src/generic/checksum.c

/* ----------------------------------------------------------------------------
 * checksum.c --- Checksum generator functions
 * nca-073-9
 *
 * Copyright (c) 1996-2000 by Netcetera AG.
 * Copyright (c) 2001 by Apache Software Foundation.
 * All rights reserved.
 *
 * See the file "license.terms" for information on usage and
 * redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * @(#) $Id$
 * ------------------------------------------------------------------------- */
#include <tcl.h>
#include "checksum.h"

unsigned short crc_lut[256] = {
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
    0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
    0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
    0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
    0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
    0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
    0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
    0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
    0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
    0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
    0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
    0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
    0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
    0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
    0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
    0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
    0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
    0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
    0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
    0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
    0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
    0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
    0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
    0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
    0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
};

/* ----------------------------------------------------------------------------
 * crcCalc -- from Tcl_Obj, calculate CRC
 * ------------------------------------------------------------------------- */
unsigned short crcCalc(Tcl_Obj * in)
{

    unsigned char *bytes = NULL;
    int bytesLen = -1;
    unsigned short word = 0;
    int i = 0;
    volatile unsigned char idx = 0;

    if (in == NULL)
	return 0;

    bytes = Tcl_GetByteArrayFromObj(in, &bytesLen);
    word = (1 | (1 << 8));

    for (i = 0; i < bytesLen; i++) {
	idx = (unsigned char) (bytes[i] ^ WEB_HIG_BYTE(word));
	word = (crc_lut[idx]) ^ (WEB_LOW_BYTE(word) << 8);
    }

    return word;
}

/* ----------------------------------------------------------------------------
 * crcAsciify -- generate ASCII rep of 2 bytes
 * ------------------------------------------------------------------------- */
Tcl_Obj *crcAsciify(unsigned short crc)
{

    Tcl_Obj *tmp = NULL;
    char tmpc1 = 0;
    char tmpc2 = 0;
    unsigned char byte = 0;

    tmp = Tcl_NewObj();
    Tcl_IncrRefCount(tmp);

    byte = WEB_HIG_BYTE(crc);

    tmpc1 = (byte / 16) + 'A';
    tmpc2 = (byte % 16) + 'A';

    Tcl_AppendToObj(tmp, &tmpc1, 1);
    Tcl_AppendToObj(tmp, &tmpc2, 1);

    byte = WEB_LOW_BYTE(crc);

    tmpc1 = (byte / 16) + 'A';
    tmpc2 = (byte % 16) + 'A';

    Tcl_AppendToObj(tmp, &tmpc1, 1);
    Tcl_AppendToObj(tmp, &tmpc2, 1);

    return tmp;
}

/* ----------------------------------------------------------------------------
 * crcDeAsciify -- from ASII rep back to 2 bytes
 * ------------------------------------------------------------------------- */
unsigned short crcDeAsciify(Tcl_Obj * in)
{

    unsigned char lowByte = 0;
    unsigned char higByte = 0;
    char *str = NULL;
    int len = 0;
    unsigned short crc = 0;

    if (in == NULL)
	return 0;

    str = Tcl_GetStringFromObj(in, &len);

    if (len != 4)
	return 0;

    higByte = ((str[0] - 'A') << 4) | ((str[1] - 'A'));
    lowByte = ((str[2] - 'A') << 4) | ((str[3] - 'A'));

    crc = (higByte << 8) | lowByte;

    return crc;
}

/* ----------------------------------------------------------------------------
 * crcCheck -- check if crc at end of string is valid for string
 * ------------------------------------------------------------------------- */
Tcl_Obj *crcCheck(Tcl_Obj * in)
{

    Tcl_Obj *crcObj = NULL;
    int len;
    int crc1;
    int crc2;

    if (in == NULL)
	return NULL;

    len = Tcl_GetCharLength(in);

    if (len < 4)
	return NULL;

    crcObj = Tcl_GetRange(in, len - 4, len - 1);
    Tcl_IncrRefCount(crcObj);

    crc1 = crcDeAsciify(crcObj);

    Tcl_DecrRefCount(crcObj);

    crcObj = Tcl_GetRange(in, 0, len - 5);
    Tcl_IncrRefCount(crcObj);

    crc2 = crcCalc(crcObj);

    if (crc2 == crc1) {

	return crcObj;
    }

    Tcl_DecrRefCount(crcObj);

    return NULL;
}

/* ----------------------------------------------------------------------------
 * crcAdd -- append crc to string
 * ------------------------------------------------------------------------- */
int crcAdd(Tcl_Obj * in)
{

    unsigned short crc = 0;
    Tcl_Obj *tmp2 = NULL;

    if (in == NULL)
	return TCL_ERROR;

    crc = crcCalc(in);
    tmp2 = crcAsciify(crc);

    if (tmp2 == NULL)
	return TCL_ERROR;

    Tcl_AppendObjToObj(in, tmp2);

    Tcl_DecrRefCount(tmp2);

    return TCL_OK;
}