Implemented smarter query values based on looking how many bytes are …

…expected

See #118

pyvisa/resources/messagebased.py

@@ -20,7 +20,7 @@
 from .. import logger
 from .. import constants
 from .. import errors
-from ..util import from_ascii_block, parse_binary, from_ieee_block, to_ieee_block, to_ascii_block, from_binary_block
+from .. import util
 
 from .resource import Resource
 
@@ -211,7 +211,7 @@ def write_ascii_values(self, message, values, converter='f', separator=',', term
                 warnings.warn("write message already ends with "
                               "termination characters", stacklevel=2)
 
-        block = to_ascii_block(values, converter, separator)
+        block = util.to_ascii_block(values, converter, separator)
 
         message = message.encode(enco) + block
 
@@ -242,7 +242,7 @@ def write_binary_values(self, message, values, datatype='f', is_big_endian=False
                 warnings.warn("write message already ends with "
                               "termination characters", stacklevel=2)
 
-        block = to_ieee_block(values, datatype, is_big_endian)
+        block = util.to_ieee_block(values, datatype, is_big_endian)
 
         message = message.encode(enco) + block
 
@@ -335,10 +335,10 @@ def read_values(self, fmt=None, container=list):
         if not fmt:
             vf = self.values_format
             if not vf.is_binary:
-                return from_ascii_block(self.read(), container)
+                return util.from_ascii_block(self.read(), container)
             data = self.read_raw()
             try:
-                return parse_binary(data, vf.is_big_endian, vf.datatype=='f')
+                return util.parse_binary(data, vf.is_big_endian, vf.datatype=='f')
             except ValueError as e:
                 try:
                     msg = e.args[0]
@@ -347,7 +347,7 @@ def read_values(self, fmt=None, container=list):
                 raise errors.InvalidBinaryFormat(msg)
 
         if fmt & 0x01 == 0: # ascii
-            return from_ascii_block(self.read())
+            return util.from_ascii_block(self.read())
 
         data = self.read_raw()
 
@@ -360,7 +360,7 @@ def read_values(self, fmt=None, container=list):
                 raise ValueError("unknown data values fmt requested")
 
             is_big_endian = fmt & 0x04 # big endian
-            return parse_binary(data, is_big_endian, is_single)
+            return util.parse_binary(data, is_big_endian, is_single)
         except ValueError as e:
             raise errors.InvalidBinaryFormat(e.args)
 
@@ -431,7 +431,7 @@ def query_ascii_values(self, message, converter='f', separator=',', container=li
 
         block = self.read()
 
-        return from_ascii_block(block, converter, separator, container)
+        return util.from_ascii_block(block, converter, separator, container)
 
     def query_binary_values(self, message, datatype='f', is_big_endian=False, container=list, delay=None, header_fmt='ieee'):
         """Converts an iterable of numbers into a block of data in the ieee format.
@@ -457,13 +457,20 @@ def query_binary_values(self, message, datatype='f', is_big_endian=False, contai
 
         block = self.read_raw()
 
+        if header_fmt == 'ieee':
+            offset, data_length = util.parse_ieee_block_header(block)
+            expected_length = offset + data_length
+
+            while len(block) < expected_length:
+                block += self.read_raw()
+
         try:
             if header_fmt == 'ieee':
-                return from_ieee_block(block, datatype, is_big_endian, container)
+                return util.from_ieee_block(block, datatype, is_big_endian, container)
             elif header_fmt == 'empty':
-                return from_binary_block(block, 0, None, datatype, is_big_endian, container)
+                return util.from_binary_block(block, 0, None, datatype, is_big_endian, container)
             elif header_fmt == 'hp':
-                return from_binary_block(block, 4, None, datatype, is_big_endian, container)
+                return util.from_binary_block(block, 4, None, datatype, is_big_endian, container)
         except ValueError as e:
             raise errors.InvalidBinaryFormat(e.args)
 

pyvisa/util.py

@@ -271,8 +271,8 @@ def parse_binary(bytes_data, is_big_endian=False, is_single=False):
     return result
 
 
-def from_ieee_block(block, datatype='f', is_big_endian=False, container=list):
-    """Convert a block in the IEEE format into an iterable of numbers.
+def parse_ieee_block_header(block):
+    """Parse the header of a IEEE block.
 
     Definite Length Arbitrary Block:
     #<header_length><data_length><data>
@@ -285,13 +285,9 @@ def from_ieee_block(block, datatype='f', is_big_endian=False, container=list):
 
     :param block: IEEE block.
     :type block: bytes
-    :param datatype: the format string for a single element. See struct module.
-    :param is_big_endian: boolean indicating endianess.
-    :param container: container type to use for the output data.
-    :return: items
-    :rtype: type(container)
+    :return: (offset, data_length)
+    :rtype: (int, int)
     """
-
     begin = block.find(b'#')
     if begin < 0:
         raise ValueError("Could not find hash sign (#) indicating the start of the block.")
@@ -313,6 +309,36 @@ def from_ieee_block(block, datatype='f', is_big_endian=False, container=list):
         # 012
         data_length = len(block) - offset - 1
 
+    return offset, data_length
+
+
+def from_ieee_block(block, datatype='f', is_big_endian=False, container=list):
+    """Convert a block in the IEEE format into an iterable of numbers.
+
+    Definite Length Arbitrary Block:
+    #<header_length><data_length><data>
+
+    The header_length specifies the size of the data_length field.
+    And the data_length field specifies the size of the data.
+
+    Indefinite Length Arbitrary Block:
+    #0<data>
+
+    :param block: IEEE block.
+    :type block: bytes
+    :param datatype: the format string for a single element. See struct module.
+    :param is_big_endian: boolean indicating endianess.
+    :param container: container type to use for the output data.
+    :return: items
+    :rtype: type(container)
+    """
+
+    offset, data_length = parse_ieee_block_header(block)
+
+    if len(block) < offset + data_length:
+        raise ValueError("Binary data is incomplete. The header states %d data bytes, "
+                         "but %d where received." % (data_length, len(block) - offset))
+
     return from_binary_block(block, offset, data_length, datatype, is_big_endian, container)