Hashing Strategy

How rninja computes cache keys.

BLAKE3

rninja uses BLAKE3 for all hashing:

• Fast: ~6 GB/s on modern CPUs
• Secure: Cryptographic strength
• Parallel: Uses all cores

Cache Key Computation

key = BLAKE3(
    rule_name +
    command_line +
    input_contents +
    environment_vars
)

What's Included

Input	Example
Rule	cc, link
Command	gcc -O2 -c ...
Source content	Hash of input files
Headers	Via depfile
Environment	CC, CFLAGS

What's NOT Included

• File paths (only content)
• Timestamps
• Machine-specific info

Why BLAKE3

Algorithm	Speed	Security
MD5	Medium	Broken
SHA-256	Slow	Good
BLAKE3	Fast	Excellent

Determinism

Same inputs always produce same key:

• Reproducible builds
• No false cache hits
• Correct invalidation