#!/bin/sh
# Extract function fingerprints from ELF binaries
# Outputs JSON array with function name, offset, size, and hashes
#
# Usage: extract-functions.sh <directory>
#
# Dependencies: objdump, readelf, sha256sum, jq

set -eu

DIR="${1:-.}"

extract_functions_from_binary() {
    local binary="$1"
    
    # Skip non-ELF files
    file "$binary" | grep -q "ELF" || return 0
    
    # Get function symbols
    objdump -t "$binary" 2>/dev/null | \
    awk '/\.text.*[0-9a-f]+.*F/ {
        # Fields: addr flags section size name
        gsub(/\*.*\*/, "", $1)  # Clean address
        if ($5 != "" && $4 != "00000000" && $4 != "0000000000000000") {
            printf "%s %s %s\n", $1, $4, $NF
        }
    }' | while read -r offset size name; do
        # Skip compiler-generated symbols
        case "$name" in
            __*|_GLOBAL_*|.plt*|.text*|frame_dummy|register_tm_clones|deregister_tm_clones)
                continue
                ;;
        esac
        
        # Convert hex size to decimal
        dec_size=$((16#$size))
        
        # Skip tiny functions (likely padding)
        [ "$dec_size" -lt 16 ] && continue
        
        # Extract function bytes and compute hash
        # Using objdump to get disassembly and hash the opcodes
        local hash=$(objdump -d --start-address="0x$offset" --stop-address="0x$((16#$offset + dec_size))" "$binary" 2>/dev/null | \
            grep "^[[:space:]]*[0-9a-f]*:" | \
            awk '{for(i=2;i<=NF;i++){if($i~/^[0-9a-f]{2}$/){printf "%s", $i}}}' | \
            sha256sum | cut -d' ' -f1)
        
        # Output JSON object
        printf '{"name":"%s","offset":"0x%s","size":%d,"hash":"%s"}\n' \
            "$name" "$offset" "$dec_size" "${hash:-unknown}"
    done
}

# Find all ELF binaries in directory
echo "["
first=true
find "$DIR" -type f -executable 2>/dev/null | while read -r binary; do
    # Check if ELF
    file "$binary" 2>/dev/null | grep -q "ELF" || continue
    
    extract_functions_from_binary "$binary" | while read -r json; do
        [ -z "$json" ] && continue
        if [ "$first" = "true" ]; then
            first=false
        else
            echo ","
        fi
        echo "$json"
    done
done
echo "]"