Function write_table_btree

internal/cbm/sqlite_writer.c:1188–1219

Write leaf pages for a table, returns root page. rowids must be sequential starting from 1 (or single-row PK text).

// Write leaf pages for a table, returns root page.
// rowids must be sequential starting from 1 (or single-row PK text).
static uint32_t write_table_btree(FILE *fp, uint32_t *next_page, const uint8_t **records,
                                  const int *record_lens, const int64_t *rowids, int count,
                                  bool first_is_page1) {
    if (count == 0) {
        // Empty table: write a single empty leaf page
        *next_page = cbm_skip_pending_byte(*next_page);
        uint32_t pnum = (*next_page)++;
        uint8_t page[CBM_PAGE_SIZE];
        memset(page, 0, CBM_PAGE_SIZE);
        int hdr = first_is_page1 ? SQLITE_HEADER_SIZE : 0;
        page[hdr] = BTREE_LEAF_TABLE;                                   // leaf table
        put_u16(page + hdr + HDR_FREEBLOCK_OFF, 0);                     // no freeblocks
        put_u16(page + hdr + HDR_CELLCOUNT_OFF, 0);                     // 0 cells
        put_u16(page + hdr + HDR_CONTENT_OFF, (uint16_t)CBM_PAGE_SIZE); // content at end of page
        page[hdr + HDR_FRAGBYTES_OFF] = 0;                              // 0 fragmented bytes
        (void)fseek(fp, (long)(pnum - SKIP_ONE) * CBM_PAGE_SIZE, SEEK_SET);
        (void)fwrite(page, SKIP_ONE, CBM_PAGE_SIZE, fp);
        return pnum;
    }

    PageBuilder pb;
    pb_init(&pb, fp, *next_page, false);
    pb.page1_offset = first_is_page1 ? SQLITE_HEADER_SIZE : 0;
    pb.ptr_offset = pb.page1_offset + BTREE_HEADER_SIZE;

    for (int i = 0; i < count; i++) {
        pb_add_table_cell_with_flush(&pb, rowids[i], records[i], record_lens[i],
                                     i > 0 ? rowids[i - SKIP_ONE] : 0);
    }

    return pb_finalize_table(&pb, next_page, rowids[count - SKIP_ONE]);
}

// Promote the last cell from current page to separator, un-add it, and flush.
static bool pb_promote_and_flush(PageBuilder *pb, uint8_t **cells, int *cell_lens, int prev_idx) {