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A fix for bug #669739 that became a mdb_crack_row4 rewrite. Thanks to Luciano Miguel Wolf and Alexandre Horst for the bug analysis and the initial patch.

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whydoubt
2004-08-05 03:33:41 +00:00
parent 8cd1797f3c
commit f2125dd3bc
5 changed files with 61 additions and 99 deletions
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10
HACKING
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@@ -147,7 +147,7 @@ The Jet3 row format is:
| ???? | 1 byte | eod | length of data from begining of record |
| ???? | n bytes | var_table[]| offset from start of row for each var_col |
| ???? | 1 byte | var_len | number of variable length columns |
| ???? | n bytes | jump_table | number of variable length columns |
| ???? | n bytes | jump_table | Jump table (see description below) |
| ???? | n bytes | null_mask | Null indicator. size is 1 byte per 8 cols |
| | | | 0 indicates a null value. Also used to |
| | | | represent value of boolean type columns |
@@ -163,9 +163,9 @@ Notes:
. The size of the null table is computed by (num_cols - 1)/8 + 1
. Fixed columns can be null (unlike some other databases).
. The var_len field indicates the size of the var_table[].
. The eod field points at the last byte of the var_cols field. It is used to
determine where the last var_col ends.
. For boolean fixed columns, the values are in null_table[]: 0 indicates a false
. The eod field points at the first byte after the var_cols field. It is used
to determine where the last var_col ends.
. For boolean fixed columns, the values are in null_table[]: 0 indicates a false
value, 1 indicates a true value
. An 0xFF stored in the var_table indicates that this column has been deleted.
@@ -199,6 +199,8 @@ Notes:
. All offsets are stored as 2 byte fields including the var_table entries.
. the jump table was (thankfully) ditched in Jet4.
. If the number of variable columns, as given in the TDEF, is 0, then the
only items in the row are num_cols, fixed_cols, and null_mask.
Each memo column (or other long binary data) in a row