/*
* Return a block of data from the decompression buffer. Decompress more
* as necessary.
*/
static ssize_t
compress_filter_read(struct archive_read_filter *self, const void **pblock)
{
struct private_data *state;
unsigned char *p, *start, *end;
int ret;
state = (struct private_data *)self->data;
if (state->end_of_stream) {
*pblock = NULL;
return (0);
}
p = start = (unsigned char *)state->out_block;
end = start + state->out_block_size;
while (p < end && !state->end_of_stream) {
if (state->stackp > state->stack) {
*p++ = *--state->stackp;
} else {
ret = next_code(self);
if (ret == -1)
state->end_of_stream = ret;
else if (ret != ARCHIVE_OK)
return (ret);
}
}
*pblock = start;
return (p - start);
}
/*
* Setup the callbacks.
*/
static int
compress_bidder_init(struct archive_read_filter *self)
{
struct private_data *state;
static const size_t out_block_size = 64 * 1024;
void *out_block;
int code;
self->code = ARCHIVE_FILTER_COMPRESS;
self->name = "compress (.Z)";
state = (struct private_data *)calloc(sizeof(*state), 1);
out_block = malloc(out_block_size);
if (state == NULL || out_block == NULL) {
free(out_block);
free(state);
archive_set_error(&self->archive->archive, ENOMEM,
"Can't allocate data for %s decompression",
self->name);
return (ARCHIVE_FATAL);
}
self->data = state;
state->out_block_size = out_block_size;
state->out_block = out_block;
self->read = compress_filter_read;
self->skip = NULL; /* not supported */
self->close = compress_filter_close;
/* XXX MOVE THE FOLLOWING OUT OF INIT() XXX */
(void)getbits(self, 8); /* Skip first signature byte. */
(void)getbits(self, 8); /* Skip second signature byte. */
code = getbits(self, 8);
state->maxcode_bits = code & 0x1f;
state->maxcode = (1 << state->maxcode_bits);
state->use_reset_code = code & 0x80;
/* Initialize decompressor. */
state->free_ent = 256;
state->stackp = state->stack;
if (state->use_reset_code)
state->free_ent++;
state->bits = 9;
state->section_end_code = (1<<state->bits) - 1;
state->oldcode = -1;
for (code = 255; code >= 0; code--) {
state->prefix[code] = 0;
state->suffix[code] = code;
}
next_code(self);
return (ARCHIVE_OK);
}
int main() {
uint64_t first_code = 20151125LL;
int row = 1;
int col = 1;
while (row != 2947 || col != 3029) {
first_code = next_code(first_code);
if (row == 1) {
row = col + 1;
col = 1;
} else {
row--;
col++;
}
}
printf("%d %d %llu\n", row, col, first_code);
}
/*
* Process the next code and fill the stack with the expansion
* of the code. Returns ARCHIVE_FATAL if there is a fatal I/O or
* format error, ARCHIVE_EOF if we hit end of data, ARCHIVE_OK otherwise.
*/
static int
next_code(struct archive_read_filter *self)
{
struct private_data *state = (struct private_data *)self->data;
int code, newcode;
static int debug_buff[1024];
static unsigned debug_index;
code = newcode = getbits(self, state->bits);
if (code < 0)
return (code);
debug_buff[debug_index++] = code;
if (debug_index >= sizeof(debug_buff)/sizeof(debug_buff[0]))
debug_index = 0;
/* If it's a reset code, reset the dictionary. */
if ((code == 256) && state->use_reset_code) {
/*
* The original 'compress' implementation blocked its
* I/O in a manner that resulted in junk bytes being
* inserted after every reset. The next section skips
* this junk. (Yes, the number of *bytes* to skip is
* a function of the current *bit* length.)
*/
int skip_bytes = state->bits -
(state->bytes_in_section % state->bits);
skip_bytes %= state->bits;
state->bits_avail = 0; /* Discard rest of this byte. */
while (skip_bytes-- > 0) {
code = getbits(self, 8);
if (code < 0)
return (code);
}
/* Now, actually do the reset. */
state->bytes_in_section = 0;
state->bits = 9;
state->section_end_code = (1 << state->bits) - 1;
state->free_ent = 257;
state->oldcode = -1;
return (next_code(self));
}
if (code > state->free_ent) {
/* An invalid code is a fatal error. */
archive_set_error(&(self->archive->archive), -1,
"Invalid compressed data");
return (ARCHIVE_FATAL);
}
/* Special case for KwKwK string. */
if (code >= state->free_ent) {
*state->stackp++ = state->finbyte;
code = state->oldcode;
}
/* Generate output characters in reverse order. */
while (code >= 256) {
*state->stackp++ = state->suffix[code];
code = state->prefix[code];
}
*state->stackp++ = state->finbyte = code;
/* Generate the new entry. */
code = state->free_ent;
if (code < state->maxcode && state->oldcode >= 0) {
state->prefix[code] = state->oldcode;
state->suffix[code] = state->finbyte;
++state->free_ent;
}
if (state->free_ent > state->section_end_code) {
state->bits++;
state->bytes_in_section = 0;
if (state->bits == state->maxcode_bits)
state->section_end_code = state->maxcode;
else
state->section_end_code = (1 << state->bits) - 1;
}
/* Remember previous code. */
state->oldcode = newcode;
return (ARCHIVE_OK);
}