/*
 * Generate OS9 CRC value
 *
 * This is a direct replacement for the Microware/Ultra-C
 * library function crc()
 *    by Steve Rance
 *    https://groups.google.com/forum/#!topic/comp.os.os9/jJONahOrBX8
 */

static long crctable[256] = {
0x000000, 0x800063, 0x8000a5, 0x0000c6, 0x800129, 0x00014a, 0x00018c, 0x8001ef,
0x800231, 0x000252, 0x000294, 0x8002f7, 0x000318, 0x80037b, 0x8003bd, 0x0003de,
0x800401, 0x000462, 0x0004a4, 0x8004c7, 0x000528, 0x80054b, 0x80058d, 0x0005ee,
0x000630, 0x800653, 0x800695, 0x0006f6, 0x800719, 0x00077a, 0x0007bc, 0x8007df,
0x800861, 0x000802, 0x0008c4, 0x8008a7, 0x000948, 0x80092b, 0x8009ed, 0x00098e,
0x000a50, 0x800a33, 0x800af5, 0x000a96, 0x800b79, 0x000b1a, 0x000bdc, 0x800bbf,
0x000c60, 0x800c03, 0x800cc5, 0x000ca6, 0x800d49, 0x000d2a, 0x000dec, 0x800d8f,
0x800e51, 0x000e32, 0x000ef4, 0x800e97, 0x000f78, 0x800f1b, 0x800fdd, 0x000fbe,
0x8010a1, 0x0010c2, 0x001004, 0x801067, 0x001188, 0x8011eb, 0x80112d, 0x00114e,
0x001290, 0x8012f3, 0x801235, 0x001256, 0x8013b9, 0x0013da, 0x00131c, 0x80137f,
0x0014a0, 0x8014c3, 0x801405, 0x001466, 0x801589, 0x0015ea, 0x00152c, 0x80154f,
0x801691, 0x0016f2, 0x001634, 0x801657, 0x0017b8, 0x8017db, 0x80171d, 0x00177e,
0x0018c0, 0x8018a3, 0x801865, 0x001806, 0x8019e9, 0x00198a, 0x00194c, 0x80192f,
0x801af1, 0x001a92, 0x001a54, 0x801a37, 0x001bd8, 0x801bbb, 0x801b7d, 0x001b1e,
0x801cc1, 0x001ca2, 0x001c64, 0x801c07, 0x001de8, 0x801d8b, 0x801d4d, 0x001d2e,
0x001ef0, 0x801e93, 0x801e55, 0x001e36, 0x801fd9, 0x001fba, 0x001f7c, 0x801f1f,
0x802121, 0x002142, 0x002184, 0x8021e7, 0x002008, 0x80206b, 0x8020ad, 0x0020ce,
0x002310, 0x802373, 0x8023b5, 0x0023d6, 0x802239, 0x00225a, 0x00229c, 0x8022ff,
0x002520, 0x802543, 0x802585, 0x0025e6, 0x802409, 0x00246a, 0x0024ac, 0x8024cf,
0x802711, 0x002772, 0x0027b4, 0x8027d7, 0x002638, 0x80265b, 0x80269d, 0x0026fe,
0x002940, 0x802923, 0x8029e5, 0x002986, 0x802869, 0x00280a, 0x0028cc, 0x8028af,
0x802b71, 0x002b12, 0x002bd4, 0x802bb7, 0x002a58, 0x802a3b, 0x802afd, 0x002a9e,
0x802d41, 0x002d22, 0x002de4, 0x802d87, 0x002c68, 0x802c0b, 0x802ccd, 0x002cae,
0x002f70, 0x802f13, 0x802fd5, 0x002fb6, 0x802e59, 0x002e3a, 0x002efc, 0x802e9f,
0x003180, 0x8031e3, 0x803125, 0x003146, 0x8030a9, 0x0030ca, 0x00300c, 0x80306f,
0x8033b1, 0x0033d2, 0x003314, 0x803377, 0x003298, 0x8032fb, 0x80323d, 0x00325e,
0x803581, 0x0035e2, 0x003524, 0x803547, 0x0034a8, 0x8034cb, 0x80340d, 0x00346e,
0x0037b0, 0x8037d3, 0x803715, 0x003776, 0x803699, 0x0036fa, 0x00363c, 0x80365f,
0x8039e1, 0x003982, 0x003944, 0x803927, 0x0038c8, 0x8038ab, 0x80386d, 0x00380e,
0x003bd0, 0x803bb3, 0x803b75, 0x003b16, 0x803af9, 0x003a9a, 0x003a5c, 0x803a3f,
0x003de0, 0x803d83, 0x803d45, 0x003d26, 0x803cc9, 0x003caa, 0x003c6c, 0x803c0f,
0x803fd1, 0x003fb2, 0x003f74, 0x803f17, 0x003ef8, 0x803e9b, 0x803e5d, 0x003e3e
};

#define UPDCRC(crc,i) (crctable[((crc) >> 16 ^ (i)) & 0xff] ^ (crc) << 8)

int os9crc(unsigned char c, int crcp)
{
 return UPDCRC(crcp, c);
}