Lua 5.3.4 里的 llex.c
以下是 llex.h 的代码，这个文件定义了一些词法分析用到的结构。其中重点是 LexState 这个结构，
#ifndef llex_h
#define llex_h
#include "lobject.h"
#include "lzio.h"
#define FIRST_RESERVED 257
#if !defined(LUA_ENV)
#define LUA_ENV "_ENV"
#endif
/*
* WARNING: if you change the order of this enumeration,
* grep "ORDER RESERVED"
*/
enum RESERVED {
/* terminal symbols denoted by reserved words */
TK_AND = FIRST_RESERVED, TK_BREAK,
TK_DO, TK_ELSE, TK_ELSEIF, TK_END, TK_FALSE, TK_FOR, TK_FUNCTION,
TK_GOTO, TK_IF, TK_IN, TK_LOCAL, TK_NIL, TK_NOT, TK_OR, TK_REPEAT,
TK_RETURN, TK_THEN, TK_TRUE, TK_UNTIL, TK_WHILE,
/* other terminal symbols */
TK_IDIV, TK_CONCAT, TK_DOTS, TK_EQ, TK_GE, TK_LE, TK_NE,
TK_SHL, TK_SHR,
TK_DBCOLON, TK_EOS,
TK_FLT, TK_INT, TK_NAME, TK_STRING
};
/* number of reserved words */
#define NUM_RESERVED (cast(int, TK_WHILE-FIRST_RESERVED+1))
typedef union {
lua_Number r;
lua_Integer i;
TString *ts;
} SemInfo; /* semantics information */
typedef struct Token {
int token;
SemInfo seminfo;
} Token;
/* state of the lexer plus state of the parser when shared by all
functions */
typedef struct LexState {
int current; /* current character (charint) */
int linenumber; /* input line counter */
int lastline; /* line of last token 'consumed' */
Token t; /* current token */
Token lookahead; /* look ahead token */
struct FuncState *fs; /* current function (parser) */
struct lua_State *L;
ZIO *z; /* input stream */
Mbuffer *buff; /* buffer for tokens */
Table *h; /* to avoid collection/reuse strings */
struct Dyndata *dyd; /* dynamic structures used by the parser */
TString *source; /* current source name */
TString *envn; /* environment variable name */
} LexState;
LUAI_FUNC void luaX_init (lua_State *L);
LUAI_FUNC void luaX_setinput (lua_State *L, LexState *ls, ZIO *z,
TString *source, int firstchar);
LUAI_FUNC TString *luaX_newstring (LexState *ls, const char *str, size_t l);
LUAI_FUNC void luaX_next (LexState *ls);
LUAI_FUNC int luaX_lookahead (LexState *ls);
LUAI_FUNC l_noret luaX_syntaxerror (LexState *ls, const char *s);
LUAI_FUNC const char *luaX_token2str (LexState *ls, int token);
#endif在 llex.c 开头，定义了 next, save 和 save_and_next 这些读取字符的方法跟宏。luaX_tokens 是记录关键字的数组，在报错的时候会用到。
#define next(ls) (ls->current = zgetc(ls->z))
#define currIsNewline(ls) (ls->current == '\n' || ls->current == '\r')
/* ORDER RESERVED */
static const char *const luaX_tokens [] = {
"and", "break", "do", "else", "elseif",
"end", "false", "for", "function", "goto", "if",
"in", "local", "nil", "not", "or", "repeat",
"return", "then", "true", "until", "while",
"//", "..", "...", "==", ">=", "<=", "~=",
"<<", ">>", "::", "<eof>",
"<number>", "<integer>", "<name>", "<string>"
};
#define save_and_next(ls) (save(ls, ls->current), next(ls))
static l_noret lexerror (LexState *ls, const char *msg, int token);
static void save (LexState *ls, int c) {
Mbuffer *b = ls->buff;
if (luaZ_bufflen(b) + 1 > luaZ_sizebuffer(b)) {
size_t newsize;
if (luaZ_sizebuffer(b) >= MAX_SIZE/2)
lexerror(ls, "lexical element too long", 0);
newsize = luaZ_sizebuffer(b) * 2;
luaZ_resizebuffer(ls->L, b, newsize);
}
b->buffer[luaZ_bufflen(b)++] = cast(char, c);
}luaX_init 这个方法应该是最简单的方法了，初始化词法分析的东西，就是生成 LUA_ENV 跟关键字的 TString，将关键字的 extra 设置上。
void luaX_init (lua_State *L) {
int i;
TString *e = luaS_newliteral(L, LUA_ENV); /* create env name */
luaC_fix(L, obj2gco(e)); /* never collect this name */
for (i=0; i<NUM_RESERVED; i++) {
TString *ts = luaS_new(L, luaX_tokens[i]);
luaC_fix(L, obj2gco(ts)); /* reserved words are never collected */
ts->extra = cast_byte(i+1); /* reserved word */
}
}luaX_setinput 这个方法设置词法分析的输入，其实主要就是用之前的看的 lzio.c 的库，另外还是设置了 LexState *ls 的属性，这个方法会在 parser 里面调用到。这里的 firstchar 是一开始读进的，parser 需要判断是否是机器码。
void luaX_setinput (lua_State *L, LexState *ls, ZIO *z, TString *source,
int firstchar) {
ls->t.token = 0;
ls->L = L;
ls->current = firstchar;
ls->lookahead.token = TK_EOS; /* no look-ahead token */
ls->z = z;
ls->fs = NULL;
ls->linenumber = 1;
ls->lastline = 1;
ls->source = source;
ls->envn = luaS_newliteral(L, LUA_ENV); /* get env name */
luaZ_resizebuffer(ls->L, ls->buff, LUA_MINBUFFER); /* initialize buffer */
}luaX_newstring 生成一个字符串 TString，为了避免被回收，把它加到 LexState *ls 的 h 里面。
/*
** creates a new string and anchors it in scanner's table so that
** it will not be collected until the end of the compilation
** (by that time it should be anchored somewhere)
*/
TString *luaX_newstring (LexState *ls, const char *str, size_t l) {
lua_State *L = ls->L;
TValue *o; /* entry for 'str' */
TString *ts = luaS_newlstr(L, str, l); /* create new string */
setsvalue2s(L, L->top++, ts); /* temporarily anchor it in stack */
o = luaH_set(L, ls->h, L->top - 1);
if (ttisnil(o)) { /* not in use yet? */
/* boolean value does not need GC barrier;
table has no metatable, so it does not need to invalidate cache */
setbvalue(o, 1); /* t[string] = true */
luaC_checkGC(L);
}
else { /* string already present */
ts = tsvalue(keyfromval(o)); /* re-use value previously stored */
}
L->top--; /* remove string from stack */
return ts;
}luaX_next 读取一个 token，记录到 LexState *ls 的 t 里面。
inclinenumber 增加 LexState *ls 的 linenumber。
/*
** increment line number and skips newline sequence (any of
** \n, \r, \n\r, or \r\n)
*/
static void inclinenumber (LexState *ls) {
int old = ls->current;
lua_assert(currIsNewline(ls));
next(ls); /* skip '\n' or '\r' */
if (currIsNewline(ls) && ls->current != old)
next(ls); /* skip '\n\r' or '\r\n' */
if (++ls->linenumber >= MAX_INT)
lexerror(ls, "chunk has too many lines", 0);
}
/*
** skip a sequence '[=*[' or ']=*]'; if sequence is well formed, return
** its number of '='s; otherwise, return a negative number (-1 iff there
** are no '='s after initial bracket)
*/
static int skip_sep (LexState *ls) {
int count = 0;
int s = ls->current;
lua_assert(s == '[' || s == ']');
save_and_next(ls);
while (ls->current == '=') {
save_and_next(ls);
count++;
}
return (ls->current == s) ? count : (-count) - 1;
}
static void read_long_string (LexState *ls, SemInfo *seminfo, int sep) {
int line = ls->linenumber; /* initial line (for error message) */
save_and_next(ls); /* skip 2nd '[' */
if (currIsNewline(ls)) /* string starts with a newline? */
inclinenumber(ls); /* skip it */
for (;;) {
switch (ls->current) {
case EOZ: { /* error */
const char *what = (seminfo ? "string" : "comment");
const char *msg = luaO_pushfstring(ls->L,
"unfinished long %s (starting at line %d)", what, line);
lexerror(ls, msg, TK_EOS);
break; /* to avoid warnings */
}
case ']': {
if (skip_sep(ls) == sep) {
save_and_next(ls); /* skip 2nd ']' */
goto endloop;
}
break;
}
case '\n': case '\r': {
save(ls, '\n');
inclinenumber(ls);
if (!seminfo) luaZ_resetbuffer(ls->buff); /* avoid wasting space */
break;
}
default: {
if (seminfo) save_and_next(ls);
else next(ls);
}
}
} endloop:
if (seminfo)
seminfo->ts = luaX_newstring(ls, luaZ_buffer(ls->buff) + (2 + sep),
luaZ_bufflen(ls->buff) - 2*(2 + sep));
}
static int check_next1 (LexState *ls, int c) {
if (ls->current == c) {
next(ls);
return 1;
}
else return 0;
}
static void esccheck (LexState *ls, int c, const char *msg) {
if (!c) {
if (ls->current != EOZ)
save_and_next(ls); /* add current to buffer for error message */
lexerror(ls, msg, TK_STRING);
}
}
static int gethexa (LexState *ls) {
save_and_next(ls);
esccheck (ls, lisxdigit(ls->current), "hexadecimal digit expected");
return luaO_hexavalue(ls->current);
}
static int readhexaesc (LexState *ls) {
int r = gethexa(ls);
r = (r << 4) + gethexa(ls);
luaZ_buffremove(ls->buff, 2); /* remove saved chars from buffer */
return r;
}
static unsigned long readutf8esc (LexState *ls) {
unsigned long r;
int i = 4; /* chars to be removed: '\', 'u', '{', and first digit */
save_and_next(ls); /* skip 'u' */
esccheck(ls, ls->current == '{', "missing '{'");
r = gethexa(ls); /* must have at least one digit */
while ((save_and_next(ls), lisxdigit(ls->current))) {
i++;
r = (r << 4) + luaO_hexavalue(ls->current);
esccheck(ls, r <= 0x10FFFF, "UTF-8 value too large");
}
esccheck(ls, ls->current == '}', "missing '}'");
next(ls); /* skip '}' */
luaZ_buffremove(ls->buff, i); /* remove saved chars from buffer */
return r;
}
static void utf8esc (LexState *ls) {
char buff[UTF8BUFFSZ];
int n = luaO_utf8esc(buff, readutf8esc(ls));
for (; n > 0; n--) /* add 'buff' to string */
save(ls, buff[UTF8BUFFSZ - n]);
}
/*
** Check whether current char is in set 'set' (with two chars) and
** saves it
*/
static int check_next2 (LexState *ls, const char *set) {
lua_assert(set[2] == '\0');
if (ls->current == set[0] || ls->current == set[1]) {
save_and_next(ls);
return 1;
}
else return 0;
}
/* LUA_NUMBER */
/*
** this function is quite liberal in what it accepts, as 'luaO_str2num'
** will reject ill-formed numerals.
*/
static int read_numeral (LexState *ls, SemInfo *seminfo) {
TValue obj;
const char *expo = "Ee";
int first = ls->current;
lua_assert(lisdigit(ls->current));
save_and_next(ls);
if (first == '0' && check_next2(ls, "xX")) /* hexadecimal? */
expo = "Pp";
for (;;) {
if (check_next2(ls, expo)) /* exponent part? */
check_next2(ls, "-+"); /* optional exponent sign */
if (lisxdigit(ls->current))
save_and_next(ls);
else if (ls->current == '.')
save_and_next(ls);
else break;
}
save(ls, '\0');
if (luaO_str2num(luaZ_buffer(ls->buff), &obj) == 0) /* format error? */
lexerror(ls, "malformed number", TK_FLT);
if (ttisinteger(&obj)) {
seminfo->i = ivalue(&obj);
return TK_INT;
}
else {
lua_assert(ttisfloat(&obj));
seminfo->r = fltvalue(&obj);
return TK_FLT;
}
}
static void read_string (LexState *ls, int del, SemInfo *seminfo) {
save_and_next(ls); /* keep delimiter (for error messages) */
while (ls->current != del) {
switch (ls->current) {
case EOZ:
lexerror(ls, "unfinished string", TK_EOS);
break; /* to avoid warnings */
case '\n':
case '\r':
lexerror(ls, "unfinished string", TK_STRING);
break; /* to avoid warnings */
case '\\': { /* escape sequences */
int c; /* final character to be saved */
save_and_next(ls); /* keep '\\' for error messages */
switch (ls->current) {
case 'a': c = '\a'; goto read_save;
case 'b': c = '\b'; goto read_save;
case 'f': c = '\f'; goto read_save;
case 'n': c = '\n'; goto read_save;
case 'r': c = '\r'; goto read_save;
case 't': c = '\t'; goto read_save;
case 'v': c = '\v'; goto read_save;
case 'x': c = readhexaesc(ls); goto read_save;
case 'u': utf8esc(ls); goto no_save;
case '\n': case '\r':
inclinenumber(ls); c = '\n'; goto only_save;
case '\\': case '\"': case '\'':
c = ls->current; goto read_save;
case EOZ: goto no_save; /* will raise an error next loop */
case 'z': { /* zap following span of spaces */
luaZ_buffremove(ls->buff, 1); /* remove '\\' */
next(ls); /* skip the 'z' */
while (lisspace(ls->current)) {
if (currIsNewline(ls)) inclinenumber(ls);
else next(ls);
}
goto no_save;
}
default: {
esccheck(ls, lisdigit(ls->current), "invalid escape sequence");
c = readdecesc(ls); /* digital escape '\ddd' */
goto only_save;
}
}
read_save:
next(ls);
/* go through */
only_save:
luaZ_buffremove(ls->buff, 1); /* remove '\\' */
save(ls, c);
/* go through */
no_save: break;
}
default:
save_and_next(ls);
}
}
save_and_next(ls); /* skip delimiter */
seminfo->ts = luaX_newstring(ls, luaZ_buffer(ls->buff) + 1,
luaZ_bufflen(ls->buff) - 2);
}
static int llex (LexState *ls, SemInfo *seminfo) {
luaZ_resetbuffer(ls->buff);
for (;;) {
switch (ls->current) {
case '\n': case '\r': { /* line breaks */
inclinenumber(ls);
break;
}
case ' ': case '\f': case '\t': case '\v': { /* spaces */
next(ls);
break;
}
case '-': { /* '-' or '--' (comment) */
next(ls);
if (ls->current != '-') return '-';
/* else is a comment */
next(ls);
if (ls->current == '[') { /* long comment? */
int sep = skip_sep(ls);
luaZ_resetbuffer(ls->buff); /* 'skip_sep' may dirty the buffer */
if (sep >= 0) {
read_long_string(ls, NULL, sep); /* skip long comment */
luaZ_resetbuffer(ls->buff); /* previous call may dirty the buff. */
break;
}
}
/* else short comment */
while (!currIsNewline(ls) && ls->current != EOZ)
next(ls); /* skip until end of line (or end of file) */
break;
}
case '[': { /* long string or simply '[' */
int sep = skip_sep(ls);
if (sep >= 0) {
read_long_string(ls, seminfo, sep);
return TK_STRING;
}
else if (sep != -1) /* '[=...' missing second bracket */
lexerror(ls, "invalid long string delimiter", TK_STRING);
return '[';
}
case '=': {
next(ls);
if (check_next1(ls, '=')) return TK_EQ;
else return '=';
}
case '<': {
next(ls);
if (check_next1(ls, '=')) return TK_LE;
else if (check_next1(ls, '<')) return TK_SHL;
else return '<';
}
case '>': {
next(ls);
if (check_next1(ls, '=')) return TK_GE;
else if (check_next1(ls, '>')) return TK_SHR;
else return '>';
}
case '/': {
next(ls);
if (check_next1(ls, '/')) return TK_IDIV;
else return '/';
}
case '~': {
next(ls);
if (check_next1(ls, '=')) return TK_NE;
else return '~';
}
case ':': {
next(ls);
if (check_next1(ls, ':')) return TK_DBCOLON;
else return ':';
}
case '"': case '\'': { /* short literal strings */
read_string(ls, ls->current, seminfo);
return TK_STRING;
}
case '.': { /* '.', '..', '...', or number */
save_and_next(ls);
if (check_next1(ls, '.')) {
if (check_next1(ls, '.'))
return TK_DOTS; /* '...' */
else return TK_CONCAT; /* '..' */
}
else if (!lisdigit(ls->current)) return '.';
else return read_numeral(ls, seminfo);
}
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9': {
return read_numeral(ls, seminfo);
}
case EOZ: {
return TK_EOS;
}
default: {
if (lislalpha(ls->current)) { /* identifier or reserved word? */
TString *ts;
do {
save_and_next(ls);
} while (lislalnum(ls->current));
ts = luaX_newstring(ls, luaZ_buffer(ls->buff),
luaZ_bufflen(ls->buff));
seminfo->ts = ts;
if (isreserved(ts)) /* reserved word? */
return ts->extra - 1 + FIRST_RESERVED;
else {
return TK_NAME;
}
}
else { /* single-char tokens (+ - / ...) */
int c = ls->current;
next(ls);
return c;
}
}
}
}
}
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 */
}luaX_lookahead 方法向前读多一个 token。
int luaX_lookahead (LexState *ls) {
lua_assert(ls->lookahead.token == TK_EOS);
ls->lookahead.token = llex(ls, &ls->lookahead.seminfo);
return ls->lookahead.token;
}const char *luaX_token2str (LexState *ls, int token) {
if (token < FIRST_RESERVED) { /* single-byte symbols? */
lua_assert(token == cast_uchar(token));
return luaO_pushfstring(ls->L, "'%c'", token);
}
else {
const char *s = luaX_tokens[token - FIRST_RESERVED];
if (token < TK_EOS) /* fixed format (symbols and reserved words)? */
return luaO_pushfstring(ls->L, "'%s'", s);
else /* names, strings, and numerals */
return s;
}
}
static const char *txtToken (LexState *ls, int token) {
switch (token) {
case TK_NAME: case TK_STRING:
case TK_FLT: case TK_INT:
save(ls, '\0');
return luaO_pushfstring(ls->L, "'%s'", luaZ_buffer(ls->buff));
default:
return luaX_token2str(ls, token);
}
}
static l_noret lexerror (LexState *ls, const char *msg, int token) {
msg = luaG_addinfo(ls->L, msg, ls->source, ls->linenumber);
if (token)
luaO_pushfstring(ls->L, "%s near %s", msg, txtToken(ls, token));
luaD_throw(ls->L, LUA_ERRSYNTAX);
}
l_noret luaX_syntaxerror (LexState *ls, const char *msg) {
lexerror(ls, msg, ls->t.token);
}