SHOW_MEM(L, ulong) /* offset */    allocate(freq, uint, MAX_SYMBOL+1);    allocate(syms, uint, MAX_SYMBOL+1);  // interp coding uses A[n]    SHOW_MEM(MAX_SYMBOL+1, uint)    SHOW_MEM(MAX_SYMBOL+1, uint)    START_OUTPUT(out_file);	OUTPUT_ULONG(out_file, MAGIC,sizeof(ulong)*8);	num_header_bits += sizeof(ulong)*8;      if (very_verbose > 0) BLOCK_SUMMARY_HEADINGS;    if (block_size > 0) {        while ((b = fread(block, sizeof(uint), block_size, in_file)) > 0) {            process_block(block, b, freq, syms, out_file);	        num_blocks++;        }    } else {        while (fread(block,sizeof(uint),1, in_file) == 1)  { /* block ahead */            up = block;            b = 0;            while (*up > 0) {                up++;                b++;	            if (b == current_array_size) {                    current_array_size <<= 1;                    if ((block = (uint *)realloc(block, current_array_size*sizeof(uint))) == NULL) {                        fprintf(stderr,"Out of memory for block\n");                        exit(-1);                    }                    up = block + b;                }                if (fread(up,sizeof(uint),1, in_file) != 1) {                    fprintf(stderr,"WARNING: last block not terminated by 0\n");                    *up = 0;                    b--; /* exclude the 0 I add in 3 lines down */                }	        }            b++; /* include the 0 */            process_block(block, b, freq, syms, out_file);	        num_blocks++;         }     }    OUTPUT_ULONG(out_file, 0, LOG2_MAX_SYMBOL);  // last block indicator n = 0    num_header_bits += LOG2_MAX_SYMBOL;    FINISH_OUTPUT(out_file);    if (verbose) print_summary_stats();} /* one_pass_encoding() *//*** Fill freq[] with freqs*/uintone_pass_freq_count(uint block[], uint b, uint freq[],uint syms[], uint ms) {    uint n, *up;        /* clear all elements up to max_symbol = ms */    for(up = freq ; up <= freq + ms ; up++)                 *up = 0;    n = 0;    for(up = block ; up < block + b ; up++) {        if (freq[*up] == 0)            syms[n++] = *up;        freq[*up]++;    }    freq[EOF_SYMBOL] = 1;    syms[n++]        = EOF_SYMBOL;    return n;}/*** INPUT:        freq[i] is the frequency of symbol i.**               syms[0..n-1] is a list of the symbols in freq[] **               with a non-zero freq** OUTPUT:       None.** SIDE EFFECTS: Outputs some bits.**               syms[i] contains the ordinal symbol # for symbol i.**               freq[i] contains the codeword length for symbol i. **** (1) Sort syms[0..n-1] using freq[syms[i]] as the key for syms[i]** (2) Run in-place Huffman on freqs to overwrite freqs with codeword lens** (3) Build cw_lens[] and then canonical coding arrays** (4) Output n.** (5) Sort syms in increasing order.** (5) Interp code syms and then output unary coded of reversed max_cw-freq[i]** (6) Overwrite syms with mapping.*/int pcmp(char *a, char *b) { return *((uint *)a) - *((uint *)b); }voidbuild_codes(FILE *out_file, uint syms[], uint freq[], uint n) {    uint i, *p;    uint max_codeword_length, min_codeword_length;    uint cw_lens[L+1];//{uint i;//fprintf(stderr,"*********************************************************\n");//fprintf(stderr,"n         : %u\n",n);//fprintf(stderr,"syms: ");//for(i=0;i<n;i++) fprintf(stderr,"%4u ",syms[i]);//fprintf(stderr,"\n");//fprintf(stderr,"freq: ");//for(i=0;i<11;i++) fprintf(stderr,"%4u ",freq[i]);//fprintf(stderr,"\n\n");//}    indirect_sort(freq, syms, syms, n);    calculate_minimum_redundancy(freq, syms, n);//{uint i;//fprintf(stderr,"freq: ");//for(i=0;i<6;i++) fprintf(stderr,"%4u ",freq[i]);//fprintf(stderr,"\n\n");//}        // calculcate max_codeword_length and set cw_lens[]    for(i = 0 ; i <= L ; i++)         cw_lens[i] = 0;    min_codeword_length = max_codeword_length = freq[syms[0]];    for(p = syms ; p < syms + n ; p++) {        if (freq[*p] > max_codeword_length)            max_codeword_length = freq[*p];        cw_lens[freq[*p]]++;    }        #ifdef OUTPUT_PRELUDE_CODELENGTHS    {        int i;        fprintf(stderr,"%d ",max_codeword_length);        for(i = 1 ; i <= max_codeword_length ; i++)            fprintf(stderr,"%d ",cw_lens[i]);        fprintf(stderr,"\n");    }    #endif    build_canonical_arrays(cw_lens, max_codeword_length);//fprintf(stderr,"*********************************************************\n");//fprintf(stderr,"n: %10u\n",n);//fprintf(stderr,"max_cw_len: %5u\n",max_codeword_length);//{uint i;//fprintf(stderr,"cw_lens : \n");//for(i=0;i<=max_codeword_length;i++)//fprintf(stderr,"%u\n",cw_lens[i]);//fprintf(stderr,"\n");//}    OUTPUT_ULONG(out_file, n, LOG2_MAX_SYMBOL);    OUTPUT_ULONG(out_file, max_codeword_length, LOG2_L);    num_header_bits += LOG2_L + LOG2_MAX_SYMBOL;    nqsort((char *)syms, n, sizeof(uint), pcmp);    #ifdef OUTPUT_PRELUDE_SUBALPHABET_GAPS    {        int i;        fprintf(stderr,"%d ",n);        fprintf(stderr,"%d ",syms[0]);        for(i = 1 ; i < n ; i++)            fprintf(stderr,"%d ",syms[i]-syms[i-1]);        fprintf(stderr,"\n");    }    #endif    for(p = syms ; p < syms + n; p++) {        OUTPUT_UNARY_CODE(out_file, max_codeword_length - freq[*p]);        num_unary_bits += max_codeword_length - freq[*p] + 1;    }    interp_encode(out_file, syms, n);    generate_mapping(cw_lens, syms, freq,  max_codeword_length, n);} /* build_codes() *//*** Build lj_base[] and offset from the codelens in A[0..n-1]** A[] need not be sorted.**** Return cw_lens[] a freq count of codeword lengths.*/voidbuild_canonical_arrays(uint cw_lens[], uint max_cw_length){    ulong *q;    uint  *p;        // build offset    q = offset;    *q = 0;    for(p = cw_lens + 1; p < cw_lens + max_cw_length ; p++, q++)        *(q+1) = *q + *p;                // generate the min_code array        // min_code[i] = (min_code[i+1] + cw_lens[i+2]) >>1    q  = min_code + max_cw_length-1;    *q = 0;    for(q--, p = cw_lens + max_cw_length ; q >= min_code ; q--, p--)        *q = (*(q+1) + *p) >> 1;         // generate the lj_base array    q  = lj_base;    unsigned long *pp = min_code;    int left_shift = (sizeof(ulong) << 3) - 1;    for(p = cw_lens + 1; q < lj_base + max_cw_length; p++, q++, pp++, left_shift--)        if (*p == 0)            *q = *(q-1);        else            *q = (*pp) << left_shift;    for( p = cw_lens + 1, q = lj_base ; *p == 0 ; p++, q++)        *q = MAX_ULONG;//{uint i;//for(i = 0 ; i < max_cw_length ; i++)//    fprintf(stderr,"%3d %8lu %8lx %8lx\n",i,offset[i],min_code[i],lj_base[i]);//fprintf(stderr,"\n");//for(i = 1 ; i <= L ; i++)//    fprintf(stderr,"%d ",cw_lens[i]);//fprintf(stderr,"\n");//}} // build_canonical_arrays()/*** INPUT: syms[0..n-1] lists symbol numbers**        freq[i] contains the codeword length of symbol i**        cw_lens[1..max_cw_length] is the number of codewords of length i**** OUTPUT: None**** SIDE EFFECTS: syms[0..max_symbol] is overwritten with canonical code mapping.**               cw_lens[] is destroyed.*/voidgenerate_mapping(uint cw_lens[],     uint syms[], uint freq[],                  uint max_cw_length, uint n) {    int i;    for( i = 1 ; i <= (int)max_cw_length ; i++)        cw_lens[i] += cw_lens[i-1];         for(i = n - 1 ; i >= 0 ; i--)        syms[syms[i]] = cw_lens[freq[syms[i]] - 1]++;//{uint i;//fprintf(stderr,"mapping\n");//for(i = 0 ; i <= n; i++)    //fprintf(stderr,"%8u %8u\n",syms[i],i);//fprintf(stderr,"\n");//}} /* generate_mapping() */