[pypy-commit] pypy default: Add support for half floats in the RPython rstruct module.

[amauryfa]

Author: Amaury Forgeot d'Arc <amauryfa at gmail.com>
Branch: 
Changeset: r93412:ca5586010ac3
Date: 2017-12-11 20:29 +0100
http://bitbucket.org/pypy/pypy/changeset/ca5586010ac3/

Log:	Add support for half floats in the RPython rstruct module.

diff --git a/rpython/rlib/rstruct/standardfmttable.py b/rpython/rlib/rstruct/standardfmttable.py
--- a/rpython/rlib/rstruct/standardfmttable.py
+++ b/rpython/rlib/rstruct/standardfmttable.py
@@ -105,6 +105,18 @@
     _pack_string(fmtiter, string, count-1)
 
 
+def pack_halffloat(fmtiter):
+    size = 2
+    fl = fmtiter.accept_float_arg()
+    try:
+        result = ieee.pack_float(fmtiter.wbuf, fmtiter.pos,
+                                 fl, size, fmtiter.bigendian)
+    except OverflowError:
+        raise StructOverflowError("float too large for format 'e'")
+    else:
+        fmtiter.advance(size)
+        return result
+
 def make_float_packer(TYPE):
     size = rffi.sizeof(TYPE)
     def packer(fmtiter):
@@ -247,6 +259,11 @@
         end = count
     fmtiter.appendobj(data[1:end])
 
+ at specialize.argtype(0)
+def unpack_halffloat(fmtiter):
+    data = fmtiter.read(2)
+    fmtiter.appendobj(ieee.unpack_float(data, fmtiter.bigendian))
+
 def make_ieee_unpacker(TYPE):
     @specialize.argtype(0)
     def unpack_ieee(fmtiter):
@@ -374,6 +391,8 @@
           'needcount' : True },
     'p':{ 'size' : 1, 'pack' : pack_pascal, 'unpack' : unpack_pascal,
           'needcount' : True },
+    'e':{ 'size' : 2, 'pack' : pack_halffloat,
+                    'unpack' : unpack_halffloat},
     'f':{ 'size' : 4, 'pack' : make_float_packer(rffi.FLOAT),
                     'unpack' : unpack_float},
     'd':{ 'size' : 8, 'pack' : make_float_packer(rffi.DOUBLE),
diff --git a/rpython/rlib/rstruct/test/test_pack.py b/rpython/rlib/rstruct/test/test_pack.py
--- a/rpython/rlib/rstruct/test/test_pack.py
+++ b/rpython/rlib/rstruct/test/test_pack.py
@@ -138,6 +138,19 @@
         self.check('f', 123.456)
         self.check('d', 123.456789)
 
+    def test_pack_halffloat(self):
+        if self.fmttable is nativefmttable.native_fmttable:
+            # Host Python cannot handle half floats.
+            return
+        size = 2
+        wbuf = MutableStringBuffer(size)
+        self.mypack_into('e', wbuf, 6.5e+04)
+        got = wbuf.finish()
+        if self.bigendian:
+            assert got == b'\x7b\xef'
+        else:
+            assert got == b'\xef\x7b'
+
     def test_float_overflow(self):
         if self.fmt_prefix == '@':
             # native packing, no overflow
diff --git a/rpython/rlib/rstruct/test/test_runpack.py b/rpython/rlib/rstruct/test/test_runpack.py
--- a/rpython/rlib/rstruct/test/test_runpack.py
+++ b/rpython/rlib/rstruct/test/test_runpack.py
@@ -78,6 +78,10 @@
         assert f != 12.34     # precision lost
         assert abs(f - 12.34) < 1E-6
 
+    def test_unpack_halffloat(self):
+        assert runpack(">e", b"\x7b\xef") == 64992.0
+        assert runpack("<e", b"\xef\x7b") == 64992.0
+
     def test_unpack_standard_little(self):
         def unpack(fmt, data):
             def fn():