Hi,
I have an FTS table with compress and uncompress options enabled. I am
using zlib(3) for doing the compression. The compression function
seems to be doing ok as I can see the size of the database coming down
drastically. But I the uncompress function is not working properly.
For example if I do a query like: "select snippet(my_fts_table) from
my_fts_table where my_fts_table match 'my query'" , it should only
output the snippets of the individual matching documents. But instead
it is sending the complete document data to the output. I am not sure
if it is the fault of my uncompress function or a bug in sqlite so
showing my compress/uncompress code here. Hope to get some insight.
Thanks
Following are the functions that I have written for compress and uncompress:
/* the compress function */
void
zip(sqlite3_context *pctx, int nval, sqlite3_value **apval)
{
const Bytef *source = sqlite3_value_text(apval[0]);
uLong sourcelen = strlen((const char *)source);
uLong destlen = (sourcelen + 12) + (int)(sourcelen + 12) * .01/100;
Bytef *dest = (Bytef *) malloc(sizeof(Bytef) * destlen);
int ret_val = compress(dest, &destlen, source, sourcelen);
if (ret_val != Z_OK) {
sqlite3_result_error(pctx, "Error in compression", -1);
}
sqlite3_result_text(pctx, (const char *)dest, -1, NULL);
return;
}
/* the uncompress function */
void
unzip(sqlite3_context *pctx, int nval, sqlite3_value **apval)
{
int ret;
unsigned int have;
z_stream strm;
size_t bufsize;
unsigned char *in;
unsigned char out[CHUNK];
unsigned char *dest = NULL;
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
strm.next_in = NULL;
strm.avail_in = 0;
ret = inflateInit(&strm);
if (ret != Z_OK) {
fprintf(stderr, "Could not initiate decompression of
database\n");
sqlite3_result_error(pctx, "Error in decompression", -1);
return;
}
in = (unsigned char *) sqlite3_value_text(apval[0]);
bufsize = strlen((const char *) in);
strm.next_in = in;
strm.avail_in = bufsize;
/* run inflate() on input until output buffer is not full */
do {
strm.avail_out = CHUNK;
strm.next_out = out;
ret = inflate(&strm, Z_NO_FLUSH);
have = CHUNK - strm.avail_out;
if (concat((char **) &dest, (const char *) strm.next_out) < 0) {
fprintf(stderr, "Error in concatnating decompressed
stream\n");
sqlite3_result_error(pctx, "Error in decompression",
-1);
return;
}
} while (strm.avail_out == 0);
inflateEnd(&strm);
sqlite3_result_text(pctx, (const char *)dest, -1, NULL);
return;
}
// concat is a utility function that concatenates its 2nd parameter at
the end of its Ist parameter.It returns a negative value on error.
--
Abhinav
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