Author: Timo Paulssen <timona...@perpetuum-immobile.de>
Branch: numpy-data-buffer
Changeset: r47793:f30d7a06caf9
Date: 2011-10-03 16:23 +0200
http://bitbucket.org/pypy/pypy/changeset/f30d7a06caf9/
Log: implement numpy.frombuffer
diff --git a/lib_pypy/numpy/__init__.py b/lib_pypy/numpy/__init__.py
--- a/lib_pypy/numpy/__init__.py
+++ b/lib_pypy/numpy/__init__.py
@@ -86,24 +86,34 @@
return array(result)
+def __from_buffer_or_datastring(buf_or_str, dt, count, offset=0):
+ _dtype = dtype(dt)
+
+ if count > 0:
+ length = count * _dtype.itemsize
+ if length + offset > len(buf_or_str):
+ raise ValueError("length of string (%d) not enough for %d %s" %
+ (len(buf_or_str), count, _dtype))
+
+ buf_or_str = buf_or_str[offset:length+offset]
+ else:
+ length = len(buf_or_str) - offset
+ buf_or_str = buf_or_str[offset:]
+ if len(buf_or_str) % _dtype.itemsize != 0:
+ raise ValueError("length of string (%d) not evenly dividable by
size of dtype (%d)" %
+ (len(buf_or_str), _dtype.itemsize))
+
+ arr = empty(length / _dtype.itemsize, dtype=_dtype)
+ arr.data[:length] = buf_or_str
+
+ return arr
+
+def frombuffer(buf, dtype=float, count=-1, offset=0):
+ return __from_buffer_or_datastring(buf, dtype, count, offset)
+
def fromstring(s, dtype=float, count=-1, sep=''):
- from _numpy import dtype as dt
if sep:
raise NotImplementedError("Cannot use fromstring with a separator yet")
- _dtype = dt(dtype)
- if count > 0:
- length = count * _dtype.itemsize
- if length > len(s):
- raise ValueError("length of string (%d) not enough for %d %s" %
(len(s), count, _dtype))
- s = s[:length]
- else:
- length = len(s)
- if len(s) % _dtype.itemsize != 0:
- raise ValueError("length of string (%d) not evenly dividable by
size of dtype (%d)" % (len(s), _dtype.itemsize))
+ return __from_buffer_or_datastring(s, dtype, count)
- arr = empty(length / _dtype.itemsize, dtype=_dtype)
- print len(arr.data), len(s), length, _dtype.itemsize
- arr.data[:length] = s
-
- return arr
diff --git a/lib_pypy/pypy_test/test_numpy.py b/lib_pypy/pypy_test/test_numpy.py
--- a/lib_pypy/pypy_test/test_numpy.py
+++ b/lib_pypy/pypy_test/test_numpy.py
@@ -96,3 +96,24 @@
assert len(a) == 4
for i in range(4):
assert a[i] == i
+
+ def test_frombuffer(self):
+ from numpy import frombuffer
+ import struct
+
+ data = "\0\1\2\3\4"
+ a = frombuffer(data, dtype="int8", count=3)
+ b = frombuffer(data, dtype="int8", count=3, offset=1)
+ # does this depend on the machine architecture? byte-order?
+ assert a[0] == 0
+ assert b[0] == a[1] == 1
+
+ data = struct.pack("iiii", 0, 1, 0, 0)
+ a = frombuffer(data, dtype="i", count=1)[0]
+ b = frombuffer(data, dtype="i", count=1, offset=1)[0]
+ c = frombuffer(data, dtype="i", count=1, offset=2)[0]
+ d = frombuffer(data, dtype="i", count=1, offset=3)[0]
+ assert a == 0
+ assert b == 1 << 24
+ assert c == 1 << 16
+ assert d == 1 << 8
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