Fossil

/*
 * gzlog.c
 * Copyright (C) 2004, 2008, 2012 Mark Adler, all rights reserved
 * For conditions of distribution and use, see copyright notice in gzlog.h
 * version 2.2, 14 Aug 2012
 */

/*
   gzlog provides a mechanism for frequently appending short strings to a gzip
   file that is efficient both in execution time and compression ratio.  The
   strategy is to write the short strings in an uncompressed form to the end of
   the gzip file, only compressing when the amount of uncompressed data has

    log_log(log, op, "start");

    /* load foo.add file if expected and present */
    if (op == APPEND_OP || op == COMPRESS_OP) {
        strcpy(log->end, ".add");
        if (stat(log->path, &st) == 0 && st.st_size) {
            len = (size_t)(st.st_size);
            if ((off_t)len != st.st_size ||
                    (data = malloc(st.st_size)) == NULL) {
                log_log(log, op, "allocation failure");
                return -2;
            }
            if ((fd = open(log->path, O_RDONLY, 0)) < 0) {
                log_log(log, op, ".add file read failure");
                return -1;
            }
            ret = (size_t)read(fd, data, len) != len;
            close(fd);
            if (ret) {
                log_log(log, op, ".add file read failure");
                return -1;
            }
            log_log(log, op, "loaded .add file");
        }

    int fd, ret;
    uint block;
    size_t len, next;
    unsigned char *data, buf[5];
    struct log *log = logd;

    /* check arguments */
    if (log == NULL || strcmp(log->id, LOGID))
        return -3;

    /* see if we lost the lock -- if so get it again and reload the extra
       field information (it probably changed), recover last operation if
       necessary */
    if (log_check(log) && log_open(log))
        return -1;

        log_touch(log);

        /* write the uncompressed data to the .add file */
        strcpy(log->end, ".add");
        fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
        if (fd < 0)
            break;
        ret = (size_t)write(fd, data, len) != len;
        if (ret | close(fd))
            break;
        log_touch(log);

        /* write the dictionary for the next compress to the .temp file */
        strcpy(log->end, ".temp");
        fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
        if (fd < 0)
            break;
        next = DICT > len ? len : DICT;
        ret = (size_t)write(fd, (char *)data + len - next, next) != next;
        if (ret | close(fd))
            break;
        log_touch(log);

        /* roll back to compressed data, mark the compress in progress */
        log->last = log->first;
        log->stored = 0;

   -3: invalid log pointer argument */
int gzlog_write(gzlog *logd, void *data, size_t len)
{
    int fd, ret;
    struct log *log = logd;

    /* check arguments */
    if (log == NULL || strcmp(log->id, LOGID))
        return -3;
    if (data == NULL || len <= 0)
        return 0;

    /* see if we lost the lock -- if so get it again and reload the extra
       field information (it probably changed), recover last operation if
       necessary */
    if (log_check(log) && log_open(log))
        return -1;

    /* create and write .add file */
    strcpy(log->end, ".add");
    fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd < 0)
        return -1;
    ret = (size_t)write(fd, data, len) != len;
    if (ret | close(fd))
        return -1;
    log_touch(log);

    /* mark log file with append in progress */
    if (log_mark(log, APPEND_OP))
        return -1;