Function pb_flush_leaf

internal/cbm/sqlite_writer.c:490–542

Flush current leaf page to file

// Flush current leaf page to file
static void pb_flush_leaf(PageBuilder *pb) {
    if (pb->cell_count == 0) {
        return;
    }

    int hdr = pb->page1_offset;
    // Write leaf page header
    pb->page[hdr + 0] = pb->is_index ? BTREE_LEAF_INDEX : BTREE_LEAF_TABLE; // leaf flag
    put_u16(pb->page + hdr + HDR_FREEBLOCK_OFF, 0);                         // first freeblock
    put_u16(pb->page + hdr + HDR_CELLCOUNT_OFF, (uint16_t)pb->cell_count);
    put_u16(pb->page + hdr + HDR_CONTENT_OFF, (uint16_t)pb->content_offset);
    pb->page[hdr + HDR_FRAGBYTES_OFF] = 0; // fragmented free bytes

    // Write page to file. Skip the pending byte page (SQLite reserved).
    pb->next_page = cbm_skip_pending_byte(pb->next_page);
    uint32_t page_num = pb->next_page;
    long offset = (long)(page_num - SKIP_ONE) * CBM_PAGE_SIZE;
    (void)fseek(pb->fp, offset, SEEK_SET);
    (void)fwrite(pb->page, SKIP_ONE, CBM_PAGE_SIZE, pb->fp);

    // Record this leaf for interior page building
    if (pb->leaf_count >= pb->leaf_cap) {
        int old_cap = pb->leaf_cap;
        pb->leaf_cap = old_cap == 0 ? INITIAL_LEAF_CAP : old_cap * GROWTH_FACTOR;
        void *tmp = realloc(pb->leaves, (size_t)pb->leaf_cap * sizeof(PageRef));
        if (!tmp) {
            /* Leave a CONSISTENT empty state: leaf_count stale at >=1 with a
             * NULL leaves array walked pb_finalize_* straight into
             * leaves[0] (null deref, clang-analyzer traced it) whenever the
             * final cell block was already flushed. Empty state routes every
             * finalize path to its existing root=0 failure return. */
            free(pb->leaves);
            pb->leaves = NULL;
            pb->leaf_count = 0;
            pb->leaf_cap = 0;
            return;
        }
        pb->leaves = (PageRef *)tmp;
        /* Zero-init new slots */
        memset(&pb->leaves[old_cap], 0, ((size_t)pb->leaf_cap - (size_t)old_cap) * sizeof(PageRef));
    }
    pb->leaves[pb->leaf_count].page_num = page_num;
    // max_key is set by caller before flush
    pb->leaf_count++;

    // Reset for next page
    pb->next_page++;
    pb->cell_count = 0;
    pb->content_offset = CBM_PAGE_SIZE;
    pb->page1_offset = 0;               // only page 1 has the 100-byte header
    pb->ptr_offset = BTREE_HEADER_SIZE; // standard B-tree header size for non-page-1
    memset(pb->page, 0, CBM_PAGE_SIZE);
}

// Check if a cell of given size fits in the current page
static bool pb_cell_fits(PageBuilder *pb, int cell_len) {