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import string
import types
## json.py implements a JSON (http://json.org) reader and writer.
## Copyright (C) 2005 Patrick D. Logan
## Contact mailto:patrickdlogan@stardecisions.com
##
## This library is free software; you can redistribute it and/or
## modify it under the terms of the GNU Lesser General Public
## License as published by the Free Software Foundation; either
## version 2.1 of the License, or (at your option) any later version.
##
## This library 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
## Lesser General Public License for more details.
##
## You should have received a copy of the GNU Lesser General Public
## License along with this library; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
class _StringGenerator(object):
def __init__(self, string):
self.string = string
self.index = -1
def peek(self):
i = self.index + 1
if i < len(self.string):
return self.string[i]
else:
return None
def next(self):
self.index += 1
if self.index < len(self.string):
return self.string[self.index]
else:
raise StopIteration
def all(self):
return self.string
class WriteException(Exception):
pass
class ReadException(Exception):
pass
class JsonReader(object):
hex_digits = {'A': 10,'B': 11,'C': 12,'D': 13,'E': 14,'F':15}
escapes = {'t':'\t','n':'\n','f':'\f','r':'\r','b':'\b'}
def read(self, s):
self._generator = _StringGenerator(s)
result = self._read()
return result
def _read(self):
self._eatWhitespace()
peek = self._peek()
if peek is None:
raise ReadException, "Nothing to read: '%s'" % self._generator.all()
if peek == '{':
return self._readObject()
elif peek == '[':
return self._readArray()
elif peek == '"':
return self._readString()
elif peek == '-' or peek.isdigit():
return self._readNumber()
elif peek == 't':
return self._readTrue()
elif peek == 'f':
return self._readFalse()
elif peek == 'n':
return self._readNull()
elif peek == '/':
self._readComment()
return self._read()
else:
raise ReadException, "Input is not valid JSON: '%s'" % self._generator.all()
def _readTrue(self):
self._assertNext('t', "true")
self._assertNext('r', "true")
self._assertNext('u', "true")
self._assertNext('e', "true")
return True
def _readFalse(self):
self._assertNext('f', "false")
self._assertNext('a', "false")
self._assertNext('l', "false")
self._assertNext('s', "false")
self._assertNext('e', "false")
return False
def _readNull(self):
self._assertNext('n', "null")
self._assertNext('u', "null")
self._assertNext('l', "null")
self._assertNext('l', "null")
return None
def _assertNext(self, ch, target):
if self._next() != ch:
raise ReadException, "Trying to read %s: '%s'" % (target, self._generator.all())
def _readNumber(self):
isfloat = False
result = self._next()
peek = self._peek()
while peek is not None and (peek.isdigit() or peek == "."):
isfloat = isfloat or peek == "."
result = result + self._next()
peek = self._peek()
try:
if isfloat:
return float(result)
else:
return int(result)
except ValueError:
raise ReadException, "Not a valid JSON number: '%s'" % result
def _readString(self):
result = ""
assert self._next() == '"'
try:
while self._peek() != '"':
ch = self._next()
if ch == "\\":
ch = self._next()
if ch in 'brnft':
ch = self.escapes[ch]
elif ch == "u":
ch4096 = self._next()
ch256 = self._next()
ch16 = self._next()
ch1 = self._next()
n = 4096 * self._hexDigitToInt(ch4096)
n += 256 * self._hexDigitToInt(ch256)
n += 16 * self._hexDigitToInt(ch16)
n += self._hexDigitToInt(ch1)
ch = unichr(n)
elif ch not in '"/\\':
raise ReadException, "Not a valid escaped JSON character: '%s' in %s" % (ch, self._generator.all())
result = result + ch
except StopIteration:
raise ReadException, "Not a valid JSON string: '%s'" % self._generator.all()
assert self._next() == '"'
return result
def _hexDigitToInt(self, ch):
try:
result = self.hex_digits[ch.upper()]
except KeyError:
try:
result = int(ch)
except ValueError:
raise ReadException, "The character %s is not a hex digit." % ch
return result
def _readComment(self):
assert self._next() == "/"
second = self._next()
if second == "/":
self._readDoubleSolidusComment()
elif second == '*':
self._readCStyleComment()
else:
raise ReadException, "Not a valid JSON comment: %s" % self._generator.all()
def _readCStyleComment(self):
try:
done = False
while not done:
ch = self._next()
done = (ch == "*" and self._peek() == "/")
if not done and ch == "/" and self._peek() == "*":
raise ReadException, "Not a valid JSON comment: %s, '/*' cannot be embedded in the comment." % self._generator.all()
self._next()
except StopIteration:
raise ReadException, "Not a valid JSON comment: %s, expected */" % self._generator.all()
def _readDoubleSolidusComment(self):
try:
ch = self._next()
while ch != "\r" and ch != "\n":
ch = self._next()
except StopIteration:
pass
def _readArray(self):
result = []
assert self._next() == '['
done = self._peek() == ']'
while not done:
item = self._read()
result.append(item)
self._eatWhitespace()
done = self._peek() == ']'
if not done:
ch = self._next()
if ch != ",":
raise ReadException, "Not a valid JSON array: '%s' due to: '%s'" % (self._generator.all(), ch)
assert ']' == self._next()
return result
def _readObject(self):
result = {}
assert self._next() == '{'
done = self._peek() == '}'
while not done:
key = self._read()
if type(key) is not types.StringType:
raise ReadException, "Not a valid JSON object key (should be a string): %s" % key
self._eatWhitespace()
ch = self._next()
if ch != ":":
raise ReadException, "Not a valid JSON object: '%s' due to: '%s'" % (self._generator.all(), ch)
self._eatWhitespace()
val = self._read()
result[key] = val
self._eatWhitespace()
done = self._peek() == '}'
if not done:
ch = self._next()
if ch != ",":
raise ReadException, "Not a valid JSON array: '%s' due to: '%s'" % (self._generator.all(), ch)
assert self._next() == "}"
return result
def _eatWhitespace(self):
p = self._peek()
while p is not None and p in string.whitespace or p == '/':
if p == '/':
self._readComment()
else:
self._next()
p = self._peek()
def _peek(self):
return self._generator.peek()
def _next(self):
return self._generator.next()
class JsonWriter(object):
def _append(self, s):
self._results.append(s)
def write(self, obj, escaped_forward_slash=False):
self._escaped_forward_slash = escaped_forward_slash
self._results = []
self._write(obj)
return "".join(self._results)
def _write(self, obj):
ty = type(obj)
if ty is types.DictType:
n = len(obj)
self._append("{")
for k, v in obj.items():
self._write(k)
self._append(":")
self._write(v)
n = n - 1
if n > 0:
self._append(",")
self._append("}")
elif ty is types.ListType or ty is types.TupleType:
n = len(obj)
self._append("[")
for item in obj:
self._write(item)
n = n - 1
if n > 0:
self._append(",")
self._append("]")
elif ty is types.StringType or ty is types.UnicodeType:
self._append('"')
obj = obj.replace('\\', r'\\')
if self._escaped_forward_slash:
obj = obj.replace('/', r'\/')
obj = obj.replace('"', r'\"')
obj = obj.replace('\b', r'\b')
obj = obj.replace('\f', r'\f')
obj = obj.replace('\n', r'\n')
obj = obj.replace('\r', r'\r')
obj = obj.replace('\t', r'\t')
self._append(obj)
self._append('"')
elif ty is types.IntType or ty is types.LongType:
self._append(str(obj))
elif ty is types.FloatType:
self._append("%f" % obj)
elif obj is True:
self._append("true")
elif obj is False:
self._append("false")
elif obj is None:
self._append("null")
else:
raise WriteException, "Cannot write in JSON: %s" % repr(obj)
def write(obj, escaped_forward_slash=False):
return JsonWriter().write(obj, escaped_forward_slash)
def read(s):
return JsonReader().read(s)
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