Add an ICU based implementation of swapcase()

src/calibre/utils/icu.c

@@ -804,6 +804,40 @@ end:
 
 } // }}}
 
+// swap_case {{{
+
+static PyObject* icu_swap_case(PyObject *self, PyObject *args) {
+    PyObject *input = NULL, *result = NULL;
+    UErrorCode status = U_ZERO_ERROR;
+    UChar *input_buf = NULL, *output_buf = NULL;
+    UChar32 *buf = NULL;
+    int32_t sz = 0, sz32 = 0, i = 0;
+
+    if (!PyArg_ParseTuple(args, "O", &input)) return NULL;
+
+    input_buf = python_to_icu(input, &sz, 1);
+    if (input_buf == NULL) goto end;
+    output_buf = (UChar*) calloc(3 * sz, sizeof(UChar));
+    buf = (UChar32*) calloc(2 * sz, sizeof(UChar32));
+    if (output_buf == NULL || buf == NULL) { PyErr_NoMemory(); goto end; }
+    u_strToUTF32(buf, 2 * sz, &sz32, input_buf, sz, &status);
+
+    for (i = 0; i < sz32; i++) {
+        if (u_islower(buf[i])) buf[i] = u_toupper(buf[i]);
+        else if (u_isupper(buf[i])) buf[i] = u_tolower(buf[i]);
+    }
+    u_strFromUTF32(output_buf, 3*sz, &sz, buf, sz32, &status);
+    if (U_FAILURE(status)) { PyErr_SetString(PyExc_ValueError, u_errorName(status)); goto end; }
+    result = icu_to_python(output_buf, sz);
+
+end:
+    if (input_buf != NULL) free(input_buf);
+    if (output_buf != NULL) free(output_buf);
+    if (buf != NULL) free(buf);
+    return result;
+
+} // }}}
+
 // set_default_encoding {{{
 static PyObject *
 icu_set_default_encoding(PyObject *self, PyObject *args) {
@@ -1058,6 +1092,10 @@ static PyMethodDef icu_methods[] = {
         "change_case(unicode object, which, locale) -> change case to one of UPPER_CASE, LOWER_CASE, TITLE_CASE"
     },
 
+    {"swap_case", icu_swap_case, METH_VARARGS,
+        "swap_case(unicode object) -> swaps the case using the simple, locale independent unicode algorithm"
+    },
+
     {"set_default_encoding", icu_set_default_encoding, METH_VARARGS,
         "set_default_encoding(encoding) -> Set the default encoding for the python unicode implementation."
     },

src/calibre/utils/icu.py

@@ -212,6 +212,11 @@ def capitalize(x):
     except (IndexError, TypeError, AttributeError):
         return x
 
+try:
+    swapcase = _icu.swap_case
+except AttributeError:  # For people running from source
+    swapcase = lambda x:x.swapcase()
+
 find = _make_func(_strcmp_template, 'find', collator='_collator', collator_func='collator', func='find')
 
 primary_find = _make_func(_strcmp_template, 'primary_find', collator='_primary_collator', collator_func='primary_collator', func='find')

src/calibre/utils/icu_test.py

@@ -90,6 +90,7 @@ class TestICU(unittest.TestCase):
             # capitals inside words
             self.ae(icu.title_case(x), titlecase(x).replace('machIne', 'Machine'))
             self.ae(icu.capitalize(x), x[0].upper() + x[1:].lower())
+            self.ae(icu.swapcase(x), x.swapcase())
 
     def test_find(self):
         ' Test searching for substrings '