#include "jvm.h"
#include "utf8.h"
#include "natives.h"
#include "instructions.h"
#include "debugging.h"
#include <string.h>

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Functions
void	initJVM (JavaVirtualMachine *jvm)
	Initializes a JavaVirtualMachine structure. More...

void	deinitJVM (JavaVirtualMachine *jvm)
	Deallocates all memory used by the JavaVirtualMachine structure. More...

void	executeJVM (JavaVirtualMachine jvm, LoadedClasses mainClass)
	Executes the main method of a given class. More...

void	setClassPath (JavaVirtualMachine jvm, const char path)
	Will set the path to look for classes when opening them. More...

uint8_t	resolveClass (JavaVirtualMachine jvm, const uint8_t className_utf8_bytes, int32_t utf8_len, LoadedClasses **outClass)
	Loads a .class file without initializing it. More...

uint8_t	resolveMethod (JavaVirtualMachine jvm, JavaClass jc, cp_info cp_method, LoadedClasses *outClass)
	Resolves a method. More...

uint8_t	resolveField (JavaVirtualMachine jvm, JavaClass jc, cp_info cp_field, LoadedClasses *outClass)
	Resolves a field. More...

uint8_t	runMethod (JavaVirtualMachine jvm, JavaClass jc, method_info *method, uint8_t numberOfParameters)
	Executes the bytecode of a given method. More...

uint8_t	getMethodDescriptorParameterCount (const uint8_t *descriptor_utf8, int32_t utf8_len)
	Gets how many operands a method descriptor requires. More...

LoadedClasses *	addClassToLoadedClasses (JavaVirtualMachine jvm, JavaClass jc)
	Adds a class to the list of all loaded classes by the JVM. More...

LoadedClasses *	isClassLoaded (JavaVirtualMachine jvm, const uint8_t utf8_bytes, int32_t utf8_len)
	Checks if a class has already been loaded by its name. More...

JavaClass *	getSuperClass (JavaVirtualMachine jvm, JavaClass jc)
	Gets the super class of a given class. More...

uint8_t	isClassSuperOf (JavaVirtualMachine jvm, JavaClass super, JavaClass *jc)
	Check if one class is a super class of another. More...

uint8_t	initClass (JavaVirtualMachine jvm, LoadedClasses lc)
	Initializes a class. More...

Reference *	newString (JavaVirtualMachine jvm, const uint8_t str, int32_t strlen)

Reference *	newClassInstance (JavaVirtualMachine jvm, LoadedClasses lc)

Reference *	newArray (JavaVirtualMachine *jvm, uint32_t length, Opcode_newarray_type type)

Reference *	newObjectArray (JavaVirtualMachine jvm, uint32_t length, const uint8_t utf8_className, int32_t utf8_len)

Reference *	newObjectMultiArray (JavaVirtualMachine jvm, int32_t dimensions, uint8_t dimensionsSize, const uint8_t *utf8_className, int32_t utf8_len)

void	deleteReference (Reference *obj)

Function Documentation

§ addClassToLoadedClasses()

LoadedClasses* addClassToLoadedClasses	(	JavaVirtualMachine *	jvm,
		JavaClass *	jc
	)

Adds a class to the list of all loaded classes by the JVM.

Parameters

JavaVirtualMachine*	jvm - the JVM that has loaded the given class
JavaClass*	jc - a class that has already been loaded and will be added to the list.

Returns: The node created to store the class.

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§ deinitJVM()

void deinitJVM ( JavaVirtualMachine * jvm )

Deallocates all memory used by the JavaVirtualMachine structure.

Parameters

JavaVirtualMachine* jvm - pointer to the structure to be deallocated.

All loaded classes and objects created during the execution of the JVM will be freed.

See also: initJVM()

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§ deleteReference()

void deleteReference ( Reference * obj )

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§ executeJVM()

void executeJVM	(	JavaVirtualMachine *	jvm,
		LoadedClasses *	mainClass
	)

Executes the main method of a given class.

Parameters

JavaVirtualMachine*	jvm - pointer to an already initialized JVM structure.
LoadedClasses*	mainClass - pointer to a class that has been loaded and contains the public void static main method.

If mainClass is a null pointer, the class at the top of the stack of loaded classes will be used as entry point. If no classes are loaded, then the status of the JVM will be changed to JVM_STATUS_MAIN_METHOD_NOT_FOUND. If mainClass is not a null pointer, the class must have been previously resolved with a call to resolveClass().

See also: resolveClass(), JavaClass

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§ getMethodDescriptorParameterCount()

uint8_t getMethodDescriptorParameterCount	(	const uint8_t *	descriptor_utf8,
		int32_t	utf8_len
	)

Gets how many operands a method descriptor requires.

Parameters

const	uint8_t* descriptor_utf8 - UTF-8 string containing the method descriptor
int32_t	utf8_len - length of the UTF-8 string

This function counts how many operands (which are 32-bit integers) are needed from a function with the given descriptor. For example, the following method:

public int mymethod(long a, byte b)

will have the following descriptor: (JB)I. When called, this method would require 3 operands to be passed as parameter, 2 to form the 64-bit long variable, and another one to form the 32-bit byte variable. A call to this function with that example descriptor will return 3, meaning that three operands should be popped from a caller frame and pushed to the callee frame.

Returns: Number of operands that need to be handled when calling a method with the given descriptor.

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§ getSuperClass()

JavaClass* getSuperClass	(	JavaVirtualMachine *	jvm,
		JavaClass *	jc
	)

Gets the super class of a given class.

Parameters

JavaVirtualMachine*	jvm - the JVM that contains the classes
JavaClass*	jc - the class that will have its super class seached.

Returns: If the class is found, returns it. Otherwise, returns NULL.

Note: This function performs a linear search, by calling isClassLoaded().

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§ initClass()

uint8_t initClass	(	JavaVirtualMachine *	jvm,
		LoadedClasses *	lc
	)

Initializes a class.

Parameters

JavaVirtualMachine*	jvm - the JVM that is being executed
LoadedClasses*	lc - node of the list of loaded classes that holds the class to be initialized.

Class initialization is done by allocating memory for the class static data. The number of bytes necessary to hold the static data is determined when the class file is opened and parsed (openClassFile()). The static data is also initialized if the static fields have a ConstantValue attribute. After allocating the static data, the method <clinit> of the class will be called, if it exists. Even if this function is called several times, class initialization is performed only once.

Returns: Will return 1 if the initialization was completed successfully. Otherwise, 0. Initialization could fail if there wasn't enough memory to allocate space for the static data or if there were any problems running its <clinit> method.

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§ initJVM()

void initJVM ( JavaVirtualMachine * jvm )

Initializes a JavaVirtualMachine structure.

Parameters

JavaVirtualMachine* jvm - pointer to the structure to be initialized.

This function must be called before calling other JavaVirtualMachine functions.

See also: executeJVM(), deinitJVM()

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§ isClassLoaded()

LoadedClasses* isClassLoaded	(	JavaVirtualMachine *	jvm,
		const uint8_t *	utf8_bytes,
		int32_t	utf8_len
	)

Checks if a class has already been loaded by its name.

Parameters

JavaVirtualMachine*	jvm - the JVM that contains a loaded clases list.
const	uint8_t* utf8_bytes - UTF-8 string containing the class name to be searched.
int32_t	utf8_len - length of the UTF-8 string.

Returns: If the class is found, returns the node containing that loaded class. Otherwise, returns NULL.

Note: This function performs a linear search.

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§ isClassSuperOf()

uint8_t isClassSuperOf	(	JavaVirtualMachine *	jvm,
		JavaClass *	super,
		JavaClass *	jc
	)

Check if one class is a super class of another.

Parameters

JavaVirtualMachine*	jvm - the JVM that holds both classes
JavaClass*	super - a class that will be checked to see if it is extended by jc.
JavaClass*	jc - the class that will be checked to see if it extends super.

Precondition: Both super and jc must be classes that have already been loaded.

Note: If super and jc point to the same class, the function returns false.

Returns: Will return 1 if super is a super class of jc. Otherwise, 0.

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§ newArray()

Reference* newArray	(	JavaVirtualMachine *	jvm,
		uint32_t	length,
		Opcode_newarray_type	type
	)

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§ newClassInstance()

Reference* newClassInstance	(	JavaVirtualMachine *	jvm,
		LoadedClasses *	lc
	)

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§ newObjectArray()

Reference* newObjectArray	(	JavaVirtualMachine *	jvm,
		uint32_t	length,
		const uint8_t *	utf8_className,
		int32_t	utf8_len
	)

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§ newObjectMultiArray()

Reference* newObjectMultiArray	(	JavaVirtualMachine *	jvm,
		int32_t *	dimensions,
		uint8_t	dimensionsSize,
		const uint8_t *	utf8_className,
		int32_t	utf8_len
	)

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§ newString()

Reference* newString	(	JavaVirtualMachine *	jvm,
		const uint8_t *	str,
		int32_t	strlen
	)

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§ resolveClass()

uint8_t resolveClass	(	JavaVirtualMachine *	jvm,
		const uint8_t *	className_utf8_bytes,
		int32_t	utf8_len,
		LoadedClasses **	outClass
	)

Loads a .class file without initializing it.

Parameters

	JavaVirtualMachine*	jvm - pointer to the JVM structure that is resolving the class
	const	uint8_t* className_utf8_bytes - UTF-8 bytes containing the class name.
	int32_t	utf8_len - length of the UTF-8 class name
[out]	LoadedClasses**	outClass - the class that has been resolved, as an element of the loaded classes table of the JVM.

This function will open the class file and read its content. All interfaces and super classes are also resolved. During class resolution, the amount of bytes required to hold an instance of that class is determined. The class will not be initialized, which means that the static data won't be allocated and the method <clinit> won't be called. To initialize a class, the function initClass() needs to be called. Class resolution may be triggered by resolution of fields, methods or some instructions that refer to classes (getstatic, new etc). All resolved classes will be added to the list of all loaded classes of the JVM. If the parameter outClass is not null, it will receive the node containig the already loaded class that was resolved by a call to this function.

Returns: Will return 1 if the resolution was completed successfully, otherwise 0. Resolution may fail if there was a problem opening and parsing any of the class files, may it be the class being resolved or a super class or interface.

See also: initClass(), resolveField(), resolveMethod()

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§ resolveField()

uint8_t resolveField	(	JavaVirtualMachine *	jvm,
		JavaClass *	jc,
		cp_info *	cp_field,
		LoadedClasses **	outClass
	)

Resolves a field.

Parameters

	JavaVirtualMachine*	jvm - pointer to the JVM structure that is running
	JavaClass*	jc - pointer to the class that holds the field being resolved in its constant pool
	cp_info*	cp_method - pointer to the element in the constant pool that contains the field to be resolved. Must be a CONSTANT_Fieldref CP entry.
[out]	LoadedClasses**	outClass - the class that contains the field that has been resolved, as an element of the loaded classes table of the JVM.

Field resolution means to resolve the class that declared the field and type of the field, if it is a class. If the type of the field is a class, then it will also be resolved, with a call to resolveClass(). The resolved classes will be added to the list of all loaded classes of the JVM. If the parameter outClass is not null, it will receive the node containig the already loaded class that declared that field.

Returns: Will return 1 if the resolution was completed successfully, otherwise 0. Resolution may fail if there was a problem with possible calls to resolveClass().

See also: resolveClass()

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§ resolveMethod()

uint8_t resolveMethod	(	JavaVirtualMachine *	jvm,
		JavaClass *	jc,
		cp_info *	cp_method,
		LoadedClasses **	outClass
	)

Resolves a method.

Parameters

	JavaVirtualMachine*	jvm - pointer to the JVM structure that is running
	JavaClass*	jc - pointer to the class that holds the method being resolved in its constant pool
	cp_info*	cp_method - pointer to the element in the constant pool that contains the method to be resolved. Must be a CONSTANT_Methodref CP entry.
[out]	LoadedClasses**	outClass - the class that contains the method that has been resolved, as an element of the loaded classes table of the JVM.

Method resolution means to resolve possible classes in its parameters or return type, and the class in which the method is defined. All identified classes will also be resolved, with a call to resolveClass(). All resolved classes will be added to the list of all loaded classes of the JVM. If the parameter outClass is not null, it will receive the node containig the already loaded class that declared that method.

Returns: Will return 1 if the resolution was completed successfully, otherwise 0. Resolution may fail if there was a problem with possible calls to resolveClass().

See also: resolveField(), resolveClass()

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§ runMethod()

uint8_t runMethod	(	JavaVirtualMachine *	jvm,
		JavaClass *	jc,
		method_info *	method,
		uint8_t	numberOfParameters
	)

Executes the bytecode of a given method.

Parameters

JavaVirtualMachine*	jvm - pointer to the JVM structure that is running.
JavaClass*	jc - pointer to the class that contains the method that will be executed.
method_info*	method - pointer to method that will be executed.
uint8_t	numberOfParameters - number of operands that need to be popped from the top frame and pushed to the frame that will be created to execute the given method (parameter passing).

This function will create a new frame and push it in the stack of frame of the JVM (FrameStack). To see what a frame is and why it is necessary, check documentation of Frame. Instruction will be fetched one by one and executed until there is no more code to be executed from this method. Then the frame will be popped.

Returns: Will return 1 if the execution was completed successfully, otherwise 0. Execution will fail if there was a problem running an instruction or some other problems, like insufficient memory, unsupported feature/instruction, unimplemented native method, etc.

See also: resolveClass()

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§ setClassPath()

void setClassPath	(	JavaVirtualMachine *	jvm,
		const char *	path
	)

Will set the path to look for classes when opening them.

Parameters

JavaVirtualMachine*	jvm - The JVM that will load classes.
const	char* path - The string containing the path.

Note: The JVM will always look for the class in the current working directory first, and then (if the file couldn't be found) look for it in the class path.

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Functions

Function Documentation

§ addClassToLoadedClasses()

§ deinitJVM()

§ deleteReference()

§ executeJVM()

§ getMethodDescriptorParameterCount()

§ getSuperClass()

§ initClass()

§ initJVM()

§ isClassLoaded()

§ isClassSuperOf()

§ newArray()

§ newClassInstance()

§ newObjectArray()

§ newObjectMultiArray()

§ newString()

§ resolveClass()

§ resolveField()

§ resolveMethod()

§ runMethod()

§ setClassPath()