File: ean.c

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/*
 * ean.c -- encoding for ean, upc and isbn
 *
 * Copyright (c) 1999 Alessandro Rubini <rubini@gnu.org>
 * Copyright (c) 1999 Prosa Srl. <prosa@prosa.it>
 * Copyright (c) 2001 Boszormenyi Zoltan <zboszor@mail.externet.hu>
 * Copyright (c) 2010, 2011 Giuseppe Scrivano (gscrivano@gnu.org)
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "barcode.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>

/*
 * IMPORTANT NOTE: if you are reading this file to learn how to add a
 * new encoding type, this is the wrong place as there are too many
 * special cases. Please refer to code39.c instead. If you want to
 * learn how UPC, EAN, ISBN work, on the other hand, I did my best to
 * commend things and hope you enjoy it.
 */

/*
 * These following static arrays are used to describe the barcode.
 *
 * The various forms of UPC and EAN are documented as using three
 * different alphabets to encode the ten digits. However, each digit
 * has exactly one encoding; only, it is sometimes mirrored. Moreover,
 * if you represent the width of each symbol (bar/space) instead of
 * the sequence of 1's and 0's, you find that even-parity and odd-parity
 * encoding are exactly the same. So, here are the digits: */
static char *digits[] = {
     "3211","2221","2122","1411","1132",
     "1231","1114","1312","1213","3112"};

/*
 * What EAN encoding does is adding a leading digit (the 13th digit).
 * Such an extra digit is encoded by mirroring three of the six digits that
 * appear in the left half of the UPC code. Here how mirroring works:
 */
static char *ean_mirrortab[] = {
     "------","--1-11","--11-1","--111-","-1--11",
     "-11--1","-111--","-1-1-1","-1-11-","-11-1-"
};

/*
 * UPC-E (the 6-digit one), instead, encodes the check character as
 * a mirroring of the symbols. This is similar, but the encoding for "0" is
 * different (EAN uses no mirroring for "0" to be compatible with UPC).
 * The same rule is used for UPC-5 (the supplemental digits for ISBN)
 */
static char *upc_mirrortab[] = {
     "---111","--1-11","--11-1","--111-","-1--11",
     "-11--1","-111--","-1-1-1","-1-11-","-11-1-"
};

/*
 * UPC-E mirroring for encoding "1"
 */
static char *upc_mirrortab1[] = {
     "111---","11-1--","11--1-","11---1","1-11--",
     "1--11-","1---11","1-1-1-","1-1--1","1--1-1"
};

/* UPC-2 has just two digits to mirror */
static char *upc_mirrortab2[] = {
    "11","1-","-1","--"
};

/*
 * initial, middle, final guard bars (first symbol is a a space).
 * EAN-13 overwrites the first "0" with "9" to make space for the extra digit.
 */
static char *guard[] = {"0a1a","1a1a1","a1a"};

/* initial, final guard bars for UPC-E*/
static char *guardE[] = {"0a1a","1a1a1a"};

/* initial and inter-char guard bars for supplementals (first is space) */
static char *guardS[] = {"9112","11"};

/*
 * These functions are shortcuts I use in the encoding engine
 */
static int ean_make_checksum(char *text, int mode)
{
    int esum = 0, osum = 0, i;
    int even=1; /* last char is even */

    if (strchr(text, ' '))
	i = strchr(text, ' ') - text; /* end of first part */
    else 
	i = strlen(text); /* end of all */

    while (i-- > 0) {
	if (even) esum += text[i]-'0';
	else      osum += text[i]-'0';
	even = !even;
    }
    if (!mode) { /* standard upc/ean checksum */
	i = (3*esum + osum) % 10;
	return (10-i) % 10; /* complement to 10 */
    } else { /* add-5 checksum */
	i = (3*esum + 9*osum);
	return i%10;
    }
}

/*
 * Check that the text can be encoded. Returns 0 or -1.
 * Accept:
 *   13 or 12 digits: EAN-13 w/ or w/o checksum
 * or
 *   8 or 7 digits: EAN-8 w/ or w/o checksum.
 * For both EAN-13 and EAN-8, accept an addon of 2 or 5 digits,
 * separated by ' '
 */
int Barcode_ean_verify(char *text)
{
    int i, len0, len, addon;
    char tmp[24], *spc;

    len = strlen(text);
    spc = strchr(text, ' ');
    if (spc) {
	len0 = spc - text;
	addon = len - len0 - 1;
	if (addon != 2 && addon != 5)
		return -1;
	for (i=len0+1; i<len; i++)
	    if (!isdigit(text[i]))
		return -1;
    } else
	len0 = len;

    for (i=0; i<len0; i++)
        if (!isdigit(text[i]))
            return -1;

    switch (len0) {
    case 8:
	strncpy(tmp, text, 7);
	tmp[7] = '\0';
	if (text[7] != (ean_make_checksum(tmp, 0) + '0'))
		return -1;
    case 7:
    	break;
    case 13:
	strncpy(tmp, text, 12);
	tmp[12] = '\0';
	if (text[12] != (ean_make_checksum(tmp, 0) + '0'))
		return -1;
    case 12:
    	break;
    default:
	return -1;
    }
    return 0;
}

/* Expand the middle part of UPC-E to UPC-A */
static char *upc_e_to_a0(char *text)
{
    static char result[16];
    strcpy(result, "00000000000"); /* 11 0's */

    switch(text[5]) { /* last char */
        case '0': case '1': case '2':
	    strncpy(result+1, text,  2); result[3]=text[5]; /* Manuf. */
	    memcpy(result+8, text+2, 3); /* Product */
	    break;
        case '3':
	    memcpy(result+1, text,   3); /* Manufacturer */
	    memcpy(result+9, text+3, 2); /* Product */
	    break;
        case '4':
	    memcpy(result+1,  text,   4); /* Manufacturer */
	    memcpy(result+10, text+4, 1); /* Product */
	    break;
        default:
	    memcpy(result+1,  text,   5); /* Manufacturer */
	    memcpy(result+10, text+5, 1); /* Product */
	    break;
    }
    return result;
}

/* Try to expand an UPC-E barcode to its UPC-A equivalent.
 * Accept 6, 7 or 8-digit sequence (not counting the addon):
 *  6:  only the middle part, encoding "0", w/o checksum.
 *  7:  the middle part, encoding "0" with a correct checksum
 *    or
 *      the middle part, encoding "0" or "1" prepended
 *  8:  fully qualified UPC-E with checksum.
 *
 * Returns a 11 digit UPC-A (w/o checksum) for valid EPC-E barcode
 * or an empty string for an invalid one.
 *
 * The checksum for UPC-E is calculated using its UPC-A equivalent.
 */
static char *upc_e_to_a(char *text)
{
    static char result[16], *spc;
    int len, chk;

    spc = strchr(text, ' ');
    if (spc)
	len = spc - text;
    else
	len = strlen(text);

    switch (len) {
    case 6:
	strcpy(result, upc_e_to_a0(text));
	return result;
    case 7:
	/* the first char is '0' or '1':
	 * valid number system for UPC-E and no checksum
	 */
	if (text[0] == '0' || text[0] == '1') {
		strcpy(result, upc_e_to_a0(text+1));
		result[0] = text[0];
		return result;
	}

	/* Find out whether the 7th char is correct checksum */
	strcpy(result, upc_e_to_a0(text));
	chk = ean_make_checksum(result, 0);

	if (chk == (text[len-1] - '0'))
		return result;
	/* Invalid 7 digit representation for UPC-E. */
	return NULL;
    case 8:
	if (text[0] == '0' || text[0] == '1') {
		strcpy(result, upc_e_to_a0(text+1));
		result[0] = text[0];
		chk = ean_make_checksum(result, 0);
		if (chk == (text[len-1] - '0'))
			return result;
	}
    default:
	/* Invalid representation for UPC-E. */
	return NULL;
    }
}

/*
 * Accept a 11 or 12 digit UPC-A barcode and
 * shrink it into an 8-digit UPC-E equivalent if possible.
 * Return NULL if impossible, the UPC-E barcode if possible.
 */
static char *upc_a_to_e(char *text)
{
    static char	result[16];
    int		len, chksum;

    len = strlen(text);
    switch (len) {
    case 12:
	strcpy(result, text);
	result[11] = '\0';
	chksum = ean_make_checksum(result, 0);
	if (text[11] != (chksum - '0'))
		return NULL;
	break;
    case 11:
	chksum = ean_make_checksum(text, 0);
	break;
    default:
	return NULL;
    }

    strcpy(result, "00000000"); /* 8 0's*/

    /* UPC-E can only be used with number system 0 or 1 */
    if (text[0] != '0' && text[0] != '1')
    	return NULL;

    result[0] = text[0];

    if ((text[3] == '0' || text[3] == '1' || text[3] == '2')
	    && !strncmp(text+4, "0000", 4)) {
 	memcpy(&result[1], text+1, 2);
 	memcpy(&result[3], text+8, 3);
	result[6] = text[3];
    } else if (!strncmp(text+4, "00000", 5)) {
 	memcpy(&result[1], text+1, 3);
 	memcpy(&result[4], text+9, 2);
	result[6] = '3';
    } else if (!strncmp(text+5, "00000", 5)) {
	memcpy(&result[1], text+1, 4);
	result[5] = text[10];
	result[6] = '4';
    } else if ((text[5] != '0') && !strncmp(text+6, "0000", 4)
	    && text[10] >= '5' && text[10] <= '9') {
 	memcpy(&result[1], text+1, 5);
	result[6] = text[10];
    } else {
	return NULL;
    }
    result[7] = chksum + '0';

    return result;
}

/*
 * UPC-A is the same as EAN, but accept
 *    12 or 11 digits (UPC-A w/ or w/o checksum)
 * or accept UPC-E as:
 *    6 digits (w/o number system and checksum): number system '0' assumed,
 *    7 digits (either w/o number system or checksum),
 *    8 digits (w/ number system and checksum)
 * plus the 2 or 5-digit add-on
 */
int Barcode_upc_verify(char *text)
{
    int i, len0, len, addon;
    char tmp[24], *spc;

    len = strlen(text);
    spc = strchr(text, ' ');
    if (spc) {
	len0 = spc - text;
	addon = len - len0 - 1;
	if (addon != 2 && addon != 5)
		return -1;
	for (i=len0+1; i<len; i++)
	    if (!isdigit(text[i]))
		return -1;
    } else
	len0 = len;

    for (i=0; i<len0; i++)
        if (!isdigit(text[i]))
            return -1;

    switch (len0) {
    case 6: case 7: case 8:
	strncpy(tmp, text, len0);
	tmp[len0] = '\0';
	if (!upc_e_to_a(tmp))
		return -1;
	break;
    case 12:
	strncpy(tmp, text, 11);
	tmp[11] = '\0';
	if (text[11] != (ean_make_checksum(tmp, 0) + '0'))
		return -1;
    case 11:
    	break;
    default:
	return -1;
    }
    return 0;
}

/*
 * Isbn is the same as EAN, just shorter. Dashes are accepted, the
 * check character (if specified) is skipped, the extra 5 digits are
 * accepted after a blank.
 */
int Barcode_isbn_verify(char *text)
{
    int i, ndigit=0;

    for (i=0; text[i]; i++) {
	if (text[i] == '-')
	    continue;
	if (isdigit(text[i])) {
	    ndigit++;
	    if (ndigit == 9) { /* got it all */
		i++; break;
	    }
	    continue;
	}
	return -1; /* found non-digit */
    }
    if (ndigit!=9) return -1; /* too short */

    /* skip an hyphen, if any */
    if (text[i] == '-')
	i++;
    /* accept one more char if any (the checksum) */
    if (isdigit(text[i]) || toupper(text[i])=='X')
	i++;
    if (text[i] == '\0')
	return 0; /* Ok */

    /* and accept the extra price tag (blank + 5 digits), if any */
    if (strlen(text+i) != 6)
	return -1;
    if (text[i] != ' ')
	return -1;
    i++; /* skip the blank */
    while (text[i]) {
	if (!isdigit(text[i]))
	    return -1;
	i++;
    }
    return 0; /* Ok: isbn + 5-digit addon */
}

static int width_of_partial(char *partial)
{
    int i=0;
    while (*partial) {
	if (isdigit(*partial))
	    i += *partial - '0';
	else if (islower(*partial))
	    i += *partial - 'a' + 1;
	partial++;
    }
    return i;
}

/*
 * The encoding functions fills the "partial" and "textinfo" fields.
 * This one deals with both upc (-A and -E) and ean (13 and 8).
 */
int Barcode_ean_encode(struct Barcode_Item *bc)
{
    static char text[24];
    static char partial[256];
    static char textinfo[256];
    char *mirror, *ptr1, *ptr2, *tptr = textinfo; /* where text is written */
    char *spc;

    enum {UPCA, UPCE, EAN13, EAN8, ISBN} encoding = ISBN;
    int i, xpos, checksum, len, len0, addon;

    if (!bc->ascii) {
	bc->error = EINVAL;
	return -1;
    }

    /* Find out whether the barcode has addon and
     * the length of the barcode w/o the addon.
     */
    len = strlen(bc->ascii);
    spc = strchr(bc->ascii, ' ');
    if (spc) {
	len0 = spc - bc->ascii;
	addon = strlen(spc + 1);
	if (addon != 2 && addon != 5) {
	    bc->error = EINVAL; /* impossible, actually */
	    return -1;
	}
    } else {
	len0 = len;
	addon = 0;
    }

    if (!bc->encoding) {
	/* ISBN already wrote what it is; if unknown, find it out */

	/*
	 * Do not decide only by barcode length, it may be ambiguous.
	 * Anyway, either the user specified the barcode type or
	 * we already found a fitting one.
	 */
	switch(bc->flags & BARCODE_ENCODING_MASK) {
	case BARCODE_EAN:
		switch (len0) {
		case 7: case 8:
			bc->encoding = strdup("EAN-8");
			encoding = EAN8;
			break;
		case 12: case 13:
			bc->encoding = strdup("EAN-13");
			encoding = EAN13;
			break;
		default:
			bc->error = -EINVAL;
			return -1;
		}
		break;

	case BARCODE_UPC:
		switch (len0) {
		case 6: case 7: case 8:
			bc->encoding = strdup("UPC-E");
			encoding = UPCE;
			break;
		case 11: case 12:
			bc->encoding = strdup("UPC-A");
			encoding = UPCA;
			break;
		default:
			bc->error = -EINVAL;
			return -1;
		}
		break;
	default:
		/* else, it's wrong (impossible, as the text is checked) */
		bc->error = -EINVAL;
		return -1;
	}
    }

    /* better safe than sorry */
    if (bc->partial)	free(bc->partial);  bc->partial =  NULL;
    if (bc->textinfo)	free(bc->textinfo); bc->textinfo = NULL;

    if (encoding == UPCA) { /* add the leading 0 (not printed) */
	text[0] = '0';
	strcpy(text+1, bc->ascii);
    } else if (encoding == UPCE) {
	strcpy(text, upc_a_to_e(upc_e_to_a(bc->ascii)));
    } else {
	strcpy(text, bc->ascii);
    }

    /*
     * build the checksum and the bars: any encoding is slightly different
     */
    if (encoding == UPCA || encoding == EAN13 || encoding == ISBN) {
	if (!(encoding == UPCA && len0 == 12) &&
		!(encoding == EAN13 && len0 == 13)) {
		checksum = ean_make_checksum(text, 0);
		text[12] = '0' + checksum; /* add it to the text */
		text[13] = '\0';
	}

	strcpy(partial, guard[0]);
	if (encoding == EAN13 || encoding == ISBN) { /* The first digit */
	    sprintf(tptr,"0:12:%c ",text[0]);
	    tptr += strlen(tptr);
	    partial[0] = '9'; /* extra space for the digit */
	} else if (encoding == UPCA)
	    partial[0] = '9'; /* UPC has one digit before the symbol, too */
	xpos = width_of_partial(partial);
	mirror = ean_mirrortab[text[0]-'0'];

	/* left part */
	for (i=1;i<7;i++) {      
	    ptr1 = partial + strlen(partial); /* target */
	    ptr2 =  digits[text[i]-'0'];      /* source */
	    strcpy(ptr1, ptr2);
	    if (mirror[i-1] == '1') {
		/* mirror this */
		ptr1[0] = ptr2[3];
		ptr1[1] = ptr2[2];
		ptr1[2] = ptr2[1];
		ptr1[3] = ptr2[0];
	    }
	    /*
	     * Write the ascii digit. UPC has a special case
	     * for the first digit, which is out of the bars
	     */
	    if (encoding == UPCA && i==1) {
		sprintf(tptr, "0:10:%c ", text[i]);
		tptr += strlen(tptr);
		ptr1[1] += 'a'-'1'; /* bars are long */
		ptr1[3] += 'a'-'1';
	    } else {
		sprintf(tptr, "%i:12:%c ", xpos, text[i]);
		tptr += strlen(tptr);
	    }
	    /* count the width of the symbol */
	    xpos += 7; /* width_of_partial(ptr2) */
	}

	strcat(partial, guard[1]); /* middle */
	xpos += width_of_partial(guard[1]);
    
	/* right part */
	for (i=7;i<13;i++) {  
	    ptr1 = partial + strlen(partial); /* target */
	    ptr2 =  digits[text[i]-'0'];      /* source */
	    strcpy(ptr1, ptr2);
	    /*
	     * Ascii digit. Once again, UPC has a special
	     * case for the last digit
	     */
	    if (encoding == UPCA && i==12) {
		sprintf(tptr, "%i:10:%c ", xpos+13, text[i]);
		tptr += strlen(tptr);
		ptr1[0] += 'a'-'1'; /* bars are long */
		ptr1[2] += 'a'-'1';
	    } else {
		sprintf(tptr, "%i:12:%c ", xpos, text[i]);
		tptr += strlen(tptr);
	    }
	    xpos += 7; /* width_of_partial(ptr2) */
	}
	tptr[-1] = '\0'; /* overwrite last space */
	strcat(partial, guard[2]); /* end */
	xpos += width_of_partial(guard[2]);

    } else if (encoding == UPCE) {
	checksum = text[7] - '0';

	strcpy(partial, guardE[0]);
	partial[0] = '9'; /* UPC-A has one digit before the symbol, too */
	xpos = width_of_partial(partial);

	/* UPC-E has the number system written before the bars. */
	sprintf(tptr, "0:10:%c ", text[0]);
	tptr += strlen(tptr);

	if (text[0] == '0')
		mirror = upc_mirrortab[checksum];
	else
		mirror = upc_mirrortab1[checksum];

	for (i=0;i<6;i++) {      
	    ptr1 = partial + strlen(partial); /* target */
	    ptr2 =  digits[text[i+1]-'0'];      /* source */
	    strcpy(ptr1, ptr2);
	    if (mirror[i] != '1') { /* negated wrt EAN13 */
		/* mirror this */
		ptr1[0] = ptr2[3];
		ptr1[1] = ptr2[2];
		ptr1[2] = ptr2[1];
		ptr1[3] = ptr2[0];
	    }
	    sprintf(tptr, "%i:12:%c ", xpos, text[i+1]);
	    tptr += strlen(tptr);
	    xpos += 7; /* width_of_partial(ptr2) */
	}

	sprintf(tptr, "%i:10:%c ", xpos+10, text[7]);
	tptr += strlen(tptr);
	ptr1[0] += 'a'-'1'; /* bars are long */
	ptr1[2] += 'a'-'1';

	tptr[-1] = '\0'; /* overwrite last space */
	strcat(partial, guardE[1]); /* end */

    } else { /* EAN-8  almost identical to EAN-13 but no mirroring */

	if (len0 != 8) {
	    checksum = ean_make_checksum(text, 0);
	    text[7] = '0' + checksum; /* add it to the text */
	    text[8] = '\0';
	}

	strcpy(partial, guard[0]);
	xpos = width_of_partial(partial);

	/* left part */
	for (i=0;i<4;i++) {      
	    strcpy(partial + strlen(partial), digits[text[i]-'0']);
	    sprintf(tptr, "%i:12:%c ", xpos, text[i]);
	    tptr += strlen(tptr);
	    xpos += 7; /* width_of_partial(digits[text[i]-'0' */
	}
	strcat(partial, guard[1]); /* middle */
	xpos += width_of_partial(guard[1]);
    
	/* right part */
	for (i=4;i<8;i++) {      
	    strcpy(partial + strlen(partial), digits[text[i]-'0']);
	    sprintf(tptr, "%i:12:%c ", xpos, text[i]);
	    tptr += strlen(tptr);
	    xpos += 7; /* width_of_partial(digits[text[i]-'0' */
	}
	tptr[-1] = '\0'; /* overwrite last space */
	strcat(partial, guard[2]); /* end */
    }

    /*
     * And that's it. Now, in case some add-on is specified it
     * must be encoded too. Look for it.
     */
    if ( (ptr1 = spc) ) {
	ptr1++;
	strcpy(text, ptr1);
	if (strlen(ptr1)==5) {
	    checksum = ean_make_checksum(text, 1 /* special way */);
	    mirror = upc_mirrortab[checksum]+1; /* only last 5 digits */
	} else {
	    checksum = atoi(text)%4;
	    mirror = upc_mirrortab2[checksum];
	}
	strcat(textinfo, " +"); strcat(partial, "+");
	tptr = textinfo + strlen(textinfo);
	for (i=0; i<strlen(text); i++) {
	    if (!i) {
		strcat(partial, guardS[0]); /* separation and head */
		xpos += width_of_partial(guardS[0]);
	    } else {
		strcat(partial, guardS[1]);
		xpos += width_of_partial(guardS[1]);
	    }
	    ptr1 = partial + strlen(partial); /* target */
	    ptr2 =  digits[text[i]-'0'];      /* source */
	    strcpy(ptr1, ptr2);
	    if (mirror[i] != '1') { /* negated wrt EAN13 */
		/* mirror this */
		ptr1[0] = ptr2[3];
		ptr1[1] = ptr2[2];
		ptr1[2] = ptr2[1];
		ptr1[3] = ptr2[0];
	    }
	    /* and the text */
	    sprintf(tptr, " %i:12:%c", xpos, text[i]);
	    tptr += strlen(tptr);
	    xpos += 7; /* width_of_partial(ptr2) */
	}
    }

    /* all done, copy results to the data structure */
    bc->partial = strdup(partial);
    if (!bc->partial) {
	bc->error = errno;
	return -1;
    }
    bc->textinfo = strdup(textinfo);
    if (!bc->textinfo) {
	bc->error = errno;
	free(bc->partial);
	bc->partial = NULL;
	return -1;
    }
    if (!bc->width)
	bc->width = width_of_partial(partial);

    return 0; /* success */
}

int Barcode_upc_encode(struct Barcode_Item *bc)
{
    return Barcode_ean_encode(bc); /* UPC is folded into EAN */
}

int Barcode_isbn_encode(struct Barcode_Item *bc)
{
    /* For ISBN we must normalize the string and prefix "978" */
    char *text = malloc(24); /* 13 + ' ' + 5 plus some slack */
    char *otext;
    int i, j, retval;

    if (!text) {
	bc->error = ENOMEM;
	return -1;
    }
    strcpy(text, "978"); j=3;

    otext = bc->ascii;
    for (i=0; otext[i]; i++) {
	if (isdigit(otext[i]))
	    text[j++] = otext[i];
	if (j == 12) /* checksum added later */
	    break;
    }
    text[j]='\0';
    if (strchr(otext, ' '))
	strcat(text, strchr(otext, ' '));
    bc->ascii = text;
    bc->encoding = strdup("ISBN");
    retval = Barcode_ean_encode(bc);
    bc->ascii = otext; /* restore ascii for the ps comments */
    free(text);
    return retval;
}