java hotspot虚拟机 - SocketOutputStream

SocketOutputStream.java

就只有这一个native方法

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/**
* Writes to the socket.
* @param fd the FileDescriptor
* @param b the data to be written
* @param off the start offset in the data
* @param len the number of bytes that are written
* @exception IOException If an I/O error has occurred.
*/
private native void socketWrite0(FileDescriptor fd, byte[] b, int off, int len) throws IOException;

SocketOutputStream.c

路径: openjdk\jdk\src\windows\native\java\net\SocketOutputStream.c

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#include <windows.h>
#include <winsock2.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <sys/types.h>

#include "java_net_SocketOutputStream.h"

#include "net_util.h"
#include "jni_util.h"

/************************************************************************
* SocketOutputStream
*/
static jfieldID IO_fd_fdID;

/*
* Class: java_net_SocketOutputStream
* Method: init
* Signature: ()V
*/
JNIEXPORT void JNICALL
Java_java_net_SocketOutputStream_init(JNIEnv *env, jclass cls) {
IO_fd_fdID = NET_GetFileDescriptorID(env);
}

/*
* Class: java_net_SocketOutputStream
* Method: socketWrite
* Signature: (Ljava/io/FileDescriptor;[BII)V
*/
JNIEXPORT void JNICALL
Java_java_net_SocketOutputStream_socketWrite0(JNIEnv *env, jobject this,
jobject fdObj, jbyteArray data,
jint off, jint len) {
char *bufP;
char BUF[MAX_BUFFER_LEN];
int buflen;
int fd;

if (IS_NULL(fdObj)) {
JNU_ThrowByName(env, JNU_JAVANETPKG "SocketException", "Socket closed");
return;
} else {
fd = (*env)->GetIntField(env, fdObj, IO_fd_fdID);
}
if (IS_NULL(data)) {
JNU_ThrowNullPointerException(env, "data argument");
return;
}

/*
* Use stack allocate buffer if possible. For large sizes we allocate
* an intermediate buffer from the heap (up to a maximum). If heap is
* unavailable just use our stack buffer.
*/
if (len <= MAX_BUFFER_LEN) {
bufP = BUF;
buflen = MAX_BUFFER_LEN;
} else {
buflen = min(MAX_HEAP_BUFFER_LEN, len);
bufP = (char *)malloc((size_t)buflen);
if (bufP == NULL) {
bufP = BUF;
buflen = MAX_BUFFER_LEN;
}
}

while(len > 0) {
int loff = 0;
int chunkLen = min(buflen, len);
int llen = chunkLen;
int retry = 0;

(*env)->GetByteArrayRegion(env, data, off, chunkLen, (jbyte *)bufP);

while(llen > 0) {
int n = send(fd, bufP + loff, llen, 0);
if (n > 0) {
llen -= n;
loff += n;
continue;
}

/*
* Due to a bug in Windows Sockets (observed on NT and Windows
* 2000) it may be necessary to retry the send. The issue is that
* on blocking sockets send/WSASend is supposed to block if there
* is insufficient buffer space available. If there are a large
* number of threads blocked on write due to congestion then it's
* possile to hit the NT/2000 bug whereby send returns WSAENOBUFS.
* The workaround we use is to retry the send. If we have a
* large buffer to send (>2k) then we retry with a maximum of
* 2k buffer. If we hit the issue with <=2k buffer then we backoff
* for 1 second and retry again. We repeat this up to a reasonable
* limit before bailing out and throwing an exception. In load
* conditions we've observed that the send will succeed after 2-3
* attempts but this depends on network buffers associated with
* other sockets draining.
*/
if (WSAGetLastError() == WSAENOBUFS) {
if (llen > MAX_BUFFER_LEN) {
buflen = MAX_BUFFER_LEN;
chunkLen = MAX_BUFFER_LEN;
llen = MAX_BUFFER_LEN;
continue;
}
if (retry >= 30) {
JNU_ThrowByName(env, JNU_JAVANETPKG "SocketException",
"No buffer space available - exhausted attempts to queue buffer");
if (bufP != BUF) {
free(bufP);
}
return;
}
Sleep(1000);
retry++;
continue;
}

/*
* Send failed - can be caused by close or write error.
*/
if (WSAGetLastError() == WSAENOTSOCK) {
JNU_ThrowByName(env, JNU_JAVANETPKG "SocketException", "Socket closed");
} else {
NET_ThrowCurrent(env, "socket write error");
}
if (bufP != BUF) {
free(bufP);
}
return;
}
len -= chunkLen;
off += chunkLen;
}

if (bufP != BUF) {
free(bufP);
}
}