platform_build_soong/cmd/symbols_map/r8.go
Colin Cross 36f55aabcd Add a symbols_map tool for extracting identifiers from elf and r8 files
Add a symbols_map tool that can extract an identifiying hash from
and elf file or an r8 dictionary.  The tool writes the hash to a
textproto, and also supports a merge mode to combine textprotos into
a output file for inclusion in the build artifacts.

Bug: 218888599
Test: m dist
Test: symbols_map_test.go
Change-Id: Icd3ed6e5510e058c92d97c78759e7a4cfcdbb6ca
2022-04-04 15:53:38 -07:00

56 lines
1.6 KiB
Go

// Copyright 2022 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"bufio"
"fmt"
"io"
"os"
"strings"
)
const hashPrefix = "# pg_map_hash: "
const hashTypePrefix = "SHA-256 "
const commentPrefix = "#"
// r8Identifier extracts the hash from the comments of a dictionary produced by R8. It returns
// an empty identifier if no matching comment was found before the first non-comment line.
func r8Identifier(filename string) (string, error) {
f, err := os.Open(filename)
if err != nil {
return "", fmt.Errorf("failed to open %s: %w", filename, err)
}
defer f.Close()
return extractR8CompilerHash(f)
}
func extractR8CompilerHash(r io.Reader) (string, error) {
s := bufio.NewScanner(r)
for s.Scan() {
line := s.Text()
if strings.HasPrefix(line, hashPrefix) {
hash := strings.TrimPrefix(line, hashPrefix)
if !strings.HasPrefix(hash, hashTypePrefix) {
return "", fmt.Errorf("invalid hash type found in %q", line)
}
return strings.TrimPrefix(hash, hashTypePrefix), nil
} else if !strings.HasPrefix(line, commentPrefix) {
break
}
}
return "", nil
}