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#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
// typedef unsigned long ulong;
typedef unsigned char uchar;
ulong allcount;
ulong counts[256];
ulong nextcount[256*256];
ulong next[256*256*256];
static inline uchar randomchar(void) {
uchar c = '\0';
ulong r = ((ulong)random())%(256+allcount);
while( r > counts[c] && c < 0xFF ) {
r-= counts[c];
r--;
c++;
}
// if( c == 0xFF )
// fprintf(stderr,"left %ld %ld\n",counts[0xFF],r);
return c;
}
static inline uchar randomchar2(int ofs) {
uchar c = '\0';
ulong r = ((ulong)random())%(256+nextcount[ofs]);
ofs <<= 8;
while( r > next[ofs+c] ) {
c++;
r-= next[ofs+c];
r--;
}
return c;
}
static void generate(int size) {
uchar c[3];
c[0] = randomchar();
putchar(c[0]);
c[1] = randomchar();
putchar(c[1]);
size--; size--;
while( size > 0 ) {
if( (random() & 7) == 0 ) {
c[2] = randomchar();
} else {
c[2] = randomchar2((((int)c[0])<<8)+c[1]);
}
putchar(c[2]);
c[0] = c[1];
c[1] = c[2];
size--;
}
}
int main(int argc, const char *argv[]) {
int i,fd;
int size;
if( argc < 4 ) {
fprintf(stderr,"Syntax: randomgen <size> <randomseed> <sample-files>\n");
return EXIT_FAILURE;
}
allcount = 0;
size = atoi(argv[1]);
srandom(atoi(argv[2]));
fprintf(stderr,"Initializing data relationships...\n");
for( i = 0 ; i < 256 ; i ++ )
counts[i] = 0;
for( i = 0 ; i < 256*256 ; i ++ )
nextcount[i] = 0;
for( i = 0 ; i < 256*256*256 ; i ++ )
next[i] = 0;
for( i = 3 ; i <argc ; i++ ) {
uchar c[3];
ssize_t r;
fprintf(stderr,"Reading '%s'\n",argv[i]);
fd = open(argv[i],O_RDONLY);
if( fd < 0 ) {
fprintf(stderr,"Error opening '%s' for reading: %m\n",argv[i]);
return EXIT_FAILURE;
}
r = read(fd,&c,3);
if( r < 0 ) {
fprintf(stderr,"Error reading from '%s': %m\n",argv[i]);
return EXIT_FAILURE;
}
if( r == 0 ) {
fprintf(stderr,"Warning: ignoring emtpy file :'%s'\n",argv[i]);
} else if( r < 3 ) {
counts[c[0]] += 5000;
allcount+= 5000;
} else {
int o;
counts[c[0]]++;
counts[c[1]]++;
allcount+=2;
do {
allcount++;
if( allcount >= ULONG_MAX-260 ) {
fprintf(stderr,"Too much sample data. Sorry!\n");
return EXIT_FAILURE;
}
counts[c[2]]++;
o = (((int)c[0])<<8)+c[1];
nextcount[o]++;
next[(o<<8)+c[2]]++;
c[0] = c[1];
c[1] = c[2];
} while( (r = read(fd,&c[2],1)) == 1);
if( r < 0 ) {
fprintf(stderr,"Error reading from '%s': %m\n",argv[i]);
return EXIT_FAILURE;
}
}
(void)close(fd);
}
fprintf(stderr,"Generating output...\n");
generate(size);
return EXIT_SUCCESS;
}
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