Issue #13624: Write a specialized UTF-8 encoder to allow more optimization
The main bottleneck was the PyUnicode_READ() macro.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index c5d361b..1eb24dd 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -4987,20 +4987,9 @@
PyObject *
_PyUnicode_AsUTF8String(PyObject *unicode, const char *errors)
{
-#define MAX_SHORT_UNICHARS 300 /* largest size we'll do on the stack */
-
- Py_ssize_t i; /* index into s of next input byte */
- PyObject *result; /* result string object */
- char *p; /* next free byte in output buffer */
- Py_ssize_t nallocated; /* number of result bytes allocated */
- Py_ssize_t nneeded; /* number of result bytes needed */
- char stackbuf[MAX_SHORT_UNICHARS * 4];
- PyObject *errorHandler = NULL;
- PyObject *exc = NULL;
- int kind;
+ enum PyUnicode_Kind kind;
void *data;
Py_ssize_t size;
- PyObject *rep = NULL;
if (!PyUnicode_Check(unicode)) {
PyErr_BadArgument();
@@ -5018,144 +5007,18 @@
data = PyUnicode_DATA(unicode);
size = PyUnicode_GET_LENGTH(unicode);
- assert(size >= 0);
-
- if (size <= MAX_SHORT_UNICHARS) {
- /* Write into the stack buffer; nallocated can't overflow.
- * At the end, we'll allocate exactly as much heap space as it
- * turns out we need.
- */
- nallocated = Py_SAFE_DOWNCAST(sizeof(stackbuf), size_t, int);
- result = NULL; /* will allocate after we're done */
- p = stackbuf;
+ switch(kind) {
+ default:
+ assert(0);
+ case PyUnicode_1BYTE_KIND:
+ /* the string cannot be ASCII, or PyUnicode_UTF8() would be set */
+ assert(!PyUnicode_IS_ASCII(unicode));
+ return ucs1lib_utf8_encoder(unicode, data, size, errors);
+ case PyUnicode_2BYTE_KIND:
+ return ucs2lib_utf8_encoder(unicode, data, size, errors);
+ case PyUnicode_4BYTE_KIND:
+ return ucs4lib_utf8_encoder(unicode, data, size, errors);
}
- else {
- /* Overallocate on the heap, and give the excess back at the end. */
- nallocated = size * 4;
- if (nallocated / 4 != size) /* overflow! */
- return PyErr_NoMemory();
- result = PyBytes_FromStringAndSize(NULL, nallocated);
- if (result == NULL)
- return NULL;
- p = PyBytes_AS_STRING(result);
- }
-
- for (i = 0; i < size;) {
- Py_UCS4 ch = PyUnicode_READ(kind, data, i++);
-
- if (ch < 0x80)
- /* Encode ASCII */
- *p++ = (char) ch;
-
- else if (ch < 0x0800) {
- /* Encode Latin-1 */
- *p++ = (char)(0xc0 | (ch >> 6));
- *p++ = (char)(0x80 | (ch & 0x3f));
- } else if (Py_UNICODE_IS_SURROGATE(ch)) {
- Py_ssize_t newpos;
- Py_ssize_t repsize, k, startpos;
- startpos = i-1;
- rep = unicode_encode_call_errorhandler(
- errors, &errorHandler, "utf-8", "surrogates not allowed",
- unicode, &exc, startpos, startpos+1, &newpos);
- if (!rep)
- goto error;
-
- if (PyBytes_Check(rep))
- repsize = PyBytes_GET_SIZE(rep);
- else
- repsize = PyUnicode_GET_LENGTH(rep);
-
- if (repsize > 4) {
- Py_ssize_t offset;
-
- if (result == NULL)
- offset = p - stackbuf;
- else
- offset = p - PyBytes_AS_STRING(result);
-
- if (nallocated > PY_SSIZE_T_MAX - repsize + 4) {
- /* integer overflow */
- PyErr_NoMemory();
- goto error;
- }
- nallocated += repsize - 4;
- if (result != NULL) {
- if (_PyBytes_Resize(&result, nallocated) < 0)
- goto error;
- } else {
- result = PyBytes_FromStringAndSize(NULL, nallocated);
- if (result == NULL)
- goto error;
- Py_MEMCPY(PyBytes_AS_STRING(result), stackbuf, offset);
- }
- p = PyBytes_AS_STRING(result) + offset;
- }
-
- if (PyBytes_Check(rep)) {
- char *prep = PyBytes_AS_STRING(rep);
- for(k = repsize; k > 0; k--)
- *p++ = *prep++;
- } else /* rep is unicode */ {
- enum PyUnicode_Kind repkind;
- void *repdata;
-
- if (PyUnicode_READY(rep) < 0)
- goto error;
- repkind = PyUnicode_KIND(rep);
- repdata = PyUnicode_DATA(rep);
-
- for(k=0; k<repsize; k++) {
- Py_UCS4 c = PyUnicode_READ(repkind, repdata, k);
- if (0x80 <= c) {
- raise_encode_exception(&exc, "utf-8",
- unicode,
- i-1, i,
- "surrogates not allowed");
- goto error;
- }
- *p++ = (char)c;
- }
- }
- Py_CLEAR(rep);
- } else if (ch < 0x10000) {
- *p++ = (char)(0xe0 | (ch >> 12));
- *p++ = (char)(0x80 | ((ch >> 6) & 0x3f));
- *p++ = (char)(0x80 | (ch & 0x3f));
- } else /* ch >= 0x10000 */ {
- assert(ch <= MAX_UNICODE);
- /* Encode UCS4 Unicode ordinals */
- *p++ = (char)(0xf0 | (ch >> 18));
- *p++ = (char)(0x80 | ((ch >> 12) & 0x3f));
- *p++ = (char)(0x80 | ((ch >> 6) & 0x3f));
- *p++ = (char)(0x80 | (ch & 0x3f));
- }
- }
-
- if (result == NULL) {
- /* This was stack allocated. */
- nneeded = p - stackbuf;
- assert(nneeded <= nallocated);
- result = PyBytes_FromStringAndSize(stackbuf, nneeded);
- }
- else {
- /* Cut back to size actually needed. */
- nneeded = p - PyBytes_AS_STRING(result);
- assert(nneeded <= nallocated);
- _PyBytes_Resize(&result, nneeded);
- }
-
- Py_XDECREF(errorHandler);
- Py_XDECREF(exc);
- return result;
- error:
- Py_XDECREF(rep);
- Py_XDECREF(errorHandler);
- Py_XDECREF(exc);
- Py_XDECREF(result);
- return NULL;
-
-#undef MAX_SHORT_UNICHARS
}
PyObject *