diff options
| -rw-r--r-- | docs/library/uctypes.rst | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/docs/library/uctypes.rst b/docs/library/uctypes.rst index 164e0eb9d..c938d74a8 100644 --- a/docs/library/uctypes.rst +++ b/docs/library/uctypes.rst @@ -29,16 +29,16 @@ Following are encoding examples for various field types: * Scalar types:: - "field_name": uctypes.UINT32 | 0 + "field_name": offset | uctypes.UINT32 in other words, value is scalar type identifier ORed with field offset (in bytes) from the start of the structure. * Recursive structures:: - "sub": (2, { - "b0": uctypes.UINT8 | 0, - "b1": uctypes.UINT8 | 1, + "sub": (offset, { + "b0": 0 | uctypes.UINT8, + "b1": 1 | uctypes.UINT8, }) i.e. value is a 2-tuple, first element of which is offset, and second is @@ -47,7 +47,7 @@ Following are encoding examples for various field types: * Arrays of primitive types:: - "arr": (uctypes.ARRAY | 0, uctypes.UINT8 | 2), + "arr": (offset | uctypes.ARRAY, size | uctypes.UINT8), i.e. value is a 2-tuple, first element of which is ARRAY flag ORed with offset, and second is scalar element type ORed number of elements @@ -55,7 +55,7 @@ Following are encoding examples for various field types: * Arrays of aggregate types:: - "arr2": (uctypes.ARRAY | 0, 2, {"b": uctypes.UINT8 | 0}), + "arr2": (offset | uctypes.ARRAY, size, {"b": 0 | uctypes.UINT8}), i.e. value is a 3-tuple, first element of which is ARRAY flag ORed with offset, second is a number of elements in array, and third is @@ -63,21 +63,21 @@ Following are encoding examples for various field types: * Pointer to a primitive type:: - "ptr": (uctypes.PTR | 0, uctypes.UINT8), + "ptr": (offset | uctypes.PTR, uctypes.UINT8), i.e. value is a 2-tuple, first element of which is PTR flag ORed with offset, and second is scalar element type. * Pointer to an aggregate type:: - "ptr2": (uctypes.PTR | 0, {"b": uctypes.UINT8 | 0}), + "ptr2": (offset | uctypes.PTR, {"b": 0 | uctypes.UINT8}), i.e. value is a 2-tuple, first element of which is PTR flag ORed with offset, second is descriptor of type pointed to. * Bitfields:: - "bitf0": uctypes.BFUINT16 | 0 | 0 << uctypes.BF_POS | 8 << uctypes.BF_LEN, + "bitf0": offset | uctypes.BFUINT16 | lsbit << uctypes.BF_POS | bitsize << uctypes.BF_LEN, i.e. value is type of scalar value containing given bitfield (typenames are similar to scalar types, but prefixes with "BF"), ORed with offset for @@ -91,9 +91,10 @@ Following are encoding examples for various field types: In the example above, first a UINT16 value will be extracted at offset 0 (this detail may be important when accessing hardware registers, where particular access size and alignment are required), and then bitfield - whose rightmost bit is least-significant bit of this UINT16, and length - is 8 bits, will be extracted - effectively, this will access - least-significant byte of UINT16. + whose rightmost bit is *lsbit* bit of this UINT16, and length + is *bitsize* bits, will be extracted. For example, if *lsbit* is 0 and + *bitsize* is 8, then effectively it will access least-significant byte + of UINT16. Note that bitfield operations are independent of target byte endianness, in particular, example above will access least-significant byte of UINT16 |