Parser/tokenizer.c

/* Tokenizer implementation */

#include "Python.h"
#include "pgenheaders.h"

#include <ctype.h>
#include <assert.h>

#include "tokenizer.h"
#include "errcode.h"

#ifndef PGEN
#include "unicodeobject.h"
#include "stringobject.h"
#include "fileobject.h"
#include "codecs.h"
#include "abstract.h"
#include "pydebug.h"
#endif /* PGEN */

extern char *PyOS_Readline(FILE *, FILE *, char *);
/* Return malloc'ed string including trailing \n;
   empty malloc'ed string for EOF;
   NULL if interrupted */

/* Don't ever change this -- it would break the portability of Python code */
#define TABSIZE 8

/* Forward */
static struct tok_state *tok_new(void);
static int tok_nextc(struct tok_state *tok);
static void tok_backup(struct tok_state *tok, int c);

/* Token names */

char *_PyParser_TokenNames[] = {
    "ENDMARKER",
    "NAME",
    "NUMBER",
    "STRING",
    "NEWLINE",
    "INDENT",
    "DEDENT",
    "LPAR",
    "RPAR",
    "LSQB",
    "RSQB",
    "COLON",
    "COMMA",
    "SEMI",
    "PLUS",
    "MINUS",
    "STAR",
    "SLASH",
    "VBAR",
    "AMPER",
    "LESS",
    "GREATER",
    "EQUAL",
    "DOT",
    "PERCENT",
    "BACKQUOTE",
    "LBRACE",
    "RBRACE",
    "EQEQUAL",
    "NOTEQUAL",
    "LESSEQUAL",
    "GREATEREQUAL",
    "TILDE",
    "CIRCUMFLEX",
    "LEFTSHIFT",
    "RIGHTSHIFT",
    "DOUBLESTAR",
    "PLUSEQUAL",
    "MINEQUAL",
    "STAREQUAL",
    "SLASHEQUAL",
    "PERCENTEQUAL",
    "AMPEREQUAL",
    "VBAREQUAL",
    "CIRCUMFLEXEQUAL",
    "LEFTSHIFTEQUAL",
    "RIGHTSHIFTEQUAL",
    "DOUBLESTAREQUAL",
    "DOUBLESLASH",
    "DOUBLESLASHEQUAL",
    "AT",
    /* This table must match the #defines in token.h! */
    "OP",
    "<ERRORTOKEN>",
    "<N_TOKENS>"
};


/* Create and initialize a new tok_state structure */

static struct tok_state *
tok_new(void)
{
    struct tok_state *tok = (struct tok_state *)PyMem_MALLOC(
                                            sizeof(struct tok_state));
    if (tok == NULL)
        return NULL;
    tok->buf = tok->cur = tok->end = tok->inp = tok->start = NULL;
    tok->done = E_OK;
    tok->fp = NULL;
    tok->tabsize = TABSIZE;
    tok->indent = 0;
    tok->indstack[0] = 0;
    tok->atbol = 1;
    tok->pendin = 0;
    tok->prompt = tok->nextprompt = NULL;
    tok->lineno = 0;
    tok->level = 0;
    tok->filename = NULL;
    tok->altwarning = 0;
    tok->alterror = 0;
    tok->alttabsize = 1;
    tok->altindstack[0] = 0;
    tok->decoding_state = 0;
    tok->decoding_erred = 0;
    tok->read_coding_spec = 0;
    tok->encoding = NULL;
    tok->cont_line = 0;
#ifndef PGEN
    tok->decoding_readline = NULL;
    tok->decoding_buffer = NULL;
#endif
    return tok;
}

#ifdef PGEN

static char *
decoding_fgets(char *s, int size, struct tok_state *tok)
{
    return fgets(s, size, tok->fp);
}

static int
decoding_feof(struct tok_state *tok)
{
    return feof(tok->fp);
}

static const char *
decode_str(const char *str, struct tok_state *tok)
{
    return str;
}

#else /* PGEN */

static char *
error_ret(struct tok_state *tok) /* XXX */
{
    tok->decoding_erred = 1;
    if (tok->fp != NULL && tok->buf != NULL) /* see PyTokenizer_Free */
        PyMem_FREE(tok->buf);
    tok->buf = NULL;
    return NULL;                /* as if it were EOF */
}

static char *
new_string(const char *s, Py_ssize_t len)
{
    char* result = (char *)PyMem_MALLOC(len + 1);
    if (result != NULL) {
        memcpy(result, s, len);
        result[len] = '\0';
    }
    return result;
}

static char *
get_normal_name(char *s)        /* for utf-8 and latin-1 */
{
    char buf[13];
    int i;
    for (i = 0; i < 12; i++) {
        int c = s[i];
        if (c == '\0') break;
        else if (c == '_') buf[i] = '-';
        else buf[i] = tolower(c);
    }
    buf[i] = '\0';
    if (strcmp(buf, "utf-8") == 0 ||
        strncmp(buf, "utf-8-", 6) == 0) return "utf-8";
    else if (strcmp(buf, "latin-1") == 0 ||
             strcmp(buf, "iso-8859-1") == 0 ||
             strcmp(buf, "iso-latin-1") == 0 ||
             strncmp(buf, "latin-1-", 8) == 0 ||
             strncmp(buf, "iso-8859-1-", 11) == 0 ||
             strncmp(buf, "iso-latin-1-", 12) == 0) return "iso-8859-1";
    else return s;
}

/* Return the coding spec in S, or NULL if none is found.  */

static char *
get_coding_spec(const char *s, Py_ssize_t size)
{
    Py_ssize_t i;
    /* Coding spec must be in a comment, and that comment must be
     * the only statement on the source code line. */
    for (i = 0; i < size - 6; i++) {
        if (s[i] == '#')
            break;
        if (s[i] != ' ' && s[i] != '\t' && s[i] != '\014')
            return NULL;
    }
    for (; i < size - 6; i++) { /* XXX inefficient search */
        const char* t = s + i;
        if (strncmp(t, "coding", 6) == 0) {
            const char* begin = NULL;
            t += 6;
            if (t[0] != ':' && t[0] != '=')
                continue;
            do {
                t++;
            } while (t[0] == '\x20' || t[0] == '\t');

            begin = t;
            while (isalnum(Py_CHARMASK(t[0])) ||
                   t[0] == '-' || t[0] == '_' || t[0] == '.')
                t++;

            if (begin < t) {
                char* r = new_string(begin, t - begin);
                char* q = get_normal_name(r);
                if (r != q) {
                    PyMem_FREE(r);
                    r = new_string(q, strlen(q));
                }
                return r;
            }
        }
    }
    return NULL;
}

/* Check whether the line contains a coding spec. If it does,
   invoke the set_readline function for the new encoding.
   This function receives the tok_state and the new encoding.
   Return 1 on success, 0 on failure.  */

static int
check_coding_spec(const char* line, Py_ssize_t size, struct tok_state *tok,
                  int set_readline(struct tok_state *, const char *))
{
    char * cs;
    int r = 1;

    if (tok->cont_line)
        /* It's a continuation line, so it can't be a coding spec. */
        return 1;
    cs = get_coding_spec(line, size);
    if (cs != NULL) {
        tok->read_coding_spec = 1;
        if (tok->encoding == NULL) {
            assert(tok->decoding_state == 1); /* raw */
            if (strcmp(cs, "utf-8") == 0 ||
                strcmp(cs, "iso-8859-1") == 0) {
                tok->encoding = cs;
            } else {
#ifdef Py_USING_UNICODE
                r = set_readline(tok, cs);
                if (r) {
                    tok->encoding = cs;
                    tok->decoding_state = -1;
                }
                else
                    PyMem_FREE(cs);
#else
                /* Without Unicode support, we cannot
                   process the coding spec. Since there
                   won't be any Unicode literals, that
                   won't matter. */
                PyMem_FREE(cs);
#endif
            }
        } else {                /* then, compare cs with BOM */
            r = (strcmp(tok->encoding, cs) == 0);
            PyMem_FREE(cs);
        }
    }
    if (!r) {
        cs = tok->encoding;
        if (!cs)
            cs = "with BOM";
        PyErr_Format(PyExc_SyntaxError, "encoding problem: %s", cs);
    }
    return r;
}

/* See whether the file starts with a BOM. If it does,
   invoke the set_readline function with the new encoding.
   Return 1 on success, 0 on failure.  */

static int
check_bom(int get_char(struct tok_state *),
          void unget_char(int, struct tok_state *),
          int set_readline(struct tok_state *, const char *),
          struct tok_state *tok)
{
    int ch1, ch2, ch3;
    ch1 = get_char(tok);
    tok->decoding_state = 1;
    if (ch1 == EOF) {
        return 1;
    } else if (ch1 == 0xEF) {
        ch2 = get_char(tok);
        if (ch2 != 0xBB) {
            unget_char(ch2, tok);
            unget_char(ch1, tok);
            return 1;
        }
        ch3 = get_char(tok);
        if (ch3 != 0xBF) {
            unget_char(ch3, tok);
            unget_char(ch2, tok);
            unget_char(ch1, tok);
            return 1;
        }
#if 0
    /* Disable support for UTF-16 BOMs until a decision
       is made whether this needs to be supported.  */
    } else if (ch1 == 0xFE) {
        ch2 = get_char(tok);
        if (ch2 != 0xFF) {
            unget_char(ch2, tok);
            unget_char(ch1, tok);
            return 1;
        }
        if (!set_readline(tok, "utf-16-be"))
            return 0;
        tok->decoding_state = -1;
    } else if (ch1 == 0xFF) {
        ch2 = get_char(tok);
        if (ch2 != 0xFE) {
            unget_char(ch2, tok);
            unget_char(ch1, tok);
            return 1;
        }
        if (!set_readline(tok, "utf-16-le"))
            return 0;
        tok->decoding_state = -1;
#endif
    } else {
        unget_char(ch1, tok);
        return 1;
    }
    if (tok->encoding != NULL)
        PyMem_FREE(tok->encoding);
    tok->encoding = new_string("utf-8", 5);     /* resulting is in utf-8 */
    return 1;
}

/* Read a line of text from TOK into S, using the stream in TOK.
   Return NULL on failure, else S.

   On entry, tok->decoding_buffer will be one of:
     1) NULL: need to call tok->decoding_readline to get a new line
     2) PyUnicodeObject *: decoding_feof has called tok->decoding_readline and
       stored the result in tok->decoding_buffer
     3) PyStringObject *: previous call to fp_readl did not have enough room
       (in the s buffer) to copy entire contents of the line read
       by tok->decoding_readline.  tok->decoding_buffer has the overflow.
       In this case, fp_readl is called in a loop (with an expanded buffer)
       until the buffer ends with a '\n' (or until the end of the file is
       reached): see tok_nextc and its calls to decoding_fgets.
*/

static char *
fp_readl(char *s, int size, struct tok_state *tok)
{
#ifndef Py_USING_UNICODE
    /* In a non-Unicode built, this should never be called. */
    Py_FatalError("fp_readl should not be called in this build.");
    return NULL; /* Keep compiler happy (not reachable) */
#else
    PyObject* utf8 = NULL;
    PyObject* buf = tok->decoding_buffer;
    char *str;
    Py_ssize_t utf8len;

    /* Ask for one less byte so we can terminate it */
    assert(size > 0);
    size--;

    if (buf == NULL) {
        buf = PyObject_CallObject(tok->decoding_readline, NULL);
        if (buf == NULL)
            return error_ret(tok);
    } else {
        tok->decoding_buffer = NULL;
        if (PyString_CheckExact(buf))
            utf8 = buf;
    }
    if (utf8 == NULL) {
        utf8 = PyUnicode_AsUTF8String(buf);
        Py_DECREF(buf);
        if (utf8 == NULL)
            return error_ret(tok);
    }
    str = PyString_AsString(utf8);
    utf8len = PyString_GET_SIZE(utf8);
    if (utf8len > size) {
        tok->decoding_buffer = PyString_FromStringAndSize(str+size, utf8len-size);
        if (tok->decoding_buffer == NULL) {
            Py_DECREF(utf8);
            return error_ret(tok);
        }
        utf8len = size;
    }
    memcpy(s, str, utf8len);
    s[utf8len] = '\0';
    Py_DECREF(utf8);
    if (utf8len == 0) return NULL; /* EOF */
    return s;
#endif
}

/* Set the readline function for TOK to a StreamReader's
   readline function. The StreamReader is named ENC.

   This function is called from check_bom and check_coding_spec.

   ENC is usually identical to the future value of tok->encoding,
   except for the (currently unsupported) case of UTF-16.

   Return 1 on success, 0 on failure. */

static int
fp_setreadl(struct tok_state *tok, const char* enc)
{
    PyObject *reader, *stream, *readline;

    /* XXX: constify filename argument. */
    stream = PyFile_FromFile(tok->fp, (char*)tok->filename, "rb", NULL);
    if (stream == NULL)
        return 0;

    reader = PyCodec_StreamReader(enc, stream, NULL);
    Py_DECREF(stream);
    if (reader == NULL)
        return 0;

    readline = PyObject_GetAttrString(reader, "readline");
    Py_DECREF(reader);
    if (readline == NULL)
        return 0;

    tok->decoding_readline = readline;
    return 1;
}

/* Fetch the next byte from TOK. */

static int fp_getc(struct tok_state *tok) {
    return getc(tok->fp);
}

/* Unfetch the last byte back into TOK.  */

static void fp_ungetc(int c, struct tok_state *tok) {
    ungetc(c, tok->fp);
}

/* Read a line of input from TOK. Determine encoding
   if necessary.  */

static char *
decoding_fgets(char *s, int size, struct tok_state *tok)
{
    char *line = NULL;
    int badchar = 0;
    for (;;) {
        if (tok->decoding_state < 0) {
            /* We already have a codec associated with
               this input. */
            line = fp_readl(s, size, tok);
            break;
        } else if (tok->decoding_state > 0) {
            /* We want a 'raw' read. */
            line = Py_UniversalNewlineFgets(s, size,
                                            tok->fp, NULL);
            break;
        } else {
            /* We have not yet determined the encoding.
               If an encoding is found, use the file-pointer
               reader functions from now on. */
            if (!check_bom(fp_getc, fp_ungetc, fp_setreadl, tok))
                return error_ret(tok);
            assert(tok->decoding_state != 0);
        }
    }
    if (line != NULL && tok->lineno < 2 && !tok->read_coding_spec) {
        if (!check_coding_spec(line, strlen(line), tok, fp_setreadl)) {
            return error_ret(tok);
        }
    }
#ifndef PGEN
    /* The default encoding is ASCII, so make sure we don't have any
       non-ASCII bytes in it. */
    if (line && !tok->encoding) {
        unsigned char *c;
        for (c = (unsigned char *)line; *c; c++)
            if (*c > 127) {
                badchar = *c;
                break;
            }
    }
    if (badchar) {
        char buf[500];
        /* Need to add 1 to the line number, since this line
           has not been counted, yet.  */
        sprintf(buf,
            "Non-ASCII character '\\x%.2x' "
            "in file %.200s on line %i, "
            "but no encoding declared; "
            "see http://www.python.org/peps/pep-0263.html for details",
            badchar, tok->filename, tok->lineno + 1);
        PyErr_SetString(PyExc_SyntaxError, buf);
        return error_ret(tok);
    }
#endif
    return line;
}

static int
decoding_feof(struct tok_state *tok)
{
    if (tok->decoding_state >= 0) {
        return feof(tok->fp);
    } else {
        PyObject* buf = tok->decoding_buffer;
        if (buf == NULL) {
            buf = PyObject_CallObject(tok->decoding_readline, NULL);
            if (buf == NULL) {
                error_ret(tok);
                return 1;
            } else {
                tok->decoding_buffer = buf;
            }
        }
        return PyObject_Length(buf) == 0;
    }
}

/* Fetch a byte from TOK, using the string buffer. */

static int
buf_getc(struct tok_state *tok) {
    return Py_CHARMASK(*tok->str++);
}

/* Unfetch a byte from TOK, using the string buffer. */

static void
buf_ungetc(int c, struct tok_state *tok) {
    tok->str--;
    assert(Py_CHARMASK(*tok->str) == c);        /* tok->cur may point to read-only segment */
}

/* Set the readline function for TOK to ENC. For the string-based
   tokenizer, this means to just record the encoding. */

static int
buf_setreadl(struct tok_state *tok, const char* enc) {
    tok->enc = enc;
    return 1;
}

/* Return a UTF-8 encoding Python string object from the
   C byte string STR, which is encoded with ENC. */

#ifdef Py_USING_UNICODE
static PyObject *
translate_into_utf8(const char* str, const char* enc) {
    PyObject *utf8;
    PyObject* buf = PyUnicode_Decode(str, strlen(str), enc, NULL);
    if (buf == NULL)
        return NULL;
    utf8 = PyUnicode_AsUTF8String(buf);
    Py_DECREF(buf);
    return utf8;
}
#endif

/* Decode a byte string STR for use as the buffer of TOK.
   Look for encoding declarations inside STR, and record them
   inside TOK.  */

static const char *
decode_str(const char *str, struct tok_state *tok)
{
    PyObject* utf8 = NULL;
    const char *s;
    const char *newl[2] = {NULL, NULL};
    int lineno = 0;
    tok->enc = NULL;
    tok->str = str;
    if (!check_bom(buf_getc, buf_ungetc, buf_setreadl, tok))
        return error_ret(tok);
    str = tok->str;             /* string after BOM if any */
    assert(str);
#ifdef Py_USING_UNICODE
    if (tok->enc != NULL) {
        utf8 = translate_into_utf8(str, tok->enc);
        if (utf8 == NULL)
            return error_ret(tok);
        str = PyString_AsString(utf8);
    }
#endif
    for (s = str;; s++) {
        if (*s == '\0') break;
        else if (*s == '\n') {
            assert(lineno < 2);
            newl[lineno] = s;
            lineno++;
            if (lineno == 2) break;
        }
    }
    tok->enc = NULL;
    /* need to check line 1 and 2 separately since check_coding_spec
       assumes a single line as input */
    if (newl[0]) {
        if (!check_coding_spec(str, newl[0] - str, tok, buf_setreadl))
            return error_ret(tok);
        if (tok->enc == NULL && newl[1]) {
            if (!check_coding_spec(newl[0]+1, newl[1] - newl[0],
                                   tok, buf_setreadl))
                return error_ret(tok);
        }
    }
#ifdef Py_USING_UNICODE
    if (tok->enc != NULL) {
        assert(utf8 == NULL);
        utf8 = translate_into_utf8(str, tok->enc);
        if (utf8 == NULL) {
            PyErr_Format(PyExc_SyntaxError,
                "unknown encoding: %s", tok->enc);
            return error_ret(tok);
        }
        str = PyString_AsString(utf8);
    }
#endif
    assert(tok->decoding_buffer == NULL);
    tok->decoding_buffer = utf8; /* CAUTION */
    return str;
}

#endif /* PGEN */

/* Set up tokenizer for string */

struct tok_state *
PyTokenizer_FromString(const char *str)
{
    struct tok_state *tok = tok_new();
    if (tok == NULL)
        return NULL;
    str = (char *)decode_str(str, tok);
    if (str == NULL) {
        PyTokenizer_Free(tok);
        return NULL;
    }

    /* XXX: constify members. */
    tok->buf = tok->cur = tok->end = tok->inp = (char*)str;
    return tok;
}


/* Set up tokenizer for file */

struct tok_state *
PyTokenizer_FromFile(FILE *fp, char *ps1, char *ps2)
{
    struct tok_state *tok = tok_new();
    if (tok == NULL)
        return NULL;
    if ((tok->buf = (char *)PyMem_MALLOC(BUFSIZ)) == NULL) {
        PyTokenizer_Free(tok);
        return NULL;
    }
    tok->cur = tok->inp = tok->buf;
    tok->end = tok->buf + BUFSIZ;
    tok->fp = fp;
    tok->prompt = ps1;
    tok->nextprompt = ps2;
    return tok;
}


/* Free a tok_state structure */

void
PyTokenizer_Free(struct tok_state *tok)
{
    if (tok->encoding != NULL)
        PyMem_FREE(tok->encoding);
#ifndef PGEN
    Py_XDECREF(tok->decoding_readline);
    Py_XDECREF(tok->decoding_buffer);
#endif
    if (tok->fp != NULL && tok->buf != NULL)
        PyMem_FREE(tok->buf);
    PyMem_FREE(tok);
}

#if !defined(PGEN) && defined(Py_USING_UNICODE)
static int
tok_stdin_decode(struct tok_state *tok, char **inp)
{
    PyObject *enc, *sysstdin, *decoded, *utf8;
    const char *encoding;
    char *converted;

    if (PySys_GetFile((char *)"stdin", NULL) != stdin)
        return 0;
    sysstdin = PySys_GetObject("stdin");
    if (sysstdin == NULL || !PyFile_Check(sysstdin))
        return 0;

    enc = ((PyFileObject *)sysstdin)->f_encoding;
    if (enc == NULL || !PyString_Check(enc))
        return 0;
    Py_INCREF(enc);

    encoding = PyString_AsString(enc);
    decoded = PyUnicode_Decode(*inp, strlen(*inp), encoding, NULL);
    if (decoded == NULL)
        goto error_clear;

    utf8 = PyUnicode_AsEncodedString(decoded, "utf-8", NULL);
    Py_DECREF(decoded);
    if (utf8 == NULL)
        goto error_clear;

    assert(PyString_Check(utf8));
    converted = new_string(PyString_AS_STRING(utf8),
                           PyString_GET_SIZE(utf8));
    Py_DECREF(utf8);
    if (converted == NULL)
        goto error_nomem;

    PyMem_FREE(*inp);
    *inp = converted;
    if (tok->encoding != NULL)
        PyMem_FREE(tok->encoding);
    tok->encoding = new_string(encoding, strlen(encoding));
    if (tok->encoding == NULL)
        goto error_nomem;

    Py_DECREF(enc);
    return 0;

error_nomem:
    Py_DECREF(enc);
    tok->done = E_NOMEM;
    return -1;

error_clear:
    Py_DECREF(enc);
    if (!PyErr_ExceptionMatches(PyExc_UnicodeDecodeError)) {
        tok->done = E_ERROR;
        return -1;
    }
    /* Fallback to iso-8859-1: for backward compatibility */
    PyErr_Clear();
    return 0;
}
#endif

/* Get next char, updating state; error code goes into tok->done */

static int
tok_nextc(register struct tok_state *tok)
{
    for (;;) {
        if (tok->cur != tok->inp) {
            return Py_CHARMASK(*tok->cur++); /* Fast path */
        }
        if (tok->done != E_OK)
            return EOF;
        if (tok->fp == NULL) {
            char *end = strchr(tok->inp, '\n');
            if (end != NULL)
                end++;
            else {
                end = strchr(tok->inp, '\0');
                if (end == tok->inp) {
                    tok->done = E_EOF;
                    return EOF;
                }
            }
            if (tok->start == NULL)
                tok->buf = tok->cur;
            tok->line_start = tok->cur;
            tok->lineno++;
            tok->inp = end;
            return Py_CHARMASK(*tok->cur++);
        }
        if (tok->prompt != NULL) {
            char *newtok = PyOS_Readline(stdin, stdout, tok->prompt);
            if (tok->nextprompt != NULL)
                tok->prompt = tok->nextprompt;
            if (newtok == NULL)
                tok->done = E_INTR;
            else if (*newtok == '\0') {
                PyMem_FREE(newtok);
                tok->done = E_EOF;
            }
#if !defined(PGEN) && defined(Py_USING_UNICODE)
            else if (tok_stdin_decode(tok, &newtok) != 0)
                PyMem_FREE(newtok);
#endif
            else if (tok->start != NULL) {
                size_t start = tok->start - tok->buf;
                size_t oldlen = tok->cur - tok->buf;
                size_t newlen = oldlen + strlen(newtok);
                char *buf = tok->buf;
                buf = (char *)PyMem_REALLOC(buf, newlen+1);
                tok->lineno++;
                if (buf == NULL) {
                    PyMem_FREE(tok->buf);
                    tok->buf = NULL;
                    PyMem_FREE(newtok);
                    tok->done = E_NOMEM;
                    return EOF;
                }
                tok->buf = buf;
                tok->cur = tok->buf + oldlen;
                tok->line_start = tok->cur;
                strcpy(tok->buf + oldlen, newtok);
                PyMem_FREE(newtok);
                tok->inp = tok->buf + newlen;
                tok->end = tok->inp + 1;
                tok->start = tok->buf + start;
            }
            else {
                tok->lineno++;
                if (tok->buf != NULL)
                    PyMem_FREE(tok->buf);
                tok->buf = newtok;
                tok->line_start = tok->buf;
                tok->cur = tok->buf;
                tok->line_start = tok->buf;
                tok->inp = strchr(tok->buf, '\0');
                tok->end = tok->inp + 1;
            }
        }
        else {
            int done = 0;
            Py_ssize_t cur = 0;
            char *pt;
            if (tok->start == NULL) {
                if (tok->buf == NULL) {
                    tok->buf = (char *)
                        PyMem_MALLOC(BUFSIZ);
                    if (tok->buf == NULL) {
                        tok->done = E_NOMEM;
                        return EOF;
                    }
                    tok->end = tok->buf + BUFSIZ;
                }
                if (decoding_fgets(tok->buf, (int)(tok->end - tok->buf),
                          tok) == NULL) {
                    tok->done = E_EOF;
                    done = 1;
                }
                else {
                    tok->done = E_OK;
                    tok->inp = strchr(tok->buf, '\0');
                    done = tok->inp[-1] == '\n';
                }
            }
            else {
                cur = tok->cur - tok->buf;
                if (decoding_feof(tok)) {
                    tok->done = E_EOF;
                    done = 1;
                }
                else
                    tok->done = E_OK;
            }
            tok->lineno++;
            /* Read until '\n' or EOF */
            while (!done) {
                Py_ssize_t curstart = tok->start == NULL ? -1 :
                          tok->start - tok->buf;
                Py_ssize_t curvalid = tok->inp - tok->buf;
                Py_ssize_t newsize = curvalid + BUFSIZ;
                char *newbuf = tok->buf;
                newbuf = (char *)PyMem_REALLOC(newbuf,
                                               newsize);
                if (newbuf == NULL) {
                    tok->done = E_NOMEM;
                    tok->cur = tok->inp;
                    return EOF;
                }
                tok->buf = newbuf;
                tok->inp = tok->buf + curvalid;
                tok->end = tok->buf + newsize;
                tok->start = curstart < 0 ? NULL :
                         tok->buf + curstart;
                if (decoding_fgets(tok->inp,
                               (int)(tok->end - tok->inp),
                               tok) == NULL) {
                    /* Break out early on decoding
                       errors, as tok->buf will be NULL
                     */
                    if (tok->decoding_erred)
                        return EOF;
                    /* Last line does not end in \n,
                       fake one */
                    strcpy(tok->inp, "\n");
                }
                tok->inp = strchr(tok->inp, '\0');
                done = tok->inp[-1] == '\n';
            }
            if (tok->buf != NULL) {
                tok->cur = tok->buf + cur;
                tok->line_start = tok->cur;
                /* replace "\r\n" with "\n" */
                /* For Mac leave the \r, giving a syntax error */
                pt = tok->inp - 2;
                if (pt >= tok->buf && *pt == '\r') {
                    *pt++ = '\n';
                    *pt = '\0';
                    tok->inp = pt;
                }
            }
        }
        if (tok->done != E_OK) {
            if (tok->prompt != NULL)
                PySys_WriteStderr("\n");
            tok->cur = tok->inp;
            return EOF;
        }
    }
    /*NOTREACHED*/
}


/* Back-up one character */

static void
tok_backup(register struct tok_state *tok, register int c)
{
    if (c != EOF) {
        if (--tok->cur < tok->buf)
            Py_FatalError("tok_backup: begin of buffer");
        if (*tok->cur != c)
            *tok->cur = c;
    }
}


/* Return the token corresponding to a single character */

int
PyToken_OneChar(int c)
{
    switch (c) {
    case '(':           return LPAR;
    case ')':           return RPAR;
    case '[':           return LSQB;
    case ']':           return RSQB;
    case ':':           return COLON;
    case ',':           return COMMA;
    case ';':           return SEMI;
    case '+':           return PLUS;
    case '-':           return MINUS;
    case '*':           return STAR;
    case '/':           return SLASH;
    case '|':           return VBAR;
    case '&':           return AMPER;
    case '<':           return LESS;
    case '>':           return GREATER;
    case '=':           return EQUAL;
    case '.':           return DOT;
    case '%':           return PERCENT;
    case '`':           return BACKQUOTE;
    case '{':           return LBRACE;
    case '}':           return RBRACE;
    case '^':           return CIRCUMFLEX;
    case '~':           return TILDE;
    case '@':       return AT;
    default:            return OP;
    }
}


int
PyToken_TwoChars(int c1, int c2)
{
    switch (c1) {
    case '=':
        switch (c2) {
        case '=':               return EQEQUAL;
        }
        break;
    case '!':
        switch (c2) {
        case '=':               return NOTEQUAL;
        }
        break;
    case '<':
        switch (c2) {
        case '>':               return NOTEQUAL;
        case '=':               return LESSEQUAL;
        case '<':               return LEFTSHIFT;
        }
        break;
    case '>':
        switch (c2) {
        case '=':               return GREATEREQUAL;
        case '>':               return RIGHTSHIFT;
        }
        break;
    case '+':
        switch (c2) {
        case '=':               return PLUSEQUAL;
        }
        break;
    case '-':
        switch (c2) {
        case '=':               return MINEQUAL;
        }
        break;
    case '*':
        switch (c2) {
        case '*':               return DOUBLESTAR;
        case '=':               return STAREQUAL;
        }
        break;
    case '/':
        switch (c2) {
        case '/':               return DOUBLESLASH;
        case '=':               return SLASHEQUAL;
        }
        break;
    case '|':
        switch (c2) {
        case '=':               return VBAREQUAL;
        }
        break;
    case '%':
        switch (c2) {
        case '=':               return PERCENTEQUAL;
        }
        break;
    case '&':
        switch (c2) {
        case '=':               return AMPEREQUAL;
        }
        break;
    case '^':
        switch (c2) {
        case '=':               return CIRCUMFLEXEQUAL;
        }
        break;
    }
    return OP;
}

int
PyToken_ThreeChars(int c1, int c2, int c3)
{
    switch (c1) {
    case '<':
        switch (c2) {
        case '<':
            switch (c3) {
            case '=':
                return LEFTSHIFTEQUAL;
            }
            break;
        }
        break;
    case '>':
        switch (c2) {
        case '>':
            switch (c3) {
            case '=':
                return RIGHTSHIFTEQUAL;
            }
            break;
        }
        break;
    case '*':
        switch (c2) {
        case '*':
            switch (c3) {
            case '=':
                return DOUBLESTAREQUAL;
            }
            break;
        }
        break;
    case '/':
        switch (c2) {
        case '/':
            switch (c3) {
            case '=':
                return DOUBLESLASHEQUAL;
            }
            break;
        }
        break;
    }
    return OP;
}

static int
indenterror(struct tok_state *tok)
{
    if (tok->alterror) {
        tok->done = E_TABSPACE;
        tok->cur = tok->inp;
        return 1;
    }
    if (tok->altwarning) {
        PySys_WriteStderr("%s: inconsistent use of tabs and spaces "
                          "in indentation\n", tok->filename);
        tok->altwarning = 0;
    }
    return 0;
}


/* Get next token, after space stripping etc. */

static int
tok_get(register struct tok_state *tok, char **p_start, char **p_end)
{
    register int c;
    int blankline;

    *p_start = *p_end = NULL;
  nextline:
    tok->start = NULL;
    blankline = 0;

    /* Get indentation level */
    if (tok->atbol) {
        register int col = 0;
        register int altcol = 0;
        tok->atbol = 0;
        for (;;) {
            c = tok_nextc(tok);
            if (c == ' ')
                col++, altcol++;
            else if (c == '\t') {
                col = (col/tok->tabsize + 1) * tok->tabsize;
                altcol = (altcol/tok->alttabsize + 1)
                    * tok->alttabsize;
            }
            else if (c == '\014') /* Control-L (formfeed) */
                col = altcol = 0; /* For Emacs users */
            else
                break;
        }
        tok_backup(tok, c);
        if (c == '#' || c == '\n') {
            /* Lines with only whitespace and/or comments
               shouldn't affect the indentation and are
               not passed to the parser as NEWLINE tokens,
               except *totally* empty lines in interactive
               mode, which signal the end of a command group. */
            if (col == 0 && c == '\n' && tok->prompt != NULL)
                blankline = 0; /* Let it through */
            else
                blankline = 1; /* Ignore completely */
            /* We can't jump back right here since we still
               may need to skip to the end of a comment */
        }
        if (!blankline && tok->level == 0) {
            if (col == tok->indstack[tok->indent]) {
                /* No change */
                if (altcol != tok->altindstack[tok->indent]) {
                    if (indenterror(tok))
                        return ERRORTOKEN;
                }
            }
            else if (col > tok->indstack[tok->indent]) {
                /* Indent -- always one */
                if (tok->indent+1 >= MAXINDENT) {
                    tok->done = E_TOODEEP;
                    tok->cur = tok->inp;
                    return ERRORTOKEN;
                }
                if (altcol <= tok->altindstack[tok->indent]) {
                    if (indenterror(tok))
                        return ERRORTOKEN;
                }
                tok->pendin++;
                tok->indstack[++tok->indent] = col;
                tok->altindstack[tok->indent] = altcol;
            }
            else /* col < tok->indstack[tok->indent] */ {
                /* Dedent -- any number, must be consistent */
                while (tok->indent > 0 &&
                    col < tok->indstack[tok->indent]) {
                    tok->pendin--;
                    tok->indent--;
                }
                if (col != tok->indstack[tok->indent]) {
                    tok->done = E_DEDENT;
                    tok->cur = tok->inp;
                    return ERRORTOKEN;
                }
                if (altcol != tok->altindstack[tok->indent]) {
                    if (indenterror(tok))
                        return ERRORTOKEN;
                }
            }
        }
    }

    tok->start = tok->cur;

    /* Return pending indents/dedents */
    if (tok->pendin != 0) {
        if (tok->pendin < 0) {
            tok->pendin++;
            return DEDENT;
        }
        else {
            tok->pendin--;
            return INDENT;
        }
    }

 again:
    tok->start = NULL;
    /* Skip spaces */
    do {
        c = tok_nextc(tok);
    } while (c == ' ' || c == '\t' || c == '\014');

    /* Set start of current token */
    tok->start = tok->cur - 1;

    /* Skip comment, while looking for tab-setting magic */
    if (c == '#') {
        static char *tabforms[] = {
            "tab-width:",                       /* Emacs */
            ":tabstop=",                        /* vim, full form */
            ":ts=",                             /* vim, abbreviated form */
            "set tabsize=",                     /* will vi never die? */
        /* more templates can be added here to support other editors */
        };
        char cbuf[80];
        char *tp, **cp;
        tp = cbuf;
        do {
            *tp++ = c = tok_nextc(tok);
        } while (c != EOF && c != '\n' &&
                 (size_t)(tp - cbuf + 1) < sizeof(cbuf));
        *tp = '\0';
        for (cp = tabforms;
             cp < tabforms + sizeof(tabforms)/sizeof(tabforms[0]);
             cp++) {
            if ((tp = strstr(cbuf, *cp))) {
                int newsize = atoi(tp + strlen(*cp));

                if (newsize >= 1 && newsize <= 40) {
                    tok->tabsize = newsize;
                    if (Py_VerboseFlag)
                        PySys_WriteStderr(
                        "Tab size set to %d\n",
                        newsize);
                }
            }
        }
        while (c != EOF && c != '\n')
            c = tok_nextc(tok);
    }

    /* Check for EOF and errors now */
    if (c == EOF) {
        return tok->done == E_EOF ? ENDMARKER : ERRORTOKEN;
    }

    /* Identifier (most frequent token!) */
    if (isalpha(c) || c == '_') {
        /* Process r"", u"" and ur"" */
        switch (c) {
        case 'b':
        case 'B':
            c = tok_nextc(tok);
            if (c == 'r' || c == 'R')
                c = tok_nextc(tok);
            if (c == '"' || c == '\'')
                goto letter_quote;
            break;
        case 'r':
        case 'R':
            c = tok_nextc(tok);
            if (c == '"' || c == '\'')
                goto letter_quote;
            break;
        case 'u':
        case 'U':
            c = tok_nextc(tok);
            if (c == 'r' || c == 'R')
                c = tok_nextc(tok);
            if (c == '"' || c == '\'')
                goto letter_quote;
            break;
        }
        while (isalnum(c) || c == '_') {
            c = tok_nextc(tok);
        }
        tok_backup(tok, c);
        *p_start = tok->start;
        *p_end = tok->cur;
        return NAME;
    }

    /* Newline */
    if (c == '\n') {
        tok->atbol = 1;
        if (blankline || tok->level > 0)
            goto nextline;
        *p_start = tok->start;
        *p_end = tok->cur - 1; /* Leave '\n' out of the string */
        tok->cont_line = 0;
        return NEWLINE;
    }

    /* Period or number starting with period? */
    if (c == '.') {
        c = tok_nextc(tok);
        if (isdigit(c)) {
            goto fraction;
        }
        else {
            tok_backup(tok, c);
            *p_start = tok->start;
            *p_end = tok->cur;
            return DOT;
        }
    }

    /* Number */
    if (isdigit(c)) {
        if (c == '0') {
            /* Hex, octal or binary -- maybe. */
            c = tok_nextc(tok);
            if (c == '.')
                goto fraction;
#ifndef WITHOUT_COMPLEX
            if (c == 'j' || c == 'J')
                goto imaginary;
#endif
            if (c == 'x' || c == 'X') {

                /* Hex */
                c = tok_nextc(tok);
                if (!isxdigit(c)) {
                    tok->done = E_TOKEN;
                    tok_backup(tok, c);
                    return ERRORTOKEN;
                }
                do {
                    c = tok_nextc(tok);
                } while (isxdigit(c));
            }
            else if (c == 'o' || c == 'O') {
                /* Octal */
                c = tok_nextc(tok);
                if (c < '0' || c >= '8') {
                    tok->done = E_TOKEN;
                    tok_backup(tok, c);
                    return ERRORTOKEN;
                }
                do {
                    c = tok_nextc(tok);
                } while ('0' <= c && c < '8');
            }
            else if (c == 'b' || c == 'B') {
                /* Binary */
                c = tok_nextc(tok);
                if (c != '0' && c != '1') {
                    tok->done = E_TOKEN;
                    tok_backup(tok, c);
                    return ERRORTOKEN;
                }
                do {
                    c = tok_nextc(tok);
                } while (c == '0' || c == '1');
            }
            else {
                int found_decimal = 0;
                /* Octal; c is first char of it */
                /* There's no 'isoctdigit' macro, sigh */
                while ('0' <= c && c < '8') {
                    c = tok_nextc(tok);
                }
                if (isdigit(c)) {
                    found_decimal = 1;
                    do {
                        c = tok_nextc(tok);
                    } while (isdigit(c));
                }
                if (c == '.')
                    goto fraction;
                else if (c == 'e' || c == 'E')
                    goto exponent;
#ifndef WITHOUT_COMPLEX
                else if (c == 'j' || c == 'J')
                    goto imaginary;
#endif
                else if (found_decimal) {
                    tok->done = E_TOKEN;
                    tok_backup(tok, c);
                    return ERRORTOKEN;
                }
            }
            if (c == 'l' || c == 'L')
                c = tok_nextc(tok);
        }
        else {
            /* Decimal */
            do {
                c = tok_nextc(tok);
            } while (isdigit(c));
            if (c == 'l' || c == 'L')
                c = tok_nextc(tok);
            else {
                /* Accept floating point numbers. */
                if (c == '.') {
        fraction:
                    /* Fraction */
                    do {
                        c = tok_nextc(tok);
                    } while (isdigit(c));
                }
                if (c == 'e' || c == 'E') {
        exponent:
                    /* Exponent part */
                    c = tok_nextc(tok);
                    if (c == '+' || c == '-')
                        c = tok_nextc(tok);
                    if (!isdigit(c)) {
                        tok->done = E_TOKEN;
                        tok_backup(tok, c);
                        return ERRORTOKEN;
                    }
                    do {
                        c = tok_nextc(tok);
                    } while (isdigit(c));
                }
#ifndef WITHOUT_COMPLEX
                if (c == 'j' || c == 'J')
                    /* Imaginary part */
        imaginary:
                    c = tok_nextc(tok);
#endif
            }
        }
        tok_backup(tok, c);
        *p_start = tok->start;
        *p_end = tok->cur;
        return NUMBER;
    }

  letter_quote:
    /* String */
    if (c == '\'' || c == '"') {
        Py_ssize_t quote2 = tok->cur - tok->start + 1;
        int quote = c;
        int triple = 0;
        int tripcount = 0;
        for (;;) {
            c = tok_nextc(tok);
            if (c == '\n') {
                if (!triple) {
                    tok->done = E_EOLS;
                    tok_backup(tok, c);
                    return ERRORTOKEN;
                }
                tripcount = 0;
                tok->cont_line = 1; /* multiline string. */
            }
            else if (c == EOF) {
                if (triple)
                    tok->done = E_EOFS;
                else
                    tok->done = E_EOLS;
                tok->cur = tok->inp;
                return ERRORTOKEN;
            }
            else if (c == quote) {
                tripcount++;
                if (tok->cur - tok->start == quote2) {
                    c = tok_nextc(tok);
                    if (c == quote) {
                        triple = 1;
                        tripcount = 0;
                        continue;
                    }
                    tok_backup(tok, c);
                }
                if (!triple || tripcount == 3)
                    break;
            }
            else if (c == '\\') {
                tripcount = 0;
                c = tok_nextc(tok);
                if (c == EOF) {
                    tok->done = E_EOLS;
                    tok->cur = tok->inp;
                    return ERRORTOKEN;
                }
            }
            else
                tripcount = 0;
        }
        *p_start = tok->start;
        *p_end = tok->cur;
        return STRING;
    }

    /* Line continuation */
    if (c == '\\') {
        c = tok_nextc(tok);
        if (c != '\n') {
            tok->done = E_LINECONT;
            tok->cur = tok->inp;
            return ERRORTOKEN;
        }
        tok->cont_line = 1;
        goto again; /* Read next line */
    }

    /* Check for two-character token */
    {
        int c2 = tok_nextc(tok);
        int token = PyToken_TwoChars(c, c2);
#ifndef PGEN
        if (Py_Py3kWarningFlag && token == NOTEQUAL && c == '<') {
            if (PyErr_WarnExplicit(PyExc_DeprecationWarning,
                                   "<> not supported in 3.x; use !=",
                                   tok->filename, tok->lineno,
                                   NULL, NULL)) {
                return ERRORTOKEN;
            }
        }
#endif
        if (token != OP) {
            int c3 = tok_nextc(tok);
            int token3 = PyToken_ThreeChars(c, c2, c3);
            if (token3 != OP) {
                token = token3;
            } else {
                tok_backup(tok, c3);
            }
            *p_start = tok->start;
            *p_end = tok->cur;
            return token;
        }
        tok_backup(tok, c2);
    }

    /* Keep track of parentheses nesting level */
    switch (c) {
    case '(':
    case '[':
    case '{':
        tok->level++;
        break;
    case ')':
    case ']':
    case '}':
        tok->level--;
        break;
    }

    /* Punctuation character */
    *p_start = tok->start;
    *p_end = tok->cur;
    return PyToken_OneChar(c);
}

int
PyTokenizer_Get(struct tok_state *tok, char **p_start, char **p_end)
{
    int result = tok_get(tok, p_start, p_end);
    if (tok->decoding_erred) {
        result = ERRORTOKEN;
        tok->done = E_DECODE;
    }
    return result;
}

/* This function is only called from parsetok. However, it cannot live
   there, as it must be empty for PGEN, and we can check for PGEN only
   in this file. */

#if defined(PGEN) || !defined(Py_USING_UNICODE)
char*
PyTokenizer_RestoreEncoding(struct tok_state* tok, int len, int* offset)
{
    return NULL;
}
#else
#ifdef Py_USING_UNICODE
static PyObject *
dec_utf8(const char *enc, const char *text, size_t len) {
    PyObject *ret = NULL;
    PyObject *unicode_text = PyUnicode_DecodeUTF8(text, len, "replace");
    if (unicode_text) {
        ret = PyUnicode_AsEncodedString(unicode_text, enc, "replace");
        Py_DECREF(unicode_text);
    }
    if (!ret) {
        PyErr_Clear();
    }
    return ret;
}
char *
PyTokenizer_RestoreEncoding(struct tok_state* tok, int len, int *offset)
{
    char *text = NULL;
    if (tok->encoding) {
        /* convert source to original encondig */
        PyObject *lineobj = dec_utf8(tok->encoding, tok->buf, len);
        if (lineobj != NULL) {
            int linelen = PyString_Size(lineobj);
            const char *line = PyString_AsString(lineobj);
            text = PyObject_MALLOC(linelen + 1);
            if (text != NULL && line != NULL) {
                if (linelen)
                    strncpy(text, line, linelen);
                text[linelen] = '\0';
            }
            Py_DECREF(lineobj);

            /* adjust error offset */
            if (*offset > 1) {
                PyObject *offsetobj = dec_utf8(tok->encoding,
                                               tok->buf, *offset-1);
                if (offsetobj) {
                    *offset = PyString_Size(offsetobj) + 1;
                    Py_DECREF(offsetobj);
                }
            }

        }
    }
    return text;

}
#endif /* defined(Py_USING_UNICODE) */
#endif


#ifdef Py_DEBUG

void
tok_dump(int type, char *start, char *end)
{
    printf("%s", _PyParser_TokenNames[type]);
    if (type == NAME || type == NUMBER || type == STRING || type == OP)
        printf("(%.*s)", (int)(end - start), start);
}

#endif