load_file.c

[詳解]

/*++
/* NAME
/*  load_file 3
/* SUMMARY
/*  load file with some prejudice
/* SYNOPSIS
/*  #include <load_file.h>
/*
/*  void    load_file(path, action, context)
/*  const char *path;
/*  void    (*action)(VSTREAM, void *);
/*  void    *context;
/* DESCRIPTION
/*  This routine reads a file and reads it again when the
/*  file changed recently.
/*
/*  Arguments:
/* .IP path
/*  The file to be opened, read-only.
/* .IP action
/*  The function that presumably reads the file.
/* .IP context
/*  Application-specific context for the action routine.
/* DIAGNOSTICS
/*  Fatal errors: out of memory, cannot open file.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <sys/stat.h>
#include <time.h>

/* Utility library. */

#include <msg.h>
#include <vstream.h>
#include <iostuff.h>
#include <load_file.h>
#include <warn_stat.h>

/* load_file - load file with some prejudice */

void    load_file(const char *path, LOAD_FILE_FN action, void *context)
{
    VSTREAM *fp;
    struct stat st;
    time_t  before;
    time_t  after;

    /*
     * Read the file again if it is hot. This may result in reading a partial
     * parameter name or missing end marker when a file changes in the middle
     * of a read.
     */
    for (before = time((time_t *) 0); /* see below */ ; before = after) {
    if ((fp = vstream_fopen(path, O_RDONLY, 0)) == 0)
        msg_fatal("open %s: %m", path);
    action(fp, context);
    if (fstat(vstream_fileno(fp), &st) < 0)
        msg_fatal("fstat %s: %m", path);
    if (vstream_ferror(fp) || vstream_fclose(fp))
        msg_fatal("read %s: %m", path);
    after = time((time_t *) 0);
    if (st.st_mtime < before - 1 || st.st_mtime > after)
        break;
    if (msg_verbose)
        msg_info("pausing to let %s cool down", path);
    doze(300000);
    }
}