A gift from Fredrik Lundh: fast C implementation of expandtabs().
I've reformatted it, added a few comments, a test for tabsize <= 0,
and used the AS_STRING macro.
diff --git a/Modules/stropmodule.c b/Modules/stropmodule.c
index 41d1ce2..e13538a 100644
--- a/Modules/stropmodule.c
+++ b/Modules/stropmodule.c
@@ -618,6 +618,80 @@
}
+static char expandtabs__doc__[] =
+"expandtabs(string, [tabsize]) -> string\n\
+\n\
+
+Expand tabs in a string, i.e. replace them by one or more spaces,\n\
+depending on the current column and the given tab size (default 8).\n\
+The column number is reset to zero after each newline occurring in the\n\
+string. This doesn't understand other non-printing characters.";
+
+static PyObject *
+strop_expandtabs(self, args)
+ PyObject *self;
+ PyObject *args;
+{
+ /* Original by Fredrik Lundh */
+ char* e;
+ char* p;
+ char* q;
+ int i, j;
+ PyObject* out;
+ char* string;
+ int stringlen;
+ int tabsize = 8;
+
+ /* Get arguments */
+ if (!PyArg_ParseTuple(args, "s#|i", &string, &stringlen, &tabsize))
+ return NULL;
+ if (tabsize < 1) {
+ PyErr_SetString(PyExc_ValueError,
+ "tabsize must be at least 1");
+ return NULL;
+ }
+
+ /* First pass: determine size of output string */
+ i = j = 0; /* j: current column; i: total of previous lines */
+ e = string + stringlen;
+ for (p = string; p < e; p++) {
+ if (*p == '\t')
+ j += tabsize - (j%tabsize);
+ else {
+ j++;
+ if (*p == '\n') {
+ i += j;
+ j = 0;
+ }
+ }
+ }
+
+ /* Second pass: create output string and fill it */
+ out = PyString_FromStringAndSize(NULL, i+j);
+ if (out == NULL)
+ return NULL;
+
+ i = 0;
+ q = PyString_AS_STRING(out);
+
+ for (p = string; p < e; p++) {
+ if (*p == '\t') {
+ j = tabsize - (i%tabsize);
+ i += j;
+ while (j-- > 0)
+ *q++ = ' ';
+ } else {
+ *q++ = *p;
+ i++;
+ if (*p == '\n')
+ i = 0;
+ }
+ }
+
+ return out;
+}
+
+
static char count__doc__[] =
"count(s, sub[, start[, end]]) -> int\n\
\n\
@@ -1167,6 +1241,7 @@
{"atol", strop_atol, 1, atol__doc__},
{"capitalize", strop_capitalize, 0, capitalize__doc__},
{"count", strop_count, 1, count__doc__},
+ {"expandtabs", strop_expandtabs, 1, expandtabs__doc__},
{"find", strop_find, 1, find__doc__},
{"join", strop_joinfields, 1, joinfields__doc__},
{"joinfields", strop_joinfields, 1, joinfields__doc__},