MacBinary is a file format that combines the two forks of a classic Mac OS file into a single file, along with HFS's extended metadata. It was used to share Mac OS files over FTP, Web or e-mail because it could be stored on computers that run operating systems with no HFS support, such as Unix or Windows.
This file describes a summary of MacBinnary I, II and III.
All integers are big-endians.
Data are arranged as follows:
data = <header 128B> + <data fork> + <padding 1> + <res fork> + <padding 2>
| Offset | Length | Contents |
|---|---|---|
| 000 | Byte | Always zero |
| 001 | Byte | Length of filename (in the range 1-31) |
| 002 | 63 Bytes | Filename (remaning bytes are zero) |
| 065 | Word | File type (4 characters) |
| 069 | Word | File creator (4 characters) |
| 073 | Byte | Finder flags: Bit 7 - isAlias. Bit 6 - isInvisible. Bit 5 - hasBundle. Bit 4 - nameLocked. Bit 3 - isStationery. Bit 2 - hasCustomIcon. Bit 1 - reserved. Bit 0 - hasBeenInited. |
| 074 | Byte | Always zero |
| 075 | Half | File's vertical position within its window |
| 077 | Half | File's horizontal position within its window |
| 079 | Half | File's window or folder ID. |
| 081 | Byte | "Protected" flag (in low order bit) |
| 082 | Byte | Always zero |
| 083 | Word | Data Fork length in B (zero if no Data Fork) |
| 087 | Word | Resource Fork length in B (zero if no R.F.) |
| 091 | Word | File's creation date |
| 095 | Word | File's "last modified" date |
| 099 | Half | Length of Get Info comment to be sent after the resource fork (if implemented, see below). |
| 101 ² | Byte | Finder Flags, bits 0-7. (Bits 8-15 are already in byte 73) Bit 7 - hasNoInits Bit 6 - isShared Bit 5 - requiresSwitchLaunch Bit 4 - ColorReserved Bits 1-3 - color Bit 0 - isOnDesk |
| 102 ³ | Word | Signature for indentification purposes (always mBIN) |
| 106 ³ | Byte | Script of file name (from the fdScript field of an fxInfo record) |
| 107 ³ | Byte | Extended Finder flags (from the fdXFlags field of an fxInfo record) |
| 108 | 8 Bytes | Unused (must be zeroed by creators, must be ignored by readers) |
| 116 ² | Word | Length of total files when packed files are unpacked. As of the writing of this document, this field has never been used. |
| 120 ² | Half | Length of a secondary header. If this is non-zero, skip this many bytes (rounded up to the next multiple of 128). This is for future expansion only, when sending files with MacBinary, this word should be zero. |
| 122 ² | Byte | Version number of MacBinary (129 for MacBinary II, 130 for MacBinary III) |
| 123 ² | Byte | Minimum MacBinary version needed to read this file (set this value at 129 for backwards compatibility with MacBinary II) |
| 124 ² | Half | CRC-16 of previous 124 bytes |
| 126 | Half | Padding (always zero) |
² These fields have been added in MacBinary II.
³ These fields have been added in MacBinary III.
Cyclic redundancy check (CRC) used in header is CRC-16-CCITT, i.e. uses
polynomial number 0x1021 and starts with 0.
Data fork directly follows the header (at byte 128). The length of these data (which can be zero) must correspond with the length given in the header (at byte 83).
Data are completed with some padding bytes (usually 0x00 but some
implementations use 0x7F) until the total length of file is a multiple of 128.
If the total length is already a multiple of 128 after adding the data fork, no
padding is added.
The ressource fork follows the same rules (i.e. padding bytes are added after the fork to keep the total length a multiple of 128).
Sources
https://en.wikipedia.org/wiki/MacBinary https://github.com/mietek/theunarchiver/wiki/MacBinarySpecs https://files.stairways.com/other/macbinaryii-standard-info.txt