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 41d1ce2c31008b3b56815884dc7b2eb893ae9f46..e13538ac251cc293cb8aab3461080def78ea7454 100644 (file)
--- a/Modules/stropmodule.c
+++ b/Modules/stropmodule.c
@@ -618,6 +618,80 @@ strop_capitalize(self, args)
 }
 
 
+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 @@ strop_methods[] = {
        {"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__},