedparser 做的。
int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
const char *mode) {
struct SParser p;
int status;
L->nny++; /* cannot yield during parsing */
p.z = z; p.name = name; p.mode = mode;
p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
p.dyd.label.arr = NULL; p.dyd.label.size = 0;
luaZ_initbuffer(L, &p.buff);
status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
luaZ_freebuffer(L, &p.buff);
luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
L->nny--;
return status;
}并且是在 ldo.c 里面的 f_parser 方法调用 luaY_parser，从这里进入 parse 的过程。f_parser 方法会判断从 Zio 读入的第一个字符，来确定是不是 Lua 的字节码，这个以后但是不知道是什么时候会讨论到。
static void f_parser (lua_State *L, void *ud) {
LClosure *cl;
struct SParser *p = cast(struct SParser *, ud);
int c = zgetc(p->z); /* read first character */
if (c == LUA_SIGNATURE[0]) {
checkmode(L, p->mode, "binary");
cl = luaU_undump(L, p->z, p->name);
}
else {
checkmode(L, p->mode, "text");
cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
}
lua_assert(cl->nupvalues == cl->p->sizeupvalues);
luaF_initupvals(L, cl);
}对于 luaY_parser 来说，主要是一些初始化的内容，其中主要初始化 LexState lexstate FuncState funcstate，用来在 mainfunc 中使用。
/*
** compiles the main function, which is a regular vararg function with an
** upvalue named LUA_ENV
*/
static void mainfunc (LexState *ls, FuncState *fs) {
BlockCnt bl;
expdesc v;
open_func(ls, fs, &bl);
fs->f->is_vararg = 1; /* main function is always declared vararg */
init_exp(&v, VLOCAL, 0); /* create and... */
newupvalue(fs, ls->envn, &v); /* ...set environment upvalue */
luaX_next(ls); /* read first token */
statlist(ls); /* parse main body */
check(ls, TK_EOS);
close_func(ls);
}mainfunc 我理解就是主函数的意思吧，是执行的最初的环境。
static void open_func (LexState *ls, FuncState *fs, BlockCnt *bl) {
Proto *f;
fs->prev = ls->fs; /* linked list of funcstates */
fs->ls = ls;
ls->fs = fs;
fs->pc = 0;
fs->lasttarget = 0;
fs->jpc = NO_JUMP;
fs->freereg = 0;
fs->nk = 0;
fs->np = 0;
fs->nups = 0;
fs->nlocvars = 0;
fs->nactvar = 0;
fs->firstlocal = ls->dyd->actvar.n;
fs->bl = NULL;
f = fs->f;
f->source = ls->source;
f->maxstacksize = 2; /* registers 0/1 are always valid */
enterblock(fs, bl, 0);
}open_func 设置 FuncState *fs 的值，记录 ls->fs 到 fs->prev 并修改成当前的 fs。
static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isloop) {
bl->isloop = isloop;
bl->nactvar = fs->nactvar;
bl->firstlabel = fs->ls->dyd->label.n;
bl->firstgoto = fs->ls->dyd->gt.n;
bl->upval = 0;
bl->previous = fs->bl;
fs->bl = bl;
lua_assert(fs->freereg == fs->nactvar);
}enterblock 方法设置 BlockCnt *bl，而且把 bl->previous 设置成 fs->bl 并把 fs->bl 改成设置后的 bl。
static void init_exp (expdesc *e, expkind k, int i) {
e->f = e->t = NO_JUMP;
e->k = k;
e->u.info = i;
}初始化 expdesc v
static int newupvalue (FuncState *fs, TString *name, expdesc *v) {
Proto *f = fs->f;
int oldsize = f->sizeupvalues;
checklimit(fs, fs->nups + 1, MAXUPVAL, "upvalues");
luaM_growvector(fs->ls->L, f->upvalues, fs->nups, f->sizeupvalues,
Upvaldesc, MAXUPVAL, "upvalues");
while (oldsize < f->sizeupvalues)
f->upvalues[oldsize++].name = NULL;
f->upvalues[fs->nups].instack = (v->k == VLOCAL);
f->upvalues[fs->nups].idx = cast_byte(v->u.info);
f->upvalues[fs->nups].name = name;
luaC_objbarrier(fs->ls->L, f, name);
return fs->nups++;
}建立 _ENV 的 upvalue。
void luaX_next (LexState *ls) {
ls->lastline = ls->linenumber;
if (ls->lookahead.token != TK_EOS) { /* is there a look-ahead token? */
ls->t = ls->lookahead; /* use this one */
ls->lookahead.token = TK_EOS; /* and discharge it */
}
else
ls->t.token = llex(ls, &ls->t.seminfo); /* read next token */
}读入第一个 token。luaX_next 方法在 llex.c 里面。
static void statlist (LexState *ls) {
/* statlist -> { stat [';'] } */
while (!block_follow(ls, 1)) {
if (ls->t.token == TK_RETURN) {
statement(ls);
return; /* 'return' must be last statement */
}
statement(ls);
}
}这个方法是具体解析的过程了，statlist 我的理解就是 statement list。以为一开始设置了主函数是多返回值，所以这里是一个 list。具体 Lua 的语法可以参考这里 The Complete Syntax of Lua
/*
** check whether current token is in the follow set of a block.
** 'until' closes syntactical blocks, but do not close scope,
** so it is handled in separate.
*/
static int block_follow (LexState *ls, int withuntil) {
switch (ls->t.token) {
case TK_ELSE: case TK_ELSEIF:
case TK_END: case TK_EOS:
return 1;
case TK_UNTIL: return withuntil;
default: return 0;
}
}block_follow 判断当前的 token 后面是否跟一个 block。
static void statement (LexState *ls) {
int line = ls->linenumber; /* may be needed for error messages */
enterlevel(ls);
switch (ls->t.token) {
case ';': { /* stat -> ';' (empty statement) */
luaX_next(ls); /* skip ';' */
break;
}
case TK_IF: { /* stat -> ifstat */
ifstat(ls, line);
break;
}
case TK_WHILE: { /* stat -> whilestat */
whilestat(ls, line);
break;
}
case TK_DO: { /* stat -> DO block END */
luaX_next(ls); /* skip DO */
block(ls);
check_match(ls, TK_END, TK_DO, line);
break;
}
case TK_FOR: { /* stat -> forstat */
forstat(ls, line);
break;
}
case TK_REPEAT: { /* stat -> repeatstat */
repeatstat(ls, line);
break;
}
case TK_FUNCTION: { /* stat -> funcstat */
funcstat(ls, line);
break;
}
case TK_LOCAL: { /* stat -> localstat */
luaX_next(ls); /* skip LOCAL */
if (testnext(ls, TK_FUNCTION)) /* local function? */
localfunc(ls);
else
localstat(ls);
break;
}
case TK_DBCOLON: { /* stat -> label */
luaX_next(ls); /* skip double colon */
labelstat(ls, str_checkname(ls), line);
break;
}
case TK_RETURN: { /* stat -> retstat */
luaX_next(ls); /* skip RETURN */
retstat(ls);
break;
}
case TK_BREAK: /* stat -> breakstat */
case TK_GOTO: { /* stat -> 'goto' NAME */
gotostat(ls, luaK_jump(ls->fs));
break;
}
default: { /* stat -> func | assignment */
exprstat(ls);
break;
}
}
lua_assert(ls->fs->f->maxstacksize >= ls->fs->freereg &&
ls->fs->freereg >= ls->fs->nactvar);
ls->fs->freereg = ls->fs->nactvar; /* free registers */
leavelevel(ls);
}statement 应该算是核心的一个方法了，毕竟表达式都是从这里展开了，关于这点，我也是看了 Lua 的语法才了解到，不看 reference 的确踩了坑。我们接下来就顺着 statement 的方法体看吧。
为了方便我们知道 llex 读入的 token 是什么，我这里记录一下，token 的 int 值。
TK_AND 257, TK_BREAK 258, TK_DO 259, TK_ELSE 260, TK_ELSEIF 261, TK_END 262, TK_FALSE 263, TK_FOR 264, TK_FUNCTION 265, TK_GOTO 266, TK_IF 267, TK_IN 268, TK_LOCAL 269, TK_NIL 270, TK_NOT 271, TK_OR 272, TK_REPEAT 273, TK_RETURN 274, TK_THEN 275, TK_TRUE 276, TK_UNTIL 277, TK_WHILE 278, TK_IDIV 279, TK_CONCAT 280, TK_DOTS 281, TK_EQ 282, TK_GE 283, TK_LE 284, TK_NE 285, TK_SHL 286, TK_SHR 287, TK_DBCOLON 288, TK_EOS 289, TK_FLT 290, TK_INT 291, TK_NAME 292, TK_STRING 293static void enterlevel (LexState *ls) {
lua_State *L = ls->L;
++L->nCcalls;
checklimit(ls->fs, L->nCcalls, LUAI_MAXCCALLS, "C levels");
}enterlevel 将 lua_State *L 的 nCcalls 的加 1。虽然看处理是记录增加了 C level 的 call，但是是为了什么，我还想明白。
如果 statement 遇到 TK_IF，则执行 ifstat(ls, line)
static void test_then_block (LexState *ls, int *escapelist) {
/* test_then_block -> [IF | ELSEIF] cond THEN block */
BlockCnt bl;
FuncState *fs = ls->fs;
expdesc v;
int jf; /* instruction to skip 'then' code (if condition is false) */
luaX_next(ls); /* skip IF or ELSEIF */
expr(ls, &v); /* read condition */
checknext(ls, TK_THEN);
if (ls->t.token == TK_GOTO || ls->t.token == TK_BREAK) {
luaK_goiffalse(ls->fs, &v); /* will jump to label if condition is true */
enterblock(fs, &bl, 0); /* must enter block before 'goto' */
gotostat(ls, v.t); /* handle goto/break */
skipnoopstat(ls); /* skip other no-op statements */
if (block_follow(ls, 0)) { /* 'goto' is the entire block? */
leaveblock(fs);
return; /* and that is it */
}
else /* must skip over 'then' part if condition is false */
jf = luaK_jump(fs);
}
else { /* regular case (not goto/break) */
luaK_goiftrue(ls->fs, &v); /* skip over block if condition is false */
enterblock(fs, &bl, 0);
jf = v.f;
}
statlist(ls); /* 'then' part */
leaveblock(fs);
if (ls->t.token == TK_ELSE ||
ls->t.token == TK_ELSEIF) /* followed by 'else'/'elseif'? */
luaK_concat(fs, escapelist, luaK_jump(fs)); /* must jump over it */
luaK_patchtohere(fs, jf);
}
static void ifstat (LexState *ls, int line) {
/* ifstat -> IF cond THEN block {ELSEIF cond THEN block} [ELSE block] END */
FuncState *fs = ls->fs;
int escapelist = NO_JUMP; /* exit list for finished parts */
test_then_block(ls, &escapelist); /* IF cond THEN block */
while (ls->t.token == TK_ELSEIF)
test_then_block(ls, &escapelist); /* ELSEIF cond THEN block */
if (testnext(ls, TK_ELSE))
block(ls); /* 'else' part */
check_match(ls, TK_END, TK_IF, line);
luaK_patchtohere(fs, escapelist); /* patch escape list to 'if' end */
}在 test_then_block 方法里面，调用了 expr(ls, &v);。这个地方是为了解析 if 后面的表达式。所以，我们要先看看 Lua 是怎么做表达式这部分的。
primaryexp -> NAME | '(' expr ')'
suffixedexp -> primaryexp { '.' NAME | '[' exp ']' | ':' NAME funcargs | funcargs }
simpleexp -> FLT | INT | STRING | NIL | TRUE | FALSE | ... | constructor | FUNCTION body | suffixedexp
subexpr -> (simpleexp | unop subexpr) { binop subexpr }
expr -> subexpr with limit 0这个就是表达式的解析方法，其中还有 unop 跟 binop，运算符的优先级跟结合性。这些都可以看下面。
/*
** {======================================================================
** Expression parsing
** =======================================================================
*/
static void primaryexp (LexState *ls, expdesc *v) {
/* primaryexp -> NAME | '(' expr ')' */
switch (ls->t.token) {
case '(': {
int line = ls->linenumber;
luaX_next(ls);
expr(ls, v);
check_match(ls, ')', '(', line);
luaK_dischargevars(ls->fs, v);
return;
}
case TK_NAME: {
singlevar(ls, v);
return;
}
default: {
luaX_syntaxerror(ls, "unexpected symbol");
}
}
}
static void suffixedexp (LexState *ls, expdesc *v) {
/* suffixedexp ->
primaryexp { '.' NAME | '[' exp ']' | ':' NAME funcargs | funcargs } */
FuncState *fs = ls->fs;
int line = ls->linenumber;
primaryexp(ls, v);
for (;;) {
switch (ls->t.token) {
case '.': { /* fieldsel */
fieldsel(ls, v);
break;
}
case '[': { /* '[' exp1 ']' */
expdesc key;
luaK_exp2anyregup(fs, v);
yindex(ls, &key);
luaK_indexed(fs, v, &key);
break;
}
case ':': { /* ':' NAME funcargs */
expdesc key;
luaX_next(ls);
checkname(ls, &key);
luaK_self(fs, v, &key);
funcargs(ls, v, line);
break;
}
case '(': case TK_STRING: case '{': { /* funcargs */
luaK_exp2nextreg(fs, v);
funcargs(ls, v, line);
break;
}
default: return;
}
}
}
static void simpleexp (LexState *ls, expdesc *v) {
/* simpleexp -> FLT | INT | STRING | NIL | TRUE | FALSE | ... |
constructor | FUNCTION body | suffixedexp */
switch (ls->t.token) {
case TK_FLT: {
init_exp(v, VKFLT, 0);
v->u.nval = ls->t.seminfo.r;
break;
}
case TK_INT: {
init_exp(v, VKINT, 0);
v->u.ival = ls->t.seminfo.i;
break;
}
case TK_STRING: {
codestring(ls, v, ls->t.seminfo.ts);
break;
}
case TK_NIL: {
init_exp(v, VNIL, 0);
break;
}
case TK_TRUE: {
init_exp(v, VTRUE, 0);
break;
}
case TK_FALSE: {
init_exp(v, VFALSE, 0);
break;
}
case TK_DOTS: { /* vararg */
FuncState *fs = ls->fs;
check_condition(ls, fs->f->is_vararg,
"cannot use '...' outside a vararg function");
init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 1, 0));
break;
}
case '{': { /* constructor */
constructor(ls, v);
return;
}
case TK_FUNCTION: {
luaX_next(ls);
body(ls, v, 0, ls->linenumber);
return;
}
default: {
suffixedexp(ls, v);
return;
}
}
luaX_next(ls);
}
static UnOpr getunopr (int op) {
switch (op) {
case TK_NOT: return OPR_NOT;
case '-': return OPR_MINUS;
case '~': return OPR_BNOT;
case '#': return OPR_LEN;
default: return OPR_NOUNOPR;
}
}
static BinOpr getbinopr (int op) {
switch (op) {
case '+': return OPR_ADD;
case '-': return OPR_SUB;
case '*': return OPR_MUL;
case '%': return OPR_MOD;
case '^': return OPR_POW;
case '/': return OPR_DIV;
case TK_IDIV: return OPR_IDIV;
case '&': return OPR_BAND;
case '|': return OPR_BOR;
case '~': return OPR_BXOR;
case TK_SHL: return OPR_SHL;
case TK_SHR: return OPR_SHR;
case TK_CONCAT: return OPR_CONCAT;
case TK_NE: return OPR_NE;
case TK_EQ: return OPR_EQ;
case '<': return OPR_LT;
case TK_LE: return OPR_LE;
case '>': return OPR_GT;
case TK_GE: return OPR_GE;
case TK_AND: return OPR_AND;
case TK_OR: return OPR_OR;
default: return OPR_NOBINOPR;
}
}
static const struct {
lu_byte left; /* left priority for each binary operator */
lu_byte right; /* right priority */
} priority[] = { /* ORDER OPR */
{10, 10}, {10, 10}, /* '+' '-' */
{11, 11}, {11, 11}, /* '*' '%' */
{14, 13}, /* '^' (right associative) */
{11, 11}, {11, 11}, /* '/' '//' */
{6, 6}, {4, 4}, {5, 5}, /* '&' '|' '~' */
{7, 7}, {7, 7}, /* '<<' '>>' */
{9, 8}, /* '..' (right associative) */
{3, 3}, {3, 3}, {3, 3}, /* ==, <, <= */
{3, 3}, {3, 3}, {3, 3}, /* ~=, >, >= */
{2, 2}, {1, 1} /* and, or */
};
#define UNARY_PRIORITY 12 /* priority for unary operators */
/*
** subexpr -> (simpleexp | unop subexpr) { binop subexpr }
** where 'binop' is any binary operator with a priority higher than 'limit'
*/
static BinOpr subexpr (LexState *ls, expdesc *v, int limit) {
BinOpr op;
UnOpr uop;
enterlevel(ls);
uop = getunopr(ls->t.token);
if (uop != OPR_NOUNOPR) {
int line = ls->linenumber;
luaX_next(ls);
subexpr(ls, v, UNARY_PRIORITY);
luaK_prefix(ls->fs, uop, v, line);
}
else simpleexp(ls, v);
/* expand while operators have priorities higher than 'limit' */
op = getbinopr(ls->t.token);
while (op != OPR_NOBINOPR && priority[op].left > limit) {
expdesc v2;
BinOpr nextop;
int line = ls->linenumber;
luaX_next(ls);
luaK_infix(ls->fs, op, v);
/* read sub-expression with higher priority */
nextop = subexpr(ls, &v2, priority[op].right);
luaK_posfix(ls->fs, op, v, &v2, line);
op = nextop;
}
leavelevel(ls);
return op; /* return first untreated operator */
}
static void expr (LexState *ls, expdesc *v) {
subexpr(ls, v, 0);
}
/* }==================================================================== */不过里面有不少是 lcode.c 的方法调用，感觉应该可以先看那部分内容可能会更好，不过现在就暂时跳过吧，而且还有跳转的部分，现在也不是太懂。
以下是 whilestat 相关的代码。
static int cond (LexState *ls) {
/* cond -> exp */
expdesc v;
expr(ls, &v); /* read condition */
if (v.k == VNIL) v.k = VFALSE; /* 'falses' are all equal here */
luaK_goiftrue(ls->fs, &v);
return v.f;
}
static void block (LexState *ls) {
/* block -> statlist */
FuncState *fs = ls->fs;
BlockCnt bl;
enterblock(fs, &bl, 0);
statlist(ls);
leaveblock(fs);
}
static void whilestat (LexState *ls, int line) {
/* whilestat -> WHILE cond DO block END */
FuncState *fs = ls->fs;
int whileinit;
int condexit;
BlockCnt bl;
luaX_next(ls); /* skip WHILE */
whileinit = luaK_getlabel(fs);
condexit = cond(ls);
enterblock(fs, &bl, 1);
checknext(ls, TK_DO);
block(ls);
luaK_jumpto(fs, whileinit);
check_match(ls, TK_END, TK_WHILE, line);
leaveblock(fs);
luaK_patchtohere(fs, condexit); /* false conditions finish the loop */
}以下是 forstat 的相关代码。
static TString *str_checkname (LexState *ls) {
TString *ts;
check(ls, TK_NAME);
ts = ls->t.seminfo.ts;
luaX_next(ls);
return ts;
}
static int exp1 (LexState *ls) {
expdesc e;
int reg;
expr(ls, &e);
luaK_exp2nextreg(ls->fs, &e);
lua_assert(e.k == VNONRELOC);
reg = e.u.info;
return reg;
}
static void forbody (LexState *ls, int base, int line, int nvars, int isnum) {
/* forbody -> DO block */
BlockCnt bl;
FuncState *fs = ls->fs;
int prep, endfor;
adjustlocalvars(ls, 3); /* control variables */
checknext(ls, TK_DO);
prep = isnum ? luaK_codeAsBx(fs, OP_FORPREP, base, NO_JUMP) : luaK_jump(fs);
enterblock(fs, &bl, 0); /* scope for declared variables */
adjustlocalvars(ls, nvars);
luaK_reserveregs(fs, nvars);
block(ls);
leaveblock(fs); /* end of scope for declared variables */
luaK_patchtohere(fs, prep);
if (isnum) /* numeric for? */
endfor = luaK_codeAsBx(fs, OP_FORLOOP, base, NO_JUMP);
else { /* generic for */
luaK_codeABC(fs, OP_TFORCALL, base, 0, nvars);
luaK_fixline(fs, line);
endfor = luaK_codeAsBx(fs, OP_TFORLOOP, base + 2, NO_JUMP);
}
luaK_patchlist(fs, endfor, prep + 1);
luaK_fixline(fs, line);
}
static void fornum (LexState *ls, TString *varname, int line) {
/* fornum -> NAME = exp1,exp1[,exp1] forbody */
FuncState *fs = ls->fs;
int base = fs->freereg;
new_localvarliteral(ls, "(for index)");
new_localvarliteral(ls, "(for limit)");
new_localvarliteral(ls, "(for step)");
new_localvar(ls, varname);
checknext(ls, '=');
exp1(ls); /* initial value */
checknext(ls, ',');
exp1(ls); /* limit */
if (testnext(ls, ','))
exp1(ls); /* optional step */
else { /* default step = 1 */
luaK_codek(fs, fs->freereg, luaK_intK(fs, 1));
luaK_reserveregs(fs, 1);
}
forbody(ls, base, line, 1, 1);
}
static void forlist (LexState *ls, TString *indexname) {
/* forlist -> NAME {,NAME} IN explist forbody */
FuncState *fs = ls->fs;
expdesc e;
int nvars = 4; /* gen, state, control, plus at least one declared var */
int line;
int base = fs->freereg;
/* create control variables */
new_localvarliteral(ls, "(for generator)");
new_localvarliteral(ls, "(for state)");
new_localvarliteral(ls, "(for control)");
/* create declared variables */
new_localvar(ls, indexname);
while (testnext(ls, ',')) {
new_localvar(ls, str_checkname(ls));
nvars++;
}
checknext(ls, TK_IN);
line = ls->linenumber;
adjust_assign(ls, 3, explist(ls, &e), &e);
luaK_checkstack(fs, 3); /* extra space to call generator */
forbody(ls, base, line, nvars - 3, 0);
}
static void forstat (LexState *ls, int line) {
/* forstat -> FOR (fornum | forlist) END */
FuncState *fs = ls->fs;
TString *varname;
BlockCnt bl;
enterblock(fs, &bl, 1); /* scope for loop and control variables */
luaX_next(ls); /* skip 'for' */
varname = str_checkname(ls); /* first variable name */
switch (ls->t.token) {
case '=': fornum(ls, varname, line); break;
case ',': case TK_IN: forlist(ls, varname); break;
default: luaX_syntaxerror(ls, "'=' or 'in' expected");
}
check_match(ls, TK_END, TK_FOR, line);
leaveblock(fs); /* loop scope ('break' jumps to this point) */
}在 forstat 的执行里面，需要申请到一些变量，这就需要下面的代码了。
static int registerlocalvar (LexState *ls, TString *varname) {
FuncState *fs = ls->fs;
Proto *f = fs->f;
int oldsize = f->sizelocvars;
luaM_growvector(ls->L, f->locvars, fs->nlocvars, f->sizelocvars,
LocVar, SHRT_MAX, "local variables");
while (oldsize < f->sizelocvars)
f->locvars[oldsize++].varname = NULL;
f->locvars[fs->nlocvars].varname = varname;
luaC_objbarrier(ls->L, f, varname);
return fs->nlocvars++;
}
static void new_localvar (LexState *ls, TString *name) {
FuncState *fs = ls->fs;
Dyndata *dyd = ls->dyd;
int reg = registerlocalvar(ls, name);
checklimit(fs, dyd->actvar.n + 1 - fs->firstlocal,
MAXVARS, "local variables");
luaM_growvector(ls->L, dyd->actvar.arr, dyd->actvar.n + 1,
dyd->actvar.size, Vardesc, MAX_INT, "local variables");
dyd->actvar.arr[dyd->actvar.n++].idx = cast(short, reg);
}
static void new_localvarliteral_ (LexState *ls, const char *name, size_t sz) {
new_localvar(ls, luaX_newstring(ls, name, sz));
}
#define new_localvarliteral(ls,v) \
new_localvarliteral_(ls, "" v, (sizeof(v)/sizeof(char))-1)
static LocVar *getlocvar (FuncState *fs, int i) {
int idx = fs->ls->dyd->actvar.arr[fs->firstlocal + i].idx;
lua_assert(idx < fs->nlocvars);
return &fs->f->locvars[idx];
}
static void adjustlocalvars (LexState *ls, int nvars) {
FuncState *fs = ls->fs;
fs->nactvar = cast_byte(fs->nactvar + nvars);
for (; nvars; nvars--) {
getlocvar(fs, fs->nactvar - nvars)->startpc = fs->pc;
}
}以下是 repeatstat 的相关代码。
static int cond (LexState *ls) {
/* cond -> exp */
expdesc v;
expr(ls, &v); /* read condition */
if (v.k == VNIL) v.k = VFALSE; /* 'falses' are all equal here */
luaK_goiftrue(ls->fs, &v);
return v.f;
}
static void repeatstat (LexState *ls, int line) {
/* repeatstat -> REPEAT block UNTIL cond */
int condexit;
FuncState *fs = ls->fs;
int repeat_init = luaK_getlabel(fs);
BlockCnt bl1, bl2;
enterblock(fs, &bl1, 1); /* loop block */
enterblock(fs, &bl2, 0); /* scope block */
luaX_next(ls); /* skip REPEAT */
statlist(ls);
check_match(ls, TK_UNTIL, TK_REPEAT, line);
condexit = cond(ls); /* read condition (inside scope block) */
if (bl2.upval) /* upvalues? */
luaK_patchclose(fs, condexit, bl2.nactvar);
leaveblock(fs); /* finish scope */
luaK_patchlist(fs, condexit, repeat_init); /* close the loop */
leaveblock(fs); /* finish loop */
}以下是 funcstat 的相关代码。
static void parlist (LexState *ls) {
/* parlist -> [ param { ',' param } ] */
FuncState *fs = ls->fs;
Proto *f = fs->f;
int nparams = 0;
f->is_vararg = 0;
if (ls->t.token != ')') { /* is 'parlist' not empty? */
do {
switch (ls->t.token) {
case TK_NAME: { /* param -> NAME */
new_localvar(ls, str_checkname(ls));
nparams++;
break;
}
case TK_DOTS: { /* param -> '...' */
luaX_next(ls);
f->is_vararg = 1; /* declared vararg */
break;
}
default: luaX_syntaxerror(ls, "<name> or '...' expected");
}
} while (!f->is_vararg && testnext(ls, ','));
}
adjustlocalvars(ls, nparams);
f->numparams = cast_byte(fs->nactvar);
luaK_reserveregs(fs, fs->nactvar); /* reserve register for parameters */
}
static void body (LexState *ls, expdesc *e, int ismethod, int line) {
/* body -> '(' parlist ')' block END */
FuncState new_fs;
BlockCnt bl;
new_fs.f = addprototype(ls);
new_fs.f->linedefined = line;
open_func(ls, &new_fs, &bl);
checknext(ls, '(');
if (ismethod) {
new_localvarliteral(ls, "self"); /* create 'self' parameter */
adjustlocalvars(ls, 1);
}
parlist(ls);
checknext(ls, ')');
statlist(ls);
new_fs.f->lastlinedefined = ls->linenumber;
check_match(ls, TK_END, TK_FUNCTION, line);
codeclosure(ls, e);
close_func(ls);
}
static int funcname (LexState *ls, expdesc *v) {
/* funcname -> NAME {fieldsel} [':' NAME] */
int ismethod = 0;
singlevar(ls, v);
while (ls->t.token == '.')
fieldsel(ls, v);
if (ls->t.token == ':') {
ismethod = 1;
fieldsel(ls, v);
}
return ismethod;
}
static void funcstat (LexState *ls, int line) {
/* funcstat -> FUNCTION funcname body */
int ismethod;
expdesc v, b;
luaX_next(ls); /* skip FUNCTION */
ismethod = funcname(ls, &v);
body(ls, &b, ismethod, line);
luaK_storevar(ls->fs, &v, &b);
luaK_fixline(ls->fs, line); /* definition "happens" in the first line */
}以下是 localfunc 的相关代码。
static void localfunc (LexState *ls) {
expdesc b;
FuncState *fs = ls->fs;
new_localvar(ls, str_checkname(ls)); /* new local variable */
adjustlocalvars(ls, 1); /* enter its scope */
body(ls, &b, 0, ls->linenumber); /* function created in next register */
/* debug information will only see the variable after this point! */
getlocvar(fs, b.u.info)->startpc = fs->pc;
}以下是 localstat 的相关代码。
static void localstat (LexState *ls) {
/* stat -> LOCAL NAME {',' NAME} ['=' explist] */
int nvars = 0;
int nexps;
expdesc e;
do {
new_localvar(ls, str_checkname(ls));
nvars++;
} while (testnext(ls, ','));
if (testnext(ls, '='))
nexps = explist(ls, &e);
else {
e.k = VVOID;
nexps = 0;
}
adjust_assign(ls, nvars, nexps, &e);
adjustlocalvars(ls, nvars);
}以下是 labelstat 和 gotostat 的相关代码。
static int newlabelentry (LexState *ls, Labellist *l, TString *name,
int line, int pc) {
int n = l->n;
luaM_growvector(ls->L, l->arr, n, l->size,
Labeldesc, SHRT_MAX, "labels/gotos");
l->arr[n].name = name;
l->arr[n].line = line;
l->arr[n].nactvar = ls->fs->nactvar;
l->arr[n].pc = pc;
l->n = n + 1;
return n;
}
/*
** check whether new label 'lb' matches any pending gotos in current
** block; solves forward jumps
*/
static void findgotos (LexState *ls, Labeldesc *lb) {
Labellist *gl = &ls->dyd->gt;
int i = ls->fs->bl->firstgoto;
while (i < gl->n) {
if (eqstr(gl->arr[i].name, lb->name))
closegoto(ls, i, lb);
else
i++;
}
}
/* check for repeated labels on the same block */
static void checkrepeated (FuncState *fs, Labellist *ll, TString *label) {
int i;
for (i = fs->bl->firstlabel; i < ll->n; i++) {
if (eqstr(label, ll->arr[i].name)) {
const char *msg = luaO_pushfstring(fs->ls->L,
"label '%s' already defined on line %d",
getstr(label), ll->arr[i].line);
semerror(fs->ls, msg);
}
}
}
/* skip no-op statements */
static void skipnoopstat (LexState *ls) {
while (ls->t.token == ';' || ls->t.token == TK_DBCOLON)
statement(ls);
}
static void labelstat (LexState *ls, TString *label, int line) {
/* label -> '::' NAME '::' */
FuncState *fs = ls->fs;
Labellist *ll = &ls->dyd->label;
int l; /* index of new label being created */
checkrepeated(fs, ll, label); /* check for repeated labels */
checknext(ls, TK_DBCOLON); /* skip double colon */
/* create new entry for this label */
l = newlabelentry(ls, ll, label, line, luaK_getlabel(fs));
skipnoopstat(ls); /* skip other no-op statements */
if (block_follow(ls, 0)) { /* label is last no-op statement in the block? */
/* assume that locals are already out of scope */
ll->arr[l].nactvar = fs->bl->nactvar;
}
findgotos(ls, &ll->arr[l]);
}
static void gotostat (LexState *ls, int pc) {
int line = ls->linenumber;
TString *label;
int g;
if (testnext(ls, TK_GOTO))
label = str_checkname(ls);
else {
luaX_next(ls); /* skip break */
label = luaS_new(ls->L, "break");
}
g = newlabelentry(ls, &ls->dyd->gt, label, line, pc);
findlabel(ls, g); /* close it if label already defined */
}以下是 retstat 的相关代码。
static int explist (LexState *ls, expdesc *v) {
/* explist -> expr { ',' expr } */
int n = 1; /* at least one expression */
expr(ls, v);
while (testnext(ls, ',')) {
luaK_exp2nextreg(ls->fs, v);
expr(ls, v);
n++;
}
return n;
}
static void retstat (LexState *ls) {
/* stat -> RETURN [explist] [';'] */
FuncState *fs = ls->fs;
expdesc e;
int first, nret; /* registers with returned values */
if (block_follow(ls, 1) || ls->t.token == ';')
first = nret = 0; /* return no values */
else {
nret = explist(ls, &e); /* optional return values */
if (hasmultret(e.k)) {
luaK_setmultret(fs, &e);
if (e.k == VCALL && nret == 1) { /* tail call? */
SET_OPCODE(getinstruction(fs,&e), OP_TAILCALL);
lua_assert(GETARG_A(getinstruction(fs,&e)) == fs->nactvar);
}
first = fs->nactvar;
nret = LUA_MULTRET; /* return all values */
}
else {
if (nret == 1) /* only one single value? */
first = luaK_exp2anyreg(fs, &e);
else {
luaK_exp2nextreg(fs, &e); /* values must go to the stack */
first = fs->nactvar; /* return all active values */
lua_assert(nret == fs->freereg - first);
}
}
}
luaK_ret(fs, first, nret);
testnext(ls, ';'); /* skip optional semicolon */
}以下是 exprstat 的相关代码。
static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e) {
FuncState *fs = ls->fs;
int extra = nvars - nexps;
if (hasmultret(e->k)) {
extra++; /* includes call itself */
if (extra < 0) extra = 0;
luaK_setreturns(fs, e, extra); /* last exp. provides the difference */
if (extra > 1) luaK_reserveregs(fs, extra-1);
}
else {
if (e->k != VVOID) luaK_exp2nextreg(fs, e); /* close last expression */
if (extra > 0) {
int reg = fs->freereg;
luaK_reserveregs(fs, extra);
luaK_nil(fs, reg, extra);
}
}
if (nexps > nvars)
ls->fs->freereg -= nexps - nvars; /* remove extra values */
}
static void assignment (LexState *ls, struct LHS_assign *lh, int nvars) {
expdesc e;
check_condition(ls, vkisvar(lh->v.k), "syntax error");
if (testnext(ls, ',')) { /* assignment -> ',' suffixedexp assignment */
struct LHS_assign nv;
nv.prev = lh;
suffixedexp(ls, &nv.v);
if (nv.v.k != VINDEXED)
check_conflict(ls, lh, &nv.v);
checklimit(ls->fs, nvars + ls->L->nCcalls, LUAI_MAXCCALLS,
"C levels");
assignment(ls, &nv, nvars+1);
}
else { /* assignment -> '=' explist */
int nexps;
checknext(ls, '=');
nexps = explist(ls, &e);
if (nexps != nvars)
adjust_assign(ls, nvars, nexps, &e);
else {
luaK_setoneret(ls->fs, &e); /* close last expression */
luaK_storevar(ls->fs, &lh->v, &e);
return; /* avoid default */
}
}
init_exp(&e, VNONRELOC, ls->fs->freereg-1); /* default assignment */
luaK_storevar(ls->fs, &lh->v, &e);
}
static void exprstat (LexState *ls) {
/* stat -> func | assignment */
FuncState *fs = ls->fs;
struct LHS_assign v;
suffixedexp(ls, &v.v);
if (ls->t.token == '=' || ls->t.token == ',') { /* stat -> assignment ? */
v.prev = NULL;
assignment(ls, &v, 1);
}
else { /* stat -> func */
check_condition(ls, v.v.k == VCALL, "syntax error");
SETARG_C(getinstruction(fs, &v.v), 1); /* call statement uses no results */
}
}