# HG changeset patch
# Parent  40f1b06ec989de042da52ac7c409febc9de59770
Issue #NNNNN: Document binascii.crc_hqx() implements CRC-CCITT

diff -r 40f1b06ec989 Doc/library/binascii.rst
--- a/Doc/library/binascii.rst	Sun Dec 18 01:37:12 2016 +0000
+++ b/Doc/library/binascii.rst	Sun Dec 18 10:43:07 2016 +0000
@@ -116,8 +116,10 @@
 
 .. function:: crc_hqx(data, value)
 
-   Compute the binhex4 crc value of *data*, starting with *value* as the
-   initial crc, and return the result.
+   Compute a 16-bit CRC value of *data*, starting with *value* as the
+   initial CRC, and return the result.  This uses the CRC-CCITT polynomial
+   ``x**16 + x**12 + x**5 + 1``, often represented as 0x1021.
+   This CRC is used in the binhex4 format.
 
 
 .. function:: crc32(data[, value])
diff -r 40f1b06ec989 Modules/binascii.c
--- a/Modules/binascii.c	Sun Dec 18 01:37:12 2016 +0000
+++ b/Modules/binascii.c	Sun Dec 18 10:43:07 2016 +0000
@@ -900,12 +900,12 @@
     crc: unsigned_int(bitwise=True)
     /
 
-Compute hqx CRC incrementally.
+Compute CRC-CCITT incrementally.
 [clinic start generated code]*/
 
 static unsigned int
 binascii_crc_hqx_impl(PyObject *module, Py_buffer *data, unsigned int crc)
-/*[clinic end generated code: output=8ec2a78590d19170 input=add8c53712ccceda]*/
+/*[clinic end generated code: output=8ec2a78590d19170 input=f18240ff8c705b79]*/
 {
     const unsigned char *bin_data;
     Py_ssize_t len;
diff -r 40f1b06ec989 Modules/clinic/binascii.c.h
--- a/Modules/clinic/binascii.c.h	Sun Dec 18 01:37:12 2016 +0000
+++ b/Modules/clinic/binascii.c.h	Sun Dec 18 10:43:07 2016 +0000
@@ -263,7 +263,7 @@
 "crc_hqx($module, data, crc, /)\n"
 "--\n"
 "\n"
-"Compute hqx CRC incrementally.");
+"Compute CRC-CCITT incrementally.");
 
 #define BINASCII_CRC_HQX_METHODDEF    \
     {"crc_hqx", (PyCFunction)binascii_crc_hqx, METH_VARARGS, binascii_crc_hqx__doc__},
@@ -550,4 +550,4 @@
 
     return return_value;
 }
-/*[clinic end generated code: output=1f8d6e48f75f6d1e input=a9049054013a1b77]*/
+/*[clinic end generated code: output=458eb09731cb7877 input=a9049054013a1b77]*/