typedef jint (JNICALL *CreateJavaVM_t)(JavaVM **pvm, void **env, void *args);
typedef jint (JNICALL *GetDefaultJavaVMInitArgs_t)(void *args);
typedef struct {
CreateJavaVM_t CreateJavaVM;
GetDefaultJavaVMInitArgs_t GetDefaultJavaVMInitArgs;
} InvocationFunctions;
jvm在启动的时候,会dlopen libjvm.so,从而定位符号JNI_CreateJavaVM和JNI_GetDefaultJavaVMInitArgs进行初始化
2、jvm的初始化属性
typedef struct JavaVMOption {
char *optionString;
void *extraInfo;
} JavaVMOption;
typedef struct JavaVMInitArgs {
jint version;
jint nOptions;
JavaVMOption *options;
jboolean ignoreUnrecognized;
} JavaVMInitArgs;
3、zip文件,用于加载jar包中的资源文件
typedef void* jzfile; //zip文件句柄
typedef struct {
char *name; /* entry name */
jlong time; /* modification time */
jlong size; /* size of uncompressed data */
jlong csize; /* size of compressed data (zero if uncompressed) */
jint crc; /* crc of uncompressed data */
char *comment; /* optional zip file comment */
jbyte *extra; /* optional extra data */
jlong pos; /* position of LOC header (if negative) or data */
} jzentry;
typedef void * * (JNICALL *ZipOpen_t)(const char *name, char **pmsg);
typedef void (JNICALL *ZipClose_t)(jzfile *zip);
typedef jzentry* (JNICALL *FindEntry_t)(jzfile *zip, const char *name, jint *sizeP, jint *nameLen);
typedef jboolean (JNICALL *ReadEntry_t)(jzfile *zip, jzentry *entry, unsigned char *buf, char *namebuf);
typedef jboolean (JNICALL *ReadMappedEntry_t)(jzfile *zip, jzentry *entry, unsigned char **buf, char *namebuf);
typedef jzentry* (JNICALL *GetNextEntry_t)(jzfile *zip, jint n);
初始化方法是动态加载libzip.so的ZIP_Open、Zip_Close、Zip_FindEntry等等方法
4、句柄
class Handle VALUE_OBJ_CLASS_SPEC {
private:
oop* _handle;
protected:
oop obj() const { return _handle == NULL ? (oop)NULL : *_handle; }
oop non_null_obj() const { assert(_handle != NULL, "resolving NULL handle"); return *_handle; }
public:
// Constructors
Handle() { _handle = NULL; }
Handle(oop obj);
#ifndef ASSERT
Handle(Thread* thread, oop obj);
#else
// Don't inline body with assert for current thread
Handle(Thread* thread, oop obj);
#endif // ASSERT
// General access
oop operator () () const { return obj(); }
oop operator -> () const { return non_null_obj(); }
bool operator == (oop o) const { return obj() == o; }
bool operator == (const Handle& h) const { return obj() == h.obj(); }
// Null checks
bool is_null() const { return _handle == NULL; }
bool not_null() const { return _handle != NULL; }
// Debugging
void print() { obj()->print(); }
// Direct interface, use very sparingly.
// Used by JavaCalls to quickly convert handles and to create handles static data structures.
// Constructor takes a dummy argument to prevent unintentional type conversion in C++.
Handle(oop *handle, bool dummy) { _handle = handle; }
// Raw handle access. Allows easy duplication of Handles. This can be very unsafe
// since duplicates is only valid as long as original handle is alive.
oop* raw_value() { return _handle; }
static oop raw_resolve(oop *handle) { return handle == NULL ? (oop)NULL : *handle; }
};
//------------------------------------------------------------------------------------------------------------------------
// Base class for Handles containing klassOops. Provides overloading of frequently
// used operators for ease of use and typed access to the Klass part.
class KlassHandle: public Handle {
protected:
klassOop obj() const { return (klassOop)Handle::obj(); }
klassOop non_null_obj() const { return (klassOop)Handle::non_null_obj(); }
Klass* as_klass() const { return non_null_obj()->klass_part(); }
public:
// Constructors
KlassHandle () : Handle() {}
KlassHandle (oop obj) : Handle(obj) {
assert(SharedSkipVerify || is_null() || obj->is_klass(), "not a klassOop");
}
KlassHandle (Klass* kl) : Handle(kl ? kl->as_klassOop() : (klassOop)NULL) {
assert(SharedSkipVerify || is_null() || obj()->is_klass(), "not a klassOop");
}
// Faster versions passing Thread
KlassHandle (Thread* thread, oop obj) : Handle(thread, obj) {
assert(SharedSkipVerify || is_null() || obj->is_klass(), "not a klassOop");
}
KlassHandle (Thread *thread, Klass* kl)
: Handle(thread, kl ? kl->as_klassOop() : (klassOop)NULL) {
assert(is_null() || obj()->is_klass(), "not a klassOop");
}
// Direct interface, use very sparingly.
// Used by SystemDictionaryHandles to create handles on existing WKKs.
// The obj of such a klass handle may be null, because the handle is formed
// during system bootstrapping.
KlassHandle(klassOop *handle, bool dummy) : Handle((oop*)handle, dummy) {
assert(SharedSkipVerify || is_null() || obj() == NULL || obj()->is_klass(), "not a klassOop");
}
// General access
klassOop operator () () const { return obj(); }
Klass* operator -> () const { return as_klass(); }
};
用来对OOP进行包装,在JVM内部直接使用的都是Handle
5、重要的变量
hotspot/src/share/vm/utilities/globalDefinitions.hpp
// Info for oops within a java object. Defaults are zero so
// things will break badly if incorrectly initialized.
int heapOopSize = 0;
int LogBytesPerHeapOop = 0;
int LogBitsPerHeapOop = 0;
int BytesPerHeapOop = 0;
int BitsPerHeapOop = 0;
// Object alignment, in units of HeapWords.
// Defaults are -1 so things will break badly if incorrectly initialized.
int MinObjAlignment = -1;
int MinObjAlignmentInBytes = -1;
int MinObjAlignmentInBytesMask = 0;
int LogMinObjAlignment = -1;
int LogMinObjAlignmentInBytes = -1;
6、常用的参数
#define THREAD __the_thread__
#define TRAPS Thread* THREAD
用于便于抛出异常,一般TRAPS作为函数的最后一个参数存在
7、GC分代类型
enum Name {
ASParNew,
ASConcurrentMarkSweep,
DefNew,
ParNew,
MarkSweepCompact,
ConcurrentMarkSweep,
Other
};
8、全局性的参数变量定义
详见:hotspot/src/share/vm/runtime/globals.hpp