/**
* 使用当前JVM的jar包
*/
void FileMapInfo::populate_header(size_t alignment) {
_header._magic = 0xf00baba2;
_header._version = _current_version;
_header._alignment = alignment;
// The following fields are for sanity checks for whether this archive
// will function correctly with this JVM and the bootclasspath it's
// invoked with.
// JVM version string ... changes on each build.
const char *vm_version = VM_Version::internal_vm_info_string();
if (strlen(vm_version) < (JVM_IDENT_MAX-1)) {
strcpy(_header._jvm_ident, vm_version);
} else {
fail_stop("JVM Ident field for shared archive is too long"
" - truncated to <%s>", _header._jvm_ident);
}
// Build checks on classpath and jar files
_header._num_jars = 0;
ClassPathEntry *cpe = ClassLoader::classpath_entry(0);
for ( ; cpe != NULL; cpe = cpe->next()) {
if (cpe->is_jar_file()) { //jar包文件
if (_header._num_jars >= JVM_SHARED_JARS_MAX) {
fail_stop("Too many jar files to share.", NULL);
}
// Jar file - record timestamp and file size.
struct stat st;
const char *path = cpe->name();
if (os::stat(path, &st) != 0) {
// If we can't access a jar file in the boot path, then we can't
// make assumptions about where classes get loaded from.
fail_stop("Unable to open jar file %s.", path);
}
_header._jar[_header._num_jars]._timestamp = st.st_mtime;
_header._jar[_header._num_jars]._filesize = st.st_size;
_header._num_jars++;
} else {
// If directories appear in boot classpath, they must be empty to
// avoid having to verify each individual class file.
const char* name = ((ClassPathDirEntry*)cpe)->name();
if (!os::dir_is_empty(name)) {
fail_stop("Boot classpath directory %s is not empty.", name);
}
}
}
}
/**
* 检查jar包是否可共享
*/
bool FileMapInfo::validate() {
if (_header._version != current_version()) {
fail_continue("The shared archive file is the wrong version.");
return false;
}
if (_header._magic != (int)0xf00baba2) {
fail_continue("The shared archive file has a bad magic number.");
return false;
}
if (strncmp(_header._jvm_ident, VM_Version::internal_vm_info_string(),
JVM_IDENT_MAX-1) != 0) {
fail_continue("The shared archive file was created by a different"
" version or build of HotSpot.");
return false;
}
// Cannot verify interpreter yet, as it can only be created after the GC
// heap has been initialized.
if (_header._num_jars >= JVM_SHARED_JARS_MAX) {
fail_continue("Too many jar files to share.");
return false;
}
// Build checks on classpath and jar files
int num_jars_now = 0;
ClassPathEntry *cpe = ClassLoader::classpath_entry(0);
for ( ; cpe != NULL; cpe = cpe->next()) {
if (cpe->is_jar_file()) { //jar包文件
if (num_jars_now < _header._num_jars) {
// Jar file - verify timestamp and file size.
struct stat st;
const char *path = cpe->name();
if (os::stat(path, &st) != 0) {
fail_continue("Unable to open jar file %s.", path);
return false;
}
//jar包已被修改,不能共享
if (_header._jar[num_jars_now]._timestamp != st.st_mtime ||
_header._jar[num_jars_now]._filesize != st.st_size) {
fail_continue("A jar file is not the one used while building"
" the shared archive file.");
return false;
}
}
++num_jars_now;
} else {
// If directories appear in boot classpath, they must be empty to
// avoid having to verify each individual class file.
const char* name = ((ClassPathDirEntry*)cpe)->name();
if (!os::dir_is_empty(name)) { //类路径
fail_continue("Boot classpath directory %s is not empty.", name);
return false;
}
}
}
if (num_jars_now < _header._num_jars) {
fail_continue("The number of jar files in the boot classpath is"
" less than the number the shared archive was created with.");
return false;
}
return true;
}
void FileMapInfo::allocate_classpath_entry_table() {
int bytes = 0;
int count = 0;
char* strptr = NULL;
char* strptr_max = NULL;
Thread* THREAD = Thread::current();
ClassLoaderData* loader_data = ClassLoaderData::the_null_class_loader_data();
size_t entry_size = SharedClassUtil::shared_class_path_entry_size();
for (int pass=0; pass<2; pass++) {
ClassPathEntry *cpe = ClassLoader::classpath_entry(0);
for (int cur_entry = 0 ; cpe != NULL; cpe = cpe->next(), cur_entry++) {
const char *name = cpe->name();
int name_bytes = (int)(strlen(name) + 1);
if (pass == 0) {
count ++;
bytes += (int)entry_size;
bytes += name_bytes;
if (TraceClassPaths || (TraceClassLoading && Verbose)) {
tty->print_cr("[Add main shared path (%s) %s]", (cpe->is_jar_file() ? "jar" : "dir"), name);
}
} else {
SharedClassPathEntry* ent = shared_classpath(cur_entry);
if (cpe->is_jar_file()) {
struct stat st;
if (os::stat(name, &st) != 0) {
// The file/dir must exist, or it would not have been added
// into ClassLoader::classpath_entry().
//
// If we can't access a jar file in the boot path, then we can't
// make assumptions about where classes get loaded from.
FileMapInfo::fail_stop("Unable to open jar file %s.", name);
}
EXCEPTION_MARK; // The following call should never throw, but would exit VM on error.
SharedClassUtil::update_shared_classpath(cpe, ent, st.st_mtime, st.st_size, THREAD);
} else {
ent->_filesize = -1;
if (!os::dir_is_empty(name)) {
ClassLoader::exit_with_path_failure("Cannot have non-empty directory in archived classpaths", name);
}
}
ent->_name = strptr;
if (strptr + name_bytes <= strptr_max) {
strncpy(strptr, name, (size_t)name_bytes); // name_bytes includes trailing 0.
strptr += name_bytes;
} else {
assert(0, "miscalculated buffer size");
}
}
}
if (pass == 0) {
EXCEPTION_MARK; // The following call should never throw, but would exit VM on error.
Array<u8>* arr = MetadataFactory::new_array<u8>(loader_data, (bytes + 7)/8, THREAD);
strptr = (char*)(arr->data());
strptr_max = strptr + bytes;
SharedClassPathEntry* table = (SharedClassPathEntry*)strptr;
strptr += entry_size * count;
_classpath_entry_table_size = count;
_classpath_entry_table = table;
_classpath_entry_size = entry_size;
}
}
}
