fix several critial bug

details
 - code refine
 "In Kotlin 1.3, it is now possible to capture the when subject into variable"
 - fix gradle version checking bug: now we can handle versions like "5.4-rc-1" and "5.4"
 - removed unwanted import of "UnImplNode"
 - add Struct3 doc

bbootimg/src/main/kotlin/Helper.kt

@@ -2,7 +2,6 @@ package cfig
 
 import cfig.io.Struct3
 import com.google.common.math.BigIntegerMath
-import com.sun.org.apache.xml.internal.utils.UnImplNode
 import org.apache.commons.codec.binary.Hex
 import org.apache.commons.compress.compressors.gzip.GzipCompressorOutputStream
 import org.apache.commons.compress.compressors.gzip.GzipParameters

bbootimg/src/main/kotlin/cfig/io/Struct3.kt

@@ -108,7 +108,7 @@ class Struct3 {
     fun calcSize(): Int? {
         var ret = 0
         for (format in formats) {
-            when (format[0]) {
+            when (val formatType = format[0]) {
                 Byte, UByte, Char, String, Type.Padding -> {
                     ret += format[1] as Int
                 }
@@ -122,7 +122,7 @@ class Struct3 {
                     ret += 8 * format[1] as Int
                 }
                 else -> {
-                    throw IllegalArgumentException("Class [" + format[0] + "] not supported")
+                    throw IllegalArgumentException("Class [" + formatType + "] not supported")
                 }
             }
         }

build.gradle

@@ -9,8 +9,9 @@ subprojects {
 // ----------------------------------------------------------------------------
 //                       global
 // ----------------------------------------------------------------------------
-
-if (Float.parseFloat(gradle.gradleVersion) < 5.0) {
+import java.util.regex.Matcher
+import java.util.regex.Pattern
+if (parseGradleVersion(gradle.gradleVersion) < 5) {
     logger.error("ERROR: Gradle Version MUST >= 5.0, current is {}", gradle.gradleVersion)
     throw new RuntimeException("ERROR: Gradle Version")
 } else {
@@ -174,3 +175,15 @@ task rr {
         rebootRecovery()
     }
 }
+
+int parseGradleVersion(String version) {
+	Pattern VERSION_PATTERN = Pattern.compile("((\\d+)(\\.\\d+)+)(-(\\p{Alpha}+)-(\\w+))?(-(SNAPSHOT|\\d{14}([-+]\\d{4})?))?")
+    Matcher matcher = VERSION_PATTERN.matcher(version)
+    if (!matcher.matches()) {
+        throw new IllegalArgumentException(format("'%s' is not a valid Gradle version string (examples: '1.0', '1.0-rc-1')", version))
+    }
+    String versionPart = matcher.group(1)
+    int majorPart = Integer.parseInt(matcher.group(2), 10)
+    logger.info("Gradle: versionPart {}, majorPart {}", versionPart, majorPart)
+	return majorPart
+}

doc/Struct3.md

@@ -0,0 +1,21 @@
+'Struct3' formats
+
+ | Format | C Type | Python type | Standard size | Type | Parameter | Size |
+ | -- | -- | -- | -- | -- | -- | -- |
+ | x | pad byte | no value |  | Type.Padding | "null,Byte,Int (only lower 8 bits are kept)" | 1 |
+ | c | char | bytes of length 1 | 1 | kotlin.Char | "Character.class (only lower 8 bits are kept, higher 8 bits are discarded)" | 1 |
+ | b | signed char | integer | 1 | kotlin.Byte | byte[] (item range: [-128~127]) | n |
+ | s | char[] | bytes |  | kotlin.String | String.class | n |
+ | B | unsigned char | integer | 1 | Kotlin.UByte | byte[] (item range: [0~255]) | n |
+ | ? | _Bool | bool | 1 |  |  |  |
+ | h | short | integer | 2 | kotlin.Short | "Int,Short, (range [-32768 , 32767])" | 2 |
+ | H | unsigned short | integer | 2 | kotlin.UShort | "Int,Short,UShort,(range [0 , 65535])" | 2 |
+ | i | int | integer | 4 | kotlin.Int | "[-2^31 , 2^31 - 1]" | 4 |
+ | l | long | integer | 4 | kotlin.Int | "[-2^31 , 2^31 - 1]" | 4 |
+ | I | unsigned int | integer | 4 | kotlin.UInt | "[0 , 2^32-1]" |  |
+ | L | unsigned long | integer | 4 | kotlin.UInt | "[0 , 2^32-1]" |  |
+ | q | long long | integer | 8 | kotlin.Long |  |  |  |
+ | Q | unsigned long long | integer | 8 | kotlin.ULong |  |  |
+ | e | (7) | float | 2 |  |  |  |
+ | f | float | float | 4 |  |  |  |
+ | d | double | float | 8 |  |  |  |