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"""Manage general information about buzhug bases :
field definitions with types and default values"""
import os
import urllib
def set_info(base,fields):
base.defaults = {}
for field in fields:
validate_field(base,field)
def validate_field(base,field_def):
"""Validate field definition"""
name,typ = field_def[:2]
if name in ['__id__','__version__']:
raise ValueError,'Field name "%s" is reserved' %name
elif name.startswith('_'):
raise ValueError,"Error for %s : names can't begin with _" \
% name
if typ not in base.types.values():
if isinstance(typ,base.__class__): # external link
base._register_base(typ)
else:
raise TypeError,"type %s not allowed" %typ
if len(field_def)>2:
# if a default value is provided, check if it is valid
default = field_def[2]
if isinstance(typ,base.__class__):
if not hasattr(default.__class__,"db") or \
not default.__class__.db is typ:
raise ValueError,'Incorrect default value for field "%s"' \
" : expected %s, got %s (class %s)" %(name,typ,
default,default.__class__)
elif not isinstance(default,typ):
raise ValueError,'Incorrect default value for field "%s"' \
" : expected %s, got %s (class %s)" %(name,typ,
default,default.__class__)
base.defaults[name] = default
else:
base.defaults[name] = None
def save_info(base):
"""Save field information in files __info___ and __defaults__"""
_info = open(base.info_name,'wb')
fields = []
for k in base.field_names:
if isinstance(base.fields[k],base.__class__):
fields.append((k,'<base>'+urllib.quote(base.fields[k].name)))
else:
fields.append((k,base.fields[k].__name__))
_info.write(' '.join(['%s:%s' %(k,v) for (k,v) in fields]))
_info.close()
out = open(os.path.join(base.name,"__defaults__"),"wb")
for field_name,default_value in base.defaults.iteritems():
if field_name in ["__id__","__version__"]:
continue
value = base._file[field_name].to_block(default_value)
out.write("%s %s" %(field_name,value))
out.close()
def read_defaults(base):
import buzhug_files
defaults = dict([(f,None) for f in base.field_names[2:]])
if os.path.exists(os.path.join(base.name,"__defaults__")):
defs = open(os.path.join(base.name,"__defaults__"),"rb").read()
ix = 0
f_name = ""
while ix<len(defs):
if defs[ix]==" ":
ix += 1
if issubclass(base._file[f_name].__class__,
buzhug_files.FixedLengthFile):
length = base._file[f_name].block_len
block = defs[ix:ix+length]
ix += length
else:
block = ""
while not defs[ix] == "\n":
block += defs[ix]
ix += 1
block += "\n"
ix += 1
defaults[f_name] = base._file[f_name].from_block(block)
f_name = ""
else:
f_name += defs[ix]
ix += 1
return defaults
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