source: downloads/boost_1_33_1/tools/build/jam_src/scan.c @ 12

/*
 * Copyright 1993-2002 Christopher Seiwald and Perforce Software, Inc.
 *
 * This file is part of Jam - see jam.c for Copyright information.
 */

# include "jam.h"
# include "lists.h"
# include "parse.h"
# include "scan.h"
# include "jamgram.h"
# include "jambase.h"
# include "newstr.h"

/*
 * scan.c - the jam yacc scanner
 *
 * 12/26/93 (seiwald) - bump buf in yylex to 10240 - yuk.
 * 09/16/94 (seiwald) - check for overflows, unmatched {}'s, etc.
 *                      Also handle tokens abutting EOF by remembering
 *                      to return EOF now matter how many times yylex()
 *                      reinvokes yyline().
 * 02/11/95 (seiwald) - honor only punctuation keywords if SCAN_PUNCT.
 * 07/27/95 (seiwald) - Include jamgram.h after scan.h, so that YYSTYPE is
 *                      defined before Linux's yacc tries to redefine it.
 */

struct keyword {
        char *word;
        int type;
} keywords[] = {
# include "jamgramtab.h"
        { 0, 0 }
} ;

struct include {
        struct include *next;   /* next serial include file */
        char    *string;        /* pointer into current line */
        char    **strings;      /* for yyfparse() -- text to parse */
        FILE    *file;          /* for yyfparse() -- file being read */
        char    *fname;         /* for yyfparse() -- file name */
        int     line;           /* line counter for error messages */
        char    buf[ 512 ];     /* for yyfparse() -- line buffer */
} ;

static struct include *incp = 0; /* current file; head of chain */

static int scanmode = SCAN_NORMAL;
static int anyerrors = 0;
static char *symdump( YYSTYPE *s );

# define BIGGEST_TOKEN 10240    /* no single token can be larger */

/* 
 * Set parser mode: normal, string, or keyword
 */

void
yymode( int n )
{
        scanmode = n;
}

void
yyerror( char *s )
{
        if( incp )
            printf( "%s:%d: ", incp->fname, incp->line );

        printf( "%s at %s\n", s, symdump( &yylval ) );

        ++anyerrors;
}

int
yyanyerrors()
{
        return anyerrors != 0;
}

void
yyfparse( char *s )
{
        struct include *i = (struct include *)malloc( sizeof( *i ) );

        /* Push this onto the incp chain. */

        i->string = "";
        i->strings = 0;
        i->file = 0;
        i->fname = copystr( s );
        i->line = 0;
        i->next = incp;
        incp = i;

        /* If the filename is "+", it means use the internal jambase. */

        if( !strcmp( s, "+" ) )
            i->strings = jambase;
}

/*
 * yyline() - read new line and return first character
 *
 * Fabricates a continuous stream of characters across include files,
 * returning EOF at the bitter end.
 */

int
yyline()
{
        struct include *i = incp;

        if( !incp )
            return EOF;

        /* Once we start reading from the input stream, we reset the */
        /* include insertion point so that the next include file becomes */
        /* the head of the list. */

        /* If there is more data in this line, return it. */

        if( *i->string )
            return *i->string++;

        /* If we're reading from an internal string list, go to the */
        /* next string. */

        if( i->strings )
        {
            if( !*i->strings )
                goto next;

            i->line++;
            i->string = *(i->strings++);
            return *i->string++;
        }

        /* If necessary, open the file */

        if( !i->file )
        {
            FILE *f = stdin;

            if( strcmp( i->fname, "-" ) && !( f = fopen( i->fname, "r" ) ) )
                perror( i->fname );

            i->file = f;
        }

        /* If there's another line in this file, start it. */

        if( i->file && fgets( i->buf, sizeof( i->buf ), i->file ) )
        {
            i->line++;
            i->string = i->buf;
            return *i->string++;
        }

    next:
        /* This include is done.  */
        /* Free it up and return EOF so yyparse() returns to parse_file(). */

        incp = i->next;

        /* Close file, free name */

        if( i->file && i->file != stdin )
            fclose( i->file );
        freestr( i->fname );
        free( (char *)i );

        return EOF;
}

/*
 * yylex() - set yylval to current token; return its type
 *
 * Macros to move things along:
 *
 *      yychar() - return and advance character; invalid after EOF
 *      yyprev() - back up one character; invalid before yychar()
 *
 * yychar() returns a continuous stream of characters, until it hits
 * the EOF of the current include file.
 */

# define yychar() ( *incp->string ? *incp->string++ : yyline() )
# define yyprev() ( incp->string-- )

int
yylex()
{
        int c;
        char buf[BIGGEST_TOKEN];
        char *b = buf;

        if( !incp )
            goto eof;

        /* Get first character (whitespace or of token) */

        c = yychar();

        if( scanmode == SCAN_STRING )
        {
            /* If scanning for a string (action's {}'s), look for the */
            /* closing brace.  We handle matching braces, if they match! */

            int nest = 1;

            while( c != EOF && b < buf + sizeof( buf ) )
            {
                    if( c == '{' )
                        nest++;

                    if( c == '}' && !--nest )
                        break;

                    *b++ = c;

                    c = yychar();

                    /* turn trailing "\r\n" sequences into plain "\n"
                     * for Cygwin
                     */
                    if (c == '\n' && b[-1] == '\r')
                        --b;
            }

            /* We ate the ending brace -- regurgitate it. */

            if( c != EOF )
                yyprev();

            /* Check obvious errors. */

            if( b == buf + sizeof( buf ) )
            {
                yyerror( "action block too big" );
                goto eof;
            }

            if( nest )
            {
                yyerror( "unmatched {} in action block" );
                goto eof;
            }

            *b = 0;
            yylval.type = STRING;
            yylval.string = newstr( buf );
        yylval.file = incp->fname;
        yylval.line = incp->line;
        
        }
        else
        {
            char *b = buf;
            struct keyword *k;
            int inquote = 0;
            int notkeyword;
                
            /* Eat white space */

            for( ;; )
            {
            /* Skip past white space */

            while( c != EOF && isspace( c ) )
                c = yychar();

            /* Not a comment?  Swallow up comment line. */

            if( c != '#' )
                break;
            while( ( c = yychar() ) != EOF && c != '\n' )
                ;
            }

            /* c now points to the first character of a token. */

            if( c == EOF )
                goto eof;

        yylval.file = incp->fname;
        yylval.line = incp->line;
        
            /* While scanning the word, disqualify it for (expensive) */
            /* keyword lookup when we can: $anything, "anything", \anything */

            notkeyword = c == '$';

            /* look for white space to delimit word */
            /* "'s get stripped but preserve white space */
            /* \ protects next character */

            while( 
                c != EOF &&
                b < buf + sizeof( buf ) &&
                ( inquote || !isspace( c ) ) )
            {
                if( c == '"' )
                {
                    /* begin or end " */
                    inquote = !inquote;
                    notkeyword = 1;
                }
                else if( c != '\\' )
                {
                    /* normal char */
                    *b++ = c;
                }
                else if( ( c = yychar()) != EOF )
            {
                    /* \c */
                    *b++ = c;
                    notkeyword = 1;
                }
                else
                {
                    /* \EOF */
                    break;
                }

                c = yychar();
            }

            /* Check obvious errors. */

            if( b == buf + sizeof( buf ) )
            {
                yyerror( "string too big" );
                goto eof;
            }

            if( inquote )
            {
                yyerror( "unmatched \" in string" );
                goto eof;
            }

            /* We looked ahead a character - back up. */

            if( c != EOF )
                yyprev();

            /* scan token table */
            /* don't scan if it's obviously not a keyword or if its */
            /* an alphabetic when were looking for punctuation */

            *b = 0;
            yylval.type = ARG;

            if( !notkeyword && !( isalpha( *buf ) && scanmode == SCAN_PUNCT ) )
            {
                for( k = keywords; k->word; k++ )
                    if( *buf == *k->word && !strcmp( k->word, buf ) )
                {
                    yylval.type = k->type;
                    yylval.string = k->word;    /* used by symdump */
                    break;
                }
            }

            if( yylval.type == ARG )
                yylval.string = newstr( buf );
        }

        if( DEBUG_SCAN )
                printf( "scan %s\n", symdump( &yylval ) );

        return yylval.type;

eof:
    yylval.file = "end-of-input"; /* just in case */
    yylval.line = 0;
        
        yylval.type = EOF;
        return yylval.type;
}

static char *
symdump( YYSTYPE *s )
{
        static char buf[ BIGGEST_TOKEN + 20 ];

        switch( s->type )
        {
        case EOF:
                sprintf( buf, "EOF" );
                break;
        case 0:
                sprintf( buf, "unknown symbol %s", s->string );
                break;
        case ARG:
                sprintf( buf, "argument %s", s->string );
                break;
        case STRING:
                sprintf( buf, "string \"%s\"", s->string );
                break;
        default:
                sprintf( buf, "keyword %s", s->string );
                break;
        }
        return buf;
}

/*  Get information about the current file and line, for those epsilon
 *  transitions that produce a parse
 */
void yyinput_stream( char** name, int* line )
{
    if (incp)
    {
        *name = incp->fname;
        *line = incp->line;
    }
    else
    {
        *name = "(builtin)";
        *line = -1;
    }
}