Changeset: 0cc344ae7097 for MonetDB URL: https://dev.monetdb.org/hg/MonetDB/rev/0cc344ae7097 Modified Files: gdk/gdk_strimps.c Branch: string_imprints Log Message:
Update comment diffs (45 lines): diff --git a/gdk/gdk_strimps.c b/gdk/gdk_strimps.c --- a/gdk/gdk_strimps.c +++ b/gdk/gdk_strimps.c @@ -16,17 +16,33 @@ * - a 64 bit mask for each item in the BAT that encodes the presence or * absence of each element of the header in the specific item. * - * A string imprint is stored in a new Heap in the BAT. + * A string imprint is stored in a new Heap in the BAT, aligned in 8 + * byte (64 bit) words. * - * In the current (byte pair) implementation the first 136 bytes - * (i.e. the first 17 64 bit quantities) in the Heap are as follows: + * The first 64 bit word describes how the header of the strimp is + * encoded. The most significant byte (v in the schematic below) is the + * version number. The second (np) is the number of pairs in the + * header. The third (b/p) is the number of bytes per pair if each pair + * is encoded using a constant number of bytes or 0 if it is utf-8. The + * next 2 bytes (hs) is the size of the header in bytes. The last 3 + * bytes needed to align to the 8 byte boundary should be zero, and are + * reserved for future use. + * + * In the current implementation we use 64 byte pairs for the header, so * - * | Version Number | ----- - * | byte pair 01 | byte pair 02 | byte pair 03 | byte pair 04 | | - * | byte pair 05 | byte pair 06 | byte pair 07 | byte pair 08 | | 17 64 bit quantities - * [...] | - * | byte pair 61 | byte pair 62 | byte pair 63 | byte pair 64 | ----- + * np == 64 + * b/p == 2 + * hs == 128 + * + * The actual header follows. If it ends before an 8 byte boundary it + * is padded with zeros. * + * | v | np | b/p | hs | reserved | 8bytes + * | | --- + * Strimp Header | + * | | hs bytes + padding + * | | | + * | | --- * The bitmasks for each string in the BAT follow after this. * * Strimp creation goes as follows: _______________________________________________ checkin-list mailing list checkin-list@monetdb.org https://www.monetdb.org/mailman/listinfo/checkin-list
