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Initial implementation of Ion 1.1 raw binary writer #660
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,175 @@ | ||
| // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
| package com.amazon.ion.impl.bin | ||
|
|
||
| import java.math.BigInteger | ||
|
|
||
| /** | ||
| * Functions for encoding FlexInts and FlexUInts. | ||
| * | ||
| * Expected usage is calling one of the `___length` functions, and then using the result as the input for | ||
| * [writeFlexIntOrUIntInto]. The length and write functions are separate so that callers can make decisions or | ||
| * compute other values based on the encoded size of the value. | ||
| */ | ||
| object FlexInt { | ||
|
|
||
| /** Determine the length of FlexUInt for the provided value. */ | ||
| @JvmStatic | ||
| fun flexUIntLength(value: Long): Int { | ||
| val numLeadingZeros = java.lang.Long.numberOfLeadingZeros(value) | ||
| val numMagnitudeBitsRequired = 64 - numLeadingZeros | ||
| return (numMagnitudeBitsRequired - 1) / 7 + 1 | ||
| } | ||
|
|
||
| /** Determine the length of FlexInt for the provided value. */ | ||
| @JvmStatic | ||
| fun flexIntLength(value: Long): Int { | ||
| val numMagnitudeBitsRequired: Int | ||
| numMagnitudeBitsRequired = if (value < 0) { | ||
| val numLeadingOnes = java.lang.Long.numberOfLeadingZeros(value.inv()) | ||
| 64 - numLeadingOnes | ||
| } else { | ||
| val numLeadingZeros = java.lang.Long.numberOfLeadingZeros(value) | ||
| 64 - numLeadingZeros | ||
| } | ||
| return numMagnitudeBitsRequired / 7 + 1 | ||
| } | ||
|
|
||
| /** | ||
| * Writes a FlexInt or FlexUInt encoding of [value] into [data] starting at [offset]. | ||
| * Use [flexIntLength] or [flexUIntLength] to get the value for the [numBytes] parameter. | ||
| */ | ||
| @JvmStatic | ||
| fun writeFlexIntOrUIntInto(data: ByteArray, offset: Int, value: Long, numBytes: Int) { | ||
| var i = offset | ||
|
|
||
| when (numBytes) { | ||
| 1 -> { | ||
| data[i] = (0x01L or (value shl 1)).toByte() | ||
| } | ||
| 2 -> { | ||
| data[i] = (0x02L or (value shl 2)).toByte() | ||
| data[++i] = (value shr 6).toByte() | ||
| } | ||
| 3 -> { | ||
| data[i] = (0x04L or (value shl 3)).toByte() | ||
| data[++i] = (value shr 5).toByte() | ||
| data[++i] = (value shr 13).toByte() | ||
| } | ||
| 4 -> { | ||
| data[i] = (0x08L or (value shl 4)).toByte() | ||
| data[++i] = (value shr 4).toByte() | ||
| data[++i] = (value shr 12).toByte() | ||
| data[++i] = (value shr 20).toByte() | ||
| } | ||
| 5 -> { | ||
| data[i] = (0x10L or (value shl 5)).toByte() | ||
| data[++i] = (value shr 3).toByte() | ||
| data[++i] = (value shr 11).toByte() | ||
| data[++i] = (value shr 19).toByte() | ||
| data[++i] = (value shr 27).toByte() | ||
| } | ||
| 6 -> { | ||
| data[i] = (0x20L or (value shl 6)).toByte() | ||
| data[++i] = (value shr 2).toByte() | ||
| data[++i] = (value shr 10).toByte() | ||
| data[++i] = (value shr 18).toByte() | ||
| data[++i] = (value shr 26).toByte() | ||
| data[++i] = (value shr 34).toByte() | ||
| } | ||
| 7 -> { | ||
| data[i] = (0x40L or (value shl 7)).toByte() | ||
| data[++i] = (value shr 1).toByte() | ||
| data[++i] = (value shr 9).toByte() | ||
| data[++i] = (value shr 17).toByte() | ||
| data[++i] = (value shr 25).toByte() | ||
| data[++i] = (value shr 33).toByte() | ||
| data[++i] = (value shr 41).toByte() | ||
| } | ||
| 8 -> { | ||
| data[i] = 0x80.toByte() | ||
| data[++i] = (value shr 0).toByte() | ||
| data[++i] = (value shr 8).toByte() | ||
| data[++i] = (value shr 16).toByte() | ||
| data[++i] = (value shr 24).toByte() | ||
| data[++i] = (value shr 32).toByte() | ||
| data[++i] = (value shr 40).toByte() | ||
| data[++i] = (value shr 48).toByte() | ||
| } | ||
| 9 -> { | ||
| data[i] = 0 | ||
| data[++i] = (0x01L or (value shl 1)).toByte() | ||
| data[++i] = (value shr 7).toByte() | ||
| data[++i] = (value shr 15).toByte() | ||
| data[++i] = (value shr 23).toByte() | ||
| data[++i] = (value shr 31).toByte() | ||
| data[++i] = (value shr 39).toByte() | ||
| data[++i] = (value shr 47).toByte() | ||
| data[++i] = (value shr 55).toByte() | ||
| } | ||
| 10 -> { | ||
| data[i] = 0 | ||
| data[++i] = (0x02L or (value shl 2)).toByte() | ||
| data[++i] = (value shr 6).toByte() | ||
| data[++i] = (value shr 14).toByte() | ||
| data[++i] = (value shr 22).toByte() | ||
| data[++i] = (value shr 30).toByte() | ||
| data[++i] = (value shr 38).toByte() | ||
| data[++i] = (value shr 46).toByte() | ||
| data[++i] = (value shr 54).toByte() | ||
| data[++i] = (value shr 62).toByte() | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /** Determine the length of FlexUInt for the provided value. */ | ||
| @JvmStatic | ||
| fun flexUIntLength(value: BigInteger): Int { | ||
| return (value.bitLength() - 1) / 7 + 1 | ||
| } | ||
|
|
||
| /** Determine the length of FlexInt for the provided value. */ | ||
| @JvmStatic | ||
| fun flexIntLength(value: BigInteger): Int { | ||
| return value.bitLength() / 7 + 1 | ||
| } | ||
|
|
||
| /** | ||
| * Writes a FlexInt or FlexUInt encoding of [value] into [data] starting at [offset]. | ||
| * Use [flexIntLength] or [flexUIntLength] to get the value for the [numBytes] parameter. | ||
| */ | ||
| @JvmStatic | ||
| fun writeFlexIntOrUIntInto(data: ByteArray, offset: Int, value: BigInteger, numBytes: Int) { | ||
| // TODO: Should we branch to the implementation for long if the number is small enough? | ||
| // https://github.com/amazon-ion/ion-java/issues/614 | ||
| val valueBytes = value.toByteArray() | ||
| var i = 0 // `i` gets incremented for every byte written. | ||
|
|
||
| // Start with leading zero bytes. | ||
| // If there's 1-8 total bytes, we need no leading zero-bytes. | ||
| // If there's 9-16 total bytes, we need one zero-byte | ||
| // If there's 17-24 total bytes, we need two zero-bytes, etc. | ||
| while (i < (numBytes - 1) / 8) { | ||
| data[offset + i] = 0 | ||
| i++ | ||
| } | ||
|
|
||
| // Write the last length bits, possibly also containing some value bits. | ||
| val remainingLengthBits = (numBytes - 1) % 8 | ||
| val lengthPart = (0x01 shl remainingLengthBits).toByte() | ||
| val valueBitOffset = remainingLengthBits + 1 | ||
| val valuePart = (valueBytes[valueBytes.size - 1].toInt() shl valueBitOffset).toByte() | ||
| data[offset + i] = (valuePart.toInt() or lengthPart.toInt()).toByte() | ||
| i++ | ||
| for (valueByteOffset in valueBytes.size - 1 downTo 1) { | ||
| // Technically it's only a nibble if the bitOffset is 4, so we call it nibble-ish | ||
| val highNibbleIsh = (valueBytes[valueByteOffset - 1].toInt() shl valueBitOffset).toByte() | ||
| val lowNibbleIsh = (valueBytes[valueByteOffset].toInt() and 0xFF shr 8 - valueBitOffset).toByte() | ||
| data[offset + i] = (highNibbleIsh.toInt() or lowNibbleIsh.toInt()).toByte() | ||
| i++ | ||
| } | ||
| if (i < numBytes) { | ||
| data[offset + i] = (valueBytes[0].toInt() shr 8 - valueBitOffset).toByte() | ||
| } | ||
| } | ||
| } | ||
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I discovered that using
whento compare directly against some constants would allow the Kotlin compiler to generate a jump table, so I figured I'd just manually unroll the old loop based logic. Now the only branching in this method is the jump table for thewhen, compared to the chainedif/elsefalling back to the loop in the previous implementation.