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"""
This module exposes the functions longlong2float() and float2longlong(),
which cast the bit pattern of a float into a long long and back.
Warning: don't use in the other direction, i.e. don't cast a random
long long to a float and back to a long long. There are corner cases
in which it does not work.
"""
from __future__ import with_statement
import sys
from rpython.annotator import model as annmodel
from rpython.rlib.rarithmetic import r_int64, intmask
from rpython.rtyper.lltypesystem import lltype, rffi
from rpython.rtyper.extregistry import ExtRegistryEntry
from rpython.translator.tool.cbuild import ExternalCompilationInfo
# -------- implement longlong2float and float2longlong --------
DOUBLE_ARRAY_PTR = lltype.Ptr(lltype.Array(rffi.DOUBLE))
LONGLONG_ARRAY_PTR = lltype.Ptr(lltype.Array(rffi.LONGLONG))
UINT_ARRAY_PTR = lltype.Ptr(lltype.Array(rffi.UINT))
FLOAT_ARRAY_PTR = lltype.Ptr(lltype.Array(rffi.FLOAT))
# these definitions are used only in tests, when not translated
def longlong2float(llval):
with lltype.scoped_alloc(DOUBLE_ARRAY_PTR.TO, 1) as d_array:
ll_array = rffi.cast(LONGLONG_ARRAY_PTR, d_array)
ll_array[0] = llval
floatval = d_array[0]
return floatval
def float2longlong(floatval):
with lltype.scoped_alloc(DOUBLE_ARRAY_PTR.TO, 1) as d_array:
ll_array = rffi.cast(LONGLONG_ARRAY_PTR, d_array)
d_array[0] = floatval
llval = ll_array[0]
return llval
def uint2singlefloat_emulator(ival):
with lltype.scoped_alloc(FLOAT_ARRAY_PTR.TO, 1) as f_array:
i_array = rffi.cast(UINT_ARRAY_PTR, f_array)
i_array[0] = ival
singlefloatval = f_array[0]
return singlefloatval
def singlefloat2uint_emulator(singlefloatval):
with lltype.scoped_alloc(FLOAT_ARRAY_PTR.TO, 1) as f_array:
i_array = rffi.cast(UINT_ARRAY_PTR, f_array)
f_array[0] = singlefloatval
ival = i_array[0]
return ival
eci = ExternalCompilationInfo(includes=['string.h', 'assert.h'],
post_include_bits=["""
static float pypy__uint2singlefloat(unsigned int x) {
float ff;
assert(sizeof(float) == 4 && sizeof(unsigned int) == 4);
memcpy(&ff, &x, 4);
return ff;
}
static unsigned int pypy__singlefloat2uint(float x) {
unsigned int ii;
assert(sizeof(float) == 4 && sizeof(unsigned int) == 4);
memcpy(&ii, &x, 4);
return ii;
}
"""])
uint2singlefloat = rffi.llexternal(
"pypy__uint2singlefloat", [rffi.UINT], rffi.FLOAT,
_callable=uint2singlefloat_emulator, compilation_info=eci,
_nowrapper=True, elidable_function=True, sandboxsafe=True)
singlefloat2uint = rffi.llexternal(
"pypy__singlefloat2uint", [rffi.FLOAT], rffi.UINT,
_callable=singlefloat2uint_emulator, compilation_info=eci,
_nowrapper=True, elidable_function=True, sandboxsafe=True)
class Float2LongLongEntry(ExtRegistryEntry):
_about_ = float2longlong
def compute_result_annotation(self, s_float):
assert annmodel.SomeFloat().contains(s_float)
return annmodel.SomeInteger(knowntype=r_int64)
def specialize_call(self, hop):
[v_float] = hop.inputargs(lltype.Float)
hop.exception_cannot_occur()
return hop.genop("convert_float_bytes_to_longlong", [v_float], resulttype=lltype.SignedLongLong)
class LongLong2FloatEntry(ExtRegistryEntry):
_about_ = longlong2float
def compute_result_annotation(self, s_longlong):
assert annmodel.SomeInteger(knowntype=r_int64).contains(s_longlong)
return annmodel.SomeFloat()
def specialize_call(self, hop):
[v_longlong] = hop.inputargs(lltype.SignedLongLong)
hop.exception_cannot_occur()
return hop.genop("convert_longlong_bytes_to_float", [v_longlong], resulttype=lltype.Float)
# ____________________________________________________________
# For encoding integers inside nonstandard NaN bit patterns.
# ff ff ff fe xx xx xx xx (signed 32-bit int)
nan_high_word_int32 = -2 # -2 == (int)0xfffffffe
nan_encoded_zero = r_int64(nan_high_word_int32 << 32)
def encode_int32_into_longlong_nan(value):
return (nan_encoded_zero +
rffi.cast(rffi.LONGLONG, rffi.cast(rffi.UINT, value)))
def decode_int32_from_longlong_nan(value):
return rffi.cast(lltype.Signed, rffi.cast(rffi.INT, value))
def is_int32_from_longlong_nan(value):
return intmask(value >> 32) == nan_high_word_int32
CAN_ALWAYS_ENCODE_INT32 = (sys.maxint == 2147483647)
def can_encode_int32(value):
if CAN_ALWAYS_ENCODE_INT32:
return True
return value == rffi.cast(lltype.Signed, rffi.cast(rffi.INT, value))
def can_encode_float(value):
return intmask(float2longlong(value) >> 32) != nan_high_word_int32
def maybe_decode_longlong_as_float(value):
# Decode a longlong value. If a float, just return it as a float.
# If an encoded integer, return a float that has the (exact) same
# value. This relies on the fact that casting from a decoded int
# to a float is an exact operation. If we had full 64-bit
# integers, this cast would loose precision. But this works
# because the integers are only 32-bit. This would also work even
# if we encoded larger integers: as long as they are encoded
# inside a subset of the mantissa of a float, then the
# cast-to-float will be exact.
if is_int32_from_longlong_nan(value):
return float(decode_int32_from_longlong_nan(value))
else:
return longlong2float(value)
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