# -*- Mode: Python -*-

cdef extern from "Python.h":
    # need to be careful, we can only use functions with
    # simple/standard refcount behaviors. [e.g., no borrowed refs]
    object PyString_FromStringAndSize (char * s, int len)
    int    PyList_Size (object)           except -1
    int    PyTuple_Size (object)          except -1
    object PySequence_GetItem (object, int index)
    int    PySequence_Size (object)       except -1
    int    PyList_Append (object, object) except -1
    int    PyList_Reverse (object)        except -1
    int    PyString_Size (object)         except -1
    object PyNumber_Long (object)
    char * PyString_AsString (object)
    void * memcpy (void *, void *, int len)

cdef object _concat (object l):
    # concat a sequence of strings
    # 1: compute length of result
    cdef int llen, rlen, i, ilen
    rlen = 0
    llen = PySequence_Size (l)
    for i from 0 <= i < llen:
        s = PySequence_GetItem (l, i)
        rlen = rlen + PyString_Size (s)
    # 2: create result
    result = PyString_FromStringAndSize (NULL, rlen)
    cdef char * rbuf
    rbuf = PyString_AsString (result)
    # 3: fill result
    for i from 0 <= i < llen:
        s = PySequence_GetItem (l, i)
        ilen = PyString_Size (s)
        memcpy (rbuf, PyString_AsString (s), ilen)
        rbuf = rbuf + ilen
    # 4: return result
    return result