source: MondoRescue/branches/2.2.9/mindi-busybox/libbb/copyfd.c@ 2861

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) 1999-2005 by Erik Andersen <andersen@codepoet.org>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"

/* Used by NOFORK applets (e.g. cat) - must not use xmalloc.
 * size < 0 means "ignore write errors", used by tar --to-command
 * size = 0 means "copy till EOF"
 */
static off_t bb_full_fd_action(int src_fd, int dst_fd, off_t size)
{
    int status = -1;
    off_t total = 0;
    bool continue_on_write_error = 0;
#if CONFIG_FEATURE_COPYBUF_KB <= 4
    char buffer[CONFIG_FEATURE_COPYBUF_KB * 1024];
    enum { buffer_size = sizeof(buffer) };
#else
    char *buffer;
    int buffer_size;
#endif

    if (size < 0) {
        size = -size;
        continue_on_write_error = 1;
    }

#if CONFIG_FEATURE_COPYBUF_KB > 4
    if (size > 0 && size <= 4 * 1024)
        goto use_small_buf;
    /* We want page-aligned buffer, just in case kernel is clever
     * and can do page-aligned io more efficiently */
    buffer = mmap(NULL, CONFIG_FEATURE_COPYBUF_KB * 1024,
            PROT_READ | PROT_WRITE,
            MAP_PRIVATE | MAP_ANON,
            /* ignored: */ -1, 0);
    buffer_size = CONFIG_FEATURE_COPYBUF_KB * 1024;
    if (buffer == MAP_FAILED) {
 use_small_buf:
        buffer = alloca(4 * 1024);
        buffer_size = 4 * 1024;
    }
#endif

    if (src_fd < 0)
        goto out;

    if (!size) {
        size = buffer_size;
        status = 1; /* copy until eof */
    }

    while (1) {
        ssize_t rd;

        rd = safe_read(src_fd, buffer, size > buffer_size ? buffer_size : size);

        if (!rd) { /* eof - all done */
            status = 0;
            break;
        }
        if (rd < 0) {
            bb_perror_msg(bb_msg_read_error);
            break;
        }
        /* dst_fd == -1 is a fake, else... */
        if (dst_fd >= 0) {
            ssize_t wr = full_write(dst_fd, buffer, rd);
            if (wr < rd) {
                if (!continue_on_write_error) {
                    bb_perror_msg(bb_msg_write_error);
                    break;
                }
                dst_fd = -1;
            }
        }
        total += rd;
        if (status < 0) { /* if we aren't copying till EOF... */
            size -= rd;
            if (!size) {
                /* 'size' bytes copied - all done */
                status = 0;
                break;
            }
        }
    }
 out:

#if CONFIG_FEATURE_COPYBUF_KB > 4
    if (buffer_size != 4 * 1024)
        munmap(buffer, buffer_size);
#endif
    return status ? -1 : total;
}


#if 0
void FAST_FUNC complain_copyfd_and_die(off_t sz)
{
    if (sz != -1)
        bb_error_msg_and_die("short read");
    /* if sz == -1, bb_copyfd_XX already complained */
    xfunc_die();
}
#endif

off_t FAST_FUNC bb_copyfd_size(int fd1, int fd2, off_t size)
{
    if (size) {
        return bb_full_fd_action(fd1, fd2, size);
    }
    return 0;
}

void FAST_FUNC bb_copyfd_exact_size(int fd1, int fd2, off_t size)
{
    off_t sz = bb_copyfd_size(fd1, fd2, size);
    if (sz == (size >= 0 ? size : -size))
        return;
    if (sz != -1)
        bb_error_msg_and_die("short read");
    /* if sz == -1, bb_copyfd_XX already complained */
    xfunc_die();
}

off_t FAST_FUNC bb_copyfd_eof(int fd1, int fd2)
{
    return bb_full_fd_action(fd1, fd2, 0);
}