494 lines
14 KiB
C
494 lines
14 KiB
C
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//==========================================================================
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// Name: varicode.h
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// Purpose: Varicode encoded and decode functions
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// Created: Nov 24, 2012
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// Authors: David Rowe
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//
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// To test:
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// $ gcc varicode.c -o varicode -DVARICODE_UNITTEST -Wall
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// $ ./varicode
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//
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// License:
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License version 2.1,
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// as published by the Free Software Foundation. This program is
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// distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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// License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, see <http://www.gnu.org/licenses/>.
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//
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//==========================================================================
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#include <assert.h>
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#include <ctype.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "varicode.h"
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#include "varicode_table.h"
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#include "debug_alloc.h"
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/*
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output is an unpacked array of bits of maximum size max_out. Note
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unpacked arrays are a more suitable form for modulator input.
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Code 1 covers the entire ASCII char set.
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*/
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int varicode_encode1(short varicode_out[], char ascii_in[], int max_out, int n_in) {
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int n_out, index, n_zeros, v_len;
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unsigned short byte1, byte2, packed;
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char c;
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n_out = 0;
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while(n_in && (n_out < max_out)) {
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c = *ascii_in;
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if ((unsigned int)c >= 128) {
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c = ' ';
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}
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index = 2*(unsigned int)(c);
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assert(index <= 254);
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byte1 = varicode_table1[index];
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byte2 = varicode_table1[index+1];
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packed = (byte1 << 8) + byte2;
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//printf("n_in: %d ascii_in: %c index: %d packed 0x%x\n", n_in, *ascii_in, index, packed);
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ascii_in++;
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n_zeros = 0;
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v_len = 0;
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while ((n_zeros < 2) && (n_out < max_out) && (v_len <= VARICODE_MAX_BITS)) {
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if (packed & 0x8000) {
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*varicode_out = 1;
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n_zeros = 0;
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}
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else {
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*varicode_out = 0;
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n_zeros++;
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}
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//printf("packed: 0x%x *varicode_out: %d n_zeros: %d v_len: %d\n", packed, *varicode_out, n_zeros,v_len );
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packed <<= 1;
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varicode_out++;
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n_out++;
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v_len++;
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}
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assert(v_len <= VARICODE_MAX_BITS);
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n_in--;
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}
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return n_out;
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}
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/*
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Code 2 covers a subset, but is more efficient that Code 1 (282
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compared to 1315 bits on unittest) Unsupported characters are
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replaced by spaces. We encode/decode two bits at a time.
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*/
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int varicode_encode2(short varicode_out[], char ascii_in[], int max_out, int n_in) {
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int n_out, n_zeros, v_len, i;
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unsigned short packed;
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n_out = 0;
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while(n_in && (n_out < max_out)) {
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packed = varicode_table2[0]; // default to space if char not found
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// see if our character exists
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for(i=0; i<sizeof(varicode_table2); i+=2) {
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if (varicode_table2[i] == *ascii_in)
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packed = (unsigned short)varicode_table2[i+1] << 8;
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}
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//printf("n_in: %d ascii_in: %c index: %d packed 0x%x\n", n_in, *ascii_in, index, packed);
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ascii_in++;
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n_zeros = 0;
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v_len = 0;
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while ((n_zeros < 2) && (n_out < max_out) && (v_len <= VARICODE_MAX_BITS)) {
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if (packed & 0x8000)
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varicode_out[0] = 1;
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else
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varicode_out[0] = 0;
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if (packed & 0x4000)
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varicode_out[1] = 1;
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else
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varicode_out[1] = 0;
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if (packed & 0xc000)
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n_zeros = 0;
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else
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n_zeros += 2;
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//printf("packed: 0x%x *varicode_out: %d n_zeros: %d v_len: %d\n", packed, *varicode_out, n_zeros,v_len );
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packed <<= 2;
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varicode_out +=2;
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n_out += 2;
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v_len += 2;
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}
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assert(v_len <= VARICODE_MAX_BITS);
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n_in--;
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}
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assert((n_out % 2) == 0); /* outputs two bits at a time */
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return n_out;
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}
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int varicode_encode(short varicode_out[], char ascii_in[], int max_out, int n_in, int code_num) {
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assert((code_num ==1) || (code_num ==2));
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if (code_num == 1)
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return varicode_encode1(varicode_out, ascii_in, max_out, n_in);
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else
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return varicode_encode2(varicode_out, ascii_in, max_out, n_in);
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}
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void varicode_decode_init(struct VARICODE_DEC *dec_states, int code_num)
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{
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assert((code_num ==1) || (code_num == 2));
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dec_states->state = 0;
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dec_states->n_zeros = 0;
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dec_states->v_len = 0;
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dec_states->packed = 0;
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dec_states->code_num = code_num;
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dec_states->n_in = 0;
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dec_states->in[0] = dec_states->in[1] = 0;
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}
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void varicode_set_code_num(struct VARICODE_DEC *dec_states, int code_num)
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{
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assert((code_num == 1) || (code_num == 2));
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dec_states->code_num = code_num;
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}
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/* Code 1 decode function, accepts one bit at a time */
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static int decode_one_bit(struct VARICODE_DEC *s, char *single_ascii, short varicode_in, int long_code)
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{
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int found=0, i;
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unsigned short byte1, byte2;
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//printf("decode_one_bit : state: %d varicode_in: %d packed: 0x%x n_zeros: %d\n",
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// s->state, varicode_in, s->packed, s->n_zeros);
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if (s->state == 0) {
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if (!varicode_in)
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return 0;
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else
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s->state = 1;
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}
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if (s->state == 1) {
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if (varicode_in) {
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s->packed |= (0x8000 >> s->v_len);
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s->n_zeros = 0;
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}
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else {
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s->n_zeros++;
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}
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s->v_len++;
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found = 0;
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/* end of character code */
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if (s->n_zeros == 2) {
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if (s->v_len) {
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/* run thru table but note with bit errors we might not actually find a match */
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byte1 = s->packed >> 8;
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//printf("looking for byte1 : 0x%x ... ", byte1);
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byte2 = s->packed & 0xff;
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for(i=0; i<128; i++) {
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if ((byte1 == varicode_table1[2*i]) && (byte2 == varicode_table1[2*i+1])) {
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found = 1;
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*single_ascii = i;
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}
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}
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}
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varicode_decode_init(s, s->code_num);
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}
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/* code can run too long if we have a bit error */
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if (s->v_len > VARICODE_MAX_BITS)
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varicode_decode_init(s, s->code_num);
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}
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return found;
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}
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/* Code 2 decode function, accepts two bits at a time */
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static int decode_two_bits(struct VARICODE_DEC *s, char *single_ascii, short varicode_in1, short varicode_in2)
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{
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int found=0, i;
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unsigned short byte1;
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if (s->state == 0) {
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if (!(varicode_in1 || varicode_in2))
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return 0;
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else
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s->state = 1;
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}
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if (s->state == 1) {
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if (varicode_in1)
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s->packed |= (0x8000 >> s->v_len);
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if (varicode_in2)
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s->packed |= (0x4000 >> s->v_len);
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if (varicode_in1 || varicode_in2)
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s->n_zeros = 0;
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else
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s->n_zeros+=2;
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s->v_len+=2;
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found = 0;
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/* end of character code */
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if (s->n_zeros == 2) {
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if (s->v_len) {
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/* run thru table but note with bit errors we might not actually find a match */
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byte1 = s->packed >> 8;
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//printf("looking for byte1 : 0x%x ... ", byte1);
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for(i=0; i<sizeof(varicode_table2); i+=2) {
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//printf("byte1: 0x%x 0x%x\n", byte1, (unsigned char)varicode_table2[i+1]);
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if (byte1 == (unsigned char)varicode_table2[i+1]) {
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found = 1;
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*single_ascii = varicode_table2[i];
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//printf("found: %d i=%d char=%c ", found, i, *single_ascii);
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}
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}
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}
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varicode_decode_init(s, s->code_num);
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}
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/* code can run too long if we have a bit error */
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if (s->v_len > VARICODE_MAX_BITS)
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varicode_decode_init(s, s->code_num);
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}
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return found;
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}
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int varicode_decode1(struct VARICODE_DEC *dec_states, char ascii_out[], short varicode_in[], int max_out, int n_in) {
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int output, n_out;
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char single_ascii = 0;
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n_out = 0;
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//printf("varicode_decode: n_in: %d\n", n_in);
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while(n_in && (n_out < max_out)) {
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output = decode_one_bit(dec_states, &single_ascii, varicode_in[0], 0);
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varicode_in++;
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n_in--;
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if (output) {
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*ascii_out++ = single_ascii;
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n_out++;
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}
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}
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return n_out;
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}
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int varicode_decode2(struct VARICODE_DEC *dec_states, char ascii_out[], short varicode_in[], int max_out, int n_in) {
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int output, n_out;
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char single_ascii = 0;
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n_out = 0;
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//printf("varicode_decode2: n_in: %d varicode_in[0] %d dec_states->n_in: %d\n", n_in, varicode_in[0], dec_states->n_in);
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//printf("%d ", varicode_in[0]);
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while(n_in && (n_out < max_out)) {
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// keep two bit buffer so we can process two at a time
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dec_states->in[0] = dec_states->in[1];
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dec_states->in[1] = varicode_in[0];
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dec_states->n_in++;
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varicode_in++;
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n_in--;
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if (dec_states->n_in == 2) {
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output = decode_two_bits(dec_states, &single_ascii, dec_states->in[0], dec_states->in[1]);
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dec_states->n_in = 0;
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if (output) {
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//printf(" output: %d single_ascii: 0x%x %c\n", output, (int)single_ascii, single_ascii);
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*ascii_out++ = single_ascii;
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n_out++;
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}
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}
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}
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return n_out;
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}
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int varicode_decode(struct VARICODE_DEC *dec_states, char ascii_out[], short varicode_in[], int max_out, int n_in) {
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if (dec_states->code_num == 1)
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return varicode_decode1(dec_states, ascii_out, varicode_in, max_out, n_in);
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else
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return varicode_decode2(dec_states, ascii_out, varicode_in, max_out, n_in);
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}
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#ifdef VARICODE_UNITTEST
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void test_varicode(int code_num) {
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char *ascii_in;
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short *varicode;
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int i, n_varicode_bits_out, n_ascii_chars_out, length, half, n_out, j, len;
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char *ascii_out;
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struct VARICODE_DEC dec_states;
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if (code_num == 1) {
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printf("long code:\n");
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length = sizeof(varicode_table1)/2;
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}
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else {
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||
|
|
printf("short code:\n");
|
||
|
|
length = sizeof(varicode_table2)/2;
|
||
|
|
}
|
||
|
|
//length = 10;
|
||
|
|
ascii_in = (char*)MALLOC(length);
|
||
|
|
varicode = (short*)MALLOC(VARICODE_MAX_BITS*sizeof(short)*length);
|
||
|
|
ascii_out = (char*)MALLOC(length);
|
||
|
|
|
||
|
|
// 1. test all Varicode codes -------------------------------------------------------------
|
||
|
|
|
||
|
|
if (code_num == 1) {
|
||
|
|
for(i=0; i<length; i++)
|
||
|
|
ascii_in[i] = (char)i;
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
for(i=0; i<length; i++)
|
||
|
|
ascii_in[i] = varicode_table2[2*i];
|
||
|
|
}
|
||
|
|
//printf(" ascii_in: %s\n", ascii_in);
|
||
|
|
n_varicode_bits_out = varicode_encode(varicode, ascii_in, VARICODE_MAX_BITS*length, length, code_num);
|
||
|
|
|
||
|
|
printf(" n_varicode_bits_out: %d\n", n_varicode_bits_out);
|
||
|
|
//for(i=0; i<n_varicode_bits_out; i++) {
|
||
|
|
// printf("%d \n", varicode[i]);
|
||
|
|
//}
|
||
|
|
|
||
|
|
// split decode in half to test how it preserves state between calls
|
||
|
|
|
||
|
|
varicode_decode_init(&dec_states, code_num);
|
||
|
|
half = n_varicode_bits_out/2;
|
||
|
|
n_ascii_chars_out = varicode_decode(&dec_states, ascii_out, varicode, length, half);
|
||
|
|
// printf(" n_ascii_chars_out: %d\n", n_ascii_chars_out);
|
||
|
|
|
||
|
|
n_ascii_chars_out += varicode_decode(&dec_states, &ascii_out[n_ascii_chars_out],
|
||
|
|
&varicode[half], length-n_ascii_chars_out, n_varicode_bits_out - half);
|
||
|
|
assert(n_ascii_chars_out == length);
|
||
|
|
|
||
|
|
printf(" n_ascii_chars_out: %d\n", n_ascii_chars_out);
|
||
|
|
printf(" average bits/character: %3.2f\n", (float)n_varicode_bits_out/n_ascii_chars_out);
|
||
|
|
|
||
|
|
//printf("ascii_out: %s\n", ascii_out);
|
||
|
|
|
||
|
|
if (memcmp(ascii_in, ascii_out, length) == 0)
|
||
|
|
printf(" Test 1 Pass\n");
|
||
|
|
else
|
||
|
|
printf(" Test 1 Fail\n");
|
||
|
|
|
||
|
|
// 2. Test some ascii with a run of zeros -----------------------------------------------------
|
||
|
|
|
||
|
|
sprintf(ascii_in, "CQ CQ CQ this is VK5DGR");
|
||
|
|
|
||
|
|
assert(strlen(ascii_in) < length);
|
||
|
|
if (code_num == 2)
|
||
|
|
for(i=0; i<strlen(ascii_in); i++)
|
||
|
|
ascii_in[i] = tolower(ascii_in[i]);
|
||
|
|
|
||
|
|
for(i=0; i<3; i++) {
|
||
|
|
n_varicode_bits_out = varicode_encode(varicode, ascii_in, VARICODE_MAX_BITS*length, strlen(ascii_in), code_num);
|
||
|
|
n_ascii_chars_out = varicode_decode(&dec_states, ascii_out, varicode, length, n_varicode_bits_out);
|
||
|
|
ascii_out[n_ascii_chars_out] = 0;
|
||
|
|
|
||
|
|
printf(" ascii_out: %s\n", ascii_out);
|
||
|
|
if (strcmp(ascii_in, ascii_out) == 0)
|
||
|
|
printf(" Test 2 Pass\n");
|
||
|
|
else
|
||
|
|
printf(" Test 2 Fail\n");
|
||
|
|
|
||
|
|
memset(varicode, 0, sizeof(short)*20);
|
||
|
|
n_ascii_chars_out = varicode_decode(&dec_states, ascii_out, varicode, length, 20);
|
||
|
|
assert(n_ascii_chars_out == 0);
|
||
|
|
}
|
||
|
|
|
||
|
|
// 3. Test receiving one bit at a time -----------------------------------------------------
|
||
|
|
|
||
|
|
sprintf(ascii_in, "s=vk5dgr qth=adelaide");
|
||
|
|
len = strlen(ascii_in);
|
||
|
|
ascii_in[len] = 13;
|
||
|
|
ascii_in[len+1] = 0;
|
||
|
|
|
||
|
|
assert(strlen(ascii_in) < length);
|
||
|
|
if (code_num == 2)
|
||
|
|
for(i=0; i<strlen(ascii_in); i++)
|
||
|
|
ascii_in[i] = tolower(ascii_in[i]);
|
||
|
|
|
||
|
|
for(i=0; i<3; i++) {
|
||
|
|
n_varicode_bits_out = varicode_encode(varicode, ascii_in, VARICODE_MAX_BITS*length, strlen(ascii_in), code_num);
|
||
|
|
printf("n_varicode_bits_out: %d\n", n_varicode_bits_out);
|
||
|
|
|
||
|
|
n_ascii_chars_out = 0;
|
||
|
|
for(j=0; j<n_varicode_bits_out; j++) {
|
||
|
|
n_out = varicode_decode(&dec_states, &ascii_out[n_ascii_chars_out], &varicode[j], 1, 1);
|
||
|
|
if (n_out)
|
||
|
|
n_ascii_chars_out++;
|
||
|
|
}
|
||
|
|
ascii_out[n_ascii_chars_out] = 0;
|
||
|
|
|
||
|
|
printf(" ascii_out: %s\n", ascii_out);
|
||
|
|
if (strcmp(ascii_in, ascii_out) == 0)
|
||
|
|
printf(" Test 3 Pass\n");
|
||
|
|
else
|
||
|
|
printf(" Test 3 Fail\n");
|
||
|
|
}
|
||
|
|
|
||
|
|
FREE(ascii_in);
|
||
|
|
FREE(ascii_out);
|
||
|
|
FREE(varicode);
|
||
|
|
}
|
||
|
|
|
||
|
|
int main(void) {
|
||
|
|
test_varicode(1);
|
||
|
|
test_varicode(2);
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
#endif
|