1 files changed, 137 insertions, 0 deletions

diff --git a/btrfs-functions.sh b/btrfs-functions.sh
new file mode 100644
index 0000000..3648c24
--- /dev/null
+++ b/btrfs-functions.sh
@@ -0,0 +1,137 @@
+push()
+{
+    $(ARGS_NE mnt src dst_dir)
+
+    now=$(date +%F.%H%M%S) || die
+    snap_dir=$mnt/snapshot.$now
+    prev_dir=$mnt/snapshot.prev
+
+    local BTRFS_RECEIVE_DESTINATION_PATH="$dst_dir"
+    push_helper true "$snap_dir" "$prev_dir" "$src" local_btrfs_receiver
+}
+
+push_simple()
+{
+    $(ARGS_NE mnt src dst_dir)
+    local BTRFS_RECEIVE_DESTINATION_PATH="$dst_dir"
+    push_helper false "$mnt" "$src" local_btrfs_receiver
+}
+
+sex()
+{
+    (set -x; "$@")
+}
+
+local_btrfs_receiver()
+{
+    btrfs receive "$BTRFS_RECEIVE_DESTINATION_PATH"
+}
+
+shellescape()
+{
+    if [ "$BASH_VERSION" ]; then
+        printf %q "$1"
+    else
+        bash -c 'printf %q "$1"' bash "$1"
+    fi
+}
+
+remote_btrfs_receiver()
+{
+    ssh "$BTRFS_RECEIVE_DESTINATION_HOST" -- "btrfs receive $(shellescape "$BTRFS_RECEIVE_DESTINATION_PATH")"
+}
+
+push_helper()
+{
+    $(ARGS     keep_as_prev snap_dir prev_dir src dst_pipe)
+    $(NONEMPTY keep_as_prev snap_dir          src dst_pipe)
+
+    local full_dest rw_dest
+
+    btrfs subvolume snapshot -r "$src" "$snap_dir" || die
+
+    if [ "$prev_dir" -a -d "$prev_dir" ]; then
+        btrfs send -p "$prev_dir" "$snap_dir"
+    else
+        btrfs send "$snap_dir"
+    fi | "$dst_pipe" || die
+
+    if [ "$dst_pipe" = local_btrfs_receiver ]; then
+        local dst="$BTRFS_RECEIVE_DESTINATION_PATH"
+        full_dest=$dst/$(basename "$snap_dir")
+        rw_dest=$full_dest.rw
+        btrfs subvolume snapshot "$full_dest" "$rw_dest"  || die
+        btrfs_replace_default_subvolume_with "$rw_dest"
+    fi
+
+    if $keep_as_prev && [ "$prev_dir" ]
+    then
+        # keep the pushed snapshot in order to reuse it on subsequent pushes.
+        with_dir "$prev_dir"  btrfs subvolume delete  || die
+        sex mv "$snap_dir" "$prev_dir"                || die
+    else
+        btrfs subvolume delete "$snap_dir"
+    fi
+}
+
+btrfs_mountpoint()
+{
+    $(ARGS_NE dir)
+    btrfs filesystem show -m "$dir" >/dev/null 2>&1
+}
+
+btrfs_get_mountpoint()
+{
+    $(ARGS_NE dir)
+    while [ "$dir" -a "$dir" != '.' ]; do
+        if btrfs_mountpoint "$dir"
+        then printf '%s\n' "$dir"
+             return
+        fi
+        dir=$(dirname "$dir")
+    done
+    false
+}
+
+btrfs_show_default_path()
+{
+    $(ARGS_NE mp)
+    local path
+    mp=$(btrfs_get_mountpoint "$mp") || die # TODO: fix caller?
+    btrfs_mountpoint "$mp" || die "not a mountpoint: $mp"
+    path=$(btrfs subvolume get-default "$mp"/|sed -n -e 's/.* path //p')
+    printf '%s\n' "$mp/$path"
+}
+
+btrfs_replace_default_subvolume_with()
+{
+    $(ARGS_NE new_default)
+    local old_default subvol_id
+    old_default=$(btrfs_show_default_path "$new_default") || die
+
+    [ "$new_default" = "$old_default" ] && return
+
+    subvol_id=$(btrfs_show_subvolume_id "$new_default")       || die
+    btrfs subvolume set-default "$subvol_id" "$new_default" || die
+    btrfs subvolume delete "$old_default"
+    sex mv "$new_default" "$old_default"
+}
+
+btrfs_show_subvolume_id()
+{
+    $(ARGS_NE path)
+    local result
+    result=$(btrfs subvolume show "$path" | sed -n -e 's/^[ \t]*Subvolume ID:[ \t]*//p')
+    if [ "$result" ]
+    then printf '%s\n' "$result"
+    else false
+    fi
+}
+
+with_dir()
+{
+    $(ARGS_NE d)
+    shift
+    [ -d "$d" ] || return 0
+    "$@" "$d"
+}