8:55 a.m.
This is only enough to be able to generate Kubevirt machine
descriptions so it does not have to deal with all the general
complexity of YAML. Only associative arrays, lists, simple types like
strings, and blocks of lines are supported.
Unfortunately even generating simple YAML safely is not easy. There
are many quirks to the format and many traps, including the dependency
between lists and associative arrays, and the lack of type safety.
---
lib/Makefile.am | 2 +
lib/YAML.ml | 187 ++++++++++++++++++++++++++++++++++++++++++++++++
lib/YAML.mli | 39 ++++++++++
3 files changed, 228 insertions(+)
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 1fab25b326..cddc3c7af5 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -31,6 +31,7 @@ SOURCES_MLI = \
config.mli \
create_ovf.mli \
DOM.mli \
+ YAML.mli \
libvirt_utils.mli \
nbdkit.mli \
networks.mli \
@@ -45,6 +46,7 @@ SOURCES_ML = \
qemuNBD.ml \
networks.ml \
DOM.ml \
+ YAML.ml \
create_ovf.ml \
libvirt_utils.ml
diff --git a/lib/YAML.ml b/lib/YAML.ml
new file mode 100644
index 0000000000..fdd16083b3
--- /dev/null
+++ b/lib/YAML.ml
@@ -0,0 +1,187 @@
+(* virt-v2v
+ * Copyright (C) 2009-2022 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *)
+
+open Std_utils
+open Tools_utils
+open Common_gettext.Gettext
+
+open Printf
+
+let spaces = String.spaces
+
+(* See YAML 1.2 section 2.4 "Tags". We're just trying to match things
+ * which might be misinterpreted so that we know when to quote strings.
+ * It doesn't matter if we match too eagerly here.
+ *)
+let re_reserved = PCRE.compile "^[\\[\\-\\]{}>|*&!%#'@,?:]"
+let re_numeric1 = PCRE.compile ~caseless:true "^[-+.0-9exo]+$"
+let re_numeric2 = PCRE.compile ~caseless:true "(inf|nan)$"
+let re_boolean = PCRE.compile ~caseless:true
"^(y|yes|n|no|true|false|on|off)$"
+
+type node =
+ | Assoc of (string * node) list
+ | List of node list
+ | String of string
+ | Int of int
+ | Bool of bool
+ | Float of float
+ | Block of string list
+type doc = Doc of node
+
+let rec doc_to_buf buf (Doc node) =
+ bprintf buf "---";
+ node_to_buf buf 0 node;
+ bprintf buf "\n"
+
+and node_to_buf buf indent = function
+ | Assoc xs -> assoc_to_buf buf indent xs
+ | List xs -> list_to_buf buf indent xs
+ | String str -> string_to_buf buf str
+ | Int i -> int_to_buf buf i
+ | Bool b -> bool_to_buf buf b
+ | Float f -> float_to_buf buf f
+ | Block lines -> block_to_buf buf indent lines
+
+and assoc_to_buf buf ?(nl = true) indent xs =
+ let nl = ref nl in
+ List.iter (
+ fun (key, value) ->
+ (* Print newline and indent, if nl is true. *)
+ if !nl then bprintf buf "\n%s" (spaces indent);
+ nl := true;
+
+ (* If the key is "#" then it is printed as a comment. *)
+ if key = "#" then (
+ match value with
+ | String comment -> bprintf buf "# %s" comment
+ | _ -> assert false
+ )
+ else (
+ bprintf buf "%s:" key;
+ (* Do we need a space after the key? This is basically
+ * about whether node_to_buf will print \n, which breaks
+ * encapsulation of this function. Make a best guess.
+ *)
+ (match value with
+ | String _ | Int _ | Bool _ | Float _ | Block _ | List [] ->
+ bprintf buf " "
+ | _ -> ()
+ );
+ (* Non-empty lists are not indented. *)
+ let indent =
+ match value with
+ | List (_::_) -> indent
+ | _ -> indent+2 in
+ node_to_buf buf indent value
+ )
+ ) xs
+
+and list_to_buf buf indent =
+ function
+ (* Special case empty list, I think is required. We could also special
+ * case other things, eg. lists of short, unquoted strings, but
+ * let's not overcomplicate things.
+ *)
+ | [] -> bprintf buf "{}"
+ | xs ->
+ List.iter (
+ fun node ->
+ bprintf buf "\n%s- " (spaces indent);
+ (* If it's an assoc list, then don't print first newline. *)
+ match node with
+ | Assoc xs -> assoc_to_buf buf ~nl:false (indent+2) xs
+ | _ -> node_to_buf buf (indent+2) node
+ ) xs
+
+(* Strings are always printed on the same line. *)
+and string_to_buf buf str =
+ if not (needs_quoting str) then bprintf buf "%s" str
+ else c_quoted_string_to_buf buf str
+
+and c_quoted_string_to_buf buf str =
+ bprintf buf "\"";
+ for i = 0 to String.length str - 1 do
+ let c = String.unsafe_get str i in
+ if c = '"' then bprintf buf "\\\""
+ else if c < ' ' then bprintf buf "\\x%02x" (Char.code c)
+ else bprintf buf "%c" c
+ done;
+ bprintf buf "\""
+
+(* It's extremely difficult to give a complete list of strings
+ * that have to be quoted, versus strings that can be safely
+ * used as barewords. For example strings like "Yes", "no",
+ * "true", "123", "123.0" cannot be written as barewords
since
+ * they will be misinterpreted as booleans, integers or floats.
+ * (These rules also depend on the version of YAML!)
+ *)
+and needs_quoting str =
+ String.length str = 0 ||
+ PCRE.matches re_reserved str ||
+ PCRE.matches re_numeric1 str ||
+ PCRE.matches re_numeric2 str ||
+ PCRE.matches re_boolean str ||
+ let n = String.length str in
+ let rec loop i =
+ if i >= n then false
+ else if String.unsafe_get str i <= ' ' then true
+ else loop (i+1)
+ in
+ loop 0
+
+and int_to_buf buf i = bprintf buf "%d" i
+
+and bool_to_buf buf b = bprintf buf "%b" b
+
+and float_to_buf buf f = bprintf buf "%f" f
+
+(* Blocks are printed using "|" + "\n" followed by the indented
lines
+ * of text. We implicitly assume that each line is followed by \n
+ * so we don't have to use a chomp mode, but this page is interesting
+ * in case we need to in future: https://yaml-multiline.info/
+ *)
+and block_to_buf buf indent lines =
+ (* If a line contains \n within the line then that indicates
+ * a bug in virt-v2v. Since this could be used to bypass
+ * indenting -- thus generating arbitrary YAML -- detect this
+ * situation and error out. As far as I'm aware, no other
+ * character in blocks needs to be handled specially.
+ *)
+ List.iter (
+ fun line ->
+ if String.contains line '\n' || String.contains line '\r' then
+ error (f_"YAML block contains newline character. \
+ This should not happen, please report a bug against \
+ virt-v2v.")
+ ) lines;
+
+ bprintf buf "|";
+ let indent = indent+2 in
+ List.iter (
+ fun line -> bprintf buf "\n%s%s" (spaces indent) line
+ ) lines
+
+let doc_to_string doc =
+ let buf = Buffer.create 4096 in
+ doc_to_buf buf doc;
+ Buffer.contents buf
+
+let doc_to_chan chan doc =
+ let buf = Buffer.create 4096 in
+ doc_to_buf buf doc;
+ Buffer.output_buffer chan buf
diff --git a/lib/YAML.mli b/lib/YAML.mli
new file mode 100644
index 0000000000..6728a2fd5f
--- /dev/null
+++ b/lib/YAML.mli
@@ -0,0 +1,39 @@
+(* virt-v2v
+ * Copyright (C) 2009-2022 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *)
+
+(** Simple YAML generator.
+
+ This doesn't attempt to model all of YAML, only enough
+ to be able to generate Kubevirt machine descriptions.
+*)
+
+type node =
+ | Assoc of (string * node) list (* dictionary of key: value *)
+ | List of node list (* list of - nodes *)
+ | String of string (* simple string *)
+ | Int of int (* integer *)
+ | Bool of bool (* bool - NB. "Norway problem" *)
+ | Float of float (* float *)
+ | Block of string list (* block of lines *)
+type doc = Doc of node
+
+val doc_to_string : doc -> string
+(** Convert a document to a string representation. *)
+
+val doc_to_chan : out_channel -> doc -> unit
+(** Write the YAML document to an output channel. *)
--
2.35.1