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Give VarInt a concept of originally serialized size.

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VarInts have multiple encodings, and during parsing we need to know
the size of the actually encoded form, not the size of the optimal
encoding.
This commit is contained in:
Matt Corallo 2012-12-30 13:47:35 -05:00 committed by Mike Hearn
parent 95b5e0d894
commit 009939f9be
3 changed files with 29 additions and 6 deletions
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4
core/src/main/java/com/google/bitcoin/core/Message.java
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@ -439,7 +439,7 @@ public abstract class Message implements Serializable {
long readVarInt(int offset) {
VarInt varint = new VarInt(bytes, cursor + offset);
cursor += offset + varint.getSizeInBytes();
cursor += offset + varint.getOriginalSizeInBytes();
return varint.value;
}
@ -462,7 +462,7 @@ public abstract class Message implements Serializable {
cursor += 1;
return "";
}
cursor += varInt.getSizeInBytes();
cursor += varInt.getOriginalSizeInBytes();
byte[] characters = new byte[(int) varInt.value];
System.arraycopy(bytes, cursor, characters, 0, characters.length);
cursor += characters.length;

8
core/src/main/java/com/google/bitcoin/core/Transaction.java
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@ -444,7 +444,7 @@ public class Transaction extends ChildMessage implements Serializable {
varint = new VarInt(buf, cursor);
long txInCount = varint.value;
cursor += varint.getSizeInBytes();
cursor += varint.getOriginalSizeInBytes();
for (i = 0; i < txInCount; i++) {
// 36 = length of previous_outpoint
@ -452,19 +452,19 @@ public class Transaction extends ChildMessage implements Serializable {
varint = new VarInt(buf, cursor);
scriptLen = varint.value;
// 4 = length of sequence field (unint32)
cursor += scriptLen + 4 + varint.getSizeInBytes();
cursor += scriptLen + 4 + varint.getOriginalSizeInBytes();
}
varint = new VarInt(buf, cursor);
long txOutCount = varint.value;
cursor += varint.getSizeInBytes();
cursor += varint.getOriginalSizeInBytes();
for (i = 0; i < txOutCount; i++) {
// 8 = length of tx value field (uint64)
cursor += 8;
varint = new VarInt(buf, cursor);
scriptLen = varint.value;
cursor += scriptLen + varint.getSizeInBytes();
cursor += scriptLen + varint.getOriginalSizeInBytes();
}
// 4 = length of lock_time field (uint32)
return cursor - offset + 4;

23
core/src/main/java/com/google/bitcoin/core/VarInt.java
View File

@ -20,9 +20,11 @@ import static com.google.bitcoin.core.Utils.isLessThanUnsigned;
public class VarInt {
public final long value;
private final int originallyEncodedSize;
public VarInt(long value) {
this.value = value;
originallyEncodedSize = getSizeInBytes();
}
// BitCoin has its own varint format, known in the C++ source as "compact size".
@ -32,23 +34,41 @@ public class VarInt {
if (first < 253) {
// 8 bits.
val = first;
originallyEncodedSize = 1;
} else if (first == 253) {
// 16 bits.
val = (0xFF & buf[offset + 1]) | ((0xFF & buf[offset + 2]) << 8);
originallyEncodedSize = 3;
} else if (first == 254) {
// 32 bits.
val = Utils.readUint32(buf, offset + 1);
originallyEncodedSize = 5;
} else {
// 64 bits.
val = Utils.readUint32(buf, offset + 1) | (Utils.readUint32(buf, offset + 5) << 32);
originallyEncodedSize = 9;
}
this.value = val;
}
/**
* Gets the number of bytes used to encode this originally if deserialized from a byte array.
* Otherwise returns the minimum encoded size
*/
public int getOriginalSizeInBytes() {
return originallyEncodedSize;
}
/**
* Gets the minimum encoded size of the value stored in this VarInt
*/
public int getSizeInBytes() {
return sizeOf(value);
}
/**
* Gets the minimum encoded size of the given value.
*/
public static int sizeOf(int value) {
// Java doesn't have the actual value of MAX_INT, as all types in Java are signed.
if (value < 253)
@ -58,6 +78,9 @@ public class VarInt {
return 5; // 1 marker + 4 data bytes
}
/**
* Gets the minimum encoded size of the given value.
*/
public static int sizeOf(long value) {
// Java doesn't have the actual value of MAX_INT, as all types in Java are signed.
if (isLessThanUnsigned(value, 253))