kobopatch-webui/wip/wasm-feasibility.md

WASM Feasibility — Confirmed

Test Results

All kobopatch tests pass under both native and WASM targets.

Native (go test ./...)

ok   github.com/pgaskin/kobopatch/kobopatch            0.003s
ok   github.com/pgaskin/kobopatch/patchfile/kobopatch   0.003s
ok   github.com/pgaskin/kobopatch/patchfile/patch32lsb  0.002s
ok   github.com/pgaskin/kobopatch/patchlib              0.796s

WASM (GOOS=js GOARCH=wasm, run via Node.js)

ok   github.com/pgaskin/kobopatch/kobopatch            0.158s
ok   github.com/pgaskin/kobopatch/patchfile/kobopatch   0.162s
ok   github.com/pgaskin/kobopatch/patchfile/patch32lsb  0.133s
ok   github.com/pgaskin/kobopatch/patchlib              9.755s

Notes

• patchlib tests are ~12x slower under WASM (9.7s vs 0.8s) — expected overhead
• All pure Go dependencies compile to WASM without issues
• No CGO, no OS-specific syscalls in the core libraries
• Go WASM executor: $(go env GOROOT)/lib/wasm/go_js_wasm_exec
• Node.js v25.8.1 used for WASM test execution

What Works in WASM

• Binary patching (patchlib)
• ARM Thumb-2 instruction assembly (patchlib/asm)
• ELF symbol table parsing (patchlib/syms)
• YAML patch format parsing (patchfile/kobopatch)
• Binary patch format parsing (patchfile/patch32lsb)
• CSS parsing (patchlib/css)
• Zlib compression/decompression
• tar.gz reading/writing
• ZIP extraction

What Won't Work in WASM (and doesn't need to)

• os.Open / os.Create — replace with in-memory I/O
• os.Chdir — not needed, use in-memory paths
• exec.Command (lrelease for translations) — skip, rare use case
• ioutil.TempDir — not needed with in-memory approach