xref: /libcore/luni/src/main/native/libcore_io_Linux.cpp

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "Posix"

#include "JNIHelp.h"
#include "JniConstants.h"
#include "JniException.h"
#include "ScopedPrimitiveArray.h"
#include "ScopedUtfChars.h"
#include "StaticAssert.h"
#include "toStringArray.h"

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/sendfile.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/utsname.h>
#include <sys/vfs.h> // Bionic doesn't have <sys/statvfs.h>
#include <unistd.h>

static void throwErrnoException(JNIEnv* env, const char* name) {
    int errnum = errno;

    jthrowable cause = NULL;
    if (env->ExceptionCheck()) {
        cause = env->ExceptionOccurred();
        env->ExceptionClear();
    }

    ScopedLocalRef<jstring> javaName(env, env->NewStringUTF(name));
    if (javaName.get() == NULL) {
        // Not really much we can do here. We're probably dead in the water,
        // but let's try to stumble on...
        env->ExceptionClear();
    }

    jobject exception;
    if (cause != NULL) {
        static jmethodID ctor = env->GetMethodID(JniConstants::errnoExceptionClass, "<init>",
                "(Ljava/lang/String;ILjava/lang/Throwable;)V");
        exception = env->NewObject(JniConstants::errnoExceptionClass, ctor,
                javaName.get(), errnum, cause);
    } else {
        static jmethodID ctor = env->GetMethodID(JniConstants::errnoExceptionClass, "<init>",
                "(Ljava/lang/String;I)V");
        exception = env->NewObject(JniConstants::errnoExceptionClass, ctor, javaName.get(), errnum);
    }
    env->Throw(reinterpret_cast<jthrowable>(exception));
}

template <typename rc_t>
static rc_t throwIfMinusOne(JNIEnv* env, const char* name, rc_t rc) {
    if (rc == rc_t(-1)) {
        throwErrnoException(env, name);
    }
    return rc;
}

template <typename T>
class IoVec {
public:
    IoVec(JNIEnv* env, size_t bufferCount) : mEnv(env), mBufferCount(bufferCount) {
    }

    bool init(jobjectArray javaBuffers, jintArray javaOffsets, jintArray javaByteCounts) {
        // We can't delete our local references until after the I/O, so make sure we have room.
        if (mEnv->PushLocalFrame(mBufferCount + 16) < 0) {
            return false;
        }
        ScopedIntArrayRO offsets(mEnv, javaOffsets);
        if (offsets.get() == NULL) {
            return false;
        }
        ScopedIntArrayRO byteCounts(mEnv, javaByteCounts);
        if (byteCounts.get() == NULL) {
            return false;
        }
        // TODO: Linux actually has a 1024 buffer limit. glibc works around this, and we should too.
        for (size_t i = 0; i < mBufferCount; ++i) {
            jobject buffer = mEnv->GetObjectArrayElement(javaBuffers, i);
            jbyte* ptr;
            if (mEnv->IsInstanceOf(buffer, JniConstants::byteArrayClass)) {
                // We need to pin the array for the duration.
                jbyteArray byteArray = reinterpret_cast<jbyteArray>(buffer);
                mScopedByteArrays.push_back(new T(mEnv, byteArray));
                ptr = const_cast<jbyte*>(mScopedByteArrays.back()->get());
            } else {
                // A direct ByteBuffer is easier.
                ptr = reinterpret_cast<jbyte*>(mEnv->GetDirectBufferAddress(buffer));
            }
            if (ptr == NULL) {
                return false;
            }
            struct iovec iov;
            iov.iov_base = reinterpret_cast<void*>(ptr + offsets[i]);
            iov.iov_len = byteCounts[i];
            mIoVec.push_back(iov);
        }
        return true;
    }

    ~IoVec() {
        for (size_t i = 0; i < mScopedByteArrays.size(); ++i) {
            delete mScopedByteArrays[i];
        }
        mEnv->PopLocalFrame(NULL);
    }

    iovec* get() {
        return &mIoVec[0];
    }

    size_t size() {
        return mBufferCount;
    }

private:
    JNIEnv* mEnv;
    size_t mBufferCount;
    std::vector<iovec> mIoVec;
    std::vector<T*> mScopedByteArrays;
};

static jobject makeStructStat(JNIEnv* env, const struct stat& sb) {
    static jmethodID ctor = env->GetMethodID(JniConstants::structStatClass, "<init>",
            "(JJIJIIJJJJJJJ)V");
    return env->NewObject(JniConstants::structStatClass, ctor,
            static_cast<jlong>(sb.st_dev), static_cast<jlong>(sb.st_ino),
            static_cast<jint>(sb.st_mode), static_cast<jlong>(sb.st_nlink),
            static_cast<jint>(sb.st_uid), static_cast<jint>(sb.st_gid),
            static_cast<jlong>(sb.st_rdev), static_cast<jlong>(sb.st_size),
            static_cast<jlong>(sb.st_atime), static_cast<jlong>(sb.st_mtime),
            static_cast<jlong>(sb.st_ctime), static_cast<jlong>(sb.st_blksize),
            static_cast<jlong>(sb.st_blocks));
}

static jobject makeStructStatFs(JNIEnv* env, const struct statfs& sb) {
    STATIC_ASSERT(sizeof(sb.f_bavail) == sizeof(jlong), statfs_not_64_bit);
    STATIC_ASSERT(sizeof(sb.f_bfree) == sizeof(jlong), statfs_not_64_bit);
    STATIC_ASSERT(sizeof(sb.f_blocks) == sizeof(jlong), statfs_not_64_bit);

    static jmethodID ctor = env->GetMethodID(JniConstants::structStatFsClass, "<init>",
            "(JJJJJJJJ)V");
    return env->NewObject(JniConstants::structStatFsClass, ctor, static_cast<jlong>(sb.f_bsize),
            static_cast<jlong>(sb.f_blocks), static_cast<jlong>(sb.f_bfree),
            static_cast<jlong>(sb.f_bavail), static_cast<jlong>(sb.f_files),
            static_cast<jlong>(sb.f_ffree), static_cast<jlong>(sb.f_namelen),
            static_cast<jlong>(sb.f_frsize));
}

static jobject makeStructUtsname(JNIEnv* env, const struct utsname& buf) {
#define TO_JAVA_STRING(NAME) \
        jstring NAME = env->NewStringUTF(buf. NAME); \
        if (NAME == NULL) return NULL;

    TO_JAVA_STRING(sysname);
    TO_JAVA_STRING(nodename);
    TO_JAVA_STRING(release);
    TO_JAVA_STRING(version);
    TO_JAVA_STRING(machine);
#undef TO_JAVA_STRING

    static jmethodID ctor = env->GetMethodID(JniConstants::structUtsnameClass, "<init>",
            "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)V");
    return env->NewObject(JniConstants::structUtsnameClass, ctor,
            sysname, nodename, release, version, machine);
};

static jobject doStat(JNIEnv* env, jstring javaPath, bool isLstat) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return NULL;
    }
    struct stat sb;
    int rc = isLstat ? TEMP_FAILURE_RETRY(lstat(path.c_str(), &sb))
                     : TEMP_FAILURE_RETRY(stat(path.c_str(), &sb));
    if (rc == -1) {
        throwErrnoException(env, isLstat ? "lstat" : "stat");
        return NULL;
    }
    return makeStructStat(env, sb);
}

static jboolean Posix_access(JNIEnv* env, jobject, jstring javaPath, jint mode) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }
    int rc = TEMP_FAILURE_RETRY(access(path.c_str(), mode));
    if (rc == -1) {
        throwErrnoException(env, "access");
    }
    return (rc == 0);
}

static void Posix_chmod(JNIEnv* env, jobject, jstring javaPath, jint mode) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return;
    }
    throwIfMinusOne(env, "chmod", TEMP_FAILURE_RETRY(chmod(path.c_str(), mode)));
}

static void Posix_close(JNIEnv* env, jobject, jobject javaFd) {
    // Get the FileDescriptor's 'fd' field and clear it.
    // We need to do this before we can throw an IOException (http://b/3222087).
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    jniSetFileDescriptorOfFD(env, javaFd, -1);

    // Even if close(2) fails with EINTR, the fd will have been closed.
    // Using TEMP_FAILURE_RETRY will either lead to EBADF or closing someone else's fd.
    // http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
    throwIfMinusOne(env, "close", close(fd));
}

static jobjectArray Posix_environ(JNIEnv* env, jobject) {
    extern char** environ; // Standard, but not in any header file.
    return toStringArray(env, environ);
}

static jint Posix_fcntlVoid(JNIEnv* env, jobject, jobject javaFd, jint cmd) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    return throwIfMinusOne(env, "fcntl", TEMP_FAILURE_RETRY(fcntl(fd, cmd)));
}

static jint Posix_fcntlLong(JNIEnv* env, jobject, jobject javaFd, jint cmd, jlong arg) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    return throwIfMinusOne(env, "fcntl", TEMP_FAILURE_RETRY(fcntl(fd, cmd, arg)));
}

static jint Posix_fcntlFlock(JNIEnv* env, jobject, jobject javaFd, jint cmd, jobject javaFlock) {
    static jfieldID typeFid = env->GetFieldID(JniConstants::structFlockClass, "l_type", "S");
    static jfieldID whenceFid = env->GetFieldID(JniConstants::structFlockClass, "l_whence", "S");
    static jfieldID startFid = env->GetFieldID(JniConstants::structFlockClass, "l_start", "J");
    static jfieldID lenFid = env->GetFieldID(JniConstants::structFlockClass, "l_len", "J");
    static jfieldID pidFid = env->GetFieldID(JniConstants::structFlockClass, "l_pid", "I");

    struct flock64 lock;
    memset(&lock, 0, sizeof(lock));
    lock.l_type = env->GetShortField(javaFlock, typeFid);
    lock.l_whence = env->GetShortField(javaFlock, whenceFid);
    lock.l_start = env->GetLongField(javaFlock, startFid);
    lock.l_len = env->GetLongField(javaFlock, lenFid);
    lock.l_pid = env->GetIntField(javaFlock, pidFid);

    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    int rc = throwIfMinusOne(env, "fcntl", TEMP_FAILURE_RETRY(fcntl(fd, cmd, &lock)));
    if (rc != -1) {
        env->SetShortField(javaFlock, typeFid, lock.l_type);
        env->SetShortField(javaFlock, whenceFid, lock.l_whence);
        env->SetLongField(javaFlock, startFid, lock.l_start);
        env->SetLongField(javaFlock, lenFid, lock.l_len);
        env->SetIntField(javaFlock, pidFid, lock.l_pid);
    }
    return rc;
}

static void Posix_fdatasync(JNIEnv* env, jobject, jobject javaFd) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    throwIfMinusOne(env, "fdatasync", TEMP_FAILURE_RETRY(fdatasync(fd)));
}

static jobject Posix_fstat(JNIEnv* env, jobject, jobject javaFd) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    struct stat sb;
    int rc = TEMP_FAILURE_RETRY(fstat(fd, &sb));
    if (rc == -1) {
        throwErrnoException(env, "fstat");
        return NULL;
    }
    return makeStructStat(env, sb);
}

static jobject Posix_fstatfs(JNIEnv* env, jobject, jobject javaFd) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    struct statfs sb;
    int rc = TEMP_FAILURE_RETRY(fstatfs(fd, &sb));
    if (rc == -1) {
        throwErrnoException(env, "fstatfs");
        return NULL;
    }
    return makeStructStatFs(env, sb);
}

static void Posix_fsync(JNIEnv* env, jobject, jobject javaFd) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    throwIfMinusOne(env, "fsync", TEMP_FAILURE_RETRY(fsync(fd)));
}

static void Posix_ftruncate(JNIEnv* env, jobject, jobject javaFd, jlong length) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    throwIfMinusOne(env, "ftruncate", TEMP_FAILURE_RETRY(ftruncate64(fd, length)));
}

static jstring Posix_getenv(JNIEnv* env, jobject, jstring javaName) {
    ScopedUtfChars name(env, javaName);
    if (name.c_str() == NULL) {
        return NULL;
    }
    return env->NewStringUTF(getenv(name.c_str()));
}

static jint Posix_ioctlInt(JNIEnv* env, jobject, jobject javaFd, jint cmd, jobject javaArg) {
    // This is complicated because ioctls may return their result by updating their argument
    // or via their return value, so we need to support both.
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    static jfieldID valueFid = env->GetFieldID(JniConstants::mutableIntClass, "value", "I");
    jint arg = env->GetIntField(javaArg, valueFid);
    int rc = throwIfMinusOne(env, "ioctl", TEMP_FAILURE_RETRY(ioctl(fd, cmd, &arg)));
    if (!env->ExceptionCheck()) {
        env->SetIntField(javaArg, valueFid, arg);
    }
    return rc;
}

static jboolean Posix_isatty(JNIEnv* env, jobject, jobject javaFd) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    return TEMP_FAILURE_RETRY(isatty(fd)) == 0;
}

static void Posix_listen(JNIEnv* env, jobject, jobject javaFd, jint backlog) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    throwIfMinusOne(env, "listen", TEMP_FAILURE_RETRY(listen(fd, backlog)));
}

static jlong Posix_lseek(JNIEnv* env, jobject, jobject javaFd, jlong offset, jint whence) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    return throwIfMinusOne(env, "lseek", TEMP_FAILURE_RETRY(lseek64(fd, offset, whence)));
}

static jobject Posix_lstat(JNIEnv* env, jobject, jstring javaPath) {
    return doStat(env, javaPath, true);
}

static void Posix_mincore(JNIEnv* env, jobject, jlong address, jlong byteCount, jbyteArray javaVector) {
    ScopedByteArrayRW vector(env, javaVector);
    if (vector.get() == NULL) {
        return;
    }
    void* ptr = reinterpret_cast<void*>(static_cast<uintptr_t>(address));
    unsigned char* vec = reinterpret_cast<unsigned char*>(vector.get());
    throwIfMinusOne(env, "mincore", TEMP_FAILURE_RETRY(mincore(ptr, byteCount, vec)));
}

static void Posix_mkdir(JNIEnv* env, jobject, jstring javaPath, jint mode) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return;
    }
    throwIfMinusOne(env, "mkdir", TEMP_FAILURE_RETRY(mkdir(path.c_str(), mode)));
}

static void Posix_mlock(JNIEnv* env, jobject, jlong address, jlong byteCount) {
    void* ptr = reinterpret_cast<void*>(static_cast<uintptr_t>(address));
    throwIfMinusOne(env, "mlock", TEMP_FAILURE_RETRY(mlock(ptr, byteCount)));
}

static jlong Posix_mmap(JNIEnv* env, jobject, jlong address, jlong byteCount, jint prot, jint flags, jobject javaFd, jlong offset) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    void* suggestedPtr = reinterpret_cast<void*>(static_cast<uintptr_t>(address));
    void* ptr = mmap(suggestedPtr, byteCount, prot, flags, fd, offset);
    if (ptr == MAP_FAILED) {
        throwErrnoException(env, "mmap");
    }
    return static_cast<jlong>(reinterpret_cast<uintptr_t>(ptr));
}

static void Posix_msync(JNIEnv* env, jobject, jlong address, jlong byteCount, jint flags) {
    void* ptr = reinterpret_cast<void*>(static_cast<uintptr_t>(address));
    throwIfMinusOne(env, "msync", TEMP_FAILURE_RETRY(msync(ptr, byteCount, flags)));
}

static void Posix_munlock(JNIEnv* env, jobject, jlong address, jlong byteCount) {
    void* ptr = reinterpret_cast<void*>(static_cast<uintptr_t>(address));
    throwIfMinusOne(env, "munlock", TEMP_FAILURE_RETRY(munlock(ptr, byteCount)));
}

static void Posix_munmap(JNIEnv* env, jobject, jlong address, jlong byteCount) {
    void* ptr = reinterpret_cast<void*>(static_cast<uintptr_t>(address));
    throwIfMinusOne(env, "munmap", TEMP_FAILURE_RETRY(munmap(ptr, byteCount)));
}

static jobject Posix_open(JNIEnv* env, jobject, jstring javaPath, jint flags, jint mode) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return NULL;
    }
    int fd = throwIfMinusOne(env, "open", TEMP_FAILURE_RETRY(open(path.c_str(), flags, mode)));
    return fd != -1 ? jniCreateFileDescriptor(env, fd) : NULL;
}

static jobjectArray Posix_pipe(JNIEnv* env, jobject) {
    int fds[2];
    throwIfMinusOne(env, "pipe", TEMP_FAILURE_RETRY(pipe(&fds[0])));
    jobjectArray result = env->NewObjectArray(2, JniConstants::fileDescriptorClass, NULL);
    if (result == NULL) {
        return NULL;
    }
    for (int i = 0; i < 2; ++i) {
        ScopedLocalRef<jobject> fd(env, jniCreateFileDescriptor(env, fds[i]));
        if (fd.get() == NULL) {
            return NULL;
        }
        env->SetObjectArrayElement(result, i, fd.get());
        if (env->ExceptionCheck()) {
            return NULL;
        }
    }
    return result;
}

static jint Posix_read(JNIEnv* env, jobject, jobject javaFd, jbyteArray javaBytes, jint byteOffset, jint byteCount) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    ScopedByteArrayRW bytes(env, javaBytes);
    if (bytes.get() == NULL) {
        return -1;
    }
    return throwIfMinusOne(env, "read", TEMP_FAILURE_RETRY(read(fd, bytes.get() + byteOffset, byteCount)));
}

static jint Posix_readDirectBuffer(JNIEnv* env, jobject, jobject javaFd, jobject byteBuffer, jint position, jint remaining) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    jbyte* ptr = reinterpret_cast<jbyte*>(env->GetDirectBufferAddress(byteBuffer));
    return throwIfMinusOne(env, "read", TEMP_FAILURE_RETRY(read(fd, ptr + position, remaining)));
}

static jint Posix_readv(JNIEnv* env, jobject, jobject javaFd, jobjectArray buffers, jintArray offsets, jintArray byteCounts) {
    IoVec<ScopedByteArrayRW> ioVec(env, env->GetArrayLength(buffers));
    if (!ioVec.init(buffers, offsets, byteCounts)) {
        return -1;
    }
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    return throwIfMinusOne(env, "readv", TEMP_FAILURE_RETRY(readv(fd, ioVec.get(), ioVec.size())));
}

static void Posix_remove(JNIEnv* env, jobject, jstring javaPath) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return;
    }
    throwIfMinusOne(env, "remove", TEMP_FAILURE_RETRY(remove(path.c_str())));
}

static void Posix_rename(JNIEnv* env, jobject, jstring javaOldPath, jstring javaNewPath) {
    ScopedUtfChars oldPath(env, javaOldPath);
    if (oldPath.c_str() == NULL) {
        return;
    }
    ScopedUtfChars newPath(env, javaNewPath);
    if (newPath.c_str() == NULL) {
        return;
    }
    throwIfMinusOne(env, "rename", TEMP_FAILURE_RETRY(rename(oldPath.c_str(), newPath.c_str())));
}

static jlong Posix_sendfile(JNIEnv* env, jobject, jobject javaOutFd, jobject javaInFd, jobject javaOffset, jlong byteCount) {
    int outFd = jniGetFDFromFileDescriptor(env, javaOutFd);
    int inFd = jniGetFDFromFileDescriptor(env, javaInFd);
    static jfieldID valueFid = env->GetFieldID(JniConstants::mutableLongClass, "value", "J");
    off_t offset = 0;
    off_t* offsetPtr = NULL;
    if (javaOffset != NULL) {
        // TODO: fix bionic so we can have a 64-bit off_t!
        offset = env->GetLongField(javaOffset, valueFid);
        offsetPtr = &offset;
    }
    jlong result = throwIfMinusOne(env, "sendfile", TEMP_FAILURE_RETRY(sendfile(outFd, inFd, offsetPtr, byteCount)));
    if (javaOffset != NULL) {
        env->SetLongField(javaOffset, valueFid, offset);
    }
    return result;
}

static void Posix_setsockoptInt(JNIEnv* env, jobject, jobject javaFd, jint level, jint option, jint value) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    throwIfMinusOne(env, "setsockopt", TEMP_FAILURE_RETRY(setsockopt(fd, level, option, &value, sizeof(value))));
}

static void Posix_shutdown(JNIEnv* env, jobject, jobject javaFd, jint how) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    throwIfMinusOne(env, "shutdown", TEMP_FAILURE_RETRY(shutdown(fd, how)));
}

static jobject Posix_socket(JNIEnv* env, jobject, jint domain, jint type, jint protocol) {
    int fd = throwIfMinusOne(env, "socket", TEMP_FAILURE_RETRY(socket(domain, type, protocol)));
    return fd != -1 ? jniCreateFileDescriptor(env, fd) : NULL;
}

static jobject Posix_stat(JNIEnv* env, jobject, jstring javaPath) {
    return doStat(env, javaPath, false);
}

static jobject Posix_statfs(JNIEnv* env, jstring javaPath) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return NULL;
    }
    struct statfs sb;
    int rc = TEMP_FAILURE_RETRY(statfs(path.c_str(), &sb));
    if (rc == -1) {
        throwErrnoException(env, "statfs");
        return NULL;
    }
    return makeStructStatFs(env, sb);
}

static jstring Posix_strerror(JNIEnv* env, jobject, jint errnum) {
    char buffer[BUFSIZ];
    const char* message = jniStrError(errnum, buffer, sizeof(buffer));
    return env->NewStringUTF(message);
}

static void Posix_symlink(JNIEnv* env, jobject, jstring javaOldPath, jstring javaNewPath) {
    ScopedUtfChars oldPath(env, javaOldPath);
    if (oldPath.c_str() == NULL) {
        return;
    }
    ScopedUtfChars newPath(env, javaNewPath);
    if (newPath.c_str() == NULL) {
        return;
    }
    throwIfMinusOne(env, "symlink", TEMP_FAILURE_RETRY(symlink(oldPath.c_str(), newPath.c_str())));
}

static jlong Posix_sysconf(JNIEnv* env, jobject, jint name) {
    // Since -1 is a valid result from sysconf(3), detecting failure is a little more awkward.
    errno = 0;
    long result = sysconf(name);
    if (result == -1L && errno == EINVAL) {
        throwErrnoException(env, "sysconf");
    }
    return result;
}

static jobject Posix_uname(JNIEnv* env, jobject) {
    struct utsname buf;
    if (throwIfMinusOne(env, "uname", TEMP_FAILURE_RETRY(uname(&buf))) == -1) {
        return NULL;
    }
    return makeStructUtsname(env, buf);
}

static jint Posix_write(JNIEnv* env, jobject, jobject javaFd, jbyteArray javaBytes, jint byteOffset, jint byteCount) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    ScopedByteArrayRO bytes(env, javaBytes);
    if (bytes.get() == NULL) {
        return -1;
    }
    return throwIfMinusOne(env, "write", TEMP_FAILURE_RETRY(write(fd, bytes.get() + byteOffset, byteCount)));
}

static jint Posix_writeDirectBuffer(JNIEnv* env, jobject, jobject javaFd, jobject byteBuffer, jint position, jint remaining) {
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    jbyte* ptr = reinterpret_cast<jbyte*>(env->GetDirectBufferAddress(byteBuffer));
    return throwIfMinusOne(env, "write", TEMP_FAILURE_RETRY(write(fd, ptr + position, remaining)));
}

static jint Posix_writev(JNIEnv* env, jobject, jobject javaFd, jobjectArray buffers, jintArray offsets, jintArray byteCounts) {
    IoVec<ScopedByteArrayRO> ioVec(env, env->GetArrayLength(buffers));
    if (!ioVec.init(buffers, offsets, byteCounts)) {
        return -1;
    }
    int fd = jniGetFDFromFileDescriptor(env, javaFd);
    return throwIfMinusOne(env, "writev", TEMP_FAILURE_RETRY(writev(fd, ioVec.get(), ioVec.size())));
}

static JNINativeMethod gMethods[] = {
    NATIVE_METHOD(Posix, access, "(Ljava/lang/String;I)Z"),
    NATIVE_METHOD(Posix, chmod, "(Ljava/lang/String;I)V"),
    NATIVE_METHOD(Posix, close, "(Ljava/io/FileDescriptor;)V"),
    NATIVE_METHOD(Posix, environ, "()[Ljava/lang/String;"),
    NATIVE_METHOD(Posix, fcntlVoid, "(Ljava/io/FileDescriptor;I)I"),
    NATIVE_METHOD(Posix, fcntlLong, "(Ljava/io/FileDescriptor;IJ)I"),
    NATIVE_METHOD(Posix, fcntlFlock, "(Ljava/io/FileDescriptor;ILlibcore/io/StructFlock;)I"),
    NATIVE_METHOD(Posix, fdatasync, "(Ljava/io/FileDescriptor;)V"),
    NATIVE_METHOD(Posix, fstat, "(Ljava/io/FileDescriptor;)Llibcore/io/StructStat;"),
    NATIVE_METHOD(Posix, fstatfs, "(Ljava/io/FileDescriptor;)Llibcore/io/StructStatFs;"),
    NATIVE_METHOD(Posix, fsync, "(Ljava/io/FileDescriptor;)V"),
    NATIVE_METHOD(Posix, ftruncate, "(Ljava/io/FileDescriptor;J)V"),
    NATIVE_METHOD(Posix, getenv, "(Ljava/lang/String;)Ljava/lang/String;"),
    NATIVE_METHOD(Posix, ioctlInt, "(Ljava/io/FileDescriptor;ILlibcore/util/MutableInt;)I"),
    NATIVE_METHOD(Posix, isatty, "(Ljava/io/FileDescriptor;)Z"),
    NATIVE_METHOD(Posix, listen, "(Ljava/io/FileDescriptor;I)V"),
    NATIVE_METHOD(Posix, lseek, "(Ljava/io/FileDescriptor;JI)J"),
    NATIVE_METHOD(Posix, lstat, "(Ljava/lang/String;)Llibcore/io/StructStat;"),
    NATIVE_METHOD(Posix, mincore, "(JJ[B)V"),
    NATIVE_METHOD(Posix, mkdir, "(Ljava/lang/String;I)V"),
    NATIVE_METHOD(Posix, mlock, "(JJ)V"),
    NATIVE_METHOD(Posix, mmap, "(JJIILjava/io/FileDescriptor;J)J"),
    NATIVE_METHOD(Posix, msync, "(JJI)V"),
    NATIVE_METHOD(Posix, munlock, "(JJ)V"),
    NATIVE_METHOD(Posix, munmap, "(JJ)V"),
    NATIVE_METHOD(Posix, open, "(Ljava/lang/String;II)Ljava/io/FileDescriptor;"),
    NATIVE_METHOD(Posix, pipe, "()[Ljava/io/FileDescriptor;"),
    NATIVE_METHOD(Posix, read, "(Ljava/io/FileDescriptor;[BII)I"),
    NATIVE_METHOD(Posix, readDirectBuffer, "(Ljava/io/FileDescriptor;Ljava/nio/ByteBuffer;II)I"),
    NATIVE_METHOD(Posix, readv, "(Ljava/io/FileDescriptor;[Ljava/lang/Object;[I[I)I"),
    NATIVE_METHOD(Posix, remove, "(Ljava/lang/String;)V"),
    NATIVE_METHOD(Posix, rename, "(Ljava/lang/String;Ljava/lang/String;)V"),
    NATIVE_METHOD(Posix, sendfile, "(Ljava/io/FileDescriptor;Ljava/io/FileDescriptor;Llibcore/util/MutableLong;J)J"),
    NATIVE_METHOD(Posix, setsockoptInt, "(Ljava/io/FileDescriptor;III)V"),
    NATIVE_METHOD(Posix, shutdown, "(Ljava/io/FileDescriptor;I)V"),
    NATIVE_METHOD(Posix, socket, "(III)Ljava/io/FileDescriptor;"),
    NATIVE_METHOD(Posix, stat, "(Ljava/lang/String;)Llibcore/io/StructStat;"),
    NATIVE_METHOD(Posix, statfs, "(Ljava/lang/String;)Llibcore/io/StructStatFs;"),
    NATIVE_METHOD(Posix, strerror, "(I)Ljava/lang/String;"),
    NATIVE_METHOD(Posix, symlink, "(Ljava/lang/String;Ljava/lang/String;)V"),
    NATIVE_METHOD(Posix, sysconf, "(I)J"),
    NATIVE_METHOD(Posix, uname, "()Llibcore/io/StructUtsname;"),
    NATIVE_METHOD(Posix, write, "(Ljava/io/FileDescriptor;[BII)I"),
    NATIVE_METHOD(Posix, writeDirectBuffer, "(Ljava/io/FileDescriptor;Ljava/nio/ByteBuffer;II)I"),
    NATIVE_METHOD(Posix, writev, "(Ljava/io/FileDescriptor;[Ljava/lang/Object;[I[I)I"),
};
int register_libcore_io_Posix(JNIEnv* env) {
    return jniRegisterNativeMethods(env, "libcore/io/Posix", gMethods, NELEM(gMethods));
}