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--- mbbsemu:development:btrieve_file_format [2020/11/14 21:06] – created tuday
+++ mbbsemu:development:btrieve_file_format [2023/10/06 23:41] (current) – external edit 127.0.0.1
@@ Line 3: / Line 3: @@
 MajorBBS/Worldgroup make use of Actian/Pervasive/Novell Btrieve as a native, persistent database platform.
-In this article we'll be discussing the Btrieve File Format as reverse engineered in the course of developing MBBSEmu.
+In this article we'll be discussing the Btrieve File Format as reverse engineered in the course of developing MBBSEmu. There is also an excellent book titled [Btrieve Complete, by Jim Kyle](https://books.google.com/books/about/Btrieve_Complete.html?id=_Vu8BaXMr4UC) which describes the file format is painstaking detail.
 # Assumptions
 * MajorBBS/Worldgroup used a version of Btrieve <= 6.0
-* MajorBBS/Worldgroup did not make use of Variable Length Records
 * MajorBBS/Worldgroup did not make use of Compressed Fields
@@ Line 53: / Line 52: @@
 ----------|------|------------|
 Duplicates | `1` | Allow duplicate key values
-Modifiable | `1 << 1` | Value can be modified
+Modifiable | `1 << 1` | Key Value can be modified
-Old Style Binary | ` 1 << 2 ` | Unknown
+Old Style Binary | `1 << 2` | Used when `UseExtendedDataType` is not set. If true, binary blob, otherwise string.
-Null0 | `1 << 3` | Unknown
+NullAllSegments | `1 << 3` | Whether the key supports null values. All segmented keys must have this same bit set.
 SegmentedKey | `1 << 4` | If the given key has any Segments
-NumberedACS | ` 1 << 5` | Unknown
+NumberedACS | ` 1 << 5` | Whether the string type uses the ACS table
 DescendingKeySegment | ` 1 << 6` | Key is stored in descending Sort Order
-SupplementalKey | `1 << 7` | Unknown
+RepeatingDuplicatesKey | `1 << 7` | Different representation of duplicate key values
+UseExtendedDataType | `1 << 8` | Whether the key uses the key data types listed below, otherwise type is defined by `Old Style Binary`.
+NullAnySegment | `1 << 9` | Whether the key supports null values. Any segmented key with this value set indicates the entire key could be null.
 ### Key Data Types
@@ Line 94: / Line 95: @@
 Page Type | Definition |
 ----------|------------|
+FCR | Contains metadata about the entire database
+ACS Page | Contains the ACS table used by the database
 Key Page | Contains the absolute offset in the Btrieve file for the specified Key value
-Key Constraint Page | Unused by MBBSEmu
 Data Page | Contains record data
+Variable Record Data Page | Contains variable record data
 While enumerating through the pages, the best method we've been able to employ to identify Page types is the following:
@@ Line 103: / Line 106: @@
 Page Type | How to Identify |
 ----------|------------|
+`FCR` | Always first page
+`ACS Page` | Always second page if exists. Starts with 0x000001000000AC
 `Key Pages` | Value `0xFFFFFFFF` at offset `0x8`
-`Key Constraint Pages` | Value `0xAC` at offset `0x6`
 `Data Pages` | Bit 7 set in the byte at offset `0x5`
+`Variable Record Data Pages` | No identifying information. Referenced via pointers inside the `Data Pages`
 # Understanding How MajorBBS/Worldgroup uses Btrieve
@@ Line 152: / Line 157: @@
 It would return the `Previous` record, which in our query would mean the user with the _second_ highest `userId`
 </markdown>
+n>