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Speedup Bech32 encode/decode #161

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Speedup Bech32 encode/decode #161

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54 changes: 20 additions & 34 deletions app/src/main/java/com/samourai/wallet/segwit/bech32/Bech32Segwit.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,6 @@

import org.apache.commons.lang3.tuple.Pair;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Bech32Segwit {

public static Pair<Byte, byte[]> decode(String hrp, String addr) throws Exception {
Expand All @@ -24,11 +20,8 @@ public static Pair<Byte, byte[]> decode(String hrp, String addr) throws Exceptio
}

byte[] data = p.getRight();
List<Byte> progBytes = new ArrayList<Byte>();
for(int i = 1; i < data.length; i++) {
progBytes.add(data[i]);
}
byte[] decoded = convertBits(progBytes, 5, 8, false);
byte[] decoded = new byte[getOutSize(data.length - 1, 5, 8, false)];
convertBits(data, 1, decoded, 0, 5, 8, false);
if(decoded.length < 2 || decoded.length > 40) {
throw new Exception("invalid decoded data length");
}
Expand All @@ -47,32 +40,32 @@ public static Pair<Byte, byte[]> decode(String hrp, String addr) throws Exceptio

public static String encode(String hrp, byte witnessVersion, byte[] witnessProgram) throws Exception {

List<Byte> progBytes = new ArrayList<Byte>();
for(int i = 0; i < witnessProgram.length; i++) {
progBytes.add(witnessProgram[i]);
}

byte[] prog = convertBits(progBytes, 8, 5, true);
byte[] data = new byte[1 + prog.length];

System.arraycopy(new byte[] { witnessVersion }, 0, data, 0, 1);
System.arraycopy(prog, 0, data, 1, prog.length);
byte[] data = new byte[1 + getOutSize(witnessProgram.length, 8, 5, true)];
data[0] = witnessVersion;
convertBits(witnessProgram, 0, data, 1, 8, 5, true);

String ret = Bech32.bech32Encode(hrp, data);

return ret;
}

private static byte[] convertBits(List<Byte> data, int fromBits, int toBits, boolean pad) throws Exception {
private static int getOutSize(int dataSize, int fromBits, int toBits, boolean pad) {
int outSize = dataSize * fromBits / toBits;
if (pad && outSize * toBits < dataSize * fromBits) {
outSize++;
}
return outSize;
}

private static void convertBits(byte[] src, int srcIdx, byte[] dest, int destIdx,
int fromBits, int toBits, boolean pad) throws Exception {

int acc = 0;
int bits = 0;
int maxv = (1 << toBits) - 1;
List<Byte> ret = new ArrayList<Byte>();

for(Byte value : data) {

short b = (short)(value.byteValue() & 0xff);
for(; srcIdx < src.length; srcIdx++) {
short b = (short)(src[srcIdx] & 0xff);

if (b < 0) {
throw new Exception();
Expand All @@ -88,26 +81,19 @@ else if ((b >> fromBits) > 0) {
bits += fromBits;
while (bits >= toBits) {
bits -= toBits;
ret.add((byte)((acc >> bits) & maxv));
dest[destIdx++] = (byte)((acc >> bits) & maxv);
}
}

if(pad && (bits > 0)) {
ret.add((byte)((acc << (toBits - bits)) & maxv));
dest[destIdx++] = (byte)((acc << (toBits - bits)) & maxv);
}
else if (bits >= fromBits || (byte)(((acc << (toBits - bits)) & maxv)) != 0) {
return null;
throw new Exception();
}
else {
;
}

byte[] buf = new byte[ret.size()];
for(int i = 0; i < ret.size(); i++) {
buf[i] = ret.get(i);
}

return buf;
}

public static byte[] getScriptPubkey(byte witver, byte[] witprog) {
Expand Down