lua源码注释-llex.c

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/*
** $Id: llex.c,v 2.20.1.2 2009/11/23 14:58:22 roberto Exp $
** Lexical Analyzer
** See Copyright Notice in lua.h
*/

#include <ctype.h>
#include <locale.h>
#include <string.h>

#define llex_c
#define LUA_CORE

#include "lua.h"

#include "ldo.h"
#include "llex.h"
#include "lobject.h"
#include "lparser.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "lzio.h"



#define next(ls) (ls->current = zgetc(ls->z))




#define currIsNewline(ls) (ls->current == '\n' || ls->current == '\r')


/* ORDER RESERVED */
const char *const luaX_tokens [] = {
"and", "break", "do", "else", "elseif",
"end", "false", "for", "function", "if",
"in", "local", "nil", "not", "or", "repeat",
"return", "then", "true", "until", "while",
"..", "...", "==", ">=", "<=", "~=",
"<number>", "<name>", "<string>", "<eof>",
NULL
};


#define save_and_next(ls) (save(ls, ls->current), next(ls))

/* 将c存到ls->buff中 */
static void save (LexState *ls, int c) {
Mbuffer *b = ls->buff;
if (b->n + 1 > b->buffsize) {
size_t newsize;
if (b->buffsize >= MAX_SIZET/2)
luaX_lexerror(ls, "lexical element too long", 0);
newsize = b->buffsize * 2;
luaZ_resizebuffer(ls->L, b, newsize);
}
b->buffer[b->n++] = cast(char, c);
}

/* 构建出关键字 */
void luaX_init (lua_State *L) {
int i;
for (i=0; i<NUM_RESERVED; i++) {
TString *ts = luaS_new(L, luaX_tokens[i]);
luaS_fix(ts); /* reserved words are never collected */
lua_assert(strlen(luaX_tokens[i])+1 <= TOKEN_LEN);
ts->tsv.reserved = cast_byte(i+1); /* reserved word */
}
}


#define MAXSRC 80


const char *luaX_token2str (LexState *ls, int token) {
if (token < FIRST_RESERVED) {
lua_assert(token == cast(unsigned char, token));
return (iscntrl(token)) ? luaO_pushfstring(ls->L, "char(%d)", token) :
luaO_pushfstring(ls->L, "%c", token);
}
else
return luaX_tokens[token-FIRST_RESERVED];
}


static const char *txtToken (LexState *ls, int token) {
switch (token) {
case TK_NAME:
case TK_STRING:
case TK_NUMBER:
save(ls, '\0');
return luaZ_buffer(ls->buff);
default:
return luaX_token2str(ls, token);
}
}


void luaX_lexerror (LexState *ls, const char *msg, int token) {
char buff[MAXSRC];
luaO_chunkid(buff, getstr(ls->source), MAXSRC);
msg = luaO_pushfstring(ls->L, "%s:%d: %s", buff, ls->linenumber, msg);
if (token)
luaO_pushfstring(ls->L, "%s near " LUA_QS, msg, txtToken(ls, token));
luaD_throw(ls->L, LUA_ERRSYNTAX);
}


void luaX_syntaxerror (LexState *ls, const char *msg) {
luaX_lexerror(ls, msg, ls->t.token);
}


TString *luaX_newstring (LexState *ls, const char *str, size_t l) {
lua_State *L = ls->L;
TString *ts = luaS_newlstr(L, str, l);
TValue *o = luaH_setstr(L, ls->fs->h, ts); /* entry for `str' */
if (ttisnil(o)) {
setbvalue(o, 1); /* make sure `str' will not be collected */
luaC_checkGC(L);
}
return ts;
}

/* 读到单个换行符\n,\r,再多读一个字符,看是否是双字符的换行\n\r,\r\n */
static void inclinenumber (LexState *ls) {
int old = ls->current;
lua_assert(currIsNewline(ls)); /* 当前是换行符 */

/* 往后再读一个字符,看看不是不是\n\r和\r\n这种双字符的换行符(仅算一次换行) */
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)
luaX_syntaxerror(ls, "chunk has too many lines");
}

/* 初始化LexState,初始化ls->buf,从ZIO读取第一个字符 */
void luaX_setinput (lua_State *L, LexState *ls, ZIO *z, TString *source) {
ls->decpoint = '.';
ls->L = L;
ls->lookahead.token = TK_EOS; /* no look-ahead token */
ls->z = z;
ls->fs = NULL; /* 尚未开始编译函数,这里置NULL */
ls->linenumber = 1; /* 当前在第一行,亲 */
ls->lastline = 1;
ls->source = source;
/* 申请属于ls->buff的私有buff */
luaZ_resizebuffer(ls->L, ls->buff, LUA_MINBUFFER); /* initialize buffer */

next(ls); /* read first char */
}



/*
** =======================================================
** LEXICAL ANALYZER
** =======================================================
*/


/* ls->current和set字符集中的某个字符匹配吗 */
static int check_next (LexState *ls, const char *set) {
if (!strchr(set, ls->current))
return 0;
save_and_next(ls);
return 1;
}

/* 将ls->buff中的from字符替换层to字符 */
static void buffreplace (LexState *ls, char from, char to) {
size_t n = luaZ_bufflen(ls->buff);
char *p = luaZ_buffer(ls->buff);
while (n--)
if (p[n] == from) p[n] = to;
}

/* 数字字符串转换为数字时失败,尝试更换成本地区的数字字符小数点后再次尝试转换 */
static void trydecpoint (LexState *ls, SemInfo *seminfo) {
/* format error: try to update decimal point separator */
struct lconv *cv = localeconv();
char old = ls->decpoint;
ls->decpoint = (cv ? cv->decimal_point[0] : '.');
buffreplace(ls, old, ls->decpoint); /* try updated decimal separator */
if (!luaO_str2d(luaZ_buffer(ls->buff), &seminfo->r)) {
/* format error with correct decimal point: no more options */
buffreplace(ls, ls->decpoint, '.'); /* undo change (for error message) */
luaX_lexerror(ls, "malformed number", TK_NUMBER);
}
}


/* LUA_NUMBER
** .123这种 123或者科学计数法形式(1.99714E+13)的数字
*/
static void read_numeral (LexState *ls, SemInfo *seminfo) {
lua_assert(isdigit(ls->current)); /* 属于 [0,9] 集合?*/
/* 读取第一部分 1.99714 */
do {
save_and_next(ls);
} while (isdigit(ls->current) || ls->current == '.');

/* 读取第二部分 E+ */
if (check_next(ls, "Ee")) /* `E'? */
check_next(ls, "+-"); /* optional exponent sign */
/* 读取第三部分 13 */
while (isalnum(ls->current) || ls->current == '_') /* 这里的_不太明白其含义 */
save_and_next(ls);
/* 主动补\0,关闭字符串 */
save(ls, '\0');
/* 不同国家不同的小数点 */
buffreplace(ls, '.', ls->decpoint); /* follow locale for decimal point */
if (!luaO_str2d(luaZ_buffer(ls->buff), &seminfo->r)) /* format error? */
trydecpoint(ls, seminfo); /* try to update decimal point separator */
}

/* 尝试读取多行字符串的开头或结尾 --[{=}[ 或者 ]{=}] */
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;
}

/* 读取一个长字符串和"结尾控制符"(长注释或String的token)(同时更新linenumber) */
static void read_long_string (LexState *ls, SemInfo *seminfo, int sep) {
int cont = 0;
(void)(cont); /* avoid warnings when `cont' is not used */
save_and_next(ls); /* skip 2nd `[' */

if (currIsNewline(ls)) /* string starts with a newline? */
inclinenumber(ls); /* skip it */

for (;;) {
switch (ls->current) {
case EOZ:
luaX_lexerror(ls, (seminfo) ? "unfinished long string" :
"unfinished long comment", TK_EOS);
break; /* to avoid warnings */
#if defined(LUA_COMPAT_LSTR)
case '[': {
if (skip_sep(ls) == sep) {
save_and_next(ls); /* skip 2nd `[' */
cont++;
#if LUA_COMPAT_LSTR == 1
if (sep == 0)
luaX_lexerror(ls, "nesting of [[...]] is deprecated", '[');
#endif
}
break;
}
#endif
case ']': {
if (skip_sep(ls) == sep) {
save_and_next(ls); /* skip 2nd `]' */
#if defined(LUA_COMPAT_LSTR) && LUA_COMPAT_LSTR == 2
cont--;
if (sep == 0 && cont >= 0) break;
#endif
goto endloop;
}
break;
}
case '\n':
case '\r': {
save(ls, '\n');
inclinenumber(ls); /* 注释的业务中也不能忘了linenumber */
if (!seminfo) luaZ_resetbuffer(ls->buff); /* avoid wasting space */
break;
}
default: {
if (seminfo) save_and_next(ls);
else next(ls);
}
}
} endloop:

/* seminfo为null是注释逻辑,注释不用管里面的具体String,否则是一个正常的String的token,需将String保存 */
if (seminfo) {
/* 2+sep:[{=}[ */
seminfo->ts = luaX_newstring(ls, luaZ_buffer(ls->buff) + (2 + sep),
luaZ_bufflen(ls->buff) - 2*(2 + sep));
}
}

/* 读一个"字符串"或'字符串'格式的字符串 */
static void read_string (LexState *ls, int del, SemInfo *seminfo) {
save_and_next(ls);
while (ls->current != del) {
switch (ls->current) {
case EOZ:
luaX_lexerror(ls, "unfinished string", TK_EOS);
continue; /* to avoid warnings */
case '\n':
case '\r':
luaX_lexerror(ls, "unfinished string", TK_STRING);
continue; /* to avoid warnings */
case '\\': { /* 可能的转移序列 */
int c;
next(ls); /* do not save the `\' */
switch (ls->current) {
case 'a': c = '\a'; break;
case 'b': c = '\b'; break;
case 'f': c = '\f'; break;
case 'n': c = '\n'; break;
case 'r': c = '\r'; break;
case 't': c = '\t'; break;
case 'v': c = '\v'; break;

/* 本身就是一个换行符 */
case '\n': /* go through */
case '\r': save(ls, '\n'); inclinenumber(ls); continue;

case EOZ: continue; /* will raise an error next loop */
default: {
if (!isdigit(ls->current))
save_and_next(ls); /* handles \\, \", \', and \? */
else { /* \xxx */
int i = 0;
c = 0;
do {
c = 10*c + (ls->current-'0');
next(ls);
} while (++i<3 && isdigit(ls->current));
if (c > UCHAR_MAX)
luaX_lexerror(ls, "escape sequence too large", TK_STRING);
save(ls, c);
}
continue;
}
}
save(ls, c);
next(ls);
continue;
}
default:
save_and_next(ls);
}
}
save_and_next(ls); /* skip delimiter(分隔符) */
seminfo->ts = luaX_newstring(ls, luaZ_buffer(ls->buff) + 1,
luaZ_bufflen(ls->buff) - 2);
}

/* 从读取下一个字符token
** 从ZIO读取下一个token到seminfo,并返回TokenType(中途可能用到lx->buff)
*/
static int llex (LexState *ls, SemInfo *seminfo) {
luaZ_resetbuffer(ls->buff);
for (;;) {
switch (ls->current) {
case '\n':
case '\r': {
inclinenumber(ls);
continue;
}
case '-': {
next(ls);
/* 单独的 - */
if (ls->current != '-') return '-';
/* else is a comment */
next(ls); /* 单行OR多行注释? */
if (ls->current == '[') {
int sep = skip_sep(ls);
luaZ_resetbuffer(ls->buff); /* `skip_sep' may dirty the buffer */
if (sep >= 0) {
read_long_string(ls, NULL, sep); /* long comment */
luaZ_resetbuffer(ls->buff);
continue;
}
}
/* else short comment */
while (!currIsNewline(ls) && ls->current != EOZ)
next(ls);
continue;
}
case '[': { /* 长字符串: [{=}[ String ]{=}] */
int sep = skip_sep(ls);
if (sep >= 0) { /* 多行字符串开头 [{=}[ */
read_long_string(ls, seminfo, sep);
return TK_STRING;
}
else if (sep == -1) return '['; /* [,others这样的开头 */
else luaX_lexerror(ls, "invalid long string delimiter", TK_STRING); /* [={=},others这样的开头 */
}
case '=': {
next(ls);
if (ls->current != '=') return '=';
else { next(ls); return TK_EQ; }
}
case '<': {
next(ls);
if (ls->current != '=') return '<';
else { next(ls); return TK_LE; }
}
case '>': {
next(ls);
if (ls->current != '=') return '>';
else { next(ls); return TK_GE; }
}
case '~': {
next(ls);
if (ls->current != '=') return '~';
else { next(ls); return TK_NE; }
}
/* 短字符串 */
case '"':
case '\'': {
read_string(ls, ls->current, seminfo);
return TK_STRING;
}
/* 看这个符号的解析,是一个深度优先的解析示例 */
case '.': {
save_and_next(ls);
if (check_next(ls, ".")) {
if (check_next(ls, "."))
return TK_DOTS; /* ... */
else return TK_CONCAT; /* .. */
}
else if (!isdigit(ls->current)) return '.';
else {
read_numeral(ls, seminfo);
return TK_NUMBER;
}
}
case EOZ: {
return TK_EOS;
}
default: {
if (isspace(ls->current)) {
lua_assert(!currIsNewline(ls)); /* 换行符在前面就被解析掉了,这里不能再是换行符了,否则就重复了 */
next(ls);
continue;
}
else if (isdigit(ls->current)) {
read_numeral(ls, seminfo);
return TK_NUMBER;
}
else if (isalpha(ls->current) || ls->current == '_') { /* 标识符 */
/* identifier or reserved word */
TString *ts;
do {
save_and_next(ls);
} while (isalnum(ls->current) || ls->current == '_'); /* 这里和上面的有一点差别 */

ts = luaX_newstring(ls, luaZ_buffer(ls->buff),
luaZ_bufflen(ls->buff));
/* 关键或保留字符串 */
if (ts->tsv.reserved > 0) /* reserved word? */
return ts->tsv.reserved - 1 + FIRST_RESERVED;
else {
seminfo->ts = ts;
return TK_NAME;
}
}
else {
int c = ls->current;
next(ls);
return c; /* single-char tokens (+ - / ...) */
}
}
}
}
}


void luaX_next (LexState *ls) {
ls->lastline = ls->linenumber
/* 已有一个准备好的lookhead'token,则取出来用 */
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 /* 读取一个token */
ls->t.token = llex(ls, &ls->t.seminfo); /* read next token */
}

/* 当前lookhead'token已过期,重新准备lookhead'token */
void luaX_lookahead (LexState *ls) {
lua_assert(ls->lookahead.token == TK_EOS);
ls->lookahead.token = llex(ls, &ls->lookahead.seminfo);
}
-------------本文结束 感谢阅读-------------