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Move IBM/IEEE float code to a separate module

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This commit is contained in:
Robert Smallshire
2011-10-20 22:14:51 +02:00
parent f9639100a6
commit 00f1347658
2 changed files with 21 additions and 40 deletions
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ibm_float.py
+19
View File
@@ -0,0 +1,19 @@
def ibm2ieee2(ibm_float):
"""
ibm2ieee2(ibm_float)
Used by permission
(C) Secchi Angelo
with thanks to Howard Lightstone and Anton Vredegoor.
"""
dividend = float(16 ** 6)
if ibm_float == 0:
return 0.0
istic, a, b, c = struct.unpack('>BBBB', ibm_float)
if istic >= 128:
sign= -1.0
istic -= 128
else:
sign = 1.0
mant= float(a << 16) + float(b << 8) + float(c)
return sign * 16 ** (istic - 64) * (mant / dividend)
segypy.py
+2 -40
View File
@@ -40,6 +40,7 @@ from numpy import arange
from revisions import SEGY_REVISION_0, SEGY_REVISION_1
from header_definition import SH_def
from trace_header_definition import STH_def
from ibm_float import ibm2ieee2
logger = logging.getLogger('segpy.segypy')
@@ -80,7 +81,7 @@ def size_in_bytes(ctype):
def getDefaultSegyHeader(ntraces=100, ns=100):
"""Remove unused import.
"""
SH = getDefaultSegyHeader()
"""
# INITIALIZE DICTIONARYTraceSequenceLine
@@ -416,8 +417,6 @@ def writeSegyStructure(filename, Data, SH, STH, endian='>'): # modified by A Sq
putValue(value, f, pos, format, endian)
# SEGY TRACES
ctype = SH_def['DataSampleFormat']['datatype'][revision][dsf]
bps = SH_def['DataSampleFormat']['bps'][revision][dsf]
@@ -459,7 +458,6 @@ def putValue(value, fileid, index, ctype='l', endian='>', number=1):
fileid.seek(index)
fileid.write(strVal)
return 1
@@ -499,42 +497,6 @@ def getValue(data, index, ctype='l', endian='>', number=1):
return Value, index_end
##############
# MISC FUNCTIONS
def ibm2Ieee(ibm_float):
"""
ibm2Ieee(ibm_float)
Used by permission
(C) Secchi Angelo
with thanks to Howard Lightstone and Anton Vredegoor.
"""
i = struct.unpack('>I', ibm_float)[0]
sign = [1, -1][bool(i & 0x100000000L)]
characteristic = ((i >> 24) & 0x7f) - 64
fraction = (i & 0xffffff) / float(0x1000000L)
return sign * 16 ** characteristic * fraction
def ibm2ieee2(ibm_float):
"""
ibm2ieee2(ibm_float)
Used by permission
(C) Secchi Angelo
with thanks to Howard Lightstone and Anton Vredegoor.
"""
dividend = float(16 ** 6)
if ibm_float == 0:
return 0.0
istic, a, b, c = struct.unpack('>BBBB', ibm_float)
if istic >= 128:
sign= -1.0
istic -= 128
else:
sign = 1.0
mant= float(a << 16) + float(b << 8) + float(c)
return sign * 16 ** (istic - 64) * (mant / dividend)
def getBytePerSample(SH):