initial: varing and smarting packing tools

.gitignore

@@ -0,0 +1,3 @@
+/.gradle/
+/.idea/
+/build/

README.md

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+# Binary tools
+
+> Work in progress not ready to any practical use
+
+Goals:
+
+- Efficient binary serialization
+- Pack/unpack byte tools
+- 2 flavors of space-effecient varint packing
+- CRCs and CRC-protected blocks
+- Async variants

build.gradle.kts

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+plugins {
+    kotlin("multiplatform") version "1.7.21"
+}
+
+group = "net.sergeych"
+version = "0.0.1-SNAPSHOT"
+
+repositories {
+    mavenCentral()
+    mavenLocal()
+    maven("https://maven.universablockchain.com/")
+}
+
+kotlin {
+    jvm {
+        compilations.all {
+            kotlinOptions.jvmTarget = "1.8"
+        }
+        withJava()
+        testRuns["test"].executionTask.configure {
+            useJUnitPlatform()
+        }
+    }
+    js(IR) {
+        browser {
+            commonWebpackConfig {
+                cssSupport.enabled = true
+            }
+        }
+    }
+    val hostOs = System.getProperty("os.name")
+    val isMingwX64 = hostOs.startsWith("Windows")
+    val nativeTarget = when {
+        hostOs == "Mac OS X" -> macosX64("native")
+        hostOs == "Linux" -> linuxX64("native")
+        isMingwX64 -> mingwX64("native")
+        else -> throw GradleException("Host OS is not supported in Kotlin/Native.")
+    }
+
+    
+    sourceSets {
+        val commonMain by getting {
+            dependencies {
+                implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4")
+                api("net.sergeych:mp_stools:1.3.2")
+            }
+        }
+        val commonTest by getting {
+            dependencies {
+                implementation(kotlin("test"))
+            }
+        }
+        val jvmMain by getting
+        val jvmTest by getting
+        val jsMain by getting
+        val jsTest by getting
+        val nativeMain by getting
+        val nativeTest by getting
+    }
+}

gradle.properties

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+kotlin.code.style=official
+kotlin.js.compiler=ir

gradlew

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+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# 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
+#
+#      https://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.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

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+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle.kts

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+
+rootProject.name = "mp_bintools"
+

src/commonMain/kotlin/net.sergeych.bintools/DataSink.kt

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+package net.sergeych.bintools
+
+abstract class DataSink {
+
+    abstract fun writeByte(data: Byte)
+
+    fun writeByte(data: Int) = writeByte(data.toByte())
+
+    open fun writeUByte(data: UByte) {
+        writeByte(data.toByte())
+    }
+
+    @Suppress("unused")
+    open fun writeBytes(data: ByteArray) {
+        for(d in data) writeByte(d)
+    }
+}
+
+class ArrayDataSink : DataSink() {
+    private val result = mutableListOf<Byte>()
+
+    override fun writeByte(data: Byte) {
+        result.add(data)
+    }
+
+    fun toByteArray() = result.toByteArray()
+}

src/commonMain/kotlin/net.sergeych.bintools/DataSource.kt

@@ -0,0 +1,30 @@
+package net.sergeych.bintools
+
+/**
+ * data input stream-like abstraction. We need it because
+ * kotlinx serialization is synchronous and there us nothing
+ * like multiplatform version of DataInput
+ *
+ */
+abstract class DataSource {
+
+    abstract fun readByte(): Byte
+
+    abstract val position: Int
+
+    open fun readUByte() = readByte().toUByte()
+
+    @Suppress("unused")
+    open fun readBytes(size: Int): ByteArray =
+        ByteArray(size).also { a ->
+            for( i in 0..size)
+                a[i] = readByte()
+        }
+}
+
+fun ByteArray.toDataSource(): DataSource =
+    object : DataSource() {
+        override var position = 0
+
+        override fun readByte(): Byte = this@toDataSource[position++]
+    }

src/commonMain/kotlin/net.sergeych.bintools/errors.kt

@@ -0,0 +1,4 @@
+package net.sergeych.bintools
+
+class FormatException(message: String="invalid format",cause: Throwable?=null):
+        Exception(message, cause)

src/commonMain/kotlin/net.sergeych.bintools/simple_codecs.kt

@@ -0,0 +1,135 @@
+package net.sergeych.bintools
+
+
+fun longToBytes(value: Long): ByteArray {
+    var l = value
+    val result = ByteArray(8)
+    for (i in 7 downTo 0) {
+        result[i] = (l and 0xFF).toByte()
+        l = l shr 8
+    }
+    return result
+}
+
+/**
+ * Convert 8 bytes to LE long
+ */
+fun bytesToLong(b: ByteArray): Long {
+    var result: Long = 0
+    for (i in 0 until 8) {
+        result = result shl 8
+        result = result or (b[i].toLong() and 0xFF)
+    }
+    return result
+}
+
+
+private val hexDigits = "0123456789ABCDEF"
+
+fun Long.encodeToHex(length: Int = 0): String {
+    var result = ""
+    var value = this
+    if (value < 0) throw IllegalArgumentException("cant convert to hex negative (ambiguous)")
+    do {
+        result = hexDigits[(value and 0x0f).toInt()] + result
+        value = value shr 4
+    } while (value > 0)
+    while (result.length < length) result = "0" + result
+    return result
+}
+
+fun Int.encodeToHex(length: Int = 0) = (toLong() and 0xFFFFffff).encodeToHex(length)
+@Suppress("unused")
+fun UInt.encodeToHex(length: Int = 0) = toLong().encodeToHex(length)
+fun Byte.encodeToHex(length: Int = 0) = (toLong() and 0xFF).encodeToHex(length)
+fun UByte.encodeToHex(length: Int = 0) = toLong().encodeToHex(length)
+@Suppress("unused")
+fun ULong.encodeToHex(length: Int = 0) = toLong().encodeToHex(length)
+
+fun ByteArray.encodeToHex(separator: String = " "): String = joinToString(separator) { it.toUByte().encodeToHex(2) }
+fun Collection<Byte>.encodeToHex(separator: String = " "): String = joinToString(separator) { it.toUByte().encodeToHex(2) }
+
+fun ByteArray.toDump(wide: Boolean = false): String = toDumpLines(wide).joinToString("\n")
+
+fun ByteArray.toDumpLines(wide: Boolean = false): List<String> {
+
+    val lineSize = if (wide) 32 else 16
+
+    fun dumpChars(_from: Int): String {
+        var from = _from
+        val b = StringBuilder(22)
+
+        b.append('|')
+        val max: Int = kotlin.math.min(size, from + lineSize)
+        while (from < max) {
+            val ch = this[from++].toInt()
+            if (ch >= ' '.code && ch < 127) b.append(ch.toChar()) else b.append('.')
+        }
+        val remainder = from % lineSize
+        if (remainder > 0) {
+            var cnt = lineSize - remainder
+            while (cnt-- > 0) b.append(' ')
+        }
+        return b.append("|").toString()
+    }
+
+
+    val lines = mutableListOf<String>()
+    if (size == 0) return lines
+    var line: StringBuilder? = null
+
+    if (size != 0) {
+        for (i in indices) {
+            if (i % lineSize == 0) {
+                if (line != null) {
+                    line.append(dumpChars(i - lineSize))
+                    lines.add(line.toString())
+                }
+                line = StringBuilder(i.encodeToHex(4))
+                line.append(' ')
+            }
+            line!!.append((this[i].toUByte()).encodeToHex(2))
+            line.append(' ')
+        }
+        if (line != null) {
+            val l = size
+            var fill = lineSize - l % lineSize
+            if (fill < lineSize) while (fill-- > 0) line.append("   ")
+            val index = l - l % lineSize
+            line.append(dumpChars(if (index < l) index else l - lineSize))
+            lines.add(line.toString())
+        }
+    }
+    return lines
+}
+
+fun String.decodeHex(): ByteArray {
+    val source = this.trim().uppercase()
+    val result = arrayListOf<Byte>()
+    var pos = 0
+    while (pos < source.length) {
+        val i = hexDigits.indexOf(source[pos++])
+        if (i < 0) throw FormatException("invalid hex digit in ${source} at ${pos - 1}")
+        if (pos >= source.length) throw FormatException(
+            "hex string must consist of bytes " +
+                    "(unexepced end of data): $source"
+        )
+        val j = hexDigits.indexOf(source[pos++])
+        if (j < 0) throw FormatException("invalid hex digit in ${source} at ${pos - 1}")
+        result.add(((i shl 4) or j).toByte())
+        while (pos < source.length && (source[pos].isWhitespace())) pos++
+    }
+    return result.toByteArray()
+}
+
+fun ByteArray.flipSelf() {
+    var i = 0
+    var j = size - 1
+    while (i < j) {
+        val x = this[i]
+        this[i++] = this[j]
+        this[j--] = x
+    }
+}
+
+fun ByteArray.flip(): ByteArray = copyOf().also { it.flipSelf() }

src/commonMain/kotlin/net.sergeych.bintools/smartint.kt

@@ -0,0 +1,150 @@
+@file:OptIn(ExperimentalUnsignedTypes::class)
+
+package com.icodici.ubdata
+
+import net.sergeych.bintools.ArrayDataSink
+import net.sergeych.bintools.DataSink
+import net.sergeych.bintools.DataSource
+import net.sergeych.bintools.toDataSource
+
+/**
+ * Smart variable-length long encoding tools, async.
+ *
+ * | Bytes sz | varint bits | smartint bits |
+ * |:-----:|:------:|:---------:|
+ * |   1   |    7   |     6     |
+ * |   2   |    14  |    14     |
+ * |   3   |    21  |    22     |
+ * |   4   |    28  |    29     |
+ * |   5   |    35  |    36     |
+ * |   6+  |    7*N |   7*N+1   |
+ * |   9   |    63  |   64      |
+ * |   10  |    64  |   ---     |
+ *
+ * In other words, except for very small numbers smartint
+ * gives 1 bit gain. So, full sized 64 bits with smartint takes
+ * 9 bytes, while varint needs 10. This could be important.
+ *
+ * Encoding is the following:
+ *
+ *    Byte 0:  bits 0..1  : type
+ *             bits 2..7 : v0
+ *
+ * Then depending on the type:
+ *
+ *    type = 0:
+ *          v0 is the resul 0..64 (or -32..32)
+ *
+ *    type = 1:
+ *          v0, v1 is the result, 14 bits
+ *
+ *    type = 2:
+ *          v0, v1, v2 are the result, 22bits
+ *
+ *    type = 3:
+ *          v0, v1, v2, varint encoded
+ *
+ *  Varint encodes bytes with last bit reserved as end
+ *  flag and first 7 bits are data bits. Last bit 0 means end of the
+ *  sequence.
+ *
+ */
+object Smartint {
+
+    private val v0limit: ULong = (1L shl 6).toULong()
+    private val v1limit = (1L shl 14).toULong()
+    private val v2limit = (1L shl 22).toULong()
+
+    fun encode(value: ULong, sink: DataSink) {
+        when {
+            value < v0limit -> encodeSeq(sink, 0, value)
+
+            value < v1limit -> encodeSeq(
+                sink,
+                1,
+                value and 0x3Fu,
+                value shr 6
+            )
+
+            value < v2limit -> encodeSeq(
+                sink,
+                2,
+                value and 0x3Fu,
+                (value shr 6) and 0xFFu,
+                (value shr 14) and 0xFFu,
+            )
+
+            else -> {
+                encodeSeq(
+                    sink,
+                    3,
+                    value and 0x3Fu,
+                    (value shr 6) and 0xFFu,
+                    (value shr 14) and 0xFFu,
+                )
+                Varint.encode(value shr 22, sink)
+            }
+        }
+    }
+
+    private fun encodeSeq(sink: DataSink, type: Int, vararg bytes: ULong) {
+        if (bytes.size == 0)
+            sink.writeByte(0)
+        else {
+            if (bytes[0] > v0limit) throw IllegalArgumentException("first number is too big")
+            sink.writeUByte(((type and 0x03) or (bytes[0] shl 2).toInt()).toUByte())
+            for (x in bytes.drop(1))
+                sink.writeUByte(x.toUByte())
+        }
+    }
+
+    fun decode(source: DataSource): ULong {
+        fun get(): ULong = source.readUByte().toULong()
+        val first = get().toUInt()
+        var type = (first and 3u).toInt()
+
+        var result: ULong = first.toULong() shr 2
+        if (type-- == 0) return result // type 0
+
+        result = result or (get() shl 6)
+        if (type-- == 0) return result  // type 1
+
+        result = result or (get() shl 14)
+        if (type == 0) return result  // type 2
+
+        return result or (Varint.decode(source) shl 22)
+    }
+
+    fun encodeSigned(value: Long, sink: DataSink) {
+        val sigBit: ULong
+        val x: ULong
+        if (value < 0) {
+            x = (-value).toULong()
+            sigBit = 1u
+        } else {
+            x = value.toULong()
+            sigBit = 0u
+        }
+        Varint.encode((x shl 1) or sigBit, sink)
+    }
+
+    fun decodeSigned(source: DataSource): Long {
+        val x = Varint.decode(source)
+        val result = (x shr 1).toLong()
+        return if ((x and 1u).toInt() != 0) -result else result
+    }
+
+    fun encode(value: ULong): ByteArray {
+        return ArrayDataSink().also { encode(value, it) }.toByteArray()
+    }
+
+    fun decode(packed: ByteArray) = decode(packed.toDataSource())
+
+    fun encodeSigned(value: Long): ByteArray {
+        return ArrayDataSink().also { encodeSigned(value, it) }.toByteArray()
+    }
+
+    fun decodeSigned(data: ByteArray): Long {
+        return decodeSigned(data.toDataSource())
+    }
+}

src/commonMain/kotlin/net.sergeych.bintools/varint.kt

@@ -0,0 +1,82 @@
+@file:OptIn(ExperimentalUnsignedTypes::class)
+
+package com.icodici.ubdata
+
+import net.sergeych.bintools.ArrayDataSink
+import net.sergeych.bintools.DataSink
+import net.sergeych.bintools.DataSource
+import net.sergeych.bintools.toDataSource
+
+/**
+ * Variable-length long integer encoding. the MSB (0x80) bit of each byte flags
+ * that it is not the last one, and all ncecssary bits are encoded with 7-bit
+ * portions, LSB to MSB (big endian of sorts).
+ *
+ * There is slower but more compact encoding variant, [Smartint] that is better when
+ * encoding numbers that needs more than 22 bits. With smaller numbers its either
+ * same or even worse, see [Smartint] docs.
+ */
+object Varint {
+    fun encodeSigned(value: Long, sink: DataSink): Unit {
+        var sigBit: ULong
+        var x: ULong
+        if (value < 0) {
+            x = (-value).toULong()
+            sigBit = 1u
+        } else {
+            x = value.toULong()
+            sigBit = 0u
+        }
+        encode((x shl 1) or sigBit, sink)
+    }
+
+    fun encode(value: ULong, dout: DataSink) {
+        var rest = value
+        do {
+            val x = (rest and 127u).toInt()
+            rest = rest shr 7
+            if (rest > 0u)
+                dout.writeByte(x or 0x80)
+            else
+                dout.writeByte(x)
+
+        } while (rest > 0u)
+    }
+
+    fun decode(source: DataSource): ULong {
+        var result: ULong = 0u
+        var count = 0
+        while (true) {
+            val x = source.readUByte().toInt()
+            result = result or ((x and 0x7F).toULong() shl count)
+            if ((x and 0x80) == 0)
+                break
+            count += 7
+        }
+        return result
+    }
+
+
+    fun decodeSigned(source: DataSource): Long {
+        val x = decode(source)
+        val result = (x shr 1).toLong()
+        return if ((x and 1u).toInt() != 0) -result else result
+    }
+
+    fun encode(value: ULong): ByteArray {
+        return ArrayDataSink().also { encode(value, it) }.toByteArray()
+    }
+
+    fun decode(packed: ByteArray) = decode(packed.toDataSource())
+
+    fun encodeSigned(value: Long): ByteArray {
+        return ArrayDataSink().also { encodeSigned(value, it) }.toByteArray()
+    }
+
+    fun decodeSigned(data: ByteArray): Long {
+        return decodeSigned(data.toDataSource())
+    }
+
+
+
+}

src/commonTest/kotlin/bintools/SmartintTest.kt

@@ -0,0 +1,44 @@
+package bintools
+
+import com.icodici.ubdata.Smartint
+import net.sergeych.bintools.encodeToHex
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class SmartintTest {
+
+    fun testValue(x: Long) {
+        assertEquals(x.toULong(), Smartint.decode(Smartint.encode(x.toULong())))
+        assertEquals(x, Smartint.decodeSigned(Smartint.encodeSigned(x)))
+        println("+ ${x}: ${Smartint.encode(x.toULong()).encodeToHex()}")
+    }
+
+    fun testAround(bits: Int) {
+        println("----- $bits -----")
+        val window = 5
+        var median: Long = (1.toULong() shl bits).toLong()
+        for( x in (median-2)..(median+2)) {
+            testValue(x)
+        }
+        median = median * 3 / 2
+        for( x in (median-5)..(median+5)) {
+            testValue(x)
+        }
+    }
+
+    @Test
+    fun encode() {
+        for( i in 0..70) testValue(i.toLong())
+        testAround(6)
+        testAround(14)
+        testAround(22)
+        testAround(29)
+        testAround(36)
+        testValue(-1)
+//        testAround(28)
+    }
+
+    @Test
+    fun decode() {
+    }
+}

src/commonTest/kotlin/bintools/VarintTest.kt

@@ -0,0 +1,40 @@
+package bintools
+
+import com.icodici.ubdata.Varint
+import net.sergeych.bintools.encodeToHex
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class VarintTest {
+
+    fun testValue(x: Long) {
+        assertEquals(x.toULong(), Varint.decode(Varint.encode(x.toULong())))
+        assertEquals(x, Varint.decodeSigned(Varint.encodeSigned(x)))
+        println("+ ${x}: ${Varint.encode(x.toULong()).encodeToHex()}")
+    }
+
+    fun testAround(bits: Int) {
+        val window = 5
+        var median: Long = (1.toULong() shl bits).toLong()
+        for( x in (median-5)..(median+5)) {
+            testValue(x)
+        }
+        median = median * 3 / 2
+        for( x in (median-5)..(median+5)) {
+            testValue(x)
+        }
+    }
+
+    @Test
+    fun encode() {
+//        for( i in 0..300) testValue(i.toLong())
+        testAround(7)
+        testAround(14)
+        testAround(21)
+        testAround(28)
+    }
+
+    @Test
+    fun decode() {
+    }
+}