/* Read the posting list for [zTerm]; AND it with the doclist [in] to
* produce the doclist [out], using the given offset [iOffset] for phrase
* matching.
* (*pSelect) is used to hold an SQLite statement used inside this function;
* the caller should initialize *pSelect to NULL before the first call.
*/
static int query_merge(fulltext_vtab *v, sqlite3_stmt **pSelect,
const char *zTerm,
DocList *pIn, int iOffset, DocList *out){
int rc;
DocListMerge merge;
if( pIn!=NULL && !pIn->nData ){
/* If [pIn] is already empty, there's no point in reading the
* posting list to AND it in; return immediately. */
return SQLITE_OK;
}
rc = term_select_doclist(v, zTerm, -1, pSelect);
if( rc!=SQLITE_ROW && rc!=SQLITE_DONE ) return rc;
mergeInit(&merge, pIn, iOffset, out);
while( rc==SQLITE_ROW ){
DocList block;
docListInit(&block, DL_POSITIONS_OFFSETS,
sqlite3_column_blob(*pSelect, 0),
sqlite3_column_bytes(*pSelect, 0));
mergeBlock(&merge, &block);
docListDestroy(&block);
rc = sqlite3_step(*pSelect);
if( rc!=SQLITE_ROW && rc!=SQLITE_DONE ){
return rc;
}
}
return SQLITE_OK;
}
static void mergeBlock(int mergeIdx, metadata_t *currBlock) {
// base case
if (mergeIdx == 7) {
return;
}
// add the current block to the freelist
if (freelist[mergeIdx] != NULL) { // if there is any other blocks in the freelist[mergeIdx]
freelist[mergeIdx]->prev = currBlock;
currBlock->next = freelist[mergeIdx];
}
freelist[mergeIdx] = currBlock;
// calculate the potential address (metadata address) of the buddy block
metadata_t *buddyBlock = (metadata_t*) ((char*)currBlock + currBlock->size);
if (buddyBlock == NULL) {
return;
}
// see if the buddy is free
if (buddyBlock->in_use) {
return;
}
// see if two blocks are of the same size
if (currBlock->size != buddyBlock->size) {
return;
}
// see if two blocks are paired correctly
int shift = (int)log2(currBlock->size) + 1;
int currBit = ((int)((char*)currBlock-(char*)heap)) >> shift & 1;
int buddyBit = ((int)((char*)buddyBlock-(char*)heap)) >> shift & 1;
if (currBit != buddyBit) {
return;
}
/*~~~~~~~if all criteira are met, merge the two blocks~~~~~~~*/
currBlock->size *= 2;
currBlock->in_use = 0;
currBlock->next = NULL;
currBlock->prev = NULL;
// remove the two blocks from the free list
if (buddyBlock->prev != NULL) {
buddyBlock->prev->next = buddyBlock->next;
if (buddyBlock->next != NULL) {
buddyBlock->next->prev = buddyBlock->prev;
}
buddyBlock->prev = NULL;
buddyBlock->next = NULL;
buddyBlock = NULL;
}
if (currBlock->next != NULL) {
freelist[mergeIdx] = currBlock->next;
} else {
freelist[mergeIdx] = NULL;
}
// recursion occurs here!
mergeBlock(mergeIdx++, currBlock);
}
void my_free(void* ptr)
{
// get the address of the metadata
char *p = (char*) ptr;
// get the address of the current
metadata_t *currBlock = (metadata_t*)(p - sizeof(metadata_t));
// detect double free
if (!currBlock->in_use) {
ERRNO = DOUBLE_FREE_DETECTED;
return;
} else {
currBlock->in_use = 0;
}
// recursively merge blocks if possible
int idx = getIdx(currBlock->size);
mergeBlock(idx, currBlock);
// set the error code
ERRNO = NO_ERROR;
}
