BUF_ERROR -5 return from uncompress ZLIB - c

Question

I am trying to unzip data in ZLIB using the uncompress function. the data to be decompressed is in a Char vector. the library was downloaded from github for C language. code below:
//C
unsigned char out[20000], u_out[20000];
size_t size_out;
unsigned char* in = ""; //non inserisco i dati di partenza per privacy
int err, i;
long int ucompSize_out;
long int compSize_out;
size_out=sizeof(out);
//codifica in base45
err=base45_decode(out,&size_out,in,strlen(in));
printf("\nbase45(%s) ", (char*)out);
printf("\n%d",err);
//decompressione zlib
ucompSize_out= strlen(out)+1;
compSize_out= compressBound(ucompSize_out);
err=uncompress ((Byte *)u_out, &ucompSize_out, (const Byte *) out, compSize_out );
printf("\nzlib(\"%s\") ", (char*)u_out);
printf("\n%d",err);
when I run this code it returns me BUF_ERROR (-5). I read on the Zlib guide that it is a problem of space for output or input but I can not figure out how to fix it
for completeness load also the functions recalled
int ZEXPORT uncompress2 (dest, destLen, source, sourceLen)
Bytef *dest;
uLongf *destLen;
const Bytef *source;
uLong *sourceLen;
{
z_stream stream;
int ZEXPORT inflateInit2_(strm, windowBits, version, stream_size)
z_streamp strm;
int windowBits;
const char *version;
int stream_size;
{
int ret;
struct inflate_state FAR *state;
if (version == Z_NULL || version[0] != ZLIB_VERSION[0] ||
stream_size != (int)(sizeof(z_stream)))
return Z_VERSION_ERROR;
if (strm == Z_NULL) return Z_STREAM_ERROR;
strm->msg = Z_NULL; /* in case we return an error */
if (strm->zalloc == (alloc_func)0) {
}
if (strm->zfree == (free_func)0)
state = (struct inflate_state FAR *)
ZALLOC(strm, 1, sizeof(struct inflate_state));
if (state == Z_NULL) return Z_MEM_ERROR;
Tracev((stderr, "inflate: allocated\n"));
strm->state = (struct internal_state FAR *)state;
state->strm = strm;
state->window = Z_NULL;
state->mode = HEAD; /* to pass state test in inflateReset2() */
ret = inflateReset2(strm, windowBits);
if (ret != Z_OK) {
ZFREE(strm, state);
strm->state = Z_NULL;
}
return ret;
}
int ZEXPORT inflateInit_(strm, version, stream_size)
z_streamp strm;
const char *version;
int stream_size;
{
return inflateInit2_(strm, DEF_WBITS, version, stream_size);
}
int err;
const uInt max = (uInt)-1;
uLong len, left;
Byte buf[1]; /* for detection of incomplete stream when *destLen == 0 */
len = *sourceLen;
if (*destLen) {
left = *destLen;
*destLen = 0;
}
else {
left = 1;
dest = buf;
}
stream.next_in = (z_const Bytef *)source;
stream.avail_in = 0;
stream.zalloc = (alloc_func)0;
stream.zfree = (free_func)0;
stream.opaque = (voidpf)0;
err = inflateInit2(&stream);
if (err != Z_OK) return err;
stream.next_out = dest;
stream.avail_out = 0;
do {
if (stream.avail_out == 0) {
stream.avail_out = left > (uLong)max ? max : (uInt)left;
left -= stream.avail_out;
}
if (stream.avail_in == 0) {
stream.avail_in = len > (uLong)max ? max : (uInt)len;
len -= stream.avail_in;
}
err = inflate(&stream, Z_NO_FLUSH);
} while (err == Z_OK);
*sourceLen -= len + stream.avail_in;
if (dest != buf)
*destLen = stream.total_out;
else if (stream.total_out && err == Z_BUF_ERROR)
left = 1;
inflateEnd(&stream);
return err == Z_STREAM_END ? Z_OK :
err == Z_NEED_DICT ? Z_DATA_ERROR :
err == Z_BUF_ERROR && left + stream.avail_out ? Z_DATA_ERROR :
err;
}
int ZEXPORT uncompress (dest, destLen, source, sourceLen)
Bytef *dest;
uLongf *destLen;
const Bytef *source;
uLong sourceLen;
{
return uncompress2(dest, destLen, source, &sourceLen);
}