#!/bin/sh
# Rebuild dist/riscvemu64-wasm.{js,wasm} from the TinyEMU source tarball.
#
# The demo does NOT use Bellard's prebuilt emulator, and this is why: his
# 2019 wasm blob does not match the 2019 source release. Compiled natively,
# that source serves our 32 MiB image over HTTP flawlessly; his blob stops
# issuing block fetches at the 16 MiB boundary, so the first read past it --
# `ls -la` stat-ing an inode table in a later block group -- wedges in the
# guest or, depending on timing, segfaults it. His own images are 4 MiB, so
# the public demo never crossed the line. Building from the released source
# gives us the code we actually audited, and it comes out half the size.
#
# The output is committed in dist/, because rebuilding it needs the
# emscripten SDK and nothing else in this demo does. Run this only to change
# or verify the emulator:
#
#   . /path/to/emsdk/emsdk_env.sh && ./build-emulator
#
# patches/0001-modern-emscripten.patch is the whole port: emcc 6.x lost
# Pointer_stringify and Runtime.dynCall, dead-strips JS library functions
# that lack __deps, and no longer coerces JS strings passed as wasm i32
# parameters. The C side is untouched except renaming our XHR helper so it
# cannot collide with emscripten's own library symbol of the same name.
set -eu

here=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
tarball="$here/../vendor/.cache/tinyemu.tar.gz"
work="$here/../build/emulator-src"

command -v emcc >/dev/null 2>&1 || {
	echo "emcc not found -- source emsdk_env.sh first (https://emscripten.org)" >&2
	exit 1
}
[ -f "$tarball" ] || {
	echo "$tarball is missing -- run ../fetch-vendor first" >&2
	exit 1
}

rm -rf "$work"
mkdir -p "$work"
tar -xzf "$tarball" -C "$work" --strip-components=1
patch -d "$work" -p1 -s <"$here/patches/0001-modern-emscripten.patch"

make -C "$work" -f Makefile.emcc -j"$(nproc 2>/dev/null || echo 4)" >/dev/null

cp "$work/riscvemu64-wasm.js" "$work/riscvemu64-wasm.wasm" "$here/dist/"
sha256sum "$here/dist/riscvemu64-wasm.js" "$here/dist/riscvemu64-wasm.wasm"