add possibly working compression algorithm

[rsbs2] / rsb-lz.c

diff --git a/rsb-lz.c b/rsb-lz.c
index c23dd5a02af56450920eb4f43f2e1e1c07155c8b..2e50252d2f1786266a114ac3bdd197a7147ff91e 100644 (file)
--- a/rsb-lz.c
+++ b/rsb-lz.c
@@ -101,40 +101,146 @@ void write_byte(unsigned char byte, struct data_out_s *data_out)
 void lz_expand(struct data_in_s *data_in, struct data_out_s *data_out)
 {
        unsigned int pos;
-       unsigned int offset;
+       unsigned int wordoffset;
        unsigned int i;
        unsigned char byte;
-       unsigned int num;
+       unsigned int wordlen;
        unsigned char buf[1024];
 
        pos = 1;
 
        while (1) {
                while (1) {
+                       /* Compressed/uncompressed? */
                        if (get_next_bit(data_in) == 0)
                                break;
 
+                       /* Uncompressed byte */
                        byte = get_next_bits(data_in, 8);
 
                        write_byte(byte, data_out);
+
+                       /* Save byte in buffer, to be reused later */
                        buf[pos] = byte;
                        pos = (pos + 1) & 0x3ff;
                }
 
-               offset = get_next_bits(data_in, 0x0a);
-               if(offset == 0)
+               /* offset for start of dictionary word */
+               wordoffset = get_next_bits(data_in, 0x0a);
+               if(wordoffset == 0)
                        return;
 
-               num = get_next_bits(data_in, 0x04) + 1;
-               for (i = 0; i <= num; i++) {
-                       byte = buf[(offset + i) & 0x3ff];
+               /* length of dictionary word used */
+               wordlen = get_next_bits(data_in, 0x04) + 1;
+               for (i = 0; i <= wordlen ; i++) {
+                       /* lookup dictionary byte */
+                       byte = buf[(wordoffset + i) & 0x3ff];
                        write_byte(byte, data_out);
+                       /* Save byte in buffer, to be reused later */
                        buf[pos] = byte;
                        pos = (pos + 1) & 0x3ff;
                }
        }
 }
 
+void set_next_bit(unsigned char *buf, unsigned int set, unsigned int *currbit) {
+       unsigned char *pos;
+       unsigned char bitpos;
+
+       if (set) {
+               pos = buf + ((*currbit) / 8);
+               bitpos = 0x80 >> ((*currbit) % 8);
+               *pos |= bitpos;
+       }
+
+       *currbit = *currbit + 1;
+}
+
+void write_bits(unsigned char *buf, unsigned int data, unsigned int bits, unsigned int *currbit) {
+       int i;
+       unsigned int bitpos;
+
+       bitpos = 1 << (bits - 1);
+
+       for (i = 0; i < bits; i++) {
+               set_next_bit(buf, data & bitpos, currbit);
+               bitpos >>= 1;
+       }
+}
+
+unsigned char *compress_lz(unsigned char *inbuf, int inlen, int *outlen)
+{
+       unsigned char *end = inbuf + inlen;
+       unsigned char *outbuf;
+       unsigned char window[1024];
+       int pos = 0;
+       int fill = 0;
+       unsigned int currbit = 0;
+       int offset;
+       int wordlen;
+       int found;
+       int i;
+
+       if ((outbuf = malloc((inlen * 2) + 4)) == NULL) {
+               perror("malloc");
+       }
+
+       *((unsigned int*)outbuf) = LZ_MAGIC;
+       currbit = 8 * 8;
+
+       while(inbuf < end) {
+               found = 0;
+               for (wordlen = 17; wordlen > 1; wordlen--) {
+                       for (offset = 1; offset < ((fill < 1023) ? fill : 1023); offset++) {
+                               if ((fill < 1023) &&
+                                   (wordlen + offset > fill))
+                                       break;
+
+                               for (i = 0; i < wordlen; i++) {
+                                       if (inbuf[i] != window[(offset + i) & 0x3ff]) {
+                                               break;
+                                       }
+                               }
+                               if (i == wordlen)
+                                       found = 1;
+                       }
+                       if (found)
+                               break;
+               }
+
+               if (found) {
+                       write_bits(outbuf, 0x00, 0x01, &currbit);
+                       write_bits(outbuf, offset, 0x0a, &currbit);
+                       write_bits(outbuf, wordlen - 1, 0x04, &currbit);
+                       for (i = 0; i < wordlen; i++) {
+                               window[pos] = *(inbuf + i);
+                               pos = (pos + 1) & 0x3ff;
+                       }
+                       inbuf += wordlen;
+
+                       if (fill < sizeof(window))
+                               fill += wordlen;
+               } else {
+                       write_bits(outbuf, 0x01, 0x01, &currbit);
+                       write_bits(outbuf, *inbuf, 0x08, &currbit);
+                       window[pos] = *inbuf;
+                       pos = (pos + 1) & 0x3ff;
+                       inbuf++;
+                       if (fill < sizeof(window))
+                               fill++;
+               }
+       }
+
+       write_bits(outbuf, 0x00, 0x01, &currbit);
+       write_bits(outbuf, 0x00, 0x0a, &currbit);
+
+       *outlen = (currbit / 8) + 1;
+
+       *((unsigned int*)(outbuf + 4)) = *outlen;
+
+       return outbuf;
+}
+
 /* Checksum is only used for the compressed firmware in 'firmware' */
 unsigned int crc_check(unsigned char *buf, unsigned int len, unsigned int magic)
 {