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stream: Add compliant handling of non-blocking read()/write().

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In case of empty non-blocking read()/write(), both return None. read()
cannot return 0, as that means EOF, so returns another value, and then
write() just follows. This is still pretty unexpected, and typical
"if not len:" check would treat this as EOF. Well, non-blocking files
require special handling!

This also kind of makes it depending on POSIX, but well, anything else
should emulate POSIX anyway ;-).
This commit is contained in:
Paul Sokolovsky 2014-05-07 01:39:38 +03:00
parent 93afa230a4
commit a592104acd
1 changed files with 21 additions and 3 deletions
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24
py/stream.c
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@ -25,6 +25,7 @@
*/
#include <string.h>
#include <errno.h>
#include "mpconfig.h"
#include "nlr.h"
@ -38,6 +39,10 @@
STATIC mp_obj_t stream_readall(mp_obj_t self_in);
// TODO: This is POSIX-specific (but then POSIX is the only real thing,
// and anything else just emulates it, right?)
#define is_nonblocking_error(errno) ((errno) == EAGAIN || (errno) == EWOULDBLOCK)
STATIC mp_obj_t stream_read(uint n_args, const mp_obj_t *args) {
struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)args[0];
if (o->type->stream_p == NULL || o->type->stream_p->read == NULL) {
@ -53,6 +58,14 @@ STATIC mp_obj_t stream_read(uint n_args, const mp_obj_t *args) {
int error;
machine_int_t out_sz = o->type->stream_p->read(o, buf, sz, &error);
if (out_sz == -1) {
if (is_nonblocking_error(error)) {
// https://docs.python.org/3.4/library/io.html#io.RawIOBase.read
// "If the object is in non-blocking mode and no bytes are available,
// None is returned."
// This is actually very weird, as naive truth check will treat
// this as EOF.
return mp_const_none;
}
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError, "[Errno %d]", error));
} else {
mp_obj_t s = mp_obj_new_str(buf, out_sz, false); // will reallocate to use exact size
@ -74,11 +87,16 @@ STATIC mp_obj_t stream_write(mp_obj_t self_in, mp_obj_t arg) {
int error;
machine_int_t out_sz = o->type->stream_p->write(self_in, bufinfo.buf, bufinfo.len, &error);
if (out_sz == -1) {
if (is_nonblocking_error(error)) {
// http://docs.python.org/3/library/io.html#io.RawIOBase.write
// "None is returned if the raw stream is set not to block and
// no single byte could be readily written to it."
// This is for consistency with read() behavior, still weird,
// see abobe.
return mp_const_none;
}
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError, "[Errno %d]", error));
} else {
// http://docs.python.org/3/library/io.html#io.RawIOBase.write
// "None is returned if the raw stream is set not to block and no single byte could be readily written to it."
// Do they mean that instead of 0 they return None?
return MP_OBJ_NEW_SMALL_INT(out_sz);
}
}