main/native/java_io_File.cpp

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 "File"

#include "JNIHelp.h"
#include "JniConstants.h"
#include "LocalArray.h"
#include "ScopedFd.h"
#include "ScopedLocalRef.h"
#include "ScopedPrimitiveArray.h"
#include "ScopedUtfChars.h"

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/vfs.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include <utime.h>

static jboolean File_deleteImpl(JNIEnv* env, jclass, jstring javaPath) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }
    return (remove(path.c_str()) == 0);
}

static bool doStat(JNIEnv* env, jstring javaPath, struct stat& sb) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }
    return (stat(path.c_str(), &sb) == 0);
}

static jlong File_lengthImpl(JNIEnv* env, jclass, jstring javaPath) {
    struct stat sb;
    if (!doStat(env, javaPath, sb)) {
        // We must return 0 for files that don't exist.
        // TODO: shouldn't we throw an IOException for ELOOP or EACCES?
        return 0;
    }

    /*
     * This android-changed code explicitly treats non-regular files (e.g.,
     * sockets and block-special devices) as having size zero. Some synthetic
     * "regular" files may report an arbitrary non-zero size, but
     * in these cases they generally report a block count of zero.
     * So, use a zero block count to trump any other concept of
     * size.
     *
     * TODO: why do we do this?
     */
    if (!S_ISREG(sb.st_mode) || sb.st_blocks == 0) {
        return 0;
    }
    return sb.st_size;
}

static jlong File_lastModifiedImpl(JNIEnv* env, jclass, jstring javaPath) {
    struct stat sb;
    if (!doStat(env, javaPath, sb)) {
        return 0;
    }
    return static_cast<jlong>(sb.st_mtime) * 1000L;
}

static jboolean File_isDirectoryImpl(JNIEnv* env, jclass, jstring javaPath) {
    struct stat sb;
    return (doStat(env, javaPath, sb) && S_ISDIR(sb.st_mode));
}

static jboolean File_isFileImpl(JNIEnv* env, jclass, jstring javaPath) {
    struct stat sb;
    return (doStat(env, javaPath, sb) && S_ISREG(sb.st_mode));
}

static jboolean doAccess(JNIEnv* env, jstring javaPath, int mode) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }
    return (access(path.c_str(), mode) == 0);
}

static jboolean File_existsImpl(JNIEnv* env, jclass, jstring javaPath) {
    return doAccess(env, javaPath, F_OK);
}

static jboolean File_canExecuteImpl(JNIEnv* env, jclass, jstring javaPath) {
    return doAccess(env, javaPath, X_OK);
}

static jboolean File_canReadImpl(JNIEnv* env, jclass, jstring javaPath) {
    return doAccess(env, javaPath, R_OK);
}

static jboolean File_canWriteImpl(JNIEnv* env, jclass, jstring javaPath) {
    return doAccess(env, javaPath, W_OK);
}

static jstring File_readlink(JNIEnv* env, jclass, jstring javaPath) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return NULL;
    }

    // We can't know how big a buffer readlink(2) will need, so we need to
    // loop until it says "that fit".
    size_t bufSize = 512;
    while (true) {
        LocalArray<512> buf(bufSize);
        ssize_t len = readlink(path.c_str(), &buf[0], buf.size() - 1);
        if (len == -1) {
            // An error occurred.
            return javaPath;
        }
        if (static_cast<size_t>(len) < buf.size() - 1) {
            // The buffer was big enough.
            buf[len] = '\0'; // readlink(2) doesn't NUL-terminate.
            return env->NewStringUTF(&buf[0]);
        }
        // Try again with a bigger buffer.
        bufSize *= 2;
    }
}

static jboolean File_setLastModifiedImpl(JNIEnv* env, jclass, jstring javaPath, jlong ms) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }

    // We want to preserve the access time.
    struct stat sb;
    if (stat(path.c_str(), &sb) == -1) {
        return JNI_FALSE;
    }

    // TODO: we could get microsecond resolution with utimes(3), "legacy" though it is.
    utimbuf times;
    times.actime = sb.st_atime;
    times.modtime = static_cast<time_t>(ms / 1000);
    return (utime(path.c_str(), &times) == 0);
}

static jboolean doChmod(JNIEnv* env, jstring javaPath, mode_t mask, bool set) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }

    struct stat sb;
    if (stat(path.c_str(), &sb) == -1) {
        return JNI_FALSE;
    }
    mode_t newMode = set ? (sb.st_mode | mask) : (sb.st_mode & ~mask);
    return (chmod(path.c_str(), newMode) == 0);
}

static jboolean File_setExecutableImpl(JNIEnv* env, jclass, jstring javaPath,
        jboolean set, jboolean ownerOnly) {
    return doChmod(env, javaPath, ownerOnly ? S_IXUSR : (S_IXUSR | S_IXGRP | S_IXOTH), set);
}

static jboolean File_setReadableImpl(JNIEnv* env, jclass, jstring javaPath,
        jboolean set, jboolean ownerOnly) {
    return doChmod(env, javaPath, ownerOnly ? S_IRUSR : (S_IRUSR | S_IRGRP | S_IROTH), set);
}

static jboolean File_setWritableImpl(JNIEnv* env, jclass, jstring javaPath,
        jboolean set, jboolean ownerOnly) {
    return doChmod(env, javaPath, ownerOnly ? S_IWUSR : (S_IWUSR | S_IWGRP | S_IWOTH), set);
}

static bool doStatFs(JNIEnv* env, jstring javaPath, struct statfs& sb) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }

    int rc = statfs(path.c_str(), &sb);
    return (rc != -1);
}

static jlong File_getFreeSpaceImpl(JNIEnv* env, jclass, jstring javaPath) {
    struct statfs sb;
    if (!doStatFs(env, javaPath, sb)) {
        return 0;
    }
    return sb.f_bfree * sb.f_bsize; // free block count * block size in bytes.
}

static jlong File_getTotalSpaceImpl(JNIEnv* env, jclass, jstring javaPath) {
    struct statfs sb;
    if (!doStatFs(env, javaPath, sb)) {
        return 0;
    }
    return sb.f_blocks * sb.f_bsize; // total block count * block size in bytes.
}

static jlong File_getUsableSpaceImpl(JNIEnv* env, jclass, jstring javaPath) {
    struct statfs sb;
    if (!doStatFs(env, javaPath, sb)) {
        return 0;
    }
    return sb.f_bavail * sb.f_bsize; // non-root free block count * block size in bytes.
}

// Iterates over the filenames in the given directory.
class ScopedReaddir {
public:
    ScopedReaddir(const char* path) {
        mDirStream = opendir(path);
        mIsBad = (mDirStream == NULL);
    }

    ~ScopedReaddir() {
        if (mDirStream != NULL) {
            closedir(mDirStream);
        }
    }

    // Returns the next filename, or NULL.
    const char* next() {
        dirent* result = NULL;
        int rc = readdir_r(mDirStream, &mEntry, &result);
        if (rc != 0) {
            mIsBad = true;
            return NULL;
        }
        return (result != NULL) ? result->d_name : NULL;
    }

    // Has an error occurred on this stream?
    bool isBad() const {
        return mIsBad;
    }

private:
    DIR* mDirStream;
    dirent mEntry;
    bool mIsBad;

    // Disallow copy and assignment.
    ScopedReaddir(const ScopedReaddir&);
    void operator=(const ScopedReaddir&);
};

// DirEntry and DirEntries is a minimal equivalent of std::forward_list
// for the filenames.
struct DirEntry {
    DirEntry(const char* filename) : name(strlen(filename)) {
        strcpy(&name[0], filename);
        next = NULL;
    }
    // On Linux, the ext family all limit the length of a directory entry to
    // less than 256 characters.
    LocalArray<256> name;
    DirEntry* next;
};

class DirEntries {
public:
    DirEntries() : mSize(0), mHead(NULL) {
    }

    ~DirEntries() {
        while (mHead) {
            pop_front();
        }
    }

    bool push_front(const char* name) {
        DirEntry* oldHead = mHead;
        mHead = new DirEntry(name);
        if (mHead == NULL) {
            return false;
        }
        mHead->next = oldHead;
        ++mSize;
        return true;
    }

    const char* front() const {
        return &mHead->name[0];
    }

    void pop_front() {
        DirEntry* popped = mHead;
        if (popped != NULL) {
            mHead = popped->next;
            --mSize;
            delete popped;
        }
    }

    size_t size() const {
        return mSize;
    }

private:
    size_t mSize;
    DirEntry* mHead;

    // Disallow copy and assignment.
    DirEntries(const DirEntries&);
    void operator=(const DirEntries&);
};

// Reads the directory referred to by 'pathBytes', adding each directory entry
// to 'entries'.
static bool readDirectory(JNIEnv* env, jstring javaPath, DirEntries& entries) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return false;
    }

    ScopedReaddir dir(path.c_str());
    if (dir.isBad()) {
        return false;
    }
    const char* filename;
    while ((filename = dir.next()) != NULL) {
        if (strcmp(filename, ".") != 0 && strcmp(filename, "..") != 0) {
            if (!entries.push_front(filename)) {
                jniThrowException(env, "java/lang/OutOfMemoryError", NULL);
                return false;
            }
        }
    }
    return true;
}

static jobjectArray File_listImpl(JNIEnv* env, jclass, jstring javaPath) {
    // Read the directory entries into an intermediate form.
    DirEntries files;
    if (!readDirectory(env, javaPath, files)) {
        return NULL;
    }
    // Translate the intermediate form into a Java String[].
    jobjectArray result = env->NewObjectArray(files.size(), JniConstants::stringClass, NULL);
    for (int i = 0; files.size() != 0; files.pop_front(), ++i) {
        ScopedLocalRef<jstring> javaFilename(env, env->NewStringUTF(files.front()));
        if (env->ExceptionCheck()) {
            return NULL;
        }
        env->SetObjectArrayElement(result, i, javaFilename.get());
        if (env->ExceptionCheck()) {
            return NULL;
        }
    }
    return result;
}

static jboolean File_mkdirImpl(JNIEnv* env, jclass, jstring javaPath) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }

    // On Android, we don't want default permissions to allow global access.
    return (mkdir(path.c_str(), S_IRWXU) == 0);
}

static jboolean File_createNewFileImpl(JNIEnv* env, jclass, jstring javaPath) {
    ScopedUtfChars path(env, javaPath);
    if (path.c_str() == NULL) {
        return JNI_FALSE;
    }

    // On Android, we don't want default permissions to allow global access.
    ScopedFd fd(open(path.c_str(), O_CREAT | O_EXCL, 0600));
    if (fd.get() != -1) {
        // We created a new file. Success!
        return JNI_TRUE;
    }
    if (errno == EEXIST) {
        // The file already exists.
        return JNI_FALSE;
    }
    jniThrowIOException(env, errno);
    return JNI_FALSE; // Ignored by Java; keeps the C++ compiler happy.
}

static jboolean File_renameToImpl(JNIEnv* env, jclass, jstring javaOldPath, jstring javaNewPath) {
    ScopedUtfChars oldPath(env, javaOldPath);
    if (oldPath.c_str() == NULL) {
        return JNI_FALSE;
    }

    ScopedUtfChars newPath(env, javaNewPath);
    if (newPath.c_str() == NULL) {
        return JNI_FALSE;
    }

    return (rename(oldPath.c_str(), newPath.c_str()) == 0);
}

static JNINativeMethod gMethods[] = {
    NATIVE_METHOD(File, canExecuteImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, canReadImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, canWriteImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, createNewFileImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, deleteImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, existsImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, getFreeSpaceImpl, "(Ljava/lang/String;)J"),
    NATIVE_METHOD(File, getTotalSpaceImpl, "(Ljava/lang/String;)J"),
    NATIVE_METHOD(File, getUsableSpaceImpl, "(Ljava/lang/String;)J"),
    NATIVE_METHOD(File, isDirectoryImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, isFileImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, lastModifiedImpl, "(Ljava/lang/String;)J"),
    NATIVE_METHOD(File, lengthImpl, "(Ljava/lang/String;)J"),
    NATIVE_METHOD(File, listImpl, "(Ljava/lang/String;)[Ljava/lang/String;"),
    NATIVE_METHOD(File, mkdirImpl, "(Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, readlink, "(Ljava/lang/String;)Ljava/lang/String;"),
    NATIVE_METHOD(File, renameToImpl, "(Ljava/lang/String;Ljava/lang/String;)Z"),
    NATIVE_METHOD(File, setExecutableImpl, "(Ljava/lang/String;ZZ)Z"),
    NATIVE_METHOD(File, setLastModifiedImpl, "(Ljava/lang/String;J)Z"),
    NATIVE_METHOD(File, setReadableImpl, "(Ljava/lang/String;ZZ)Z"),
    NATIVE_METHOD(File, setWritableImpl, "(Ljava/lang/String;ZZ)Z"),
};
int register_java_io_File(JNIEnv* env) {
    return jniRegisterNativeMethods(env, "java/io/File", gMethods, NELEM(gMethods));
}