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context: adding ContextExternalModuleLoader class
This patch adds class ContextExternalModuleLoader, which adds ability to add custom module load callback, which allows user to load modules from remote source etc. Closes: #103 Signed-off-by: Stefan Gula <steweg@gmail.com> Signed-off-by: Samuel Gauthier <samuel.gauthier@6wind.com>
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‎cffi/cdefs.h‎

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Original file line numberDiff line numberDiff line change
@@ -1071,6 +1071,11 @@ typedef enum {
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LY_ERR lys_parse(struct ly_ctx *, struct ly_in *, LYS_INFORMAT, const char **, struct lys_module **);
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LY_ERR ly_ctx_new_ylpath(const char *, const char *, LYD_FORMAT, int, struct ly_ctx **);
10731073
LY_ERR ly_ctx_get_yanglib_data(const struct ly_ctx *, struct lyd_node **, const char *, ...);
1074+
typedef void (*ly_module_imp_data_free_clb)(void *, void *);
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typedef LY_ERR (*ly_module_imp_clb)(const char *, const char *, const char *, const char *, void *, LYS_INFORMAT *, const char **, ly_module_imp_data_free_clb *);
1076+
void ly_ctx_set_module_imp_clb(struct ly_ctx *, ly_module_imp_clb, void *);
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extern "Python" void lypy_module_imp_data_free_clb(void *, void *);
1078+
extern "Python" LY_ERR lypy_module_imp_clb(const char *, const char *, const char *, const char *, void *, LYS_INFORMAT *, const char **, ly_module_imp_data_free_clb *);
10741079

10751080
LY_ERR lydict_insert(const struct ly_ctx *, const char *, size_t, const char **);
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LY_ERR lydict_remove(const struct ly_ctx *, const char *);

‎libyang/context.py‎

Lines changed: 168 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44
# SPDX-License-Identifier: MIT
55

66
import os
7-
from typing import IO, Any, Iterator, Optional, Union
7+
from typing import IO, Any, Callable, Iterator, Optional, Tuple, Union
88

99
from _libyang import ffi, lib
1010
from .data import (
@@ -19,9 +19,173 @@
1919
from .util import DataType, IOType, LibyangError, c2str, data_load, str2c
2020

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# -------------------------------------------------------------------------------------
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@ffi.def_extern(name="lypy_module_imp_data_free_clb")
24+
def libyang_c_module_imp_data_free_clb(cdata, user_data):
25+
instance = ffi.from_handle(user_data)
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instance.free_module_data(cdata)
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28+
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# -------------------------------------------------------------------------------------
30+
@ffi.def_extern(name="lypy_module_imp_clb")
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def libyang_c_module_imp_clb(
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mod_name,
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mod_rev,
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submod_name,
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submod_rev,
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user_data,
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fmt,
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module_data,
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free_module_data,
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):
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"""
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Implement the C callback function for loading modules from any location.
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:arg c_str mod_name:
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The YANG module name
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:arg c_str mod_rev:
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The YANG module revision
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:arg c_str submod_name:
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The YANG submodule name
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:arg c_str submod_rev:
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The YANG submodule revision
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:arg user_data:
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The user data provided by user during registration. In this implementation
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it is always considered to be handle of Python object
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:arg fmt:
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The output pointer where to set the format of schema
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:arg module_data:
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The output pointer where to set the schema data itself
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:arg free_module_data:
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The output pointer of callback function which will be called when the schema
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data are no longer needed
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:returns:
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The LY_SUCCESS in case the needed YANG (sub)module schema was found
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The LY_ENOT in case the needed YANG (sub)module schema was not found
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"""
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fmt[0] = lib.LYS_IN_UNKNOWN
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module_data[0] = ffi.NULL
69+
free_module_data[0] = lib.lypy_module_imp_data_free_clb
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instance = ffi.from_handle(user_data)
71+
ret = instance.get_module_data(
72+
c2str(mod_name), c2str(mod_rev), c2str(submod_name), c2str(submod_rev)
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)
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if ret is None:
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return lib.LY_ENOT
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in_fmt, content = ret
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fmt[0] = schema_in_format(in_fmt)
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module_data[0] = content
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return lib.LY_SUCCESS
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81+
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# -------------------------------------------------------------------------------------
83+
class ContextExternalModuleLoader:
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__slots__ = (
85+
"_cdata",
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"_module_data_clb",
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"_cffi_handle",
88+
"_cdata_modules",
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)
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def __init__(self, cdata) -> None:
92+
self._cdata = cdata # C type: "struct ly_ctx *"
93+
self._module_data_clb = None
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self._cffi_handle = ffi.new_handle(self)
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self._cdata_modules = []
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def free_module_data(self, cdata) -> None:
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"""
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Free previously stored data, obtained after a get_module_data.
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:arg cdata:
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The pointer to YANG modelu schema (c_str), which shall be released from memory
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"""
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self._cdata_modules.remove(cdata)
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106+
def get_module_data(
107+
self,
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mod_name: Optional[str],
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mod_rev: Optional[str],
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submod_name: Optional[str],
111+
submod_rev: Optional[str],
112+
) -> Optional[Tuple[str, str]]:
113+
"""
114+
Get the YANG module schema data based requirements from libyang_c_module_imp_clb
115+
function and forward that request to user Python based callback function.
116+
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The returned data from callback function are stored within the context to make sure
118+
of no memory access issues. These data a stored until the free_module_data function
119+
is called directly by libyang.
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:arg self
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This instance on context
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:arg mod_name:
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The optional YANG module name
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:arg mod_rev:
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The optional YANG module revision
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:arg submod_name:
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The optional YANG submodule name
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:arg submod_rev:
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The optional YANG submodule revision
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132+
:returns:
133+
Tuple of format string and YANG (sub)module schema
134+
"""
135+
if self._module_data_clb is None:
136+
return "", None
137+
fmt_str, module_data = self._module_data_clb(
138+
mod_name, mod_rev, submod_name, submod_rev
139+
)
140+
if module_data is None:
141+
return fmt_str, None
142+
module_data_c = str2c(module_data)
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self._cdata_modules.append(module_data_c)
144+
return fmt_str, module_data_c
145+
146+
def set_module_data_clb(
147+
self,
148+
clb: Optional[
149+
Callable[
150+
[Optional[str], Optional[str], Optional[str], Optional[str]],
151+
Optional[Tuple[str, str]],
152+
]
153+
] = None,
154+
) -> None:
155+
"""
156+
Set the callback function, which will be called if libyang context would like to
157+
load module or submodule, which is not locally available in context path(s).
158+
159+
:arg self
160+
This instance on context
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:arg clb:
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The callback function. The expected arguments are:
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mod_name: Module name
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mod_rev: Module revision
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submod_name: Submodule name
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submod_rev: Submodule revision
167+
The expeted return value is either:
168+
tuple of:
169+
format: The string format of the loaded data
170+
data: The YANG (sub)module data as string
171+
or None in case of error
172+
"""
173+
self._module_data_clb = clb
174+
if clb is None:
175+
lib.ly_ctx_set_module_imp_clb(self._cdata, ffi.NULL, ffi.NULL)
176+
else:
177+
lib.ly_ctx_set_module_imp_clb(
178+
self._cdata, lib.lypy_module_imp_clb, self._cffi_handle
179+
)
180+
181+
22182
# -------------------------------------------------------------------------------------
23183
class Context:
24-
__slots__ = ("cdata", "__dict__")
184+
__slots__ = (
185+
"cdata",
186+
"external_module_loader",
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"__dict__",
188+
)
25189

26190
def __init__(
27191
self,
@@ -37,6 +201,7 @@ def __init__(
37201
):
38202
if cdata is not None:
39203
self.cdata = ffi.cast("struct ly_ctx *", cdata)
204+
self.external_module_loader = ContextExternalModuleLoader(self.cdata)
40205
return # already initialized
41206

42207
options = 0
@@ -90,6 +255,7 @@ def __init__(
90255
)
91256
if not self.cdata:
92257
raise self.error("cannot create context")
258+
self.external_module_loader = ContextExternalModuleLoader(self.cdata)
93259

94260
def compile_schema(self):
95261
ret = lib.ly_ctx_compile(self.cdata)

‎tests/test_context.py‎

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -124,3 +124,26 @@ def test_ctx_disable_searchdirs(self):
124124
with Context(YANG_DIR, disable_searchdirs=True) as ctx:
125125
with self.assertRaises(LibyangError):
126126
ctx.load_module("yolo-nodetypes")
127+
128+
def test_ctx_using_clb(self):
129+
def get_module_valid_clb(mod_name, *_):
130+
YOLO_NODETYPES_MOD_PATH = os.path.join(YANG_DIR, "yolo/yolo-nodetypes.yang")
131+
self.assertEqual(mod_name, "yolo-nodetypes")
132+
with open(YOLO_NODETYPES_MOD_PATH, encoding="utf-8") as f:
133+
mod_str = f.read()
134+
return "yang", mod_str
135+
136+
def get_module_invalid_clb(mod_name, *_):
137+
return None
138+
139+
with Context(YANG_DIR, disable_searchdirs=True) as ctx:
140+
with self.assertRaises(LibyangError):
141+
ctx.load_module("yolo-nodetypes")
142+
143+
ctx.external_module_loader.set_module_data_clb(get_module_invalid_clb)
144+
with self.assertRaises(LibyangError):
145+
mod = ctx.load_module("yolo-nodetypes")
146+
147+
ctx.external_module_loader.set_module_data_clb(get_module_valid_clb)
148+
mod = ctx.load_module("yolo-nodetypes")
149+
self.assertIsInstance(mod, Module)

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