SARC

SARCs are archive files.

Structure

The basic structure of SARC files is documented on the MK8 wiki.

Hash algorithm

The algorithm given on the MK8 wiki is not fully correct: it fails to account for the fact that Nintendo's algorithm uses an unsigned 32-bit integer for the hash variable, and a signed char variable.

Here is an accurate implementation of the algorithm, written in C++:

const uint32_t multiplier = 0x65;
const char* string = "月クッパ戦Lv3(クリア後).baglshpp";
uint32_t hash = 0;
int i = 0;
while (true) {
  char c = string[i++]; // *signed* char
  if (!c)
    break;
  hash = hash * multiplier + c;
}

It appears that Nintendo's compiler treats a char as a signed type.

Usage in Breath of the Wild

SARCs are used extensively in Breath of the Wild to keep related data in memory and minimise loading times.

Extensions

Archives have a wide range of extensions. However, the file format is completely the same regardless of the extension.

The following extensions are specific to the game:

• pack
• bactorpack
• bmodelsh
• beventpack
• stera
• stats

The following extensions are used by Nintendo libraries that are included in the game (non exhaustive list):

• sarc
• bgenv
• genvb
• blarc

Data alignment

Some files have specific alignment requirements (e.g. for GPU data). Because Nintendo's SARC library returns file data by giving pointers to the data section directly, special care must be taken to pack files in a way that satisfies all alignment requirements.

Nintendo libraries do not use BotW's resource system and expect files to be properly aligned. This is the case for layout archives (blarc) and agl environment files (Pack/Bootup.pack/Env/env.genvb).

However unlike most other Nintendo games, for files that are managed by the game's resource system, aligning archive file data is usually unnecessary because the system will automatically allocate an aligned buffer and copy the archive data into it.

Tools

Because of the alignment problem and file size limitations due to Breath of the Wild's resource system, only the following tools are recommended:

Extension:DynamicPageList3 (DPL3), version 3.6.1: Error: MediaWiki\Extension\DynamicPageList3\Query::buildAndSelect: The DynamicPageList3 extension (version 3.6.1) produced a SQL statement which led to a Database error.<br/>The reason may be an internal error of DynamicPageList3 or an error that you made; especially when using parameters like 'categoryregexp' or 'titleregexp'. Usage of non-greedy <code>*?</code> matching patterns are not supported.<br/>The error message was:<br/><code></code>

We strongly advise against using other tools because they do not handle file alignment properly.