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/********************************************************
Audio Tools, a module and set of tools for manipulating audio data
Copyright (C) 2007-2015 Brian Langenberger
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*******************************************************/
/*This is a set of reusable routines for opening a BitstreamReader
wrapped around the os.urandom function call
for generating individual bits of dither for an audio stream.*/
/*this is quite similar to br_read_python
except that it pulls data from os.urandom()*/
static unsigned
read_os_random(void *user_data,
uint8_t* buffer,
unsigned buffer_size)
{
PyObject *os_module = user_data;
/*call unrandom() function on os module*/
PyObject* read_result =
PyObject_CallMethod(os_module, "urandom", "I", buffer_size);
char *string;
Py_ssize_t string_size;
unsigned to_copy;
if (read_result == NULL) {
/*some exception occurred, so clear result and return no bytes
(which will likely turn into an I/O exception later)*/
PyErr_Clear();
return 0;
}
/*get string data from returned object*/
if (PyBytes_AsStringAndSize(read_result,
&string,
&string_size) == -1) {
/*got something that wasn't a string from .read()
so clear exception and return no bytes*/
Py_DECREF(read_result);
PyErr_Clear();
return 0;
}
/*write either "buffer_size" or "string_size" bytes to buffer
whichever is less*/
if (string_size >= buffer_size) {
/*truncate strings larger than expected*/
to_copy = buffer_size;
} else {
to_copy = (unsigned)string_size;
}
memcpy(buffer, (uint8_t*)string, to_copy);
/*perform cleanup and return bytes actually read*/
Py_DECREF(read_result);
return to_copy;
}
static int
close_os_random(void *user_data)
{
return 0;
}
static void
free_os_random(void *user_data)
{
PyObject *os_module = user_data;
Py_XDECREF(os_module);
}
/*returns a BitstreamReader for reading 1 bit white noise dither values
or NULL if an error occurs opening the os module*/
static BitstreamReader*
open_dither(void)
{
PyObject* os_module;
if ((os_module = PyImport_ImportModule("os")) != NULL) {
return br_open_external(os_module,
BS_BIG_ENDIAN,
4096,
read_os_random,
NULL, /*unseekable stream*/
NULL, /*unseekable stream*/
NULL, /*unseekable stream*/
NULL, /*unseekable stream*/
close_os_random,
free_os_random);
} else {
return NULL;
}
}
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