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 *
 * Copyright (C) 2014-2019 Appsicle
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 *
 ******************************************************************************/

package com.questdb.cairo;

import com.questdb.log.Log;
import com.questdb.log.LogFactory;
import com.questdb.std.Files;
import com.questdb.std.FilesFacade;
import com.questdb.std.str.LPSZ;

public class AppendMemory extends VirtualMemory {
    private static final Log LOG = LogFactory.getLog(AppendMemory.class);
    private FilesFacade ff;
    private long fd = -1;
    private long pageAddress = 0;

    public AppendMemory(FilesFacade ff, LPSZ name, long pageSize) {
        of(ff, name, pageSize);
    }

    public AppendMemory() {
    }

    static void bestEffortClose(FilesFacade ff, Log log, long fd, boolean truncate, long size, long mapPageSize) {
        try {
            if (truncate) {
                if (ff.truncate(fd, size)) {
                    log.info().$("truncated and closed [fd=").$(fd).$(']').$();
                } else {
                    if (ff.isRestrictedFileSystem()) {
                        // Windows does truncate file if it has a mapped page somewhere, could be another handle and process.
                        // To make it work size needs to be rounded up to nearest page.
                        long n = size / mapPageSize;
                        if (ff.truncate(fd, (n + 1) * mapPageSize)) {
                            log.info().$("truncated and closed, second attempt [fd=").$(fd).$(']').$();
                            return;
                        }
                    }
                    log.info().$("closed without truncate [fd=").$(fd).$(", errno=").$(ff.errno()).$(']').$();
                }
            } else {
                log.info().$("closed [fd=").$(fd).$(']').$();
            }
        } finally {
            ff.close(fd);
        }
    }

    @Override
    public void close() {
        close(true);
    }

    public final void setSize(long size) {
        jumpTo(size);
    }

    public void truncate() {
        if (fd == -1) {
            // are we closed ?
            return;
        }

        releaseCurrentPage();
        if (!ff.truncate(fd, getMapPageSize())) {
            throw CairoException.instance(ff.errno()).put("Cannot truncate fd=").put(fd).put(" to ").put(getMapPageSize()).put(" bytes");
        }
        updateLimits(0, pageAddress = mapPage(0));
        LOG.info().$("truncated [fd=").$(fd).$(']').$();
    }

    public final void close(boolean truncate) {
        long sz = getAppendOffset();
        releaseCurrentPage();
        super.close();
        if (fd != -1) {
            try {
                bestEffortClose(ff, LOG, fd, truncate, sz, getMapPageSize());
            } finally {
                fd = -1;
            }
        }
    }

    public long getFd() {
        return fd;
    }

    public final void of(FilesFacade ff, LPSZ name, long pageSize) {
        close();
        this.ff = ff;
        setPageSize(pageSize);
        fd = ff.openRW(name);
        if (fd == -1) {
            throw CairoException.instance(ff.errno()).put("Cannot open ").put(name);
        }
        LOG.info().$("open ").$(name).$(" [fd=").$(fd).$(']').$();
    }

    FilesFacade getFilesFacade() {
        return ff;
    }

    @Override
    protected long mapWritePage(int page) {
        releaseCurrentPage();
        return pageAddress = mapPage(page);
    }

    @Override
    protected void release(int page, long address) {
        ff.munmap(address, getPageSize(page));
    }

    private long mapPage(int page) {
        long target = pageOffset(page + 1);
        if (ff.length(fd) < target && !ff.truncate(fd, target)) {
            throw CairoException.instance(ff.errno()).put("Appender resize failed fd=").put(fd).put(", size=").put(target);
        }
        long offset = pageOffset(page);
        long address = ff.mmap(fd, getMapPageSize(), offset, Files.MAP_RW);
        if (address == -1) {
            throw CairoException.instance(ff.errno()).put("Cannot mmap append fd=").put(fd).put(", offset=").put(offset).put(", size=").put(getMapPageSize());
        }
        return address;
    }

    private void releaseCurrentPage() {
        if (pageAddress != 0) {
            release(0, pageAddress);
            pageAddress = 0;
        }
    }
}