add comments about compression algorithm implementation

[rsbs2] / rsb-lz.c

diff --git a/rsb-lz.c b/rsb-lz.c
index 5f290d8fdad2bc4e71adc8dccdfb007d934398a7..4dddd9b37997d778f316472bad6cb7e736ab0d59 100644 (file)
--- a/rsb-lz.c
+++ b/rsb-lz.c
@@ -15,10 +15,10 @@ void err_exit(const char *fname)
 }
 
 struct data_in_s {
 }
 
 struct data_in_s {

-       unsigned char *start; /* 0 */
-       unsigned char *stop; /* 4 */
-       unsigned char bitpos; /* 8 */
-       unsigned char byte; /* 9 */
+       unsigned char *start;
+       unsigned char *stop;
+       unsigned char bitpos;
+       unsigned char byte;

 };
 
 struct data_out_s {
 };
 
 struct data_out_s {


@@ -39,52 +39,53 @@ unsigned char get_next_in_byte(struct data_in_s *data_in)
        return byte;
 }
 
        return byte;
 }
 

-unsigned char fn_59848(struct data_in_s *data_in)
+unsigned char get_next_bit(struct data_in_s *data_in)

 {
 {

-       unsigned char r5;
+       unsigned char bitval;

 
        if (data_in->bitpos == 0x80) {
                data_in->byte = get_next_in_byte(data_in);
        }
 
 
        if (data_in->bitpos == 0x80) {
                data_in->byte = get_next_in_byte(data_in);
        }
 

-       r5 = data_in->bitpos & data_in->byte;
+       bitval = data_in->bitpos & data_in->byte;

 
        data_in->bitpos >>= 1;
        if (data_in->bitpos == 0) {
                data_in->bitpos = 0x80;
        }
 
 
        data_in->bitpos >>= 1;
        if (data_in->bitpos == 0) {
                data_in->bitpos = 0x80;
        }
 

-       if (r5 == 0)
+       if (bitval == 0)

                return 0;
 
        return 1;
 }
 
                return 0;
 
        return 1;
 }
 

-unsigned int fn_598b4(struct data_in_s *r11_data, unsigned int r10_arg2)
+unsigned int get_next_bits(struct data_in_s *data_in, unsigned int bits)

 {
 {

-       unsigned int r6;
-       unsigned int r7;
+       unsigned int bit;
+       unsigned int next_bits;

 
 

-       r6 = 1 << (r10_arg2 - 1);
+       bit = 1 << (bits - 1);

 
 

-       r7 = 0;
-       while (r6 != 0) {
-               if (r11_data->bitpos == 0x80) {
-                       r11_data->byte = get_next_in_byte(r11_data);
+       next_bits = 0;
+       while (bit != 0) {
+               if (data_in->bitpos == 0x80) {
+                       data_in->byte = get_next_in_byte(data_in);

                }
                }

-               if ((r11_data->bitpos & r11_data->byte) != 0)
-                       r7 = r7 | r6;

 
 

-               r6 = r6 >> 1;
+               if ((data_in->bitpos & data_in->byte) != 0)
+                       next_bits = next_bits | bit;
+
+               bit = bit >> 1;

 
 

-               r11_data->bitpos >>= 1;
+               data_in->bitpos >>= 1;

 
 

-               if(r11_data->bitpos == 0) {
-                       r11_data->bitpos = 0x80;
+               if(data_in->bitpos == 0) {
+                       data_in->bitpos = 0x80;

                }
        }
 
                }
        }
 

-       return r7;
+       return next_bits;

 }
 
 void write_byte(unsigned char byte, struct data_out_s *data_out)
 }
 
 void write_byte(unsigned char byte, struct data_out_s *data_out)


@@ -97,87 +98,82 @@ void write_byte(unsigned char byte, struct data_out_s *data_out)
        data_out->pos++;
 }
 
        data_out->pos++;
 }
 

-void lz_expand(struct data_in_s *r10_data, struct data_out_s *data_out)
+void lz_expand(struct data_in_s *data_in, struct data_out_s *data_out)

 {
 {

-       unsigned int r5;
-       unsigned int r2;
-       unsigned char r4;
-       unsigned int r6;
-       unsigned int r7;
-       unsigned int r11;
-       unsigned char arr_59b64[1024];
+       unsigned int pos;
+       unsigned int wordoffset;
+       unsigned int i;
+       unsigned char byte;
+       unsigned int wordlen;
+       unsigned char buf[1024];

 
 

-       r5 = 1;
+       pos = 1;

 
        while (1) {
                while (1) {
 
        while (1) {
                while (1) {

-                       r2 = fn_59848(r10_data);
-                       if (r2 == 0)
+                       /* Compressed/uncompressed? */
+                       if (get_next_bit(data_in) == 0)

                                break;
 
                                break;
 

-                       r2 = fn_598b4(r10_data, 8) & 0xff;
+                       /* Uncompressed byte */
+                       byte = get_next_bits(data_in, 8);

 
 

-                       write_byte(r2, data_out);
-                       arr_59b64[r5] = r2 & 0xff;
-                       r5 = (r5 + 1) & 0x3ff;
+                       write_byte(byte, data_out);
+
+                       /* Save byte in buffer, to be reused later */
+                       buf[pos] = byte;
+                       pos = (pos + 1) & 0x3ff;

                }
 
                }
 

-               r11 = fn_598b4(r10_data, 0x0a);
-               if(r11 == 0)
+               /* offset for start of dictionary word */
+               wordoffset = get_next_bits(data_in, 0x0a);
+               if(wordoffset == 0)

                        return;
 
                        return;
 

-               r2 = fn_598b4(r10_data, 0x04);
-               r7 = r2 + 1;
-               r6 = 0;
-               while (r6 <= r7) {
-                       r2 = (r6 + r11) & 0x3ff;
-                       r4 = arr_59b64[r2];
-                       write_byte(r4, data_out);
-                       arr_59b64[r5] = r4;
-                       r5 = (r5 + 1) & 0x3ff;
-                       r6++;
+               /* 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;

                }
        }
 }
 
 /* Checksum is only used for the compressed firmware in 'firmware' */
                }
        }
 }
 
 /* Checksum is only used for the compressed firmware in 'firmware' */

-#if 0
-unsigned int crc_check_59684(unsigned char *arg1, unsigned int arg2, unsigned int magic)
+unsigned int crc_check(unsigned char *buf, unsigned int len, unsigned int magic)

 {
 {

-       unsigned int r3;
-       unsigned int r4;
-       unsigned int r5;
-
-#if 0
-       if (r0 < 0xc0000000)
-               return 1;
-#endif
+       unsigned int file_crc;
+       unsigned int my_len;
+       unsigned int crc;
+       unsigned int my_magic;

 
 

-       /* ??? */
-       r4 = *((unsigned int*)arg1 + 0x20);
-       r5 = *((unsigned int*)arg1 + 0x24);
+       my_len = *((unsigned int*)(buf + 0x20));
+       my_magic = *((unsigned int*)(buf + 0x24));

 
 

-       printf("magic: 0x%08x <-> 0x%08x\n", r5, magic);
-       if (r5 != magic)
+       if (my_magic != magic) {
+               printf("\nmagic: 0x%08x <-> 0x%08x\n", my_magic, magic);

                return 2;
                return 2;

+       }

        
        

-       if (arg2 >= r4)
-               r5 = 0;
-       else
+       if (len < my_len)

                return 3;
 
                return 3;
 

-       r5 = ~rsb_crc(~0x00, arg1, r4);
-       r3 = *((unsigned int*)(arg1 + r4));
-       printf("Checksums: 0x%02x <-> 0x%02x\n", r5, r3);
+       crc = ~rsb_crc(~0x00, buf, len);
+       file_crc = *((unsigned int*)(buf + len));

 
 

-       if (r3 == r5)
-               return 0;
+       if (file_crc != crc) {
+               printf("\nChecksums: 0x%08x <-> 0x%08x!\n", crc, file_crc);
+               return 4;
+       }

 
 

-       return 4;
+       return 0;

 }
 }

-#endif

 
 

-void extract_lz_file(unsigned char *inbuf, unsigned char *name)
+void extract_lz_file(unsigned char *inbuf, unsigned char *name, unsigned char check_crc)

 {
        unsigned int len;
        unsigned char *outbuf;
 {
        unsigned int len;
        unsigned char *outbuf;


@@ -207,16 +203,17 @@ void extract_lz_file(unsigned char *inbuf, unsigned char *name)
 
        lz_expand(&data_in, &data_out);
 
 
        lz_expand(&data_in, &data_out);
 

-#if 0
-       /* Checksum is only used for the compressed firmware in 'firmware' */
-       r3 = r7 + 0x20;
-       r5 = *((unsigned int*)r3);
+       if (check_crc) {
+               unsigned int crclen;
+               int ret;

 
 

-       if ((ret = crc_check_59684(r7, r5, 0x46335053)) != 0) {
-               printf("crc_check return: %d\n", ret);
-               err_exit(__func__);
+               crclen = *((unsigned int*)(outbuf + 0x20));
+
+               if ((ret = crc_check(outbuf, crclen, 0x46335053)) != 0) {
+                       printf("crc_check return: %d\n", ret);
+                       err_exit(__func__);
+               }

        }
        }

-#endif

 
        write_file((char*)name, outbuf, len);
        
 
        write_file((char*)name, outbuf, len);