text: /*
  ** $Id: liolib.c,v 2.73.1.4 2010/05/14 15:33:51 roberto Exp $
  ** Standard I/O (and system) library
  ** See Copyright Notice in lua.h
  ** IO库
  */
  
  
  #include <errno.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  #define liolib_c
  #define LUA_LIB
  
  #include "lua.h"
  
  #include "lauxlib.h"
  #include "lualib.h"
  
  
  
  #define IO_INPUT	1
  #define IO_OUTPUT	2
  
  
  static const char *const fnames[] = {"input", "output"};
  
  
  static int pushresult (lua_State *L, int i, const char *filename) {
    int en = errno;  /* calls to Lua API may change this value */
    if (i) {
      lua_pushboolean(L, 1);
      return 1;
    }
    else {
      lua_pushnil(L);
      if (filename)
        lua_pushfstring(L, "%s: %s", filename, strerror(en));
      else
        lua_pushfstring(L, "%s", strerror(en));
      lua_pushinteger(L, en);
      return 3;
    }
  }
  
  
  static void fileerror (lua_State *L, int arg, const char *filename) {
    lua_pushfstring(L, "%s: %s", filename, strerror(errno));
    luaL_argerror(L, arg, lua_tostring(L, -1));
  }
  
  
  #define tofilep(L)	((FILE **)luaL_checkudata(L, 1, LUA_FILEHANDLE))
  
  
  static int io_type (lua_State *L) {
    void *ud;
    luaL_checkany(L, 1);
    ud = lua_touserdata(L, 1);
    lua_getfield(L, LUA_REGISTRYINDEX, LUA_FILEHANDLE);
    if (ud == NULL || !lua_getmetatable(L, 1) || !lua_rawequal(L, -2, -1))
      lua_pushnil(L);  /* not a file */
    else if (*((FILE **)ud) == NULL)
      lua_pushliteral(L, "closed file");
    else
      lua_pushliteral(L, "file");
    return 1;
  }
  
  
  static FILE *tofile (lua_State *L) {
    FILE **f = tofilep(L);
    if (*f == NULL)
      luaL_error(L, "attempt to use a closed file");
    return *f;
  }
  
  
  
  /*
  ** When creating file handles, always creates a `closed' file handle
  ** before opening the actual file; so, if there is a memory error, the
  ** file is not left opened.
  */
  static FILE **newfile (lua_State *L) {
    FILE **pf = (FILE **)lua_newuserdata(L, sizeof(FILE *));
    *pf = NULL;  /* file handle is currently `closed' */
    luaL_getmetatable(L, LUA_FILEHANDLE);
    lua_setmetatable(L, -2);
    return pf;
  }
  
  
  /*
  ** function to (not) close the standard files stdin, stdout, and stderr
  */
  static int io_noclose (lua_State *L) {
    lua_pushnil(L);
    lua_pushliteral(L, "cannot close standard file");
    return 2;
  }
  
  
  /*
  ** function to close 'popen' files
  */
  static int io_pclose (lua_State *L) {
    FILE **p = tofilep(L);
    int ok = lua_pclose(L, *p);
    *p = NULL;
    return pushresult(L, ok, NULL);
  }
  
  
  /*
  ** function to close regular files
  */
  static int io_fclose (lua_State *L) {
    FILE **p = tofilep(L);
    int ok = (fclose(*p) == 0);
    *p = NULL;
    return pushresult(L, ok, NULL);
  }
  
  
  static int aux_close (lua_State *L) {
    lua_getfenv(L, 1);
    lua_getfield(L, -1, "__close");
    return (lua_tocfunction(L, -1))(L);
  }
  
  
  static int io_close (lua_State *L) {
    if (lua_isnone(L, 1))
      lua_rawgeti(L, LUA_ENVIRONINDEX, IO_OUTPUT);
    tofile(L);  /* make sure argument is a file */
    return aux_close(L);
  }
  
  
  static int io_gc (lua_State *L) {
    FILE *f = *tofilep(L);
    /* ignore closed files */
    if (f != NULL)
      aux_close(L);
    return 0;
  }
  
  
  static int io_tostring (lua_State *L) {
    FILE *f = *tofilep(L);
    if (f == NULL)
      lua_pushliteral(L, "file (closed)");
    else
      lua_pushfstring(L, "file (%p)", f);
    return 1;
  }
  
  
  static int io_open (lua_State *L) {
    const char *filename = luaL_checkstring(L, 1);
    const char *mode = luaL_optstring(L, 2, "r");
    FILE **pf = newfile(L);
    *pf = fopen(filename, mode);
    return (*pf == NULL) ? pushresult(L, 0, filename) : 1;
  }
  
  
  /*
  ** this function has a separated environment, which defines the
  ** correct __close for 'popen' files
  */
  static int io_popen (lua_State *L) {
    const char *filename = luaL_checkstring(L, 1);
    const char *mode = luaL_optstring(L, 2, "r");
    FILE **pf = newfile(L);
    *pf = lua_popen(L, filename, mode);
    return (*pf == NULL) ? pushresult(L, 0, filename) : 1;
  }
  
  
  static int io_tmpfile (lua_State *L) {
    FILE **pf = newfile(L);
    *pf = tmpfile();
    return (*pf == NULL) ? pushresult(L, 0, NULL) : 1;
  }
  
  
  static FILE *getiofile (lua_State *L, int findex) {
    FILE *f;
    lua_rawgeti(L, LUA_ENVIRONINDEX, findex);
    f = *(FILE **)lua_touserdata(L, -1);
    if (f == NULL)
      luaL_error(L, "standard %s file is closed", fnames[findex - 1]);
    return f;
  }
  
  
  static int g_iofile (lua_State *L, int f, const char *mode) {
    if (!lua_isnoneornil(L, 1)) {
      const char *filename = lua_tostring(L, 1);
      if (filename) {
        FILE **pf = newfile(L);
        *pf = fopen(filename, mode);
        if (*pf == NULL)
          fileerror(L, 1, filename);
      }
      else {
        tofile(L);  /* check that it's a valid file handle */
        lua_pushvalue(L, 1);
      }
      lua_rawseti(L, LUA_ENVIRONINDEX, f);
    }
    /* return current value */
    lua_rawgeti(L, LUA_ENVIRONINDEX, f);
    return 1;
  }
  
  
  static int io_input (lua_State *L) {
    return g_iofile(L, IO_INPUT, "r");
  }
  
  
  static int io_output (lua_State *L) {
    return g_iofile(L, IO_OUTPUT, "w");
  }
  
  
  static int io_readline (lua_State *L);
  
  
  static void aux_lines (lua_State *L, int idx, int toclose) {
    lua_pushvalue(L, idx);
    lua_pushboolean(L, toclose);  /* close/not close file when finished */
    lua_pushcclosure(L, io_readline, 2);
  }
  
  
  static int f_lines (lua_State *L) {
    tofile(L);  /* check that it's a valid file handle */
    aux_lines(L, 1, 0);
    return 1;
  }
  
  
  static int io_lines (lua_State *L) {
    if (lua_isnoneornil(L, 1)) {  /* no arguments? */
      /* will iterate over default input */
      lua_rawgeti(L, LUA_ENVIRONINDEX, IO_INPUT);
      return f_lines(L);
    }
    else {
      const char *filename = luaL_checkstring(L, 1);
      FILE **pf = newfile(L);
      *pf = fopen(filename, "r");
      if (*pf == NULL)
        fileerror(L, 1, filename);
      aux_lines(L, lua_gettop(L), 1);
      return 1;
    }
  }
  
  
  /*
  ** {======================================================
  ** READ
  ** =======================================================
  */
  
  
  static int read_number (lua_State *L, FILE *f) {
    lua_Number d;
    if (fscanf(f, LUA_NUMBER_SCAN, &d) == 1) {
      lua_pushnumber(L, d);
      return 1;
    }
    else {
      lua_pushnil(L);  /* "result" to be removed */
      return 0;  /* read fails */
    }
  }
  
  
  static int test_eof (lua_State *L, FILE *f) {
    int c = getc(f);
    ungetc(c, f);
    lua_pushlstring(L, NULL, 0);
    return (c != EOF);
  }
  
  
  static int read_line (lua_State *L, FILE *f) {
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    for (;;) {
      size_t l;
      char *p = luaL_prepbuffer(&b);
      if (fgets(p, LUAL_BUFFERSIZE, f) == NULL) {  /* eof? */
        luaL_pushresult(&b);  /* close buffer */
        return (lua_objlen(L, -1) > 0);  /* check whether read something */
      }
      l = strlen(p);
      if (l == 0 || p[l-1] != '\n')
        luaL_addsize(&b, l);
      else {
        luaL_addsize(&b, l - 1);  /* do not include `eol' */
        luaL_pushresult(&b);  /* close buffer */
        return 1;  /* read at least an `eol' */
      }
    }
  }
  
  
  static int read_chars (lua_State *L, FILE *f, size_t n) {
    size_t rlen;  /* how much to read */
    size_t nr;  /* number of chars actually read */
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    rlen = LUAL_BUFFERSIZE;  /* try to read that much each time */
    do {
      char *p = luaL_prepbuffer(&b);
      if (rlen > n) rlen = n;  /* cannot read more than asked */
      nr = fread(p, sizeof(char), rlen, f);
      luaL_addsize(&b, nr);
      n -= nr;  /* still have to read `n' chars */
    } while (n > 0 && nr == rlen);  /* until end of count or eof */
    luaL_pushresult(&b);  /* close buffer */
    return (n == 0 || lua_objlen(L, -1) > 0);
  }
  
  
  static int g_read (lua_State *L, FILE *f, int first) {
    int nargs = lua_gettop(L) - 1;
    int success;
    int n;
    clearerr(f);
    if (nargs == 0) {  /* no arguments? */
      success = read_line(L, f);
      n = first+1;  /* to return 1 result */
    }
    else {  /* ensure stack space for all results and for auxlib's buffer */
      luaL_checkstack(L, nargs+LUA_MINSTACK, "too many arguments");
      success = 1;
      for (n = first; nargs-- && success; n++) {
        if (lua_type(L, n) == LUA_TNUMBER) {
          size_t l = (size_t)lua_tointeger(L, n);
          success = (l == 0) ? test_eof(L, f) : read_chars(L, f, l);
        }
        else {
          const char *p = lua_tostring(L, n);
          luaL_argcheck(L, p && p[0] == '*', n, "invalid option");
          switch (p[1]) {
            case 'n':  /* number */
              success = read_number(L, f);
              break;
            case 'l':  /* line */
              success = read_line(L, f);
              break;
            case 'a':  /* file */
              read_chars(L, f, ~((size_t)0));  /* read MAX_SIZE_T chars */
              success = 1; /* always success */
              break;
            default:
              return luaL_argerror(L, n, "invalid format");
          }
        }
      }
    }
    if (ferror(f))
      return pushresult(L, 0, NULL);
    if (!success) {
      lua_pop(L, 1);  /* remove last result */
      lua_pushnil(L);  /* push nil instead */
    }
    return n - first;
  }
  
  
  static int io_read (lua_State *L) {
    return g_read(L, getiofile(L, IO_INPUT), 1);
  }
  
  
  static int f_read (lua_State *L) {
    return g_read(L, tofile(L), 2);
  }
  
  
  static int io_readline (lua_State *L) {
    FILE *f = *(FILE **)lua_touserdata(L, lua_upvalueindex(1));
    int sucess;
    if (f == NULL)  /* file is already closed? */
      luaL_error(L, "file is already closed");
    sucess = read_line(L, f);
    if (ferror(f))
      return luaL_error(L, "%s", strerror(errno));
    if (sucess) return 1;
    else {  /* EOF */
      if (lua_toboolean(L, lua_upvalueindex(2))) {  /* generator created file? */
        lua_settop(L, 0);
        lua_pushvalue(L, lua_upvalueindex(1));
        aux_close(L);  /* close it */
      }
      return 0;
    }
  }
  
  /* }====================================================== */
  
  
  static int g_write (lua_State *L, FILE *f, int arg) {
    int nargs = lua_gettop(L) - 1;
    int status = 1;
    for (; nargs--; arg++) {
      if (lua_type(L, arg) == LUA_TNUMBER) {
        /* optimization: could be done exactly as for strings */
        status = status &&
            fprintf(f, LUA_NUMBER_FMT, lua_tonumber(L, arg)) > 0;
      }
      else {
        size_t l;
        const char *s = luaL_checklstring(L, arg, &l);
        status = status && (fwrite(s, sizeof(char), l, f) == l);
      }
    }
    return pushresult(L, status, NULL);
  }
  
  
  static int io_write (lua_State *L) {
    return g_write(L, getiofile(L, IO_OUTPUT), 1);
  }
  
  
  static int f_write (lua_State *L) {
    return g_write(L, tofile(L), 2);
  }
  
  
  static int f_seek (lua_State *L) {
    static const int mode[] = {SEEK_SET, SEEK_CUR, SEEK_END};
    static const char *const modenames[] = {"set", "cur", "end", NULL};
    FILE *f = tofile(L);
    int op = luaL_checkoption(L, 2, "cur", modenames);
    long offset = luaL_optlong(L, 3, 0);
    op = fseek(f, offset, mode[op]);
    if (op)
      return pushresult(L, 0, NULL);  /* error */
    else {
      lua_pushinteger(L, ftell(f));
      return 1;
    }
  }
  
  
  static int f_setvbuf (lua_State *L) {
    static const int mode[] = {_IONBF, _IOFBF, _IOLBF};
    static const char *const modenames[] = {"no", "full", "line", NULL};
    FILE *f = tofile(L);
    int op = luaL_checkoption(L, 2, NULL, modenames);
    lua_Integer sz = luaL_optinteger(L, 3, LUAL_BUFFERSIZE);
    int res = setvbuf(f, NULL, mode[op], sz);
    return pushresult(L, res == 0, NULL);
  }
  
  
  
  static int io_flush (lua_State *L) {
    return pushresult(L, fflush(getiofile(L, IO_OUTPUT)) == 0, NULL);
  }
  
  
  static int f_flush (lua_State *L) {
    return pushresult(L, fflush(tofile(L)) == 0, NULL);
  }
  
  
  static const luaL_Reg iolib[] = {
    {"close", io_close},
    {"flush", io_flush},
    {"input", io_input},
    {"lines", io_lines},
    {"open", io_open},
    {"output", io_output},
    {"popen", io_popen},
    {"read", io_read},
    {"tmpfile", io_tmpfile},
    {"type", io_type},
    {"write", io_write},
    {NULL, NULL}
  };
  
  
  static const luaL_Reg flib[] = {
    {"close", io_close},
    {"flush", f_flush},
    {"lines", f_lines},
    {"read", f_read},
    {"seek", f_seek},
    {"setvbuf", f_setvbuf},
    {"write", f_write},
    {"__gc", io_gc},
    {"__tostring", io_tostring},
    {NULL, NULL}
  };
  
  
  static void createmeta (lua_State *L) {
    luaL_newmetatable(L, LUA_FILEHANDLE);  /* create metatable for file handles */
    lua_pushvalue(L, -1);  /* push metatable */
    lua_setfield(L, -2, "__index");  /* metatable.__index = metatable */
    luaL_register(L, NULL, flib);  /* file methods */
  }
  
  
  static void createstdfile (lua_State *L, FILE *f, int k, const char *fname) {
    *newfile(L) = f;
    if (k > 0) {
      lua_pushvalue(L, -1);
      lua_rawseti(L, LUA_ENVIRONINDEX, k);
    }
    lua_pushvalue(L, -2);  /* copy environment */
    lua_setfenv(L, -2);  /* set it */
    lua_setfield(L, -3, fname);
  }
  
  
  static void newfenv (lua_State *L, lua_CFunction cls) {
    lua_createtable(L, 0, 1);
    lua_pushcfunction(L, cls);
    lua_setfield(L, -2, "__close");
  }
  
  
  LUALIB_API int luaopen_io (lua_State *L) {
    createmeta(L);
    /* create (private) environment (with fields IO_INPUT, IO_OUTPUT, __close) */
    newfenv(L, io_fclose);
    lua_replace(L, LUA_ENVIRONINDEX);
    /* open library */
    luaL_register(L, LUA_IOLIBNAME, iolib);
    /* create (and set) default files */
    newfenv(L, io_noclose);  /* close function for default files */
    createstdfile(L, stdin, IO_INPUT, "stdin");
    createstdfile(L, stdout, IO_OUTPUT, "stdout");
    createstdfile(L, stderr, 0, "stderr");
    lua_pop(L, 1);  /* pop environment for default files */
    lua_getfield(L, -1, "popen");
    newfenv(L, io_pclose);  /* create environment for 'popen' */
    lua_setfenv(L, -2);  /* set fenv for 'popen' */
    lua_pop(L, 1);  /* pop 'popen' */
    return 1;
  }
  
  