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from rpython.rtyper.lltypesystem import lltype, llmemory
from rpython.rtyper.lltypesystem.lloperation import llop
from rpython.rtyper.lltypesystem.rstr import STR, mallocstr
from rpython.rtyper.annlowlevel import llstr, hlstr
from rpython.rlib.objectmodel import specialize
from rpython.rlib.buffer import GCBuffer
from rpython.rlib import jit
@GCBuffer.decorate
class MutableStringBuffer(GCBuffer):
"""
A writeable buffer to incrementally fill a string of a fixed size.
You can fill the string by calling setitem, setslice and typed_write, and
get the result by calling finish().
After you call finish(), you can no longer modify the buffer. There is no
check, you will probably get a segfault after translation.
You can call finish() only once.
"""
_attrs_ = ['readonly', 'll_val', 'size']
_immutable_ = True
def __init__(self, size):
self.readonly = False
self.size = size
self.ll_val = mallocstr(size)
def getlength(self):
return self.size
def finish(self):
if not self.ll_val:
raise ValueError("Cannot call finish() twice")
result = hlstr(self.ll_val)
self.ll_val = lltype.nullptr(STR)
self.readonly = True
return result
def as_str(self):
raise ValueError('as_str() is not supported. Use finish() instead')
def _hlstr(self):
assert not we_are_translated() # debug only
return hlstr(self.ll_val)
def setitem(self, index, char):
self.ll_val.chars[index] = char
@staticmethod
def _get_gc_data_offset():
return (llmemory.offsetof(STR, 'chars') +
llmemory.itemoffsetof(STR.chars, 0))
def _get_gc_data(self):
return lltype.cast_opaque_ptr(llmemory.GCREF, self.ll_val)
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