// stb_c_lexer.h - v0.05 - public domain Sean Barrett 2013
// lexer for making little C-like languages with recursive-descent parsers
//
// This file provides both the interface and the implementation.
// To instantiate the implementation,
//      #define STB_C_LEXER_IMPLEMENTATION
// in *ONE* source file, before #including this file.
//
// The default configuration is fairly close to a C lexer, although
// suffixes on integer constants are not handled (you can override this).
//
// History:
//     0.05
//        refixed get_location because github version had lost the fix
//     0.04
//        fix octal parsing bug
//     0.03
//        added STB_C_LEX_DISCARD_PREPROCESSOR option
//        refactor API to simplify (only one struct instead of two)
//        change literal enum names to have 'lit' at the end
//     0.02
//        first public release
//
// Status:
//     - haven't tested compiling as C++
//     - haven't tested the float parsing path
//     - haven't tested the non-default-config paths (e.g. non-stdlib)
//     - only tested default-config paths by eyeballing output of self-parse
//
//     - haven't implemented multiline strings
//     - haven't implemented octal/hex character constants
//     - haven't implemented support for unicode CLEX_char
//     - need to expand error reporting so you don't just get "CLEX_parse_error"

#ifndef STB_C_LEXER_DEFINITIONS
// to change the default parsing rules, copy the following lines
// into your C/C++ file *before* including this, and then replace
// the Y's with N's for the ones you don't want.
// --BEGIN--

#define STB_C_LEX_C_DECIMAL_INTS    Y   //  "0|[1-9][0-9]*"                        CLEX_intlit
#define STB_C_LEX_C_HEX_INTS        Y   //  "0x[0-9a-fA-F]+"                       CLEX_intlit
#define STB_C_LEX_C_OCTAL_INTS      Y   //  "[0-7]+"                               CLEX_intlit
#define STB_C_LEX_C_DECIMAL_FLOATS  Y   //  "[0-9]*(.[0-9]*([eE]-?[0-9]+)?)        CLEX_floatlit
#define STB_C_LEX_C_IDENTIFIERS     Y   //  "[_a-zA-Z][_a-zA-Z0-9]*"               CLEX_id
#define STB_C_LEX_C_DQ_STRINGS      Y   //  double-quote-delimited strings with escapes  CLEX_dqstring
#define STB_C_LEX_C_SQ_STRINGS      N   //  single-quote-delimited strings with escapes  CLEX_ssstring
#define STB_C_LEX_C_CHARS           Y   //  single-quote-delimited character with escape CLEX_charlits
#define STB_C_LEX_C_COMMENTS        Y   //  "/* comment */"
#define STB_C_LEX_CPP_COMMENTS      Y   //  "// comment to end of line\n"
#define STB_C_LEX_C_COMPARISONS     Y   //  "==" CLEX_eq  "!=" CLEX_noteq   "<=" CLEX_lesseq  ">=" CLEX_greatereq
#define STB_C_LEX_C_LOGICAL         Y   //  "&&"  CLEX_andand   "||"  CLEX_oror
#define STB_C_LEX_C_SHIFTS          Y   //  "<<"  CLEX_shl      ">>"  CLEX_shr
#define STB_C_LEX_C_INCREMENTS      Y   //  "++"  CLEX_plusplus "--"  CLEX_minusminus
#define STB_C_LEX_C_ARROW           Y   //  "->"  CLEX_arrow
#define STB_C_LEX_EQUAL_ARROW       N   //  "=>"  CLEX_eqarrow
#define STB_C_LEX_C_BITWISEEQ       Y   //  "&="  CLEX_andeq    "|="  CLEX_oreq     "^="  CLEX_xoreq
#define STB_C_LEX_C_ARITHEQ         Y   //  "+="  CLEX_pluseq   "-="  CLEX_minuseq
                                        //  "*="  CLEX_muleq    "/="  CLEX_diveq    "%=" CLEX_modeq
                                        //  if both STB_C_LEX_SHIFTS & STB_C_LEX_ARITHEQ:
                                        //                      "<<=" CLEX_shleq    ">>=" CLEX_shreq

#define STB_C_LEX_PARSE_SUFFIXES    N   // letters after numbers are parsed as part of those numbers, and must be in suffix list below
#define STB_C_LEX_DECIMAL_SUFFIXES  ""  // decimal integer suffixes e.g. "uUlL" -- these are returned as-is in string storage
#define STB_C_LEX_HEX_SUFFIXES      ""  // e.g. "uUlL"
#define STB_C_LEX_OCTAL_SUFFIXES    ""  // e.g. "uUlL"
#define STB_C_LEX_FLOAT_SUFFIXES    ""  //

#define STB_C_LEX_0_IS_EOF             N  // if Y, ends parsing at '\0'; if N, returns '\0' as token
#define STB_C_LEX_INTEGERS_AS_DOUBLES  N  // parses integers as doubles so they can be larger than 'int', but only if STB_C_LEX_STDLIB==N
#define STB_C_LEX_MULTILINE_DSTRINGS   N  // allow newlines in double-quoted strings
#define STB_C_LEX_MULTILINE_SSTRINGS   N  // allow newlines in single-quoted strings
#define STB_C_LEX_USE_STDLIB           Y  // use strtod,strtol for parsing #s; otherwise inaccurate hack
#define STB_C_LEX_DOLLAR_IDENTIFIER    Y  // allow $ as an identifier character
#define STB_C_LEX_FLOAT_NO_DECIMAL     Y  // allow floats that have no decimal point if they have an exponent

#define STB_C_LEX_DEFINE_ALL_TOKEN_NAMES  N   // if Y, all CLEX_ token names are defined, even if never returned
                                              // leaving it as N should help you catch config bugs

#define STB_C_LEX_DISCARD_PREPROCESSOR    Y   // discard C-preprocessor directives (e.g. after prepocess
                                              // still have #line, #pragma, etc)

//#define STB_C_LEX_ISWHITE(str)    ... // return length in bytes of first character if it is whitespace

#define STB_C_LEXER_DEFINITIONS         // This line prevents the header file from replacing your definitions
// --END--

#endif

#ifndef INCLUDE_STB_C_LEXER_H
#define INCLUDE_STB_C_LEXER_H

typedef struct
{
   // lexer variables
   char *input_stream;
   char *eof;
   char *parse_point;
   char *string_storage;
   int   string_storage_len;

   // lexer parse location for error messages
   char *where_firstchar;
   char *where_lastchar;

   // lexer token variables
   long token;
   double real_number;
   long   int_number;
   char *string;
   int string_len;
} stb_lexer;

typedef struct
{
   int line_number;
   int line_offset;
} stb_lex_location;

#ifdef __cplusplus
extern "C" {
#endif

extern void stb_c_lexer_init(stb_lexer *lexer, const char *input_stream, const char *input_stream_end, char *string_store, int store_length);
// this function initialize the 'lexer' structure
//   Input:
//   - input_stream points to the file to parse, loaded into memory
//   - input_stream_end points to the end of the file, or NULL if you use 0-for-EOF
//   - string_store is storage the lexer can use for storing parsed strings and identifiers
//   - store_length is the length of that storage

extern int stb_c_lexer_get_token(stb_lexer *lexer);
// this function returns non-zero if a token is parsed, or 0 if at EOF
//   Output:
//   - lexer->token is the token ID, which is unicode code point for a single-char token, < 0 for a multichar or eof or error
//   - lexer->real_number is a double constant value for CLEX_floatlit, or CLEX_intlit if STB_C_LEX_INTEGERS_AS_DOUBLES
//   - lexer->int_number is an integer constant for CLEX_intlit if !STB_C_LEX_INTEGERS_AS_DOUBLES, or character for CLEX_charlit
//   - lexer->string is a 0-terminated string for CLEX_dqstring or CLEX_sqstring or CLEX_identifier
//   - lexer->string_len is the byte length of lexer->string

extern void stb_c_lexer_get_location(const stb_lexer *lexer, const char *where, stb_lex_location *loc);
// this inefficient function returns the line number and character offset of a
// given location in the file as returned by stb_lex_token. Because it's inefficient,
// you should only call it for errors, not for every token.
// For error messages of invalid tokens, you typically want the location of the start
// of the token (which caused the token to be invalid). For bugs involving legit
// tokens, you can report the first or the range.
//    Output:
//    - loc->line_number is the line number in the file, counting from 1, of the location
//    - loc->line_offset is the char-offset in the line, counting from 0, of the location


#ifdef __cplusplus
}
#endif

#endif // INCLUDE_STB_C_LEXER_H

#ifdef STB_C_LEXER_IMPLEMENTATION

   #if defined(Y) || defined(N)
   #error "Can only use stb_c_lex in contexts where the preprocessor symbols 'Y' and 'N' are not defined"
   #endif


// Hacky definitions so we can easily #if on them
#define Y(x) 1
#define N(x) 0

#if STB_C_LEX_USE_STDLIB(x)
#define STB__CLEX_use_stdlib
#include <stdlib.h>
#endif

#if STB_C_LEX_INTEGERS_AS_DOUBLES(x)
typedef double     stb__clex_int;
#define intfield   real_number
#define STB__clex_int_as_double
#else
typedef long       stb__clex_int;
#define intfield   int_number
#endif

// Convert these config options to simple conditional #defines so we can more
// easily test them once we've change the meaning of Y/N

#if STB_C_LEX_PARSE_SUFFIXES(x)
#define STB__clex_parse_suffixes
#endif

#if STB_C_LEX_C_DECIMAL_INTS(x) || STB_C_LEX_C_HEX_INTS(x) || STB_C_LEX_DEFINE_ALL_TOKEN_NAMES(x)
#define STB__clex_define_int
#endif

#if (STB_C_LEX_C_ARITHEQ(x) && STB_C_LEX_C_SHIFTS(x)) || STB_C_LEX_DEFINE_ALL_TOKEN_NAMES(x)
#define STB__clex_define_shifts
#endif

#if STB_C_LEX_C_HEX_INTS(x)
#define STB__clex_hex_ints
#endif

#if STB_C_LEX_C_DECIMAL_INTS(x)
#define STB__clex_decimal_ints
#endif

#if STB_C_LEX_C_OCTAL_INTS(x)
#define STB__clex_octal_ints
#endif

#if STB_C_LEX_C_DECIMAL_FLOATS(x)
#define STB__clex_decimal_floats
#endif

#if STB_C_LEX_DISCARD_PREPROCESSOR(x)
#define STB__clex_discard_preprocessor
#endif

// Now pick a definition of Y/N that's conducive to
// defining the enum of token names.
#if STB_C_LEX_DEFINE_ALL_TOKEN_NAMES(x) || defined(STB_C_LEXER_SELF_TEST)
  #undef  N
  #define N(a) Y(a)
#else
  #undef  N
  #define N(a)
#endif

#undef  Y
#define Y(a) a,

enum
{
   CLEX_eof = 256,
   CLEX_parse_error,

#ifdef STB__clex_define_int
   CLEX_intlit,
#endif

   STB_C_LEX_C_DECIMAL_FLOATS( CLEX_floatlit    )
   STB_C_LEX_C_IDENTIFIERS(  CLEX_id            )
   STB_C_LEX_C_DQ_STRINGS(   CLEX_dqstring      )
   STB_C_LEX_C_SQ_STRINGS(   CLEX_sqstring      )
   STB_C_LEX_C_CHARS(        CLEX_charlit       )
   STB_C_LEX_C_COMPARISONS(  CLEX_eq            )
   STB_C_LEX_C_COMPARISONS(  CLEX_noteq         )
   STB_C_LEX_C_COMPARISONS(  CLEX_lesseq        )
   STB_C_LEX_C_COMPARISONS(  CLEX_greatereq     )
   STB_C_LEX_C_LOGICAL(      CLEX_andand        )
   STB_C_LEX_C_LOGICAL(      CLEX_oror          )
   STB_C_LEX_C_SHIFTS(       CLEX_shl           )
   STB_C_LEX_C_SHIFTS(       CLEX_shr           )
   STB_C_LEX_C_INCREMENTS(   CLEX_plusplus      )
   STB_C_LEX_C_INCREMENTS(   CLEX_minusminus    )
   STB_C_LEX_C_ARITHEQ(      CLEX_pluseq        )
   STB_C_LEX_C_ARITHEQ(      CLEX_minuseq       )
   STB_C_LEX_C_ARITHEQ(      CLEX_muleq         )
   STB_C_LEX_C_ARITHEQ(      CLEX_diveq         )
   STB_C_LEX_C_ARITHEQ(      CLEX_modeq         )
   STB_C_LEX_C_BITWISEEQ(    CLEX_andeq         )
   STB_C_LEX_C_BITWISEEQ(    CLEX_oreq          )
   STB_C_LEX_C_BITWISEEQ(    CLEX_xoreq         )
   STB_C_LEX_C_ARROW(        CLEX_arrow         )
   STB_C_LEX_EQUAL_ARROW(    CLEX_eqarrow       )

#ifdef STB__clex_define_shifts
   CLEX_shleq, CLEX_shreq, 
#endif

   CLEX_first_unused_token

#undef Y
#define Y(a) a
};

// Now for the rest of the file we'll use the basic definition where
// where Y expands to its contents and N expands to nothing
#undef N
#define N(a)

// API function
void stb_c_lexer_init(stb_lexer *lexer, const char *input_stream, const char *input_stream_end, char *string_store, int store_length)
{
   lexer->input_stream = (char *) input_stream;
   lexer->eof = (char *) input_stream_end;
   lexer->parse_point = (char *) input_stream;
   lexer->string_storage = string_store;
   lexer->string_storage_len = store_length;
}

// API function
void stb_c_lexer_get_location(const stb_lexer *lexer, const char *where, stb_lex_location *loc)
{
   char *p = lexer->input_stream;
   int line_number = 1;
   int char_offset = 0;
   while (*p && p < where) {
      if (*p == '\n' || *p == '\r') {
         p += (p[0]+p[1] == '\r'+'\n' ? 2 : 1); // skip newline
         line_number += 1;
         char_offset = 0;
      } else {
         ++p;
         ++char_offset;
      }
   }
   loc->line_number = line_number;
   loc->line_offset = char_offset;
}

// main helper function for returning a parsed token
static int stb__clex_token(stb_lexer *lexer, int token, char *start, char *end)
{
   lexer->token = token;
   lexer->where_firstchar = start;
   lexer->where_lastchar = end;
   lexer->parse_point = end+1;
   return 1;
}

// helper function for returning eof
static int stb__clex_eof(stb_lexer *lexer)
{
   lexer->token = CLEX_eof;
   return 0;
}

static int stb__clex_iswhite(int x)
{
   return x == ' ' || x == '\t' || x == '\r' || x == '\n' || x == '\f';
}

static const char *stb__strchr(const char *str, int ch)
{
   for (; *str; ++str) 
      if (*str == ch)
         return str;
   return 0;
}

// parse suffixes at the end of a number
static int stb__clex_parse_suffixes(stb_lexer *lexer, long tokenid, char *start, char *cur, const char *suffixes)
{
   #ifdef STB__clex_parse_suffixes
   lexer->string = lexer->string_storage;
   lexer->string_len = 0;

   while ((*cur >= 'a' && *cur <= 'z') || (*cur >= 'A' && *cur <= 'Z')) {
      if (stb__strchr(suffixes, *cur) == 0)
         return stb__clex_token(lexer, CLEX_parse_error, start, cur);
      if (lexer->string_len+1 >= lexer->string_storage_len)
         return stb__clex_token(lexer, CLEX_parse_error, start, cur);
      lexer->string[lexer->string_len++] = *cur++;
   }
   #else
   suffixes = suffixes; // attempt to suppress warnings
   #endif
   return stb__clex_token(lexer, tokenid, start, cur-1);
}

#ifndef STB__CLEX_use_stdlib
static double stb__clex_parse_float(char *p, char **q)
{
   double value=0;
   while (*p >= '0' && *p <= '9')
      value = value*10 + (*p++ - '0');
   if (*p == '.') {
      double powten=1, addend = 0;
      ++p;
      while (*p >= '0' && *p <= '9') {
         addend = addend + 10*(*p++ - '0');
         powten *= 10;
      }
      value += addend / powten;
   }
   if (*p == 'e' || *p == 'E') {
      int sign = p[1] == '-';
      int exponent=0;
      double pow10=1;
      p += 1+sign;
      while (*p >= '0' && *p <= '9')
         exponent = exponent*10 + (*p++ - '0');
      // can't use pow() from stdlib, so do it slow way
      while (exponent-- > 0)
         pow10 *= 10;
      if (sign)
         value /= pow10;
      else
         value *= pow10;
   }
   *q = p;
   return value;
}
#endif

static int stb__clex_parse_char(char *p, char **q)
{
   if (*p == '\\') {
      *q = p+2; // tentatively guess we'll parse two characters
      switch(p[1]) {
         case '\\': return '\\';
         case '\'': return '\'';
         case '"': return '"';
         case 't': return '\t';
         case 'f': return '\f';
         case 'n': return '\n';
         case 'r': return '\r';
         case '0': return '\0'; // @TODO ocatal constants
         case 'x': case 'X': return -1; // @TODO hex constants
         case 'u': return -1; // @TODO unicode constants
      }
   }
   *q = p+1;
   return (unsigned char) *p;
}

static int stb__clex_parse_string(stb_lexer *lexer, char *p, int type)
{
   char *start = p;
   char delim = *p++; // grab the " or ' for later matching
   char *out = lexer->string_storage;
   char *outend = lexer->string_storage + lexer->string_storage_len;
   while (*p != delim) {
      int n;
      if (*p == '\\') {
         char *q;
         n = stb__clex_parse_char(p, &q);
         if (n < 0)
            return stb__clex_token(lexer, CLEX_parse_error, start, q);
         p = q;
      } else {
         // @OPTIMIZE: could speed this up by looping-while-not-backslash
         n = (unsigned char) *p++;
      }
      if (out+1 > outend)
         return stb__clex_token(lexer, CLEX_parse_error, start, p);
      // @TODO expand unicode escapes to UTF8
      *out++ = (char) n;
   }
   *out = 0;
   lexer->string = lexer->string_storage;
   lexer->string_len = out - lexer->string_storage;
   return stb__clex_token(lexer, type, start, p+1);
}

int stb_c_lexer_get_token(stb_lexer *lexer)
{
   char *p = lexer->parse_point;

   // skip whitespace and comments
   for (;;) {
      #ifdef STB_C_LEX_ISWHITE
      while (p != lexer->stream_end) {
         int n;
         n = STB_C_LEX_ISWHITE(p);
         if (n == 0) break;
         if (lexer->eof && lexer+n > lexer->eof)
            return stb__clex_token(tok, CLEX_parse_error, p,lexer->eof-1);
         p += n;
      }
      #else
      while (p != lexer->eof && stb__clex_iswhite(*p))
         ++p;
      #endif

      STB_C_LEX_CPP_COMMENTS(
         if (p != lexer->eof && p[0] == '/' && p[1] == '/') {
            while (p != lexer->eof && *p != '\r' && *p != '\n')
               ++p;
            continue;
         }
      )

      STB_C_LEX_C_COMMENTS(
         if (p != lexer->eof && p[0] == '/' && p[1] == '*') {
            char *start = p;
            p += 2;
            while (p != lexer->eof && (p[0] != '*' || p[1] != '/'))
               ++p;
            if (p == lexer->eof)
               return stb__clex_token(lexer, CLEX_parse_error, start, p-1);
            p += 2;
            continue;
         }
      )

      #ifdef STB__clex_discard_preprocessor
         // @TODO this discards everything after a '#', regardless
         // of where in the line the # is, rather than requiring it
         // be at the start. (because this parser doesn't otherwise
         // check for line breaks!)
         if (p != lexer->eof && p[0] == '#') {
            while (p != lexer->eof && *p != '\r' && *p != '\n')
               ++p;
            continue;
         }
      #endif

      break;
   }

   if (p == lexer->eof)
      return stb__clex_eof(lexer);

   switch (*p) {
      default:
         if (   (*p >= 'a' && *p <= 'z')
             || (*p >= 'A' && *p <= 'Z')
             || *p == '_' || (unsigned char) *p >= 128    // >= 128 is UTF8 char
             STB_C_LEX_DOLLAR_IDENTIFIER( || *p == '$' ) )
         {
            int n = 0;
            lexer->string = lexer->string_storage;
            lexer->string_len = n;
            do {
               if (n+1 >= lexer->string_storage_len)
                  return stb__clex_token(lexer, CLEX_parse_error, p, p+n);
               lexer->string[n] = p[n];
               ++n;
            } while (
                  (p[n] >= 'a' && p[n] <= 'z')
               || (p[n] >= 'A' && p[n] <= 'Z')
               || (p[n] >= '0' && p[n] <= '9') // allow digits in middle of identifier
               || p[n] == '_' || (unsigned char) p[n] >= 128
                STB_C_LEX_DOLLAR_IDENTIFIER( || p[n] == '$' )
            );
            lexer->string[n] = 0;
            return stb__clex_token(lexer, CLEX_id, p, p+n-1);
         }
 
         // check for EOF
         STB_C_LEX_0_IS_EOF(
            if (*p == 0)
               return stb__clex_eof(tok);
         )

      single_char:         
         // not an identifier, return the character as itself
         return stb__clex_token(lexer, *p, p, p);

      case '+':
         if (p+1 != lexer->eof) {
            STB_C_LEX_C_INCREMENTS(if (p[1] == '+') return stb__clex_token(lexer, CLEX_plusplus, p,p+1);)
            STB_C_LEX_C_ARITHEQ(   if (p[1] == '=') return stb__clex_token(lexer, CLEX_pluseq  , p,p+1);)
         }
         goto single_char;
      case '-':
         if (p+1 != lexer->eof) {
            STB_C_LEX_C_INCREMENTS(if (p[1] == '-') return stb__clex_token(lexer, CLEX_minusminus, p,p+1);)
            STB_C_LEX_C_ARITHEQ(   if (p[1] == '=') return stb__clex_token(lexer, CLEX_minuseq   , p,p+1);)
            STB_C_LEX_C_ARROW(     if (p[1] == '>') return stb__clex_token(lexer, CLEX_arrow     , p,p+1);)
         }
         goto single_char;
      case '&':
         if (p+1 != lexer->eof) {
            STB_C_LEX_C_LOGICAL(  if (p[1] == '&') return stb__clex_token(lexer, CLEX_andand, p,p+1);)
            STB_C_LEX_C_BITWISEEQ(if (p[1] == '=') return stb__clex_token(lexer, CLEX_andeq , p,p+1);)
         }
         goto single_char;
      case '|':
         if (p+1 != lexer->eof) {
            STB_C_LEX_C_LOGICAL(  if (p[1] == '|') return stb__clex_token(lexer, CLEX_oror, p,p+1);)
            STB_C_LEX_C_BITWISEEQ(if (p[1] == '=') return stb__clex_token(lexer, CLEX_oreq, p,p+1);)
         }
         goto single_char;
      case '=':
         if (p+1 != lexer->eof) {
            STB_C_LEX_C_COMPARISONS(if (p[1] == '=') return stb__clex_token(lexer, CLEX_eq, p,p+1);)
            STB_C_LEX_EQUAL_ARROW(  if (p[1] == '>') return stb__clex_token(lexer, CLEX_eqarrow, p,p+1);)
         }
         goto single_char;
      case '!':
         STB_C_LEX_C_COMPARISONS(if (p+1 != lexer->eof && p[1] == '=') return stb__clex_token(lexer, CLEX_noteq, p,p+1);)
         goto single_char;
      case '^':
         STB_C_LEX_C_BITWISEEQ(if (p+1 != lexer->eof && p[1] == '=') return stb__clex_token(lexer, CLEX_xoreq, p,p+1));
         goto single_char;
      case '%':
         STB_C_LEX_C_ARITHEQ(if (p+1 != lexer->eof && p[1] == '=') return stb__clex_token(lexer, CLEX_modeq, p,p+1));
         goto single_char;
      case '*':
         STB_C_LEX_C_ARITHEQ(if (p+1 != lexer->eof && p[1] == '=') return stb__clex_token(lexer, CLEX_muleq, p,p+1));
         goto single_char;
      case '/':
         STB_C_LEX_C_ARITHEQ(if (p+1 != lexer->eof && p[1] == '=') return stb__clex_token(lexer, CLEX_diveq, p,p+1));
         goto single_char;
      case '<':
         if (p+1 != lexer->eof) {
            STB_C_LEX_C_COMPARISONS(if (p[1] == '=') return stb__clex_token(lexer, CLEX_lesseq, p,p+1);)
            STB_C_LEX_C_SHIFTS(     if (p[1] == '<') {
                                       STB_C_LEX_C_ARITHEQ(if (p+2 != lexer->eof && p[2] == '=')
                                                              return stb__clex_token(lexer, CLEX_shleq, p,p+2);)
                                       return stb__clex_token(lexer, CLEX_shl, p,p+1);
                                    }
                              )
         }
         goto single_char;
      case '>':
         if (p+1 != lexer->eof) {
            STB_C_LEX_C_COMPARISONS(if (p[1] == '=') return stb__clex_token(lexer, CLEX_greatereq, p,p+1);)
            STB_C_LEX_C_SHIFTS(     if (p[1] == '>') {
                                       STB_C_LEX_C_ARITHEQ(if (p+2 != lexer->eof && p[2] == '=')
                                                              return stb__clex_token(lexer, CLEX_shreq, p,p+2);)
                                       return stb__clex_token(lexer, CLEX_shr, p,p+1);
                                    }
                              )
         }
         goto single_char;

      case '"':
         STB_C_LEX_C_DQ_STRINGS(return stb__clex_parse_string(lexer, p, CLEX_dqstring);)
         goto single_char;
      case '\'':
         STB_C_LEX_C_SQ_STRINGS(return stb__clex_parse_string(lexer, p, CLEX_sqstring);)
         STB_C_LEX_C_CHARS(
         {
            char *start = p;
            lexer->int_number = stb__clex_parse_char(p+1, &p);
            if (lexer->int_number < 0)
               return stb__clex_token(lexer, CLEX_parse_error, start,start);
            if (p == lexer->eof || *p != '\'')
               return stb__clex_token(lexer, CLEX_parse_error, start,p);
            return stb__clex_token(lexer, CLEX_charlit, start, p+1);
         })
         goto single_char;

      case '0':
         #ifdef STB__clex_hex_ints
            if (p+1 != lexer->eof) {
               if (p[1] == 'x' || p[1] == 'X') {
                  char *q = p+2;
                  #ifdef STB__CLEX_use_stdlib
                  lexer->int_number = strtol((char *) p, (char **) q, 16);
                  #else
                  stb__clex_int n=0;
                  while (q != lexer->eof) {
                     if (*q >= '0' && *q <= '9')
                        n = n*16 + (*q - '0');
                     else if (*q >= 'a' && *q <= 'f')
                        n = n*16 + (*q - 'a') + 10;
                     else if (*q >= 'A' && *q <= 'F')
                        n = n*16 + (*q - 'A') + 10;
                     else
                        break;
                     ++q;
                  }
                  lexer->int_field = n; // int_field is macro that expands to real_number/int_number depending on type of n
                  #endif
                  if (q == p+2)
                     return stb__clex_token(lexer, CLEX_parse_error, p-2,p-1);
                  return stb__clex_parse_suffixes(lexer, CLEX_intlit, p,q, STB_C_LEX_HEX_SUFFIXES);
               }
            }
         #endif // STB__clex_hex_ints
         // can't test for octal because we might parse '0.0' as float or as '0' '.' '0',
         // so have to do float first

         /* FALL THROUGH */
      case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9':

         #ifdef STB__clex_decimal_floats
         {
            char *q = p;
            while (q != lexer->eof && (*q >= '0' && *q <= '9'))
               ++q;
            if (q != lexer->eof) {
               if (*q == '.' STB_C_LEX_FLOAT_NO_DECIMAL(|| *q == 'e' || *q == 'E')) {
                  #ifdef STB__CLEX_use_stdlib
                  lexer->real_number = strtod((char *) p, (char**) &q);
                  #else
                  lexer->real_number = stb__clex_parse_float(p, &q);
                  #endif

                  return stb__clex_parse_suffixes(lexer, CLEX_floatlit, p,q, STB_C_LEX_FLOAT_SUFFIXES);

               }
            }
         }
         #endif // STB__clex_decimal_floats

         #ifdef STB__clex_octal_ints
         if (p[0] == '0') {
            char *q = p;
            #ifdef STB__CLEX_use_stdlib
            lexer->int_number = strtol((char *) p, (char **) &q, 8);
            #else
            stb__clex_int n=0;
            while (q != lexer->eof) {
               if (*q >= '0' && *q <= '7')
                  n = n*8 + (q - '0');
               else
                  break;
               ++q;
            }
            if (q != lexer->eof && (*q == '8' || *q=='9'))
               return stb__clex_token(tok, CLEX_parse_error, p, q);
            lexer->int_field = n;
            #endif
            return stb__clex_parse_suffixes(lexer, CLEX_intlit, p,q, STB_C_LEX_OCTAL_SUFFIXES);
         }
         #endif // STB__clex_octal_ints

         #ifdef STB__clex_decimal_ints
         {
            char *q = p;
            #ifdef STB__CLEX_use_stdlib
            lexer->int_number = strtol((char *) p, (char **) &q, 10);
            #else
            stb__clex_int n=0;
            while (q != lexer->eof) {
               if (*q >= '0' && *q <= '9')
                  n = n*10 + (q - '0');
               else
                  break;
               ++q;
            }
            lexer->int_field = n;
            #endif
            return stb__clex_parse_suffixes(lexer, CLEX_intlit, p,q, STB_C_LEX_OCTAL_SUFFIXES);
         }
         #endif // STB__clex_decimal_ints
         goto single_char;
   }
}
#endif // STB_C_LEXER_IMPLEMENTATION

#ifdef STB_C_LEXER_SELF_TEST

#include <stdio.h>

static void print_token(stb_lexer *lexer)
{
   switch (lexer->token) {
      case CLEX_id        : printf("_%s", lexer->string); break;
      case CLEX_eq        : printf("=="); break;
      case CLEX_noteq     : printf("!="); break;
      case CLEX_lesseq    : printf("<="); break;
      case CLEX_greatereq : printf(">="); break;
      case CLEX_andand    : printf("&&"); break;
      case CLEX_oror      : printf("||"); break;
      case CLEX_shl       : printf("<<"); break;
      case CLEX_shr       : printf(">>"); break;
      case CLEX_plusplus  : printf("++"); break;
      case CLEX_minusminus: printf("--"); break;
      case CLEX_arrow     : printf("->"); break;
      case CLEX_andeq     : printf("&="); break;
      case CLEX_oreq      : printf("|="); break;
      case CLEX_xoreq     : printf("^="); break;
      case CLEX_pluseq    : printf("+="); break;
      case CLEX_minuseq   : printf("-="); break;
      case CLEX_muleq     : printf("*="); break;
      case CLEX_diveq     : printf("/="); break;
      case CLEX_modeq     : printf("%%="); break;
      case CLEX_shleq     : printf("<<="); break;
      case CLEX_shreq     : printf(">>="); break;
      case CLEX_eqarrow   : printf("=>"); break;
      case CLEX_dqstring  : printf("\"%s\"", lexer->string); break;
      case CLEX_sqstring  : printf("'\"%s\"'", lexer->string); break;
      case CLEX_charlit   : printf("'%s'", lexer->string); break;
      #if defined(STB__clex_int_as_double) && !defined(STB__CLEX_use_stdlib)
      case CLEX_intlit    : printf("#%g", lexer->real_number); break;
      #else
      case CLEX_intlit    : printf("#%ld", lexer->int_number); break;
      #endif
      case CLEX_floatlit  : printf("%g", lexer->real_number); break;
      default:
         if (lexer->token >= 0 && lexer->token < 256)
            printf("%c", (int) lexer->token);
         else {
            printf("<<<UNKNOWN TOKEN %ld >>>\n", lexer->token);
         }
         break;
   }
}

/* Force a test
of parsing
multiline comments */

/*/ comment /*/
/**/ extern /**/

int main(int argc, char **argv)
{
   FILE *f = fopen("stb_c_lexer.h", "rb");
   char *text = (char *) malloc(1 << 20);
   int len = f ? fread(text, 1, 1<<20, f) : -1;
   stb_lexer lex;
   if (len < 0) {
      fprintf(stderr, "Error opening file\n");
      return 1;
   }
   fclose(f);

   stb_c_lexer_init(&lex, text, text+len, (char *) malloc(1<<16), 1<<16);
   while (stb_c_lexer_get_token(&lex)) {
      if (lex.token == CLEX_parse_error) {
         printf("\n<<<PARSE ERROR>>>\n");
         break;
      }
      print_token(&lex);
      printf("  ");
   }
   return 0;
}
#endif