Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/classLoader.hpp"

 #include "classfile/javaClasses.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "classfile/vmSymbols.hpp"

 #include "code/icBuffer.hpp"

 #include "code/vtableStubs.hpp"

 #include "gc_implementation/shared/vmGCOperations.hpp"

 #include "interpreter/interpreter.hpp"

 #include "memory/allocation.inline.hpp"

 #include "oops/oop.inline.hpp"

 #include "prims/jvm.h"

 #include "prims/jvm_misc.hpp"

 #include "prims/privilegedStack.hpp"

 #include "runtime/arguments.hpp"

 #include "runtime/frame.inline.hpp"

 #include "runtime/interfaceSupport.hpp"

 #include "runtime/java.hpp"

 #include "runtime/javaCalls.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/os.hpp"

 #include "runtime/stubRoutines.hpp"

 #include "services/attachListener.hpp"

 #include "services/threadService.hpp"

 #include "utilities/defaultStream.hpp"

 #include "utilities/events.hpp"

 #ifdef TARGET_OS_FAMILY_linux

 # include "os_linux.inline.hpp"

 # include "thread_linux.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_solaris

 # include "os_solaris.inline.hpp"

 # include "thread_solaris.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_windows

 # include "os_windows.inline.hpp"

 # include "thread_windows.inline.hpp"

 #endif

 # include <signal.h>

 OSThread*         os::_starting_thread    = NULL;

 address           os::_polling_page       = NULL;

 volatile int32_t* os::_mem_serialize_page = NULL;

 uintptr_t         os::_serialize_page_mask = 0;

 long              os::_rand_seed          = 1;

 int               os::_processor_count    = 0;

 size_t            os::_page_sizes[os::page_sizes_max];

 #ifndef PRODUCT

 julong os::num_mallocs = 0;         // # of calls to malloc/realloc

 julong os::alloc_bytes = 0;         // # of bytes allocated

 julong os::num_frees = 0;           // # of calls to free

 julong os::free_bytes = 0;          // # of bytes freed

 #endif

 // Fill in buffer with current local time as an ISO-8601 string.

 // E.g., yyyy-mm-ddThh:mm:ss-zzzz.

 // Returns buffer, or NULL if it failed.

 // This would mostly be a call to

 //     strftime(...., "%Y-%m-%d" "T" "%H:%M:%S" "%z", ....)

 // except that on Windows the %z behaves badly, so we do it ourselves.

 // Also, people wanted milliseconds on there,

 // and strftime doesn't do milliseconds.

 char* os::iso8601_time(char* buffer, size_t buffer_length) {

   // Output will be of the form "YYYY-MM-DDThh:mm:ss.mmm+zzzz\0"

   //                                      1         2

   //                             12345678901234567890123456789

   static const char* iso8601_format =

     "%04d-%02d-%02dT%02d:%02d:%02d.%03d%c%02d%02d";

   static const size_t needed_buffer = 29;

   // Sanity check the arguments

   if (buffer == NULL) {

     assert(false, "NULL buffer");

     return NULL;

   }

   if (buffer_length < needed_buffer) {

     assert(false, "buffer_length too small");

     return NULL;

   }

   // Get the current time

   jlong milliseconds_since_19700101 = javaTimeMillis();

   const int milliseconds_per_microsecond = 1000;

   const time_t seconds_since_19700101 =

     milliseconds_since_19700101 / milliseconds_per_microsecond;

   const int milliseconds_after_second =

     milliseconds_since_19700101 % milliseconds_per_microsecond;

   // Convert the time value to a tm and timezone variable

   struct tm time_struct;

   if (localtime_pd(&seconds_since_19700101, &time_struct) == NULL) {

     assert(false, "Failed localtime_pd");

     return NULL;

   }

   const time_t zone = timezone;

   // If daylight savings time is in effect,

   // we are 1 hour East of our time zone

   const time_t seconds_per_minute = 60;

   const time_t minutes_per_hour = 60;

   const time_t seconds_per_hour = seconds_per_minute * minutes_per_hour;

   time_t UTC_to_local = zone;

   if (time_struct.tm_isdst > 0) {

     UTC_to_local = UTC_to_local - seconds_per_hour;

   }

   // Compute the time zone offset.

   //    localtime_pd() sets timezone to the difference (in seconds)

   //    between UTC and and local time.

   //    ISO 8601 says we need the difference between local time and UTC,

   //    we change the sign of the localtime_pd() result.

   const time_t local_to_UTC = -(UTC_to_local);

   // Then we have to figure out if if we are ahead (+) or behind (-) UTC.

   char sign_local_to_UTC = '+';

   time_t abs_local_to_UTC = local_to_UTC;

   if (local_to_UTC < 0) {

     sign_local_to_UTC = '-';

     abs_local_to_UTC = -(abs_local_to_UTC);

   }

   // Convert time zone offset seconds to hours and minutes.

   const time_t zone_hours = (abs_local_to_UTC / seconds_per_hour);

   const time_t zone_min =

     ((abs_local_to_UTC % seconds_per_hour) / seconds_per_minute);

   // Print an ISO 8601 date and time stamp into the buffer

   const int year = 1900 + time_struct.tm_year;

   const int month = 1 + time_struct.tm_mon;

   const int printed = jio_snprintf(buffer, buffer_length, iso8601_format,

                                    year,

                                    month,

                                    time_struct.tm_mday,

                                    time_struct.tm_hour,

                                    time_struct.tm_min,

                                    time_struct.tm_sec,

                                    milliseconds_after_second,

                                    sign_local_to_UTC,

                                    zone_hours,

                                    zone_min);

   if (printed == 0) {

     assert(false, "Failed jio_printf");

     return NULL;

   }

   return buffer;

 }

 OSReturn os::set_priority(Thread* thread, ThreadPriority p) {

 #ifdef ASSERT

   if (!(!thread->is_Java_thread() ||

          Thread::current() == thread  ||

          Threads_lock->owned_by_self()

          || thread->is_Compiler_thread()

         )) {

     assert(false, "possibility of dangling Thread pointer");

   }

 #endif

   if (p >= MinPriority && p <= MaxPriority) {

     int priority = java_to_os_priority[p];

     return set_native_priority(thread, priority);

   } else {

     assert(false, "Should not happen");

     return OS_ERR;

   }

 }

 OSReturn os::get_priority(const Thread* const thread, ThreadPriority& priority) {

   int p;

   int os_prio;

   OSReturn ret = get_native_priority(thread, &os_prio);

   if (ret != OS_OK) return ret;

   for (p = MaxPriority; p > MinPriority && java_to_os_priority[p] > os_prio; p--) ;

   priority = (ThreadPriority)p;

   return OS_OK;

 }

 // --------------------- sun.misc.Signal (optional) ---------------------

 // SIGBREAK is sent by the keyboard to query the VM state

 #ifndef SIGBREAK

 #define SIGBREAK SIGQUIT

 #endif

 // sigexitnum_pd is a platform-specific special signal used for terminating the Signal thread.

 static void signal_thread_entry(JavaThread* thread, TRAPS) {

   os::set_priority(thread, NearMaxPriority);

   while (true) {

     int sig;

     {

       // FIXME : Currently we have not decieded what should be the status

       //         for this java thread blocked here. Once we decide about

       //         that we should fix this.

       sig = os::signal_wait();

     }

     if (sig == os::sigexitnum_pd()) {

        // Terminate the signal thread

        return;

     }

     switch (sig) {

       case SIGBREAK: {

         // Check if the signal is a trigger to start the Attach Listener - in that

         // case don't print stack traces.

         if (!DisableAttachMechanism && AttachListener::is_init_trigger()) {

           continue;

         }

         // Print stack traces

         // Any SIGBREAK operations added here should make sure to flush

         // the output stream (e.g. tty->flush()) after output.  See 4803766.

         // Each module also prints an extra carriage return after its output.

         VM_PrintThreads op;

         VMThread::execute(&op);

         VM_PrintJNI jni_op;

         VMThread::execute(&jni_op);

         VM_FindDeadlocks op1(tty);

         VMThread::execute(&op1);

         Universe::print_heap_at_SIGBREAK();

         if (PrintClassHistogram) {

           VM_GC_HeapInspection op1(gclog_or_tty, true /* force full GC before heap inspection */,

                                    true /* need_prologue */);

           VMThread::execute(&op1);

         }

         if (JvmtiExport::should_post_data_dump()) {

           JvmtiExport::post_data_dump();

         }

         break;

       }

       default: {

         // Dispatch the signal to java

         HandleMark hm(THREAD);

         klassOop k = SystemDictionary::resolve_or_null(vmSymbols::sun_misc_Signal(), THREAD);

         KlassHandle klass (THREAD, k);

         if (klass.not_null()) {

           JavaValue result(T_VOID);

           JavaCallArguments args;

           args.push_int(sig);

           JavaCalls::call_static(

             &result,

             klass,

             vmSymbols::dispatch_name(),

             vmSymbols::int_void_signature(),

             &args,

             THREAD

           );

         }

         if (HAS_PENDING_EXCEPTION) {

           // tty is initialized early so we don't expect it to be null, but

           // if it is we can't risk doing an initialization that might

           // trigger additional out-of-memory conditions

           if (tty != NULL) {

             char klass_name[256];

             char tmp_sig_name[16];

             const char* sig_name = "UNKNOWN";

             instanceKlass::cast(PENDING_EXCEPTION->klass())->

               name()->as_klass_external_name(klass_name, 256);

             if (os::exception_name(sig, tmp_sig_name, 16) != NULL)

               sig_name = tmp_sig_name;

             warning("Exception %s occurred dispatching signal %s to handler"

                     "- the VM may need to be forcibly terminated",

                     klass_name, sig_name );

           }

           CLEAR_PENDING_EXCEPTION;

         }

       }

     }

   }

 }

 void os::signal_init() {

   if (!ReduceSignalUsage) {

     // Setup JavaThread for processing signals

     EXCEPTION_MARK;

     klassOop k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);

     instanceKlassHandle klass (THREAD, k);

     instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);

     const char thread_name[] = "Signal Dispatcher";

     Handle string = java_lang_String::create_from_str(thread_name, CHECK);

     // Initialize thread_oop to put it into the system threadGroup

     Handle thread_group (THREAD, Universe::system_thread_group());

     JavaValue result(T_VOID);

     JavaCalls::call_special(&result, thread_oop,

                            klass,

                            vmSymbols::object_initializer_name(),

                            vmSymbols::threadgroup_string_void_signature(),

                            thread_group,

                            string,

                            CHECK);

     KlassHandle group(THREAD, SystemDictionary::ThreadGroup_klass());

     JavaCalls::call_special(&result,

                             thread_group,

                             group,

                             vmSymbols::add_method_name(),

                             vmSymbols::thread_void_signature(),

                             thread_oop,         // ARG 1

                             CHECK);

     os::signal_init_pd();

     { MutexLocker mu(Threads_lock);

       JavaThread* signal_thread = new JavaThread(&signal_thread_entry);

       // At this point it may be possible that no osthread was created for the

       // JavaThread due to lack of memory. We would have to throw an exception

       // in that case. However, since this must work and we do not allow

       // exceptions anyway, check and abort if this fails.

       if (signal_thread == NULL || signal_thread->osthread() == NULL) {

         vm_exit_during_initialization("java.lang.OutOfMemoryError",

                                       "unable to create new native thread");

       }

       java_lang_Thread::set_thread(thread_oop(), signal_thread);

       java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);

       java_lang_Thread::set_daemon(thread_oop());

       signal_thread->set_threadObj(thread_oop());

       Threads::add(signal_thread);

       Thread::start(signal_thread);

     }

     // Handle ^BREAK

     os::signal(SIGBREAK, os::user_handler());

   }

 }

 void os::terminate_signal_thread() {

   if (!ReduceSignalUsage)

     signal_notify(sigexitnum_pd());

 }

 // --------------------- loading libraries ---------------------

 typedef jint (JNICALL *JNI_OnLoad_t)(JavaVM *, void *);

 extern struct JavaVM_ main_vm;

 static void* _native_java_library = NULL;

 void* os::native_java_library() {

   if (_native_java_library == NULL) {

     char buffer[JVM_MAXPATHLEN];

     char ebuf[1024];

     // Try to load verify dll first. In 1.3 java dll depends on it and is not

     // always able to find it when the loading executable is outside the JDK.

     // In order to keep working with 1.2 we ignore any loading errors.

     dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(), "verify");

     dll_load(buffer, ebuf, sizeof(ebuf));

     // Load java dll

     dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(), "java");

     _native_java_library = dll_load(buffer, ebuf, sizeof(ebuf));

     if (_native_java_library == NULL) {

       vm_exit_during_initialization("Unable to load native library", ebuf);

     }

   }

   static jboolean onLoaded = JNI_FALSE;

   if (onLoaded) {

     // We may have to wait to fire OnLoad until TLS is initialized.

     if (ThreadLocalStorage::is_initialized()) {

       // The JNI_OnLoad handling is normally done by method load in

       // java.lang.ClassLoader$NativeLibrary, but the VM loads the base library

       // explicitly so we have to check for JNI_OnLoad as well

       const char *onLoadSymbols[] = JNI_ONLOAD_SYMBOLS;

       JNI_OnLoad_t JNI_OnLoad = CAST_TO_FN_PTR(

           JNI_OnLoad_t, dll_lookup(_native_java_library, onLoadSymbols[0]));

       if (JNI_OnLoad != NULL) {

         JavaThread* thread = JavaThread::current();

         ThreadToNativeFromVM ttn(thread);

         HandleMark hm(thread);

         jint ver = (*JNI_OnLoad)(&main_vm, NULL);

         onLoaded = JNI_TRUE;

         if (!Threads::is_supported_jni_version_including_1_1(ver)) {

           vm_exit_during_initialization("Unsupported JNI version");

         }

       }

     }

   }

   return _native_java_library;

 }

 // --------------------- heap allocation utilities ---------------------

 char *os::strdup(const char *str) {

   size_t size = strlen(str);

   char *dup_str = (char *)malloc(size + 1);

   if (dup_str == NULL) return NULL;

   strcpy(dup_str, str);

   return dup_str;

 }

 #ifdef ASSERT

 #define space_before             (MallocCushion + sizeof(double))

 #define space_after              MallocCushion

 #define size_addr_from_base(p)   (size_t*)(p + space_before - sizeof(size_t))

 #define size_addr_from_obj(p)    ((size_t*)p - 1)

 // MallocCushion: size of extra cushion allocated around objects with +UseMallocOnly

 // NB: cannot be debug variable, because these aren't set from the command line until

 // *after* the first few allocs already happened

 #define MallocCushion            16

 #else

 #define space_before             0

 #define space_after              0

 #define size_addr_from_base(p)   should not use w/o ASSERT

 #define size_addr_from_obj(p)    should not use w/o ASSERT

 #define MallocCushion            0

 #endif

 #define paranoid                 0  /* only set to 1 if you suspect checking code has bug */

 #ifdef ASSERT

 inline size_t get_size(void* obj) {

   size_t size = *size_addr_from_obj(obj);

   if (size < 0) {

     fatal(err_msg("free: size field of object #" PTR_FORMAT " was overwritten ("

                   SIZE_FORMAT ")", obj, size));

   }

   return size;

 }

 u_char* find_cushion_backwards(u_char* start) {

   u_char* p = start;

   while (p[ 0] != badResourceValue || p[-1] != badResourceValue ||

          p[-2] != badResourceValue || p[-3] != badResourceValue) p--;

   // ok, we have four consecutive marker bytes; find start

   u_char* q = p - 4;

   while (*q == badResourceValue) q--;

   return q + 1;

 }

 u_char* find_cushion_forwards(u_char* start) {

   u_char* p = start;

   while (p[0] != badResourceValue || p[1] != badResourceValue ||

          p[2] != badResourceValue || p[3] != badResourceValue) p++;

   // ok, we have four consecutive marker bytes; find end of cushion

   u_char* q = p + 4;

   while (*q == badResourceValue) q++;

   return q - MallocCushion;

 }

 void print_neighbor_blocks(void* ptr) {

   // find block allocated before ptr (not entirely crash-proof)

   if (MallocCushion < 4) {

     tty->print_cr("### cannot find previous block (MallocCushion < 4)");

     return;

   }

   u_char* start_of_this_block = (u_char*)ptr - space_before;

   u_char* end_of_prev_block_data = start_of_this_block - space_after -1;

   // look for cushion in front of prev. block

   u_char* start_of_prev_block = find_cushion_backwards(end_of_prev_block_data);

   ptrdiff_t size = *size_addr_from_base(start_of_prev_block);

   u_char* obj = start_of_prev_block + space_before;

   if (size <= 0 ) {

     // start is bad; mayhave been confused by OS data inbetween objects

     // search one more backwards

     start_of_prev_block = find_cushion_backwards(start_of_prev_block);

     size = *size_addr_from_base(start_of_prev_block);

     obj = start_of_prev_block + space_before;

   }

   if (start_of_prev_block + space_before + size + space_after == start_of_this_block) {

     tty->print_cr("### previous object: " PTR_FORMAT " (" SSIZE_FORMAT " bytes)", obj, size);

   } else {

     tty->print_cr("### previous object (not sure if correct): " PTR_FORMAT " (" SSIZE_FORMAT " bytes)", obj, size);

   }

   // now find successor block

   u_char* start_of_next_block = (u_char*)ptr + *size_addr_from_obj(ptr) + space_after;

   start_of_next_block = find_cushion_forwards(start_of_next_block);

   u_char* next_obj = start_of_next_block + space_before;

   ptrdiff_t next_size = *size_addr_from_base(start_of_next_block);

   if (start_of_next_block[0] == badResourceValue &&

       start_of_next_block[1] == badResourceValue &&

       start_of_next_block[2] == badResourceValue &&

       start_of_next_block[3] == badResourceValue) {

     tty->print_cr("### next object: " PTR_FORMAT " (" SSIZE_FORMAT " bytes)", next_obj, next_size);

   } else {

     tty->print_cr("### next object (not sure if correct): " PTR_FORMAT " (" SSIZE_FORMAT " bytes)", next_obj, next_size);

   }

 }

 void report_heap_error(void* memblock, void* bad, const char* where) {

   tty->print_cr("## nof_mallocs = " UINT64_FORMAT ", nof_frees = " UINT64_FORMAT, os::num_mallocs, os::num_frees);

   tty->print_cr("## memory stomp: byte at " PTR_FORMAT " %s object " PTR_FORMAT, bad, where, memblock);

   print_neighbor_blocks(memblock);

   fatal("memory stomping error");

 }

 void verify_block(void* memblock) {

   size_t size = get_size(memblock);

   if (MallocCushion) {

     u_char* ptr = (u_char*)memblock - space_before;

     for (int i = 0; i < MallocCushion; i++) {

       if (ptr[i] != badResourceValue) {

         report_heap_error(memblock, ptr+i, "in front of");

       }

     }

     u_char* end = (u_char*)memblock + size + space_after;

     for (int j = -MallocCushion; j < 0; j++) {

       if (end[j] != badResourceValue) {

         report_heap_error(memblock, end+j, "after");

       }

     }

   }

 }

 #endif

 void* os::malloc(size_t size) {

   NOT_PRODUCT(inc_stat_counter(&num_mallocs, 1));

   NOT_PRODUCT(inc_stat_counter(&alloc_bytes, size));

   if (size == 0) {

     // return a valid pointer if size is zero

     // if NULL is returned the calling functions assume out of memory.

     size = 1;

   }

   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());

   u_char* ptr = (u_char*)::malloc(size + space_before + space_after);

 #ifdef ASSERT

   if (ptr == NULL) return NULL;

   if (MallocCushion) {

     for (u_char* p = ptr; p < ptr + MallocCushion; p++) *p = (u_char)badResourceValue;

     u_char* end = ptr + space_before + size;

     for (u_char* pq = ptr+MallocCushion; pq < end; pq++) *pq = (u_char)uninitBlockPad;

     for (u_char* q = end; q < end + MallocCushion; q++) *q = (u_char)badResourceValue;

   }

   // put size just before data

   *size_addr_from_base(ptr) = size;

 #endif

   u_char* memblock = ptr + space_before;

   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {

     tty->print_cr("os::malloc caught, " SIZE_FORMAT " bytes --> " PTR_FORMAT, size, memblock);

     breakpoint();

   }

   debug_only(if (paranoid) verify_block(memblock));

   if (PrintMalloc && tty != NULL) tty->print_cr("os::malloc " SIZE_FORMAT " bytes --> " PTR_FORMAT, size, memblock);

   return memblock;

 }

 void* os::realloc(void *memblock, size_t size) {

 #ifndef ASSERT

   NOT_PRODUCT(inc_stat_counter(&num_mallocs, 1));

   NOT_PRODUCT(inc_stat_counter(&alloc_bytes, size));

   return ::realloc(memblock, size);

 #else

   if (memblock == NULL) {

     return malloc(size);

   }

   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {

     tty->print_cr("os::realloc caught " PTR_FORMAT, memblock);

     breakpoint();

   }

   verify_block(memblock);

   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());

   if (size == 0) return NULL;

   // always move the block

   void* ptr = malloc(size);

   if (PrintMalloc) tty->print_cr("os::remalloc " SIZE_FORMAT " bytes, " PTR_FORMAT " --> " PTR_FORMAT, size, memblock, ptr);

   // Copy to new memory if malloc didn't fail

   if ( ptr != NULL ) {

     memcpy(ptr, memblock, MIN2(size, get_size(memblock)));

     if (paranoid) verify_block(ptr);

     if ((intptr_t)ptr == (intptr_t)MallocCatchPtr) {

       tty->print_cr("os::realloc caught, " SIZE_FORMAT " bytes --> " PTR_FORMAT, size, ptr);

       breakpoint();

     }

     free(memblock);

   }

   return ptr;

 #endif

 }

 void  os::free(void *memblock) {

   NOT_PRODUCT(inc_stat_counter(&num_frees, 1));

 #ifdef ASSERT

   if (memblock == NULL) return;

   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {

     if (tty != NULL) tty->print_cr("os::free caught " PTR_FORMAT, memblock);

     breakpoint();

   }

   verify_block(memblock);

   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());

   // Added by detlefs.

   if (MallocCushion) {

     u_char* ptr = (u_char*)memblock - space_before;

     for (u_char* p = ptr; p < ptr + MallocCushion; p++) {

       guarantee(*p == badResourceValue,

                 "Thing freed should be malloc result.");

       *p = (u_char)freeBlockPad;

     }

     size_t size = get_size(memblock);

     inc_stat_counter(&free_bytes, size);

     u_char* end = ptr + space_before + size;

     for (u_char* q = end; q < end + MallocCushion; q++) {

       guarantee(*q == badResourceValue,

                 "Thing freed should be malloc result.");

       *q = (u_char)freeBlockPad;

     }

     if (PrintMalloc && tty != NULL)

       fprintf(stderr, "os::free " SIZE_FORMAT " bytes --> " PTR_FORMAT "\n", size, (uintptr_t)memblock);

   } else if (PrintMalloc && tty != NULL) {

     // tty->print_cr("os::free %p", memblock);

     fprintf(stderr, "os::free " PTR_FORMAT "\n", (uintptr_t)memblock);

   }

 #endif

   ::free((char*)memblock - space_before);

 }

 void os::init_random(long initval) {

   _rand_seed = initval;

 }

 long os::random() {

   /* standard, well-known linear congruential random generator with

    * next_rand = (16807*seed) mod (2**31-1)

    * see

    * (1) "Random Number Generators: Good Ones Are Hard to Find",

    *      S.K. Park and K.W. Miller, Communications of the ACM 31:10 (Oct 1988),

    * (2) "Two Fast Implementations of the 'Minimal Standard' Random

    *     Number Generator", David G. Carta, Comm. ACM 33, 1 (Jan 1990), pp. 87-88.

   */

   const long a = 16807;

   const unsigned long m = 2147483647;

   const long q = m / a;        assert(q == 127773, "weird math");

   const long r = m % a;        assert(r == 2836, "weird math");

   // compute az=2^31p+q

   unsigned long lo = a * (long)(_rand_seed & 0xFFFF);

   unsigned long hi = a * (long)((unsigned long)_rand_seed >> 16);

   lo += (hi & 0x7FFF) << 16;

   // if q overflowed, ignore the overflow and increment q

   if (lo > m) {

     lo &= m;

     ++lo;

   }

   lo += hi >> 15;

   // if (p+q) overflowed, ignore the overflow and increment (p+q)

   if (lo > m) {

     lo &= m;

     ++lo;

   }

   return (_rand_seed = lo);

 }

 // The INITIALIZED state is distinguished from the SUSPENDED state because the

 // conditions in which a thread is first started are different from those in which

 // a suspension is resumed.  These differences make it hard for us to apply the

 // tougher checks when starting threads that we want to do when resuming them.

 // However, when start_thread is called as a result of Thread.start, on a Java

 // thread, the operation is synchronized on the Java Thread object.  So there

 // cannot be a race to start the thread and hence for the thread to exit while

 // we are working on it.  Non-Java threads that start Java threads either have

 // to do so in a context in which races are impossible, or should do appropriate

 // locking.

 void os::start_thread(Thread* thread) {

   // guard suspend/resume

   MutexLockerEx ml(thread->SR_lock(), Mutex::_no_safepoint_check_flag);

   OSThread* osthread = thread->osthread();

   osthread->set_state(RUNNABLE);

   pd_start_thread(thread);

 }

 //---------------------------------------------------------------------------

 // Helper functions for fatal error handler

 void os::print_hex_dump(outputStream* st, address start, address end, int unitsize) {

   assert(unitsize == 1 || unitsize == 2 || unitsize == 4 || unitsize == 8, "just checking");

   int cols = 0;

   int cols_per_line = 0;

   switch (unitsize) {

     case 1: cols_per_line = 16; break;

     case 2: cols_per_line = 8;  break;

     case 4: cols_per_line = 4;  break;

     case 8: cols_per_line = 2;  break;

     default: return;

   }

   address p = start;

   st->print(PTR_FORMAT ":   ", start);

   while (p < end) {

     switch (unitsize) {

       case 1: st->print("%02x", *(u1*)p); break;

       case 2: st->print("%04x", *(u2*)p); break;

       case 4: st->print("%08x", *(u4*)p); break;

       case 8: st->print("%016" FORMAT64_MODIFIER "x", *(u8*)p); break;

     }

     p += unitsize;

     cols++;

     if (cols >= cols_per_line && p < end) {

        cols = 0;

        st->cr();

        st->print(PTR_FORMAT ":   ", p);

     } else {

        st->print(" ");

     }

   }

   st->cr();

 }

 void os::print_environment_variables(outputStream* st, const char** env_list,

                                      char* buffer, int len) {

   if (env_list) {

     st->print_cr("Environment Variables:");

     for (int i = 0; env_list[i] != NULL; i++) {

       if (getenv(env_list[i], buffer, len)) {

         st->print(env_list[i]);

         st->print("=");

         st->print_cr(buffer);

       }

     }

   }

 }

 void os::print_cpu_info(outputStream* st) {

   // cpu

   st->print("CPU:");

   st->print("total %d", os::processor_count());

   // It's not safe to query number of active processors after crash

   // st->print("(active %d)", os::active_processor_count());

   st->print(" %s", VM_Version::cpu_features());

   st->cr();

   pd_print_cpu_info(st);

 }

 void os::print_date_and_time(outputStream *st) {

   time_t tloc;

   (void)time(&tloc);

   st->print("time: %s", ctime(&tloc));  // ctime adds newline.

   double t = os::elapsedTime();

   // NOTE: It tends to crash after a SEGV if we want to printf("%f",...) in

   //       Linux. Must be a bug in glibc ? Workaround is to round "t" to int

   //       before printf. We lost some precision, but who cares?

   st->print_cr("elapsed time: %d seconds", (int)t);

 }

 // moved from debug.cpp (used to be find()) but still called from there

 // The verbose parameter is only set by the debug code in one case

 void os::print_location(outputStream* st, intptr_t x, bool verbose) {

   address addr = (address)x;

   CodeBlob* b = CodeCache::find_blob_unsafe(addr);

   if (b != NULL) {

     if (b->is_buffer_blob()) {

       // the interpreter is generated into a buffer blob

       InterpreterCodelet* i = Interpreter::codelet_containing(addr);

       if (i != NULL) {

         st->print_cr(INTPTR_FORMAT " is an Interpreter codelet", addr);

         i->print_on(st);

         return;

       }

       if (Interpreter::contains(addr)) {

         st->print_cr(INTPTR_FORMAT " is pointing into interpreter code"

                      " (not bytecode specific)", addr);

         return;

       }

       //

       if (AdapterHandlerLibrary::contains(b)) {

         st->print_cr(INTPTR_FORMAT " is an AdapterHandler", addr);

         AdapterHandlerLibrary::print_handler_on(st, b);

       }

       // the stubroutines are generated into a buffer blob

       StubCodeDesc* d = StubCodeDesc::desc_for(addr);

       if (d != NULL) {

         d->print_on(st);

         if (verbose) st->cr();

         return;

       }

       if (StubRoutines::contains(addr)) {

         st->print_cr(INTPTR_FORMAT " is pointing to an (unnamed) "

                      "stub routine", addr);

         return;

       }

       // the InlineCacheBuffer is using stubs generated into a buffer blob

       if (InlineCacheBuffer::contains(addr)) {

         st->print_cr(INTPTR_FORMAT " is pointing into InlineCacheBuffer", addr);

         return;

       }

       VtableStub* v = VtableStubs::stub_containing(addr);

       if (v != NULL) {

         v->print_on(st);

         return;

       }

     }

     if (verbose && b->is_nmethod()) {

       ResourceMark rm;

       st->print("%#p: Compiled ", addr);

       ((nmethod*)b)->method()->print_value_on(st);

       st->print("  = (CodeBlob*)" INTPTR_FORMAT, b);

       st->cr();

       return;

     }

     st->print(INTPTR_FORMAT " ", b);

     if ( b->is_nmethod()) {

       if (b->is_zombie()) {

         st->print_cr("is zombie nmethod");

       } else if (b->is_not_entrant()) {

         st->print_cr("is non-entrant nmethod");

       }

     }

     b->print_on(st);

     return;

   }

   if (Universe::heap()->is_in(addr)) {

     HeapWord* p = Universe::heap()->block_start(addr);

     bool print = false;

     // If we couldn't find it it just may mean that heap wasn't parseable

     // See if we were just given an oop directly

     if (p != NULL && Universe::heap()->block_is_obj(p)) {

       print = true;

     } else if (p == NULL && ((oopDesc*)addr)->is_oop()) {

       p = (HeapWord*) addr;

       print = true;

     }

     if (print) {

       st->print_cr(INTPTR_FORMAT " is an oop", addr);

       oop(p)->print_on(st);

       if (p != (HeapWord*)x && oop(p)->is_constMethod() &&

           constMethodOop(p)->contains(addr)) {

         Thread *thread = Thread::current();

         HandleMark hm(thread);

         methodHandle mh (thread, constMethodOop(p)->method());

         if (!mh->is_native()) {

           st->print_cr("bci_from(%p) = %d; print_codes():",

                         addr, mh->bci_from(address(x)));

           mh->print_codes_on(st);

         }

       }

       return;

     }

   } else {

     if (Universe::heap()->is_in_reserved(addr)) {

       st->print_cr(INTPTR_FORMAT " is an unallocated location "

                    "in the heap", addr);

       return;

     }

   }

   if (JNIHandles::is_global_handle((jobject) addr)) {

     st->print_cr(INTPTR_FORMAT " is a global jni handle", addr);

     return;

   }

   if (JNIHandles::is_weak_global_handle((jobject) addr)) {

     st->print_cr(INTPTR_FORMAT " is a weak global jni handle", addr);

     return;

   }

 #ifndef PRODUCT

   // we don't keep the block list in product mode

   if (JNIHandleBlock::any_contains((jobject) addr)) {

     st->print_cr(INTPTR_FORMAT " is a local jni handle", addr);

     return;

   }

 #endif

   for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {

     // Check for privilege stack

     if (thread->privileged_stack_top() != NULL &&

         thread->privileged_stack_top()->contains(addr)) {

       st->print_cr(INTPTR_FORMAT " is pointing into the privilege stack "

                    "for thread: " INTPTR_FORMAT, addr, thread);

       if (verbose) thread->print_on(st);

       return;

     }

     // If the addr is a java thread print information about that.

     if (addr == (address)thread) {

       if (verbose) {

         thread->print_on(st);

       } else {

         st->print_cr(INTPTR_FORMAT " is a thread", addr);

       }

       return;

     }

     // If the addr is in the stack region for this thread then report that

     // and print thread info

     if (thread->stack_base() >= addr &&

         addr > (thread->stack_base() - thread->stack_size())) {

       st->print_cr(INTPTR_FORMAT " is pointing into the stack for thread: "

                    INTPTR_FORMAT, addr, thread);

       if (verbose) thread->print_on(st);

       return;

     }

   }

   // Try an OS specific find

   if (os::find(addr, st)) {

     return;

   }

   st->print_cr(INTPTR_FORMAT " is an unknown value", addr);

 }

 // Looks like all platforms except IA64 can use the same function to check

 // if C stack is walkable beyond current frame. The check for fp() is not

 // necessary on Sparc, but it's harmless.

 bool os::is_first_C_frame(frame* fr) {

 #ifdef IA64

   // In order to walk native frames on Itanium, we need to access the unwind

   // table, which is inside ELF. We don't want to parse ELF after fatal error,

   // so return true for IA64. If we need to support C stack walking on IA64,

   // this function needs to be moved to CPU specific files, as fp() on IA64

   // is register stack, which grows towards higher memory address.

   return true;

 #endif

   // Load up sp, fp, sender sp and sender fp, check for reasonable values.

   // Check usp first, because if that's bad the other accessors may fault

   // on some architectures.  Ditto ufp second, etc.

   uintptr_t fp_align_mask = (uintptr_t)(sizeof(address)-1);

   // sp on amd can be 32 bit aligned.

   uintptr_t sp_align_mask = (uintptr_t)(sizeof(int)-1);

   uintptr_t usp    = (uintptr_t)fr->sp();

   if ((usp & sp_align_mask) != 0) return true;

   uintptr_t ufp    = (uintptr_t)fr->fp();

   if ((ufp & fp_align_mask) != 0) return true;

   uintptr_t old_sp = (uintptr_t)fr->sender_sp();

   if ((old_sp & sp_align_mask) != 0) return true;

   if (old_sp == 0 || old_sp == (uintptr_t)-1) return true;

   uintptr_t old_fp = (uintptr_t)fr->link();

   if ((old_fp & fp_align_mask) != 0) return true;

   if (old_fp == 0 || old_fp == (uintptr_t)-1 || old_fp == ufp) return true;

   // stack grows downwards; if old_fp is below current fp or if the stack

   // frame is too large, either the stack is corrupted or fp is not saved

   // on stack (i.e. on x86, ebp may be used as general register). The stack

   // is not walkable beyond current frame.

   if (old_fp < ufp) return true;

   if (old_fp - ufp > 64 * K) return true;

   return false;

 }

 #ifdef ASSERT

 extern "C" void test_random() {

   const double m = 2147483647;

   double mean = 0.0, variance = 0.0, t;

   long reps = 10000;

   unsigned long seed = 1;

   tty->print_cr("seed %ld for %ld repeats...", seed, reps);

   os::init_random(seed);

   long num;

   for (int k = 0; k < reps; k++) {

     num = os::random();

     double u = (double)num / m;

     assert(u >= 0.0 && u <= 1.0, "bad random number!");

     // calculate mean and variance of the random sequence

     mean += u;

     variance += (u*u);

   }

   mean /= reps;

   variance /= (reps - 1);

   assert(num == 1043618065, "bad seed");

   tty->print_cr("mean of the 1st 10000 numbers: %f", mean);

   tty->print_cr("variance of the 1st 10000 numbers: %f", variance);

   const double eps = 0.0001;

   t = fabsd(mean - 0.5018);

   assert(t < eps, "bad mean");

   t = (variance - 0.3355) < 0.0 ? -(variance - 0.3355) : variance - 0.3355;

   assert(t < eps, "bad variance");

 }

 #endif

 // Set up the boot classpath.

 char* os::format_boot_path(const char* format_string,

                            const char* home,

                            int home_len,

                            char fileSep,

                            char pathSep) {

     assert((fileSep == '/' && pathSep == ':') ||

            (fileSep == '\\' && pathSep == ';'), "unexpected seperator chars");

     // Scan the format string to determine the length of the actual

     // boot classpath, and handle platform dependencies as well.

     int formatted_path_len = 0;

     const char* p;

     for (p = format_string; *p != 0; ++p) {

         if (*p == '%') formatted_path_len += home_len - 1;

         ++formatted_path_len;

     }

     char* formatted_path = NEW_C_HEAP_ARRAY(char, formatted_path_len + 1);

     if (formatted_path == NULL) {

         return NULL;

     }

     // Create boot classpath from format, substituting separator chars and

     // java home directory.

     char* q = formatted_path;

     for (p = format_string; *p != 0; ++p) {

         switch (*p) {

         case '%':

             strcpy(q, home);

             q += home_len;

             break;

         case '/':

             *q++ = fileSep;

             break;

         case ':':

             *q++ = pathSep;

             break;

         default:

             *q++ = *p;

         }

     }

     *q = '\0';

     assert((q - formatted_path) == formatted_path_len, "formatted_path size botched");

     return formatted_path;

 }

 bool os::set_boot_path(char fileSep, char pathSep) {

     const char* home = Arguments::get_java_home();

     int home_len = (int)strlen(home);

     static const char* meta_index_dir_format = "%/lib/";

     static const char* meta_index_format = "%/lib/meta-index";

     char* meta_index = format_boot_path(meta_index_format, home, home_len, fileSep, pathSep);

     if (meta_index == NULL) return false;

     char* meta_index_dir = format_boot_path(meta_index_dir_format, home, home_len, fileSep, pathSep);

     if (meta_index_dir == NULL) return false;

     Arguments::set_meta_index_path(meta_index, meta_index_dir);

     // Any modification to the JAR-file list, for the boot classpath must be

     // aligned with install/install/make/common/Pack.gmk. Note: boot class

     // path class JARs, are stripped for StackMapTable to reduce download size.

     static const char classpath_format[] =

         "%/lib/resources.jar:"

         "%/lib/rt.jar:"

         "%/lib/sunrsasign.jar:"

         "%/lib/jsse.jar:"

         "%/lib/jce.jar:"

         "%/lib/charsets.jar:"

         "%/classes";

     char* sysclasspath = format_boot_path(classpath_format, home, home_len, fileSep, pathSep);

     if (sysclasspath == NULL) return false;

     Arguments::set_sysclasspath(sysclasspath);

     return true;

 }

 /*

  * Splits a path, based on its separator, the number of

  * elements is returned back in n.

  * It is the callers responsibility to:

  *   a> check the value of n, and n may be 0.

  *   b> ignore any empty path elements

  *   c> free up the data.

  */

 char** os::split_path(const char* path, int* n) {

   *n = 0;

   if (path == NULL || strlen(path) == 0) {

     return NULL;

   }

   const char psepchar = *os::path_separator();

   char* inpath = (char*)NEW_C_HEAP_ARRAY(char, strlen(path) + 1);

   if (inpath == NULL) {

     return NULL;

   }

   strncpy(inpath, path, strlen(path));

   int count = 1;

   char* p = strchr(inpath, psepchar);

   // Get a count of elements to allocate memory

   while (p != NULL) {

     count++;

     p++;

     p = strchr(p, psepchar);

   }

   char** opath = (char**) NEW_C_HEAP_ARRAY(char*, count);

   if (opath == NULL) {

     return NULL;

   }

   // do the actual splitting

   p = inpath;

   for (int i = 0 ; i < count ; i++) {

     size_t len = strcspn(p, os::path_separator());

     if (len > JVM_MAXPATHLEN) {

       return NULL;

     }

     // allocate the string and add terminator storage

     char* s  = (char*)NEW_C_HEAP_ARRAY(char, len + 1);

     if (s == NULL) {

       return NULL;

     }

     strncpy(s, p, len);

     s[len] = '\0';

     opath[i] = s;

     p += len + 1;

   }

   FREE_C_HEAP_ARRAY(char, inpath);

   *n = count;

   return opath;

 }

 void os::set_memory_serialize_page(address page) {

   int count = log2_intptr(sizeof(class JavaThread)) - log2_intptr(64);

   _mem_serialize_page = (volatile int32_t *)page;

   // We initialize the serialization page shift count here

   // We assume a cache line size of 64 bytes

   assert(SerializePageShiftCount == count,

          "thread size changed, fix SerializePageShiftCount constant");

   set_serialize_page_mask((uintptr_t)(vm_page_size() - sizeof(int32_t)));

 }

 static volatile intptr_t SerializePageLock = 0;

 // This method is called from signal handler when SIGSEGV occurs while the current

 // thread tries to store to the "read-only" memory serialize page during state

 // transition.

 void os::block_on_serialize_page_trap() {

   if (TraceSafepoint) {

     tty->print_cr("Block until the serialize page permission restored");

   }

   // When VMThread is holding the SerializePageLock during modifying the

   // access permission of the memory serialize page, the following call

   // will block until the permission of that page is restored to rw.

   // Generally, it is unsafe to manipulate locks in signal handlers, but in

   // this case, it's OK as the signal is synchronous and we know precisely when

   // it can occur.

   Thread::muxAcquire(&SerializePageLock, "set_memory_serialize_page");

   Thread::muxRelease(&SerializePageLock);

 }

 // Serialize all thread state variables

 void os::serialize_thread_states() {

   // On some platforms such as Solaris & Linux, the time duration of the page

   // permission restoration is observed to be much longer than expected  due to

   // scheduler starvation problem etc. To avoid the long synchronization

   // time and expensive page trap spinning, 'SerializePageLock' is used to block

   // the mutator thread if such case is encountered. See bug 6546278 for details.

   Thread::muxAcquire(&SerializePageLock, "serialize_thread_states");

   os::protect_memory((char *)os::get_memory_serialize_page(),

                      os::vm_page_size(), MEM_PROT_READ);

   os::protect_memory((char *)os::get_memory_serialize_page(),

                      os::vm_page_size(), MEM_PROT_RW);

   Thread::muxRelease(&SerializePageLock);

 }

 // Returns true if the current stack pointer is above the stack shadow

 // pages, false otherwise.

 bool os::stack_shadow_pages_available(Thread *thread, methodHandle method) {

   assert(StackRedPages > 0 && StackYellowPages > 0,"Sanity check");

   address sp = current_stack_pointer();

   // Check if we have StackShadowPages above the yellow zone.  This parameter

   // is dependent on the depth of the maximum VM call stack possible from

   // the handler for stack overflow.  'instanceof' in the stack overflow

   // handler or a println uses at least 8k stack of VM and native code

   // respectively.

   const int framesize_in_bytes =

     Interpreter::size_top_interpreter_activation(method()) * wordSize;

   int reserved_area = ((StackShadowPages + StackRedPages + StackYellowPages)

                       * vm_page_size()) + framesize_in_bytes;

   // The very lower end of the stack

   address stack_limit = thread->stack_base() - thread->stack_size();

   return (sp > (stack_limit + reserved_area));

 }

 size_t os::page_size_for_region(size_t region_min_size, size_t region_max_size,

                                 uint min_pages)

 {

   assert(min_pages > 0, "sanity");

   if (UseLargePages) {

     const size_t max_page_size = region_max_size / min_pages;

     for (unsigned int i = 0; _page_sizes[i] != 0; ++i) {

       const size_t sz = _page_sizes[i];

       const size_t mask = sz - 1;

       if ((region_min_size & mask) == 0 && (region_max_size & mask) == 0) {

         // The largest page size with no fragmentation.

         return sz;

       }

       if (sz <= max_page_size) {

         // The largest page size that satisfies the min_pages requirement.

         return sz;

       }

     }

   }

   return vm_page_size();

 }

 #ifndef PRODUCT

 void os::trace_page_sizes(const char* str, const size_t* page_sizes, int count)

 {

   if (TracePageSizes) {

     tty->print("%s: ", str);

     for (int i = 0; i < count; ++i) {

       tty->print(" " SIZE_FORMAT, page_sizes[i]);

     }

     tty->cr();

   }

 }

 void os::trace_page_sizes(const char* str, const size_t region_min_size,

                           const size_t region_max_size, const size_t page_size,

                           const char* base, const size_t size)

 {

   if (TracePageSizes) {

     tty->print_cr("%s:  min=" SIZE_FORMAT " max=" SIZE_FORMAT

                   " pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT

                   " size=" SIZE_FORMAT,

                   str, region_min_size, region_max_size,

                   page_size, base, size);

   }

 }

 #endif  // #ifndef PRODUCT

 // This is the working definition of a server class machine:

 // >= 2 physical CPU's and >=2GB of memory, with some fuzz

 // because the graphics memory (?) sometimes masks physical memory.

 // If you want to change the definition of a server class machine

 // on some OS or platform, e.g., >=4GB on Windohs platforms,

 // then you'll have to parameterize this method based on that state,

 // as was done for logical processors here, or replicate and

 // specialize this method for each platform.  (Or fix os to have

 // some inheritance structure and use subclassing.  Sigh.)

 // If you want some platform to always or never behave as a server

 // class machine, change the setting of AlwaysActAsServerClassMachine

 // and NeverActAsServerClassMachine in globals*.hpp.

 bool os::is_server_class_machine() {

   // First check for the early returns

   if (NeverActAsServerClassMachine) {

     return false;

   }

   if (AlwaysActAsServerClassMachine) {

     return true;

   }

   // Then actually look at the machine

   bool         result            = false;

   const unsigned int    server_processors = 2;

   const julong server_memory     = 2UL * G;

   // We seem not to get our full complement of memory.

   //     We allow some part (1/8?) of the memory to be "missing",

   //     based on the sizes of DIMMs, and maybe graphics cards.

   const julong missing_memory   = 256UL * M;

   /* Is this a server class machine? */

   if ((os::active_processor_count() >= (int)server_processors) &&

       (os::physical_memory() >= (server_memory - missing_memory))) {

     const unsigned int logical_processors =

       VM_Version::logical_processors_per_package();

     if (logical_processors > 1) {

       const unsigned int physical_packages =

         os::active_processor_count() / logical_processors;

       if (physical_packages > server_processors) {

         result = true;

       }

     } else {

       result = true;

     }

   }

   return result;

 }

 // Read file line by line, if line is longer than bsize,

 // skip rest of line.

 int os::get_line_chars(int fd, char* buf, const size_t bsize){

   size_t sz, i = 0;

   // read until EOF, EOL or buf is full

   while ((sz = (int) read(fd, &buf[i], 1)) == 1 && i < (bsize-2) && buf[i] != '\n') {

      ++i;

   }

   if (buf[i] == '\n') {

     // EOL reached so ignore EOL character and return

     buf[i] = 0;

     return (int) i;

   }

   buf[i+1] = 0;

   if (sz != 1) {

     // EOF reached. if we read chars before EOF return them and

     // return EOF on next call otherwise return EOF

     return (i == 0) ? -1 : (int) i;

   }

   // line is longer than size of buf, skip to EOL

   char ch;

   while (read(fd, &ch, 1) == 1 && ch != '\n') {

     // Do nothing

   }

   // return initial part of line that fits in buf.

   // If we reached EOF, it will be returned on next call.

   return (int) i;

 }