AidlMethodSpec.kt
/*
* Copyright 2022 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.
*/
package androidx.privacysandbox.tools.core.generator.poet
import com.google.common.hash.Hashing
private val AIDL_MAX_TRANSACTION_ID = 16777114UL
/** The number of transaction IDs that we reserve for our own purposes. */
private val RESERVED_ID_COUNT = 100UL
private val JAVA_MAX_METHOD_COUNT = 65535UL
internal data class AidlMethodSpec(
val name: String,
val parameters: List<AidlParameterSpec>,
val transactionId: Int,
) {
constructor(name: String, parameters: List<AidlParameterSpec>) : this(
name,
parameters,
aidlTransactionId(name, parameters)
)
override fun toString(): String {
val params = parameters.joinToString(", ")
return "void $name($params) = $transactionId;"
}
class Builder(val name: String) {
private val parameters = mutableListOf<AidlParameterSpec>()
private var transactionId: Int? = null
fun addParameter(parameter: AidlParameterSpec) {
parameters.add(parameter)
}
fun addParameter(name: String, type: AidlTypeSpec) {
addParameter(AidlParameterSpec(name, type, isIn = type.isList || type.isParcelable))
}
fun build(): AidlMethodSpec {
val txId = transactionId
if (txId == null) {
return AidlMethodSpec(name, parameters)
}
// TODO(b/271114359): Add special handling for manually-supplied transaction IDs
return AidlMethodSpec(name, parameters, txId)
}
}
}
// This method must remain backwards-compatible to ensure SDK compatibility.
internal fun aidlTransactionId(name: String, parameters: List<AidlParameterSpec>): Int {
val hash = Hashing.farmHashFingerprint64().hashString(
signature(name, parameters),
Charsets.UTF_8,
).asLong().toULong()
val maxValue = AIDL_MAX_TRANSACTION_ID - RESERVED_ID_COUNT - JAVA_MAX_METHOD_COUNT + 1UL
// toInt is safe because $maxValue is well under 2^32 (in fact, under 2^24)
return (hash % maxValue).toInt()
}
// This method must remain backwards-compatible to ensure SDK compatibility.
private fun signature(name: String, parameters: List<AidlParameterSpec>): String {
val params = parameters.joinToString(",") { it.type.signature() }
return "$name($params)"
}
// This method must remain backwards-compatible to ensure SDK compatibility.
private fun AidlTypeSpec.signature(): String =
innerType.qualifiedName + (if (isList) "[]" else "")