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#!/usr/bin/env bash
set -euo pipefail

# Files to scan/patch
BROWSERS=$'/opt/google/chrome-beta/chrome
/opt/google/chrome-unstable/chrome
/opt/google/chrome/chrome
/opt/vivaldi/vivaldi-bin'

# Hex patterns
PATCH_BYTES=$'\x1f\x47\x6b\x47\x1f'
ORIG_BYTES=$'\x08\x4d\x56\x4d\x08'

find_offset() {
    # Print byte offset of the ALL match
    local f=$1
    rg -a -b -o $ORIG_BYTES --no-filename --no-line-number -- "$f" | cut -d: -f1
}

patch_at() {
    # Overwrite 5 bytes at given byte OFFSET
    local f=$1 off=$2
    printf "$PATCH_BYTES" | dd conv=notrunc of="$f" bs=1 seek="$off" status=none
}

for browser in $BROWSERS; do
    [ -f "$browser" ] || continue
    echo "Checking and patching freetype filters in $browser. This can take a while..."

    off=$(find_offset "$browser" || true)
    if [ -z "${off:-}" ]; then
        echo ">  Original filter pattern not found in $browser. It might have already been patched."
        continue
    fi

    printf ">  Original filter pattern found in %s. Patching at offset 0x%x\n" "$browser" "$off"
    if patch_at "$browser" "$off"; then
        echo ">  Patch successfully"
    else
        echo ">  Failed to patch"
    fi
done