[Python-Dev] PEP 393 review (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Mon Aug 29 21:20:53 CEST 2011

Am 29.08.2011 11:03, schrieb Dirkjan Ochtman:

On Sun, Aug 28, 2011 at 21:47, "Martin v. Löwis" <martin at v.loewis.de> wrote:

result strings. In PEP 393, a buffer must be scanned for the highest code point, which means that each byte must be inspected twice (a second time when the copying occurs). This may be a silly question: are there things in place to optimize this for the case where two strings are combined? E.g. highest character in combined string is max(highest character in either of the strings).

Unicode_Concat goes like this

maxchar = PyUnicode_MAX_CHAR_VALUE(u);
if (PyUnicode_MAX_CHAR_VALUE(v) > maxchar)
    maxchar = PyUnicode_MAX_CHAR_VALUE(v);

/* Concat the two Unicode strings */
w = (PyUnicodeObject *) PyUnicode_New(
                        PyUnicode_GET_LENGTH(u) +

PyUnicode_GET_LENGTH(v), maxchar); if (w == NULL) goto onError; PyUnicode_CopyCharacters(w, 0, u, 0, PyUnicode_GET_LENGTH(u)); PyUnicode_CopyCharacters(w, PyUnicode_GET_LENGTH(u), v, 0, PyUnicode_GET_LENGTH(v));

Also, this PEP makes me wonder if there should be a way to distinguish between language PEPs and (CPython) implementation PEPs, by adding a tag or using the PEP number ranges somehow.

Well, no. This would equally apply to every single patch, and is just not feasible. Instead, alternative implementations typically target a CPython version, and then find out what features they need to implement to claim conformance.

Regards, Martin

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