NSA
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This is a NScripter archive format.
Structure
| Header | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Size | Content | Description | ||||||||||||
| 2Bytes | Number of files | |||||||||||||
| 4Bytes | Index Size | |||||||||||||
| Index | ||||||||||||||
| Size | Content | Description | ||||||||||||
| (Length)+1Byte | File name | Terminated with 0x00 | ||||||||||||
| 1Bytes | Compress Switch | 00=false 01=true 02=wtf | ||||||||||||
| 4Bytes | Offset | |||||||||||||
| 4Bytes | Compressed Size | |||||||||||||
| 4Bytes | Uncompressed Size | |||||||||||||
Note: All numbers are big endian.
Research
| First 5 Index Entries for 'arc.nsa' of みずいろ | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Index Size | Filename | Offset | Filesize1 | Filesize2 | ||||||||||
| 22bytes | b\00.jpg | 0 | 155636 | 155636 | ||||||||||
| 23bytes | b\001.jpg | 155636 | 140467 | 140467 | ||||||||||
| 22bytes | b\01.jpg | 296103 | 169994 | 169994 | ||||||||||
| 22bytes | b\01.jpg | 466097 | 136249 | 136249 | ||||||||||
| 22bytes | b\05.jpg | 602346 | 150570 | 150570 | ||||||||||
Two file sizes suggest the archive supports compression. However in this case, it does not appear to be used due to same size for both filesize values. Compression method is unknown, if actually supported. Due to how the format is structured, the full index must be processed from start to end since each index entry is not a fixed size. Full index size is known, however, so can be done with single read into buffer. Then processed, however it means the full index is always loaded in memory. PC game so that doesn't really matter.
Tools
-n/a-