JACOBIN-605 Code cleanup and comment expansion in codeCheck.go

platypusguy · Jan 6, 2025 · 5b58df8 · 5b58df8
1 parent 69351f5
commit 5b58df8
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Showing 2 changed files with 68 additions and 59 deletions.
diff --git a/src/classloader/codeCheck.go b/src/classloader/codeCheck.go
@@ -1,6 +1,6 @@
 /*
  * Jacobin VM - A Java virtual machine
- * Copyright (c) 2024 by the Jacobin Authors. All rights reserved.
+ * Copyright (c) 2024-5 by the Jacobin Authors. All rights reserved.
  * Licensed under Mozilla Public License 2.0 (MPL 2.0)  Consult jacobin.org.
  */
 
@@ -22,6 +22,9 @@ import (
 // to performs the check. It then uses the skip table to determine the number of bytes
 // to skip to the next bytecode. If an error occurs, a ClassFormatException is thrown.
 
+// NOTE: The unit tests for these functions are in codeCheck_test.go in the jvm directory.
+// Placed there to avoid circular dependencies.
+
 var bytecodeSkipTable = map[byte]int{
 	0x00: 1, // NOP
 	0x01: 1, // ACONST_NULL
@@ -484,6 +487,8 @@ func CheckCodeValidity(code []byte, cp *CPool) error {
 }
 
 // === check functions in alpha order by name of bytecode ===
+
+// GOTO 0xA7
 func checkGoto() int {
 	jumpTo := int(int16(Code[PC+1])*256 + int16(Code[PC+2]))
 	if PC+jumpTo < 0 || PC+jumpTo >= len(Code) {
@@ -492,6 +497,7 @@ func checkGoto() int {
 	return 3
 }
 
+// GOTO_W 0xC8
 func checkGotow() int {
 	jumpTo := int(types.FourBytesToInt64(Code[PC+1], Code[PC+2], Code[PC+3], Code[PC+4]))
 	if PC+jumpTo < 0 || PC+jumpTo >= len(Code) {
@@ -500,47 +506,7 @@ func checkGotow() int {
 	return 5
 }
 
-func checkLookupswitch() int { // need to check this
-	basePC := PC
-
-	paddingBytes := 4 - ((PC + 1) % 4)
-	if paddingBytes == 4 {
-		paddingBytes = 0
-	}
-	basePC += paddingBytes
-	basePC += 4 // jump size for default
-
-	npairs := binary.BigEndian.Uint32(
-		[]byte{Code[basePC+1], Code[basePC+2], Code[basePC+3], Code[basePC+4]})
-
-	basePC += 4
-	basePC += int(npairs) * 8
-
-	return (basePC - PC) + 1
-}
-
-func checkTableswitch() int {
-	basePC := PC
-
-	paddingBytes := 4 - ((PC + 1) % 4)
-	if paddingBytes == 4 {
-		paddingBytes = 0
-	}
-	basePC += paddingBytes
-	basePC += 4 // jump size for default
-	low := types.FourBytesToInt64(Code[basePC+1], Code[basePC+2], Code[basePC+3], Code[basePC+4])
-	high := types.FourBytesToInt64(Code[basePC+5], Code[basePC+6], Code[basePC+7], Code[basePC+8])
-	basePC += 8 // 4 bytes for low, 4 bytes for high
-
-	if !(low <= high) {
-		return ERROR_OCCURRED
-	}
-
-	offsetsCount := high - low + 1
-	basePC += int(offsetsCount) * 4
-	return (basePC - PC) + 1
-}
-
+// IF_ACMPEQ 0xA5 (and the many other IF* bytecodes)
 func checkIf() int { // most IF* bytecodes come here. Jump if condition is met
 	jumpSize := int(int16(Code[PC+1])*256 + int16(Code[PC+2]))
 	if PC+jumpSize < 0 || PC+jumpSize >= len(Code) {
@@ -549,27 +515,27 @@ func checkIf() int { // most IF* bytecodes come here. Jump if condition is met
 	return 3
 }
 
-// INVOKEVIRTUAL 0xB6
-func checkInvokevirtual() int {
-	// check that the index points to a method reference in the CP
+// INVOKESPECIAL 0xB7
+func checkInvokespecial() int {
+	// check that the index points to a method or interface reference in the CP
 	CPslot := (int(Code[PC+1]) * 256) + int(Code[PC+2]) // next 2 bytes point to CP entry
 	if CPslot < 1 || CPslot >= len(CP.CpIndex) {
 		return ERROR_OCCURRED
 	}
 
 	CPentry := CP.CpIndex[CPslot]
-	if CPentry.Type != MethodRef {
-		// because this is not a ClassFormatError, we emit a trace message here
-		errMsg := fmt.Sprintf("%s:\n INVOKEVIRTUAL at %d: CP entry (%d) is not a method reference",
+	if CPentry.Type != MethodRef && CPentry.Type != Interface {
+		// because this is not a ClassFormatError, we output a trace error message here
+		errMsg := fmt.Sprintf("%s:\n INVOKESPECIAL at %d: CP entry (%d) is not a method or interface reference",
 			excNames.JVMexceptionNames[excNames.VerifyError], PC, CPentry.Type)
 		trace.Error(errMsg)
 		return ERROR_OCCURRED
 	}
 	return 3
 }
 
-// INVOKESPECIAL 0xB7
-func checkInvokespecial() int {
+// INVOKESTATIC 0xB8
+func checkInvokestatic() int {
 	// check that the index points to a method or interface reference in the CP
 	CPslot := (int(Code[PC+1]) * 256) + int(Code[PC+2]) // next 2 bytes point to CP entry
 	if CPslot < 1 || CPslot >= len(CP.CpIndex) {
@@ -578,34 +544,77 @@ func checkInvokespecial() int {
 
 	CPentry := CP.CpIndex[CPslot]
 	if CPentry.Type != MethodRef && CPentry.Type != Interface {
-		// because this is not a ClassFormatError, we output a trace error message here
-		errMsg := fmt.Sprintf("%s:\n INVOKESPECIAL at %d: CP entry (%d) is not a method or interface reference",
+		// because this is not a ClassFormatError, we output a trace message here
+		errMsg := fmt.Sprintf("%s:\n INVOKESTATIC at %d: CP entry (%d) is not a method or interface reference",
 			excNames.JVMexceptionNames[excNames.VerifyError], PC, CPentry.Type)
 		trace.Error(errMsg)
 		return ERROR_OCCURRED
 	}
 	return 3
 }
 
-// INVOKESTATIC 0xB8
-func checkInvokestatic() int {
-	// check that the index points to a method or interface reference in the CP
+// INVOKEVIRTUAL 0xB6
+func checkInvokevirtual() int {
+	// check that the index points to a method reference in the CP
 	CPslot := (int(Code[PC+1]) * 256) + int(Code[PC+2]) // next 2 bytes point to CP entry
 	if CPslot < 1 || CPslot >= len(CP.CpIndex) {
 		return ERROR_OCCURRED
 	}
 
 	CPentry := CP.CpIndex[CPslot]
-	if CPentry.Type != MethodRef && CPentry.Type != Interface {
-		// because this is not a ClassFormatError, we output a trace message here
-		errMsg := fmt.Sprintf("%s:\n INVOKESTATIC at %d: CP entry (%d) is not a method or interface reference",
+	if CPentry.Type != MethodRef {
+		// because this is not a ClassFormatError, we emit a trace message here
+		errMsg := fmt.Sprintf("%s:\n INVOKEVIRTUAL at %d: CP entry (%d) is not a method reference",
 			excNames.JVMexceptionNames[excNames.VerifyError], PC, CPentry.Type)
 		trace.Error(errMsg)
 		return ERROR_OCCURRED
 	}
 	return 3
 }
 
+// LOOKUPSWITCH 0xAB
+func checkLookupswitch() int { // need to check this
+	basePC := PC
+
+	paddingBytes := 4 - ((PC + 1) % 4)
+	if paddingBytes == 4 {
+		paddingBytes = 0
+	}
+	basePC += paddingBytes
+	basePC += 4 // jump size for default
+
+	npairs := binary.BigEndian.Uint32(
+		[]byte{Code[basePC+1], Code[basePC+2], Code[basePC+3], Code[basePC+4]})
+
+	basePC += 4
+	basePC += int(npairs) * 8
+
+	return (basePC - PC) + 1
+}
+
+// TABLESWITCH 0xAA
+func checkTableswitch() int {
+	basePC := PC
+
+	paddingBytes := 4 - ((PC + 1) % 4)
+	if paddingBytes == 4 {
+		paddingBytes = 0
+	}
+	basePC += paddingBytes
+	basePC += 4 // jump size for default
+	low := types.FourBytesToInt64(Code[basePC+1], Code[basePC+2], Code[basePC+3], Code[basePC+4])
+	high := types.FourBytesToInt64(Code[basePC+5], Code[basePC+6], Code[basePC+7], Code[basePC+8])
+	basePC += 8 // 4 bytes for low, 4 bytes for high
+
+	if !(low <= high) {
+		return ERROR_OCCURRED
+	}
+
+	offsetsCount := high - low + 1
+	basePC += int(offsetsCount) * 4
+	return (basePC - PC) + 1
+}
+
 // === utility functions ===
 
 // a one-byte opcode that has nothing that can be checked

diff --git a/src/config/buildno.go b/src/config/buildno.go
@@ -8,4 +8,4 @@
 
 package config
 
-var BuildNo = 3411
+var BuildNo = 3413
Original file line number	Diff line number	Diff line change
Expand Up		@@ -8,4 +8,4 @@

		package config

		var BuildNo = 3411
		var BuildNo = 3413