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library.c
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library.c
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/*
* Author: Andrey Semenov, 2022
*/
#include <stddef.h>
#include "library.h"
#define PyBytesObject_SIZE (offsetof(PyBytesObject, ob_sval) + 1)
#define BIG_STRING_SORT_BUFSIZE 1 << 20 // 1 MiB
// 0.1 of a second
static const struct timespec err_recovery_time = {
.tv_sec = 0,
.tv_nsec = 100000000
};
static void BigStringSort__count_chars(size_t counters[],
const size_t chunk_size,
size_t *to_read,
const uint8_t *const buf) {
*to_read -= chunk_size;
for ( uint32_t i = 0; i < chunk_size; i++ ) {
counters[buf[i]]++;
}
}
PyObject *BigStringSort_call(__attribute__((unused)) PyObject *self, PyObject *arg) {
PyThreadState *_save = PyEval_SaveThread();
size_t counters[256] = {0};
char *path;
// uses Py_LIMITED_API function, though still works on CPython3.9
if ( (path = PyUnicode_AsUTF8(arg)) == NULL ) {
PyEval_RestoreThread(_save);
return NULL;
}
FILE *fd;
if ( !(fd = fopen(path, "r")) ) {
PyEval_RestoreThread(_save);
PyErr_SetFromErrno(PyExc_OSError);
return NULL;
}
struct stat path_stat;
if ( stat(path, &path_stat) ) {
fclose(fd);
PyEval_RestoreThread(_save);
PyErr_SetFromErrno(PyExc_OSError);
return NULL;
}
if ( ( size_t ) path_stat.st_size > ( size_t ) PY_SSIZE_T_MAX - PyBytesObject_SIZE ) {
fclose(fd);
PyEval_RestoreThread(_save);
PyErr_SetString(PyExc_OverflowError,
"byte string is too large");
return NULL;
}
PyBytesObject *retval;
if ( (retval = ( PyBytesObject * ) PyObject_Malloc(PyBytesObject_SIZE + path_stat.st_size)) == NULL ) {
fclose(fd);
PyEval_RestoreThread(_save);
return PyErr_NoMemory();
}
size_t to_read = path_stat.st_size;
uint8_t *buf = NULL;
if ( (buf = malloc(BIG_STRING_SORT_BUFSIZE)) == NULL ) {
PyEval_RestoreThread(_save);
PyErr_SetFromErrno(PyExc_OSError);
goto err_obj_cleanup;
}
uint8_t err_count = 0;
while ( to_read ) {
size_t chunk_size = fread(buf, 1, BIG_STRING_SORT_BUFSIZE, fd);
if ( chunk_size != BIG_STRING_SORT_BUFSIZE && chunk_size != to_read ) {
BigStringSort__count_chars(counters, chunk_size, &to_read, buf);
if ( feof(fd) ) {
PyEval_RestoreThread(_save);
PyErr_SetString(PyExc_BrokenPipeError, "File was shrunk while being read");
goto err_buf_cleanup;
}
if ( ferror(fd) ) {
if ( err_count >= 10 ) {
char err_text[255] = {0};
sprintf(err_text,
"Could not read the contents of the file (10 failed attempts at region %lu)",
path_stat.st_size - to_read);
PyEval_RestoreThread(_save);
PyErr_SetString(PyExc_IOError, err_text);
goto err_buf_cleanup;
}
err_count++;
struct timespec rem = {0};
if ( clock_gettime(CLOCK_MONOTONIC, &rem) ) {
PyEval_RestoreThread(_save);
PyErr_SetFromErrno(PyExc_OSError);
goto err_buf_cleanup;
}
rem.tv_sec += 1 * ( int ) ((rem.tv_nsec + err_recovery_time.tv_nsec) >= 1000000000);
rem.tv_nsec += err_recovery_time.tv_nsec;
rem.tv_nsec -= (1000000000 * ( int ) (rem.tv_nsec >= 1000000000));
if ( clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &rem, NULL) ) {
PyEval_RestoreThread(_save);
PyErr_SetFromErrno(PyExc_OSError);
goto err_buf_cleanup;
}
clearerr(fd);
continue;
}
}
err_count = 0;
BigStringSort__count_chars(counters, chunk_size, &to_read, buf);
}
free(buf);
// throws a ResourceWarning so a user could catch it and decide if there's a need to recover and how
// no hard recovery is needed since the main function is done and results are only needed to be properly returned
if ( fclose(fd) ) {
PyEval_RestoreThread(_save);
PyErr_WarnEx(PyExc_ResourceWarning, strerror(errno), 1);
_save = PyEval_SaveThread();
}
PyObject_INIT_VAR(retval, &PyBytes_Type, path_stat.st_size);
retval->ob_shash = -1;
retval->ob_sval[path_stat.st_size] = '\0';
size_t position = 0;
for ( uint16_t char_val = 0; char_val < 256; char_val++ ) {
if ( !counters[char_val] )
continue;
memset(retval->ob_sval + position, char_val, counters[char_val]);
position += counters[char_val];
}
PyEval_RestoreThread(_save);
return ( PyObject * ) retval;
err_buf_cleanup:
free(buf);
err_obj_cleanup:
fclose(fd);
PyObject_Free(retval);
return NULL;
}
__attribute__((unused)) PyMODINIT_FUNC PyInit_big_string_sort(void) {
PyObject *m = NULL;
if ( PyType_Ready(&BigStringSortType) < 0 ) {
goto fail;
}
m = PyModule_Create(&BigStringSort_module);
if ( m == NULL ) {
goto fail;
}
if ( PyModule_AddObject(m, "BigStringSort", ( PyObject * ) &BigStringSortType) < 0 ) {
goto fail;
}
return m;
fail:
Py_XDECREF(m);
return NULL;
}