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145 lines
4.4 KiB
145 lines
4.4 KiB
from six.moves import xrange
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def _is_array(obj):
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return isinstance(obj, list)
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def get(obj, path):
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"""
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Looks up and returns a path in the object. Returns None if the path isn't there.
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"""
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for part in path:
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try:
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obj = obj[part]
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except(KeyError, IndexError):
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return None
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return obj
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def glob(obj, path, func, extra_arg):
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"""
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Resolves wildcards in `path`, calling func for all matching paths. Returns the number of
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times that func was called.
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obj - An object to scan.
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path - Path to an item in an object or an array in obj. May contain the special key '*', which
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-- for arrays only -- means "for all indices".
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func - Will be called as func(subobj, key, fullPath, extraArg).
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extra_arg - An arbitrary value to pass along to func, for convenience.
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Returns count of matching paths, for which func got called.
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"""
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return _globHelper(obj, path, path, func, extra_arg)
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def _globHelper(obj, path, full_path, func, extra_arg):
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for i, part in enumerate(path[:-1]):
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if part == "*" and _is_array(obj):
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# We got an array wildcard
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subpath = path[i + 1:]
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count = 0
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for subobj in obj:
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count += _globHelper(subobj, subpath, full_path, func, extra_arg)
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return count
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try:
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obj = obj[part]
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except:
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raise Exception("gpath.glob: non-existent object at " +
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describe(full_path[:len(full_path) - len(path) + i + 1]))
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return func(obj, path[-1], full_path, extra_arg) or 1
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def place(obj, path, value):
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"""
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Sets or deletes an object property in DocObj.
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gpath - Path to an Object in obj.
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value - Any value. Setting None will remove the selected object key.
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"""
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return glob(obj, path, _placeHelper, value)
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def _placeHelper(subobj, key, full_path, value):
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if not isinstance(subobj, dict):
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raise Exception("gpath.place: not a plain object at " + describe(dirname(full_path)))
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if value is not None:
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subobj[key] = value
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elif key in subobj:
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del subobj[key]
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def _checkIsArray(subobj, errPrefix, index, itemPath, isInsert):
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"""
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This is a helper for checking operations on arrays, and throwing descriptive errors.
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"""
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if subobj is None:
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raise Exception(errPrefix + ": non-existent object at " + describe(dirname(itemPath)))
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elif not _is_array(subobj):
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raise Exception(errPrefix + ": not an array at " + describe(dirname(itemPath)))
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else:
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length = len(subobj)
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validIndex = (isinstance(index, int) and index >= 0 and index < length)
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validInsertIndex = (index is None or index == length)
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if not (validIndex or (isInsert and validInsertIndex)):
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raise Exception(errPrefix + ": invalid array index: " + describe(itemPath))
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def insert(obj, path, value):
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"""
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Inserts an element into an array in DocObj.
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gpath - Path to an item in an array in obj.
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The new value will be inserted before the item pointed to by gpath.
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The last component of gpath may be null, in which case the value is appended at the end.
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value - Any value.
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"""
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return glob(obj, path, _insertHelper, value)
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def _insertHelper(subobj, index, fullPath, value):
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_checkIsArray(subobj, "gpath.insert", index, fullPath, True)
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if index is None:
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subobj.append(value)
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else:
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subobj.insert(index, value)
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def update(obj, path, value):
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"""
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Updates an element in an array in DocObj.
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gpath - Path to an item in an array in obj.
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value - Any value.
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"""
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return glob(obj, path, _updateHelper, value)
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def _updateHelper(subobj, index, fullPath, value):
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if index == '*':
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_checkIsArray(subobj, "gpath.update", None, fullPath, True)
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for i in xrange(len(subobj)):
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subobj[i] = value
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return len(subobj)
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else:
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_checkIsArray(subobj, "gpath.update", index, fullPath, False)
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subobj[index] = value
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def remove(obj, path):
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"""
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Removes an element from an array in DocObj.
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gpath - Path to an item in an array in obj.
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"""
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return glob(obj, path, _removeHelper, None)
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def _removeHelper(subobj, index, fullPath, _):
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_checkIsArray(subobj, "gpath.remove", index, fullPath, False)
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del subobj[index]
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def dirname(path):
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"""
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Returns path without the last component, like a directory name in a filesystem path.
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"""
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return path[:-1]
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def basename(path):
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"""
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Returns the last component of path, like base name of a filesystem path.
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"""
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return path[-1] if path else None
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def describe(path):
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"""
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Returns a human-readable representation of path.
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"""
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return "/" + "/".join(str(p) for p in path)
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