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SARC: Difference between revisions
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== Structure == | == Structure == | ||
The basic structure of SARC files is documented on the [[mk8:SARC (File Format)|MK8 wiki]]. | The basic structure of SARC files is documented on the [[mk8:SARC (File Format)|MK8 wiki]]. | ||
=== Hash algorithm === | |||
Nintendo's algorithm uses an unsigned 32-bit integer for the hash variable. Also note that Nintendo iterates over each byte, not each string character. | |||
Here is an accurate implementation of the algorithm, written in C++: | |||
<source lang="c++"> | |||
// key is equal to 0x65 | |||
u32 calcHash32(const sead::SafeString& str, u32 key) | |||
{ | |||
const char* str_ = str.cstr(); | |||
u32 result = 0; | |||
// Each character must be treated as a signed value. | |||
// The cast to s8 (not s32) is necessary to avoid unsigned conversions. | |||
for (s32 i = 0; str_[i] != '\0'; i++) | |||
result = result * key + s8(str_[i]); | |||
return result; | |||
} | |||
</source> | |||
Note that in older versions of sead, characters were not explicitly casted to <code>s8</code> so the end result would depend on the signedness of <code>char</code> (which is implementation-defined). For GHS compiled code on the Wii U, <code>char</code> is unsigned whereas it's signed with Clang (AArch64 target). PC tools most likely use a signed <code>char</code> as that is the default signedness for x86 targets. | |||
In newer versions of sead, an explicit cast to <code>signed char</code>, aka <code>std::int8_t</code>, aka <code>s8</code>, was added to ensure hashes are the same regardless of the target platform. Without the cast, non-ASCII characters (e.g. Japanese UTF-8 bytes) would result in hashes being different across platforms. | |||
== Usage in ''Breath of the Wild'' == | == Usage in ''Breath of the Wild'' == | ||