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#4 Opcode parser to support branch byte
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@amosshi
amosshi committed Sep 1, 2019
1 parent aea5446 commit 6c4c9b4
Showing 1 changed file with 48 additions and 24 deletions.
72 changes: 48 additions & 24 deletions FormatCLASS/src/main/java/org/freeinternals/format/classfile/Opcode.java
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,11 @@ public static enum Instruction {
* {@link #instanceof_}.
*
* @return The postfix "_" from the name
*
* @see #goto_
* @see #return_
* @see #new_
* @see #instanceof_
*/
String getName() {
String name = super.name();
Expand Down Expand Up @@ -938,42 +943,42 @@ private static InstructionParsed parseInstruction(final PosDataInputStream pdis)
// Execution then proceeds at that offset from the address of the opCode of this if<cond> instruction.
// The target address must be that of an opCode of an instruction within the method that contains this if<cond> instruction.
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.ifeq.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.ifeq.name();
} else if (Opcode.Instruction.ifne.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.ifne.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.ifne.name();
} else if (Opcode.Instruction.iflt.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.iflt.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.iflt.name();
} else if (Opcode.Instruction.ifge.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.ifge.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.ifge.name();
} else if (Opcode.Instruction.ifgt.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.ifgt.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.ifgt.name();
} else if (Opcode.Instruction.ifle.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.ifle.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.ifle.name();
} else if (Opcode.Instruction.if_icmpeq.code == opcode) {
// if_icmp<cond>: if_icmpeq = 159 (0x9f) if_icmpne = 160 (0xa0) if_icmplt = 161 (0xa1) if_icmpge = 162 (0xa2) if_icmpgt = 163 (0xa3) if_icmple = 164 (0xa4)
// Branch if int comparison succeeds
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.if_icmpeq.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_icmpeq.name();
} else if (Opcode.Instruction.if_icmpne.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.if_icmpne.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_icmpne.name();
} else if (Opcode.Instruction.if_icmplt.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.if_icmplt.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_icmplt.name();
} else if (Opcode.Instruction.if_icmpge.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, result.opCodeText = Opcode.Instruction.if_icmpge.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_icmpge.name();
} else if (Opcode.Instruction.if_icmpgt.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.if_icmpgt.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_icmpgt.name();
} else if (Opcode.Instruction.if_icmple.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.if_icmple.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_icmple.name();
} else if (Opcode.Instruction.if_acmpeq.code == opcode) {
// if_acmp<cond>: if_acmpeq = 165 (0xa5) if_acmpne = 166 (0xa6)
// Branch if reference comparison succeeds
Expand All @@ -985,18 +990,18 @@ private static InstructionParsed parseInstruction(final PosDataInputStream pdis)
// Execution then proceeds at that offset from the address of the opCode of this if_acmp<cond> instruction.
// The target address must be that of an opCode of an instruction within the method that contains this if_acmp<cond> instruction.
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.if_acmpeq.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_acmpeq.name();
} else if (Opcode.Instruction.if_acmpne.code == opcode) {
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.if_acmpne.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.if_acmpne.name();
} else if (Opcode.Instruction.goto_.code == opcode) {
// Branch always
// The unsigned bytes branchbyte1 and branchbyte2 are used to construct a signed 16-bit branchoffset,
// where branchoffset is (branchbyte1 << 8) | branchbyte2.
// Execution proceeds at that offset from the address of the opCode of this goto instruction.
// The target address must be that of an opCode of an instruction within the method that contains this goto instruction.
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.goto_.getName(), result.branchbyte);
result.opCodeText = Opcode.Instruction.goto_.getName();
} else if (Opcode.Instruction.jsr.code == opcode) {
// Jump subroutine
// The address of the opCode of the instruction immediately following this jsr instruction
Expand All @@ -1006,7 +1011,7 @@ private static InstructionParsed parseInstruction(final PosDataInputStream pdis)
// Execution proceeds at that offset from the address of this jsr instruction.
// The target address must be that of an opCode of an instruction within the method that contains this jsr instruction.
result.branchbyte = Integer.valueOf(pdis.readShort());
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.jsr.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.jsr.name();
} else if (Opcode.Instruction.ret.code == opcode) {
// Return from subroutine
// The index is an unsigned byte between 0 and 255, inclusive.
Expand Down Expand Up @@ -1166,23 +1171,23 @@ private static InstructionParsed parseInstruction(final PosDataInputStream pdis)
} else if (Opcode.Instruction.ifnull.code == opcode) {
// Branch if reference is null
result.branchbyte = pdis.readUnsignedShort();
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.ifnull.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.ifnull.name();
} else if (Opcode.Instruction.ifnonnull.code == opcode) {
// Branch if reference not null
result.branchbyte = pdis.readUnsignedShort();
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.ifnonnull.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.ifnonnull.name();
} else if (Opcode.Instruction.goto_w.code == opcode) {
// Branch always (wide index)
result.branchbyte = pdis.readInt();
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.goto_w.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.goto_w.name();
} else if (Opcode.Instruction.jsr_w.code == opcode) {
// Jump subroutine (wide index)
// --
// The unsigned branchbyte1, branchbyte2, branchbyte3, and branchbyte4 are used to
// construct a signed 32-bit offset, where the offset is
// (branchbyte1 << 24) | (branchbyte2 << 16) | (branchbyte3 << 8) | branchbyte4.
result.branchbyte = pdis.readInt();
result.opCodeText = String.format(FORMAT_OPCODE_LOCAL, Opcode.Instruction.jsr_w.name(), result.branchbyte);
result.opCodeText = Opcode.Instruction.jsr_w.name();
} else if (Opcode.Instruction.breakpoint.code == opcode) {
// Reserved opcodes
result.opCodeText = Opcode.Instruction.breakpoint.name();
Expand Down Expand Up @@ -1372,6 +1377,16 @@ public static class InstructionParsed {
this.opCode = opcode;
}

/**
* Get the absolute value of the branch byte, if {@link #branchbyte} is not null.
*
* @return Absolute value of the {@link #branchbyte}; return <code>null</code> in case {@link #branchbyte} is null
* @see #branchbyte
*/
public Integer getAbsoluteBranchByte(){
return (this.branchbyte != null) ? this.offset + this.branchbyte : null;
}

/**
* Getter for {@link #opCodeText}.
*
Expand All @@ -1392,7 +1407,14 @@ public Integer getCpindex() {

@Override
public String toString() {
return String.format("offset %04d: opcode [%02X] %s", this.offset, this.opCode, this.opCodeText);
String s = String.format("offset %04d: opcode [%02X] %s", this.offset, this.opCode, this.opCodeText);

if (this.branchbyte != null) {
String branch = String.format(" %d (branch byte offset = %d)", this.getAbsoluteBranchByte(), this.branchbyte);
s += branch;
}

return s;
}

/**
Expand All @@ -1403,16 +1425,18 @@ public String toString() {
* @return {@link Instruction} analysis result
*/
public String toString(ClassFile cf) {
String s = this.toString();

if (this.cpIndex != null) {
String cpDesc = cf.getCPDescription(this.cpIndex);
// Avoid too long description
if (cpDesc.length() > 1000) {
cpDesc = cpDesc.substring(1, 1000);
}
return this.toString() + " - " + cpDesc;
} else {
return this.toString();
s = s + " - " + cpDesc;
}

return s;
}
}
}

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