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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. Signed-off-by: Stefan Gula <steweg@gmail.com>
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3 files changed

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‎cffi/cdefs.h

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Original file line numberDiff line numberDiff line change
@@ -946,6 +946,11 @@ typedef enum {
946946
LY_ERR lys_parse(struct ly_ctx *, struct ly_in *, LYS_INFORMAT, const char **, struct lys_module **);
947947
LY_ERR ly_ctx_new_ylpath(const char *, const char *, LYD_FORMAT, int, struct ly_ctx **);
948948
LY_ERR ly_ctx_get_yanglib_data(const struct ly_ctx *, struct lyd_node **, const char *, ...);
949+
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 *);
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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 *);
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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 *);
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struct lyd_meta {
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struct lyd_node *parent;

‎libyang/context.py

Lines changed: 171 additions & 2 deletions
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@@ -4,7 +4,7 @@
44
# SPDX-License-Identifier: MIT
55

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

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from _libyang import ffi, lib
1010
from .data import (
@@ -19,9 +19,176 @@
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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")
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def libyang_c_module_imp_data_free_clb(cdata, user_data):
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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,
39+
free_module_data,
40+
):
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"""
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Implements the C callback function for loading modules from any location.
43+
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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
55+
: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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"""
67+
fmt[0] = lib.LYS_IN_UNKNOWN
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module_data[0] = ffi.NULL
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free_module_data[0] = lib.lypy_module_imp_data_free_clb
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instance = ffi.from_handle(user_data)
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ret = instance.get_module_data(
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c2str(mod_name), c2str(mod_rev), c2str(submod_name), c2str(submod_rev)
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)
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if ret is None:
75+
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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# -------------------------------------------------------------------------------------
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class ContextExternalModuleLoader:
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__slots__ = (
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"_cdata",
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"_module_data_clb",
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"_cffi_handle",
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"_cdata_modules",
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)
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def __init__(self, cdata) -> None:
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self._cdata = cdata # C type: "struct ly_ctx *"
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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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Gets the YANG module schema data based requirements from libyang_c_module_imp_clb
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function and forward that request to user Python based callback function.
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The returned data from callback function are stored within the context to make sure
102+
of no memory access issues. These data a stored until the free_module_data function
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is called directly by libyang
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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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"""
108+
self._cdata_modules.remove(cdata)
109+
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def get_module_data(
111+
self,
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mod_name: Optional[str],
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mod_rev: Optional[str],
114+
submod_name: Optional[str],
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submod_rev: Optional[str],
116+
) -> Optional[Tuple[str, str]]:
117+
"""
118+
Gets the YANG module schema data based requirements from libyang_c_module_imp_clb
119+
function and forward that request to user Python based callback function.
120+
The returned data from callback function are stored within the context to make sure
121+
of no memory access issues. These data a stored until the free_module_data function
122+
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:
129+
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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:returns:
136+
Tuple of format string and YANG (sub)module schema
137+
"""
138+
if self._module_data_clb is None:
139+
return "", None
140+
fmt_str, module_data = self._module_data_clb(
141+
mod_name, mod_rev, submod_name, submod_rev
142+
)
143+
if module_data is None:
144+
return fmt_str, None
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module_data_c = str2c(module_data)
146+
self._cdata_modules.append(module_data_c)
147+
return fmt_str, module_data_c
148+
149+
def set_module_data_clb(
150+
self,
151+
clb: Optional[
152+
Callable[
153+
[Optional[str], Optional[str], Optional[str], Optional[str]],
154+
Optional[Tuple[str, str]],
155+
]
156+
] = None,
157+
) -> None:
158+
"""
159+
Sets the callback function, which will be called if libyang context would like to
160+
load module or submodule, which is not locally available in context path(s).
161+
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:arg self
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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
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The expeted return value is either:
171+
tuple of:
172+
format: The string format of the loaded data
173+
data: The YANG (sub)module data as string
174+
or None in case of error
175+
"""
176+
self._module_data_clb = clb
177+
if clb is None:
178+
lib.ly_ctx_set_module_imp_clb(self._cdata, ffi.NULL, ffi.NULL)
179+
else:
180+
lib.ly_ctx_set_module_imp_clb(
181+
self._cdata, lib.lypy_module_imp_clb, self._cffi_handle
182+
)
183+
184+
22185
# -------------------------------------------------------------------------------------
23186
class Context:
24-
__slots__ = ("cdata", "__dict__")
187+
__slots__ = (
188+
"cdata",
189+
"external_module_loader",
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"__dict__",
191+
)
25192

26193
def __init__(
27194
self,
@@ -36,6 +203,7 @@ def __init__(
36203
):
37204
if cdata is not None:
38205
self.cdata = ffi.cast("struct ly_ctx *", cdata)
206+
self.external_module_loader = ContextExternalModuleLoader(self.cdata)
39207
return # already initialized
40208

41209
options = 0
@@ -87,6 +255,7 @@ def __init__(
87255
)
88256
if not self.cdata:
89257
raise self.error("cannot create context")
258+
self.external_module_loader = ContextExternalModuleLoader(self.cdata)
90259

91260
def compile_schema(self):
92261
ret = lib.ly_ctx_compile(self.cdata)

‎tests/test_context.py

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Original file line numberDiff line numberDiff line change
@@ -116,3 +116,26 @@ def test_ctx_disable_searchdirs(self):
116116
with Context(YANG_DIR, disable_searchdirs=True) as ctx:
117117
with self.assertRaises(LibyangError):
118118
ctx.load_module("yolo-nodetypes")
119+
120+
def test_ctx_using_clb(self):
121+
def get_module_valid_clb(mod_name, *_):
122+
YOLO_NODETYPES_MOD_PATH = os.path.join(YANG_DIR, "yolo/yolo-nodetypes.yang")
123+
self.assertEqual(mod_name, "yolo-nodetypes")
124+
with open(YOLO_NODETYPES_MOD_PATH, encoding="utf-8") as f:
125+
mod_str = f.read()
126+
return "yang", mod_str
127+
128+
def get_module_invalid_clb(mod_name, *_):
129+
return None
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131+
with Context(YANG_DIR, disable_searchdirs=True) as ctx:
132+
with self.assertRaises(LibyangError):
133+
ctx.load_module("yolo-nodetypes")
134+
135+
ctx.external_module_loader.set_module_data_clb(get_module_invalid_clb)
136+
with self.assertRaises(LibyangError):
137+
mod = ctx.load_module("yolo-nodetypes")
138+
139+
ctx.external_module_loader.set_module_data_clb(get_module_valid_clb)
140+
mod = ctx.load_module("yolo-nodetypes")
141+
self.assertIsInstance(mod, Module)

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