Pharo image is a binary file containing a snapshot of the runtime. However, there is only a little documentation about its structure (how information is encoded as bytes). This page is an early work to document the binary format of Pharo images.
Each image has a format. The format can be retrieved by reading the 4 first bytes of an image file. These bytes encode an integer from least significant to most significant byte (little-endian).
On MacOS, you can use od shell command to show these 4 bytes:
od -t x1 -N 4 Pharo.imageYou will get an output as follow:
0000000 b5 09 01 00
0000004
Which correspond to 68021 in decimal.
| Pharo version | Image format code | Image first 4 bytes (hex) |
|---|---|---|
| version <= 1.3 | 6504 | 68 19 00 00 |
| 1.3 < version <= 5.0-preSpur | 6505 | 69 19 00 00 |
| version (32bits) >= 5.0 | 6521 | 79 19 00 00 |
| version (64bits) >= 5.0 | 68021 | b5 09 01 00 |