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updates to the format documentation from various folks
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Brian Bruns
59
HACKING
59
HACKING
@@ -78,9 +78,13 @@ Not a lot is known about this page, and it is one of the least documented page
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types. However, it contains things like Jet version, encryption keys, and name
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of the creating program.
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Offset 0x14 contains the Jet version of this database: 0x00 for 3, 0x01 for 4.
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Offset 0x14 contains the Jet version of this database: 0x00 for 3, 0x01 for 4,
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0x02 for 5, 0x03 for Access 2010.
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This is used by the mdb-ver utility to determine the Jet version.
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The 14 bytes starting at 0x42 are the (encrypted) database password.
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The 4 bytes at 0x3e on the Database Definition Page are the database key.
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Data Pages
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----------
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@@ -220,6 +224,13 @@ else
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The length (partial if type 2) for the memo is:
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memo_page_len = offset_stop - offset_start
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Update: The bitmask can't be an entire byte long.
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OLE fields can hold up to 1gig. That requires at least 30 bits, leaving only 2
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bits for flags. Maybe sometimes 0xC0000000 is ignored?
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See http://office.microsoft.com/en-us/access-help/access-2007-specifications-HA010030739.aspx
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Number of characters in a Memo field: 65,535 when entering data through the
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user interface; 2 gigabytes of character storage when entering data
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programmatically. That would mean 31 bits for length.
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LVAL (Long Value) Pages
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-----------------------
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@@ -286,7 +297,7 @@ next_pg field.
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| ???? | 2 bytes | num_var_cols| Number of variable columns in table |
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| ???? | 2 bytes | num_cols | Number of columns in table (repeat) |
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| ???? | 4 bytes | num_idx | Number of indexes in table |
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| ???? | 4 bytes | num_real_idx| Number of indexes in table (repeat) |
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| ???? | 4 bytes | num_real_idx| Number of index entries |
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| ???? | 4 bytes | used_pages | Points to a record containing the |
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| | | | usage bitmask for this table. |
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| ???? | 4 bytes | free_pages | Points to a similar record as above, |
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@@ -307,7 +318,7 @@ next_pg field.
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| ???? | 1 byte | precision | precision if numeric column |
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| ???? | 1 byte | scale | scale if numeric column |
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| ???? | 2 bytes | ??? | |
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| ???? | 1 byte | bitmask | low order bit indicates variable columns |
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| ???? | 1 byte | bitmask | See Column flags bellow |
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| ???? | 2 bytes | offset_F | Offset for fixed length columns |
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| ???? | 2 bytes | col_len | Length of the column (0 if memo) |
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+-------------------------------------------------------------------------+
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@@ -331,7 +342,7 @@ next_pg field.
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+-------------------------------------------------------------------------+
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| ???? | 4 bytes | index_num | Number of the index |
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| | | |(warn: not always in the sequential order)|
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| ???? | 4 bytes | index_num2 | Number of the index (repeat) |
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| ???? | 4 bytes | index_num2 | Index into index cols list |
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| 0x00 | 1 byte | ??? | |
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| 0xFF | 4 bytes | ??? | |
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| 0x00 | 4 bytes | ??? | |
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@@ -343,8 +354,11 @@ next_pg field.
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| ???? | 1 byte | idx_name_len| len of the name of the index |
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| ???? | n bytes | idx_name | Name of the index |
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+-------------------------------------------------------------------------+
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| ???? | n bytes | ??? | |
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| 0xFF | 2 bytes | ??? | End of the tableDef ? |
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| Iterate while col_num != 0xffff |
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+-------------------------------------------------------------------------+
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| ???? | 2 bytes | col_num | Column number with variable length |
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| ???? | 4 bytes | arg1 | |
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| ???? | 4 bytes | arg2 | |
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+-------------------------------------------------------------------------+
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+-------------------------------------------------------------------------+
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@@ -363,7 +377,7 @@ next_pg field.
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| ???? | 2 bytes | num_var_cols| Number of variable columns in table |
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| ???? | 2 bytes | num_cols | Number of columns in table (repeat) |
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| ???? | 4 bytes | num_idx | Number of indexes in table |
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| ???? | 4 bytes | num_real_idx| Number of indexes in table (repeat) |
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| ???? | 4 bytes | num_real_idx| Number of index entries |
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| ???? | 4 bytes | used_pages | Points to a record containing the |
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| | | | usage bitmask for this table. |
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| ???? | 4 bytes | free_pages | Points to a similar record as above, |
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@@ -382,8 +396,8 @@ next_pg field.
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| ???? | 2 bytes | col_num | Column Number (includes deleted columns) |
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| ???? | 2 bytes | offset_V | Offset for variable length columns |
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| ???? | 2 bytes | col_num | Column Number |
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| ???? | 4 bytes | ??? | prec/scale? verify |
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| ???? | 1 byte | bitmask | low order bit indicates variable columns |
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| ???? | 4 bytes | ??? | prec/scale? or LCID (0x409=English)? |
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| ???? | 1 byte | bitmask | See column flags bellow |
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| ???? | 1 byte | ??? | seems to be 1 when variable len |
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| 0000 | 4 bytes | ??? | |
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| ???? | 2 bytes | offset_F | Offset for fixed length columns |
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@@ -413,7 +427,7 @@ next_pg field.
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| ???? | 4 bytes | unknown | matches first unknown definition block |
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| ???? | 4 bytes | index_num | Number of the index |
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| | | |(warn: not always in the sequential order)|
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| ???? | 4 bytes | index_num2 | Number of the index (repeat) |
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| ???? | 4 bytes | index_num2 | Index into index cols list |
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| 0x00 | 1 byte | ??? | |
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| 0xFF | 4 bytes | ??? | |
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| 0x00 | 4 bytes | ??? | |
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@@ -426,9 +440,24 @@ next_pg field.
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| ???? | 2 bytes | idx_name_len| len of the name of the index |
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| ???? | n bytes | idx_name | Name of the index (UCS-2) |
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+-------------------------------------------------------------------------+
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| ???? | n bytes | ??? | |
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| 0xFF | 2 bytes | ??? | End of the tableDef ? |
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| Iterate while col_num != 0xffff |
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+-------------------------------------------------------------------------+
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| ???? | 2 bytes | col_num | Column number with variable length |
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| ???? | 4 bytes | arg1 | |
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| ???? | 4 bytes | arg2 | |
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+-------------------------------------------------------------------------+
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Columns flags (not complete):
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0x01: variable length column
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0x02: can be null
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0x04: is auto long
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0x10: replication related field (or hidden?). These columns start with "s_" or
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"Gen_" (the "Gen_" fields are for memo fields)
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0x40: is auto guid
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0x80: hyperlink. Syntax is "Link Title#http://example.com/somepage.html#" or
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"#PAGE.HTM#"
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In Access 2007 and Access 2010, "Complex Columns" (multivalued fields, version
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history, attachments) always have the flag byte set to exactly 0x07.
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Index flags (not complete):
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0x01 Unique
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@@ -444,11 +473,11 @@ Column Type may be one of the following (not complete):
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MONEY = 0x05 /* Currency (64 bits) */
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FLOAT = 0x06 /* Single (32 bits) */
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DOUBLE = 0x07 /* Double (64 bits) */
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SDATETIME = 0x08 /* Short Date/Time (64 bits) */
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DATETIME = 0x08 /* Date/Time (64 bits) */
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BINARY = 0x09 /* Binary (255 bytes) */
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TEXT = 0x0A /* Text (255 bytes) */
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OLE = 0x0B /* OLE */
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MEMO = 0x0C /* Memo, Hyperlink */
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OLE = 0x0B /* OLE = Long binary */
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MEMO = 0x0C /* Memo = Long text*/
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UNKNOWN_0D = 0x0D
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UNKNOWN_0E = 0x0E
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REPID = 0x0F /* GUID */
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