PDCLib / functions / _PDCLIB / print.c

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/* $Id$ */

/* _PDCLIB_print( const char *, struct _PDCLIB_status_t * )

   This file is part of the Public Domain C Library (PDCLib).
   Permission is granted to use, modify, and / or redistribute at will.
*/

#include <stdio.h>
#include <stdint.h>
#include <stdarg.h>
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdbool.h>
#include <limits.h>

#ifndef REGTEST

/* Using an integer's bits as flags for both the conversion flags and length
   modifiers.
*/
/* FIXME: one too many flags to work on a 16-bit machine, join some (e.g. the
          width flags) into a combined field.
*/
#define E_minus    (1<<0)
#define E_plus     (1<<1)
#define E_alt      (1<<2)
#define E_space    (1<<3)
#define E_zero     (1<<4)
#define E_done     (1<<5)
#define E_char     (1<<6)
#define E_short    (1<<7)
#define E_long     (1<<8)
#define E_llong    (1<<9)
#define E_intmax   (1<<10)
#define E_size     (1<<11)
#define E_ptrdiff  (1<<12)
#define E_intptr   (1<<13)
#define E_ldouble  (1<<14)
#define E_lower    (1<<15)
#define E_unsigned (1<<16)

/* This macro delivers a given character to either a memory buffer or a stream,
   depending on the contents of 'status' (struct _PDCLIB_status_t).
   x - the character to be delivered
   i - pointer to number of characters already delivered in this call
   n - pointer to maximum number of characters to be delivered in this call
   s - the buffer into which the character shall be delivered
*/
#define PUT( x ) \
do { \
    int character = x; \
    if ( status->i < status->n ) { \
        if ( status->stream != NULL ) \
            putc( character, status->stream ); \
        else \
            status->s[status->i] = character; \
    } \
    ++(status->i); \
} while ( 0 )

/* Maximum number of output characters = 
 *   number of bits in (u)intmax_t / number of bits per character in smallest 
 *   base. Smallest base is octal, 3 bits/char.
 *
 * Additionally require 2 extra characters for prefixes
 */
static const size_t maxIntLen = sizeof(intmax_t) * CHAR_BIT / 3 + 1;

static void int2base( uintmax_t value, struct _PDCLIB_status_t * status )
{
    char sign = 0;
    if ( ! ( status->flags & E_unsigned ) ) 
    {
        intmax_t signval = (intmax_t) value;
        bool negative = signval < 0;
        value = signval < 0 ? -signval : signval;

        if ( negative ) 
        {
            sign = '-';
        } 
        else if ( status->flags & E_plus ) 
        {
            sign = '+';
        }
        else if (status->flags & E_space )
        {
            sign = ' ';
        }
    }

    // The user could theoretically ask for a silly buffer length here. 
    // Perhaps after a certain size we should malloc? Or do we refuse to protect
    // them from their own stupidity?
    size_t bufLen = (status->width > maxIntLen ? status->width : maxIntLen) + 2;
    char outbuf[bufLen];
    char * outend = outbuf + bufLen;
    unsigned written = 0;

    // Build up our output string - backwards
    {
        const char * digits = (status->flags & E_lower) ? 
                                _PDCLIB_digits : _PDCLIB_Xdigits;
        uintmax_t remaining = value;
        if(status->prec != 0 || remaining != 0) do {
            uintmax_t digit = remaining % status->base;
            remaining /= status->base;

            outend[-++written] = digits[digit];
        } while(remaining != 0);
    }

    // Pad field out to the precision specification
    while( (long) written < status->prec ) outend[-++written] = '0';

    // If a field width specified, and zero padding was requested, then pad to
    // the field width
    unsigned padding = 0;
    if ( ( ! ( status->flags & E_minus ) ) && ( status->flags & E_zero ) )    
    {
        while( written < status->width ) 
        {
            outend[-++written] = '0';
            padding++;
        }
    }

    // Prefixes
    if ( sign != 0 )
    {
        if ( padding == 0 ) written++;
        outend[-written] = sign;
    }
    else if ( status->flags & E_alt )
    {
        switch ( status->base )
        {
            case 8:
                if ( outend[-written] != '0' ) outend[-++written] = '0';
                break;
            case 16:
                // No prefix if zero
                if ( value == 0 ) break;

                written += padding < 2 ? 2 - padding : 0;
                outend[-written    ] = '0';
                outend[-written + 1] = (status->flags & E_lower) ? 'x' : 'X';
                break;
            default:
                break;
        }
    }

    // Space padding to field width
    if ( ! ( status->flags & ( E_minus | E_zero ) ) )
    {
        while( written < status->width ) outend[-++written] = ' ';
    }

    // Write output
    status->current = written;
    while ( written )
        PUT( outend[-written--] );
}

static void printstr( const char * str, struct _PDCLIB_status_t * status )
{
    if ( status->width == 0 || status->flags & E_minus )
    {
        // Simple case or left justification
        while ( str[status->current] && 
            ( status->prec < 0 || (long)status->current < status->prec ) )
        {
            PUT( str[status->current++] );
        }

        while( status->current < status->width ) 
        {
            PUT( ' ' );
            status->current++;
        }
    } else {
        // Right justification
        size_t len = status->prec >= 0 ? strnlen( str, status->prec ) 
                                       :  strlen( str );
        int padding = status->width - len;
        while((long)status->current < padding)
        {
            PUT( ' ' );
            status->current++;
        }

        for( size_t i = 0; i != len; i++ )
        {
            PUT( str[i] );
            status->current++;
        }
    }
}

static void printchar( char chr, struct _PDCLIB_status_t * status )
{
    if( ! ( status->flags & E_minus ) )
    {
        // Right justification
        for( ; status->current + 1 < status->width; status->current++)
        {
            PUT( ' ' );
        }
        PUT( chr );
        status->current++;
    } else {
        // Left justification
        PUT( chr );
        status->current++;

        for( ; status->current < status->width; status->current++)
        {
            PUT( ' ' );
        }
    }
}

const char * _PDCLIB_print( const char * spec, struct _PDCLIB_status_t * status )
{
    const char * orig_spec = spec;
    if ( *(++spec) == '%' )
    {
        /* %% -> print single '%' */
        PUT( *spec );
        return ++spec;
    }
    /* Initializing status structure */
    status->flags = 0;
    status->base  = 0;
    status->current  = 0;
    status->width = 0;
    status->prec  = EOF;

    /* First come 0..n flags */
    do
    {
        switch ( *spec )
        {
            case '-':
                /* left-aligned output */
                status->flags |= E_minus;
                ++spec;
                break;
            case '+':
                /* positive numbers prefixed with '+' */
                status->flags |= E_plus;
                ++spec;
                break;
            case '#':
                /* alternative format (leading 0x for hex, 0 for octal) */
                status->flags |= E_alt;
                ++spec;
                break;
            case ' ':
                /* positive numbers prefixed with ' ' */
                status->flags |= E_space;
                ++spec;
                break;
            case '0':
                /* right-aligned padding done with '0' instead of ' ' */
                status->flags |= E_zero;
                ++spec;
                break;
            default:
                /* not a flag, exit flag parsing */
                status->flags |= E_done;
                break;
        }
    } while ( ! ( status->flags & E_done ) );

    /* Optional field width */
    if ( *spec == '*' )
    {
        /* Retrieve width value from argument stack */
        int width = va_arg( status->arg, int );
        if ( width < 0 )
        {
            status->flags |= E_minus;
            status->width = abs( width );
        }
        else
        {
            status->width = width;
        }
        ++spec;
    }
    else
    {
        /* If a width is given, strtol() will return its value. If not given,
           strtol() will return zero. In both cases, endptr will point to the
           rest of the conversion specifier - just what we need.
        */
        status->width = (int)strtol( spec, (char**)&spec, 10 );
    }

    /* Optional precision */
    if ( *spec == '.' )
    {
        ++spec;
        if ( *spec == '*' )
        {
            /* Retrieve precision value from argument stack. A negative value
               is as if no precision is given - as precision is initalized to
               EOF (negative), there is no need for testing for negative here.
            */
            status->prec = va_arg( status->arg, int );
            ++spec;
        }
        else
        {
            status->prec = (int)strtol( spec, (char**) &spec, 10 );
        }
        /* Having a precision cancels out any zero flag. */
        status->flags &= ~E_zero;
    }

    /* Optional length modifier
       We step one character ahead in any case, and step back only if we find
       there has been no length modifier (or step ahead another character if it
       has been "hh" or "ll").
    */
    switch ( *(spec++) )
    {
        case 'h':
            if ( *spec == 'h' )
            {
                /* hh -> char */
                status->flags |= E_char;
                ++spec;
            }
            else
            {
                /* h -> short */
                status->flags |= E_short;
            }
            break;
        case 'l':
            if ( *spec == 'l' )
            {
                /* ll -> long long */
                status->flags |= E_llong;
                ++spec;
            }
            else
            {
                /* k -> long */
                status->flags |= E_long;
            }
            break;
        case 'j':
            /* j -> intmax_t, which might or might not be long long */
            status->flags |= E_intmax;
            break;
        case 'z':
            /* z -> size_t, which might or might not be unsigned int */
            status->flags |= E_size;
            break;
        case 't':
            /* t -> ptrdiff_t, which might or might not be long */
            status->flags |= E_ptrdiff;
            break;
        case 'L':
            /* L -> long double */
            status->flags |= E_ldouble;
            break;
        default:
            --spec;
            break;
    }

    /* Conversion specifier */
    switch ( *spec )
    {
        case 'd':
            /* FALLTHROUGH */
        case 'i':
            status->base = 10;
            break;
        case 'o':
            status->base = 8;
            status->flags |= E_unsigned;
            break;
        case 'u':
            status->base = 10;
            status->flags |= E_unsigned;
            break;
        case 'x':
            status->base = 16;
            status->flags |= ( E_lower | E_unsigned );
            break;
        case 'X':
            status->base = 16;
            status->flags |= E_unsigned;
            break;
        case 'f':
        case 'F':
        case 'e':
        case 'E':
        case 'g':
        case 'G':
            break;
        case 'a':
        case 'A':
            break;
        case 'c':
            /* TODO: wide chars. */
            printchar( va_arg( status->arg, int ), status );
            return ++spec;
        case 's':
            /* TODO: wide chars. */
            {
                char * s = va_arg( status->arg, char * );
                printstr( s, status );
                return ++spec;
            }
        case 'p':
            /* TODO: E_long -> E_intptr */
            status->base = 16;
            status->flags |= ( E_lower | E_unsigned | E_alt | E_long );
            break;
        case 'n':
           {
               int * val = va_arg( status->arg, int * );
               *val = status->i;
               return ++spec;
           }
        default:
            /* No conversion specifier. Bad conversion. */
            return orig_spec;
    }

    /* Do the actual output based on our findings */
    if ( status->base != 0 )
    {
        /* Integer conversions */
        /* TODO: Check for invalid flag combinations. */
        if ( status->flags & E_unsigned )
        {
            uintmax_t value;
            switch ( status->flags & ( E_char | E_short | E_long | E_llong | E_size ) )
            {
                case E_char:
                    value = (uintmax_t)(unsigned char)va_arg( status->arg, int );
                    break;
                case E_short:
                    value = (uintmax_t)(unsigned short)va_arg( status->arg, int );
                    break;
                case 0:
                    value = (uintmax_t)va_arg( status->arg, unsigned int );
                    break;
                case E_long:
                    value = (uintmax_t)va_arg( status->arg, unsigned long );
                    break;
                case E_llong:
                    value = (uintmax_t)va_arg( status->arg, unsigned long long );
                    break;
                case E_size:
                    value = (uintmax_t)va_arg( status->arg, size_t );
                    break;
            }
            int2base( value, status );
        }
        else
        {
            switch ( status->flags & ( E_char | E_short | E_long | E_llong | E_intmax ) )
            {
                case E_char:
                    int2base( (intmax_t)(char)va_arg( status->arg, int ), status );
                    break;
                case E_short:
                    int2base( (intmax_t)(short)va_arg( status->arg, int ), status );
                    break;
                case 0:
                    int2base( (intmax_t)va_arg( status->arg, int ), status );
                    break;
                case E_long:
                    int2base( (intmax_t)va_arg( status->arg, long ), status );
                    break;
                case E_llong:
                    int2base( (intmax_t)va_arg( status->arg, long long ), status );
                    break;
                case E_ptrdiff:
                    int2base( (intmax_t)va_arg( status->arg, ptrdiff_t ), status );
                    break;
                case E_intmax:
                    int2base( va_arg( status->arg, intmax_t ), status );
                    break;
            }
        }
        if ( status->flags & E_minus )
        {
            while ( status->current < status->width )
            {
                PUT( ' ' );
                ++(status->current);
            }
        }
        if ( status->i >= status->n && status->n > 0 )
        {
            status->s[status->n - 1] = '\0';
        }
    }
    return ++spec;
}

#endif

#ifdef TEST
#define _PDCLIB_FILEID "_PDCLIB/print.c"
#define _PDCLIB_STRINGIO

#include <_PDCLIB_test.h>

#ifndef REGTEST
static int testprintf( char * buffer, const char * format, ... )
{
    /* Members: base, flags, n, i, current, s, width, prec, stream, arg      */
    struct _PDCLIB_status_t status;
    status.base = 0;
    status.flags = 0;
    status.n = 100;
    status.i = 0;
    status.current = 0;
    status.s = buffer;
    status.width = 0;
    status.prec = 0;
    status.stream = NULL;
    va_start( status.arg, format );
    memset( buffer, '\0', 100 );
    if ( *(_PDCLIB_print( format, &status )) != '\0' )
    {
        printf( "_PDCLIB_print() did not return end-of-specifier on '%s'.\n", format );
        ++TEST_RESULTS;
    }
    va_end( status.arg );
    return status.i;
}
#endif

#define TEST_CONVERSION_ONLY

int main( void )
{
#ifndef REGTEST
    char target[100];
#include "printf_testcases.h"
#endif
    return TEST_RESULTS;
}

#endif
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