idmap2: replace std::pair<bool, T> with Result<T>
Introduce a new type Result<T> to indicate if an operation succeeded or
not, and if it did, to hold the return value of the operation. This is
the same as how std::pair<bool, T> is already used in the codebase, so
replace all instances with Result<T> to improve clarity.
Result<T> is simply an alias for std::optional<T>. The difference is
semantic: use Result<T> as the return value for functions that can fail,
use std::optional<T> when values are truly optional. This is modelled
after Rust's std::result and std::option.
A future change may graduate Result<T> to a proper class which can hold
additional details on why an operation failed, such as a string or an
error code. As a special case, continue to use std::unique_ptr<T>
instead of Result<std::unique_ptr<T>> for now: the latter would increase
code complexity without added benefit.
Test: make idmap2_tests
Change-Id: I2a8355107ed2b6485409e5e655a84cf1e20b9911
diff --git a/cmds/idmap2/idmap2/Lookup.cpp b/cmds/idmap2/idmap2/Lookup.cpp
index 020c443..8d0cee5 100644
--- a/cmds/idmap2/idmap2/Lookup.cpp
+++ b/cmds/idmap2/idmap2/Lookup.cpp
@@ -36,6 +36,7 @@
#include "idmap2/CommandLineOptions.h"
#include "idmap2/Idmap.h"
+#include "idmap2/Result.h"
#include "idmap2/Xml.h"
#include "idmap2/ZipFile.h"
@@ -53,39 +54,40 @@
using android::idmap2::CommandLineOptions;
using android::idmap2::IdmapHeader;
using android::idmap2::ResourceId;
+using android::idmap2::Result;
using android::idmap2::Xml;
using android::idmap2::ZipFile;
using android::util::Utf16ToUtf8;
namespace {
-std::pair<bool, ResourceId> WARN_UNUSED ParseResReference(const AssetManager2& am,
- const std::string& res,
- const std::string& fallback_package) {
+
+Result<ResourceId> WARN_UNUSED ParseResReference(const AssetManager2& am, const std::string& res,
+ const std::string& fallback_package) {
// first, try to parse as a hex number
char* endptr = nullptr;
ResourceId resid;
resid = strtol(res.c_str(), &endptr, 16);
if (*endptr == '\0') {
- return std::make_pair(true, resid);
+ return {resid};
}
// next, try to parse as a package:type/name string
resid = am.GetResourceId(res, "", fallback_package);
if (is_valid_resid(resid)) {
- return std::make_pair(true, resid);
+ return {resid};
}
// end of the road: res could not be parsed
- return std::make_pair(false, 0);
+ return {};
}
-std::pair<bool, std::string> WARN_UNUSED GetValue(const AssetManager2& am, ResourceId resid) {
+Result<std::string> WARN_UNUSED GetValue(const AssetManager2& am, ResourceId resid) {
Res_value value;
ResTable_config config;
uint32_t flags;
ApkAssetsCookie cookie = am.GetResource(resid, false, 0, &value, &config, &flags);
if (cookie == kInvalidCookie) {
- return std::make_pair(false, "");
+ return {};
}
std::string out;
@@ -123,31 +125,31 @@
out.append(StringPrintf("dataType=0x%02x data=0x%08x", value.dataType, value.data));
break;
}
- return std::make_pair(true, out);
+ return {out};
}
-std::pair<bool, std::string> GetTargetPackageNameFromManifest(const std::string& apk_path) {
+Result<std::string> GetTargetPackageNameFromManifest(const std::string& apk_path) {
const auto zip = ZipFile::Open(apk_path);
if (!zip) {
- return std::make_pair(false, "");
+ return {};
}
const auto entry = zip->Uncompress("AndroidManifest.xml");
if (!entry) {
- return std::make_pair(false, "");
+ return {};
}
const auto xml = Xml::Create(entry->buf, entry->size);
if (!xml) {
- return std::make_pair(false, "");
+ return {};
}
const auto tag = xml->FindTag("overlay");
if (!tag) {
- return std::make_pair(false, "");
+ return {};
}
const auto iter = tag->find("targetPackage");
if (iter == tag->end()) {
- return std::make_pair(false, "");
+ return {};
}
- return std::make_pair(true, iter->second);
+ return {iter->second};
}
} // namespace
@@ -195,14 +197,14 @@
}
apk_assets.push_back(std::move(target_apk));
- bool lookup_ok;
- std::tie(lookup_ok, target_package_name) =
+ const Result<std::string> package_name =
GetTargetPackageNameFromManifest(idmap_header->GetOverlayPath().to_string());
- if (!lookup_ok) {
+ if (!package_name) {
out_error << "error: failed to parse android:targetPackage from overlay manifest"
<< std::endl;
return false;
}
+ target_package_name = *package_name;
} else if (target_path != idmap_header->GetTargetPath()) {
out_error << "error: different target APKs (expected target APK " << target_path << " but "
<< idmap_path << " has target APK " << idmap_header->GetTargetPath() << ")"
@@ -227,21 +229,18 @@
am.SetApkAssets(raw_pointer_apk_assets);
am.SetConfiguration(config);
- ResourceId resid;
- bool lookup_ok;
- std::tie(lookup_ok, resid) = ParseResReference(am, resid_str, target_package_name);
- if (!lookup_ok) {
+ const Result<ResourceId> resid = ParseResReference(am, resid_str, target_package_name);
+ if (!resid) {
out_error << "error: failed to parse resource ID" << std::endl;
return false;
}
- std::string value;
- std::tie(lookup_ok, value) = GetValue(am, resid);
- if (!lookup_ok) {
- out_error << StringPrintf("error: resource 0x%08x not found", resid) << std::endl;
+ const Result<std::string> value = GetValue(am, *resid);
+ if (!value) {
+ out_error << StringPrintf("error: resource 0x%08x not found", *resid) << std::endl;
return false;
}
- std::cout << value << std::endl;
+ std::cout << *value << std::endl;
return true;
}
diff --git a/cmds/idmap2/include/idmap2/ResourceUtils.h b/cmds/idmap2/include/idmap2/ResourceUtils.h
index 88a835b..d106f19 100644
--- a/cmds/idmap2/include/idmap2/ResourceUtils.h
+++ b/cmds/idmap2/include/idmap2/ResourceUtils.h
@@ -18,19 +18,18 @@
#define IDMAP2_INCLUDE_IDMAP2_RESOURCEUTILS_H_
#include <string>
-#include <utility>
#include "android-base/macros.h"
#include "androidfw/AssetManager2.h"
#include "idmap2/Idmap.h"
+#include "idmap2/Result.h"
namespace android {
namespace idmap2 {
namespace utils {
-std::pair<bool, std::string> WARN_UNUSED ResToTypeEntryName(const AssetManager2& am,
- ResourceId resid);
+Result<std::string> WARN_UNUSED ResToTypeEntryName(const AssetManager2& am, ResourceId resid);
} // namespace utils
} // namespace idmap2
diff --git a/cmds/idmap2/include/idmap2/Result.h b/cmds/idmap2/include/idmap2/Result.h
new file mode 100644
index 0000000..6189ea3
--- /dev/null
+++ b/cmds/idmap2/include/idmap2/Result.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef IDMAP2_INCLUDE_IDMAP2_RESULT_H_
+#define IDMAP2_INCLUDE_IDMAP2_RESULT_H_
+
+#include <optional>
+
+namespace android::idmap2 {
+
+template <typename T>
+using Result = std::optional<T>;
+
+static constexpr std::nullopt_t kResultError = std::nullopt;
+
+} // namespace android::idmap2
+
+#endif // IDMAP2_INCLUDE_IDMAP2_RESULT_H_
diff --git a/cmds/idmap2/include/idmap2/ZipFile.h b/cmds/idmap2/include/idmap2/ZipFile.h
index 328bd36..9edbbe0 100644
--- a/cmds/idmap2/include/idmap2/ZipFile.h
+++ b/cmds/idmap2/include/idmap2/ZipFile.h
@@ -19,10 +19,10 @@
#include <memory>
#include <string>
-#include <utility>
#include "android-base/macros.h"
#include "ziparchive/zip_archive.h"
+#include "idmap2/Result.h"
namespace android {
namespace idmap2 {
@@ -43,7 +43,7 @@
static std::unique_ptr<const ZipFile> Open(const std::string& path);
std::unique_ptr<const MemoryChunk> Uncompress(const std::string& entryPath) const;
- std::pair<bool, uint32_t> Crc(const std::string& entryPath) const;
+ Result<uint32_t> Crc(const std::string& entryPath) const;
~ZipFile();
diff --git a/cmds/idmap2/libidmap2/Idmap.cpp b/cmds/idmap2/libidmap2/Idmap.cpp
index 5a47e30..1ef3267 100644
--- a/cmds/idmap2/libidmap2/Idmap.cpp
+++ b/cmds/idmap2/libidmap2/Idmap.cpp
@@ -33,6 +33,7 @@
#include "idmap2/Idmap.h"
#include "idmap2/ResourceUtils.h"
+#include "idmap2/Result.h"
#include "idmap2/ZipFile.h"
namespace android {
@@ -143,18 +144,16 @@
return false;
}
- bool status;
- uint32_t target_crc;
- std::tie(status, target_crc) = target_zip->Crc("resources.arsc");
- if (!status) {
+ Result<uint32_t> target_crc = target_zip->Crc("resources.arsc");
+ if (!target_crc) {
out_error << "error: failed to get target crc" << std::endl;
return false;
}
- if (target_crc_ != target_crc) {
+ if (target_crc_ != *target_crc) {
out_error << base::StringPrintf(
"error: bad target crc: idmap version 0x%08x, file system version 0x%08x",
- target_crc_, target_crc)
+ target_crc_, *target_crc)
<< std::endl;
return false;
}
@@ -165,17 +164,16 @@
return false;
}
- uint32_t overlay_crc;
- std::tie(status, overlay_crc) = overlay_zip->Crc("resources.arsc");
- if (!status) {
+ Result<uint32_t> overlay_crc = overlay_zip->Crc("resources.arsc");
+ if (!overlay_crc) {
out_error << "error: failed to get overlay crc" << std::endl;
return false;
}
- if (overlay_crc_ != overlay_crc) {
+ if (overlay_crc_ != *overlay_crc) {
out_error << base::StringPrintf(
"error: bad overlay crc: idmap version 0x%08x, file system version 0x%08x",
- overlay_crc_, overlay_crc)
+ overlay_crc_, *overlay_crc)
<< std::endl;
return false;
}
@@ -322,17 +320,20 @@
std::unique_ptr<IdmapHeader> header(new IdmapHeader());
header->magic_ = kIdmapMagic;
header->version_ = kIdmapCurrentVersion;
- bool crc_status;
- std::tie(crc_status, header->target_crc_) = target_zip->Crc("resources.arsc");
- if (!crc_status) {
+
+ Result<uint32_t> crc = target_zip->Crc("resources.arsc");
+ if (!crc) {
out_error << "error: failed to get zip crc for target" << std::endl;
return nullptr;
}
- std::tie(crc_status, header->overlay_crc_) = overlay_zip->Crc("resources.arsc");
- if (!crc_status) {
+ header->target_crc_ = *crc;
+
+ crc = overlay_zip->Crc("resources.arsc");
+ if (!crc) {
out_error << "error: failed to get zip crc for overlay" << std::endl;
return nullptr;
}
+ header->overlay_crc_ = *crc;
if (target_apk_path.size() > sizeof(header->target_path_)) {
out_error << "error: target apk path \"" << target_apk_path << "\" longer that maximum size "
@@ -358,15 +359,14 @@
const auto end = overlay_pkg->end();
for (auto iter = overlay_pkg->begin(); iter != end; ++iter) {
const ResourceId overlay_resid = *iter;
- bool lookup_ok;
- std::string name;
- std::tie(lookup_ok, name) = utils::ResToTypeEntryName(overlay_asset_manager, overlay_resid);
- if (!lookup_ok) {
+ Result<std::string> name = utils::ResToTypeEntryName(overlay_asset_manager, overlay_resid);
+ if (!name) {
continue;
}
// prepend "<package>:" to turn name into "<package>:<type>/<name>"
- name = base::StringPrintf("%s:%s", target_pkg->GetPackageName().c_str(), name.c_str());
- const ResourceId target_resid = NameToResid(target_asset_manager, name);
+ const std::string full_name =
+ base::StringPrintf("%s:%s", target_pkg->GetPackageName().c_str(), name->c_str());
+ const ResourceId target_resid = NameToResid(target_asset_manager, full_name);
if (target_resid == 0) {
continue;
}
diff --git a/cmds/idmap2/libidmap2/PrettyPrintVisitor.cpp b/cmds/idmap2/libidmap2/PrettyPrintVisitor.cpp
index 492e6f0..fb3bc5b 100644
--- a/cmds/idmap2/libidmap2/PrettyPrintVisitor.cpp
+++ b/cmds/idmap2/libidmap2/PrettyPrintVisitor.cpp
@@ -15,7 +15,6 @@
*/
#include <string>
-#include <utility>
#include "android-base/macros.h"
#include "android-base/stringprintf.h"
@@ -23,6 +22,7 @@
#include "idmap2/PrettyPrintVisitor.h"
#include "idmap2/ResourceUtils.h"
+#include "idmap2/Result.h"
namespace android {
namespace idmap2 {
@@ -63,11 +63,9 @@
stream_ << base::StringPrintf("0x%08x -> 0x%08x", target_resid, overlay_resid);
if (target_package_loaded) {
- bool lookup_ok;
- std::string name;
- std::tie(lookup_ok, name) = utils::ResToTypeEntryName(target_am_, target_resid);
- if (lookup_ok) {
- stream_ << " " << name;
+ Result<std::string> name = utils::ResToTypeEntryName(target_am_, target_resid);
+ if (name) {
+ stream_ << " " << *name;
}
}
stream_ << std::endl;
diff --git a/cmds/idmap2/libidmap2/RawPrintVisitor.cpp b/cmds/idmap2/libidmap2/RawPrintVisitor.cpp
index 57cfc8e..7c24445 100644
--- a/cmds/idmap2/libidmap2/RawPrintVisitor.cpp
+++ b/cmds/idmap2/libidmap2/RawPrintVisitor.cpp
@@ -16,7 +16,6 @@
#include <cstdarg>
#include <string>
-#include <utility>
#include "android-base/macros.h"
#include "android-base/stringprintf.h"
@@ -24,6 +23,7 @@
#include "idmap2/RawPrintVisitor.h"
#include "idmap2/ResourceUtils.h"
+#include "idmap2/Result.h"
using android::ApkAssets;
@@ -75,14 +75,13 @@
const ResourceId target_resid =
RESID(last_seen_package_id_, te.GetTargetTypeId(), te.GetEntryOffset() + i);
const ResourceId overlay_resid = RESID(last_seen_package_id_, te.GetOverlayTypeId(), entry);
- bool lookup_ok = false;
- std::string name;
+ Result<std::string> name;
if (target_package_loaded) {
- std::tie(lookup_ok, name) = utils::ResToTypeEntryName(target_am_, target_resid);
+ name = utils::ResToTypeEntryName(target_am_, target_resid);
}
- if (lookup_ok) {
+ if (name) {
print(static_cast<uint32_t>(entry), "0x%08x -> 0x%08x %s", target_resid, overlay_resid,
- name.c_str());
+ name->c_str());
} else {
print(static_cast<uint32_t>(entry), "0x%08x -> 0x%08x", target_resid, overlay_resid);
}
diff --git a/cmds/idmap2/libidmap2/ResourceUtils.cpp b/cmds/idmap2/libidmap2/ResourceUtils.cpp
index e98f843..5c89783 100644
--- a/cmds/idmap2/libidmap2/ResourceUtils.cpp
+++ b/cmds/idmap2/libidmap2/ResourceUtils.cpp
@@ -15,12 +15,12 @@
*/
#include <string>
-#include <utility>
#include "androidfw/StringPiece.h"
#include "androidfw/Util.h"
#include "idmap2/ResourceUtils.h"
+#include "idmap2/Result.h"
using android::StringPiece16;
using android::util::Utf16ToUtf8;
@@ -29,11 +29,10 @@
namespace idmap2 {
namespace utils {
-std::pair<bool, std::string> WARN_UNUSED ResToTypeEntryName(const AssetManager2& am,
- ResourceId resid) {
+Result<std::string> WARN_UNUSED ResToTypeEntryName(const AssetManager2& am, ResourceId resid) {
AssetManager2::ResourceName name;
if (!am.GetResourceName(resid, &name)) {
- return std::make_pair(false, "");
+ return {};
}
std::string out;
if (name.type != nullptr) {
@@ -47,7 +46,7 @@
} else {
out += Utf16ToUtf8(StringPiece16(name.entry16, name.entry_len));
}
- return std::make_pair(true, out);
+ return {out};
}
} // namespace utils
diff --git a/cmds/idmap2/libidmap2/ZipFile.cpp b/cmds/idmap2/libidmap2/ZipFile.cpp
index 3f2079a..9fb611d 100644
--- a/cmds/idmap2/libidmap2/ZipFile.cpp
+++ b/cmds/idmap2/libidmap2/ZipFile.cpp
@@ -16,8 +16,8 @@
#include <memory>
#include <string>
-#include <utility>
+#include "idmap2/Result.h"
#include "idmap2/ZipFile.h"
namespace android {
@@ -57,10 +57,10 @@
return chunk;
}
-std::pair<bool, uint32_t> ZipFile::Crc(const std::string& entryPath) const {
+Result<uint32_t> ZipFile::Crc(const std::string& entryPath) const {
::ZipEntry entry;
int32_t status = ::FindEntry(handle_, ::ZipString(entryPath.c_str()), &entry);
- return std::make_pair(status == 0, entry.crc32);
+ return status == 0 ? Result<uint32_t>(entry.crc32) : kResultError;
}
} // namespace idmap2
diff --git a/cmds/idmap2/tests/ResourceUtilsTests.cpp b/cmds/idmap2/tests/ResourceUtilsTests.cpp
index 0547fa0..7f60d75 100644
--- a/cmds/idmap2/tests/ResourceUtilsTests.cpp
+++ b/cmds/idmap2/tests/ResourceUtilsTests.cpp
@@ -16,13 +16,13 @@
#include <memory>
#include <string>
-#include <utility>
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "androidfw/ApkAssets.h"
#include "idmap2/ResourceUtils.h"
+#include "idmap2/Result.h"
#include "TestHelpers.h"
@@ -52,17 +52,14 @@
};
TEST_F(ResourceUtilsTests, ResToTypeEntryName) {
- bool lookup_ok;
- std::string name;
- std::tie(lookup_ok, name) = utils::ResToTypeEntryName(GetAssetManager(), 0x7f010000u);
- ASSERT_TRUE(lookup_ok);
- ASSERT_EQ(name, "integer/int1");
+ Result<std::string> name = utils::ResToTypeEntryName(GetAssetManager(), 0x7f010000u);
+ ASSERT_TRUE(name);
+ ASSERT_EQ(*name, "integer/int1");
}
TEST_F(ResourceUtilsTests, ResToTypeEntryNameNoSuchResourceId) {
- bool lookup_ok;
- std::tie(lookup_ok, std::ignore) = utils::ResToTypeEntryName(GetAssetManager(), 0x7f123456u);
- ASSERT_FALSE(lookup_ok);
+ Result<std::string> name = utils::ResToTypeEntryName(GetAssetManager(), 0x7f123456u);
+ ASSERT_FALSE(name);
}
} // namespace idmap2
diff --git a/cmds/idmap2/tests/ZipFileTests.cpp b/cmds/idmap2/tests/ZipFileTests.cpp
index a504d31..6e4a501 100644
--- a/cmds/idmap2/tests/ZipFileTests.cpp
+++ b/cmds/idmap2/tests/ZipFileTests.cpp
@@ -16,8 +16,8 @@
#include <cstdio> // fclose
#include <string>
-#include <utility>
+#include "idmap2/Result.h"
#include "idmap2/ZipFile.h"
#include "gmock/gmock.h"
@@ -44,14 +44,12 @@
auto zip = ZipFile::Open(GetTestDataPath() + "/target/target.apk");
ASSERT_THAT(zip, NotNull());
- bool status;
- uint32_t crc;
- std::tie(status, crc) = zip->Crc("AndroidManifest.xml");
- ASSERT_TRUE(status);
- ASSERT_EQ(crc, 0x762f3d24);
+ Result<uint32_t> crc = zip->Crc("AndroidManifest.xml");
+ ASSERT_TRUE(crc);
+ ASSERT_EQ(*crc, 0x762f3d24);
- std::tie(status, std::ignore) = zip->Crc("does-not-exist");
- ASSERT_FALSE(status);
+ Result<uint32_t> crc2 = zip->Crc("does-not-exist");
+ ASSERT_FALSE(crc2);
}
TEST(ZipFileTests, Uncompress) {
