From 7f7c84b10a5f3b2f783955b01f55e0f913ac459f Mon Sep 17 00:00:00 2001 From: Paul Sokolovsky Date: Wed, 18 May 2016 02:40:03 +0300 Subject: py/stream: Support both "exact size" and "one underlying call" operations. Both read and write operations support variants where either a) a single call is made to the undelying stream implementation and returned buffer length may be less than requested, or b) calls are repeated until requested amount of data is collected, shorter amount is returned only in case of EOF or error. These operations are available from the level of C support functions to be used by other C modules to implementations of Python methods to be used in user-facing objects. The rationale of these changes is to allow to write concise and robust code to work with *blocking* streams of types prone to short reads, like serial interfaces and sockets. Particular object types may select "exact" vs "once" types of methods depending on their needs. E.g., for sockets, revc() and send() methods continue to be "once", while read() and write() thus converted to "exactly" versions. These changes don't affect non-blocking handling, e.g. trying "exact" method on the non-blocking socket will return as much data as available without blocking. No data available is continued to be signaled as None return value to read() and write(). From the point of view of CPython compatibility, this model is a cross between its io.RawIOBase and io.BufferedIOBase abstract classes. For blocking streams, it works as io.BufferedIOBase model (guaranteeing lack of short reads/writes), while for non-blocking - as io.RawIOBase, returning None in case of lack of data (instead of raising expensive exception, as required by io.BufferedIOBase). Such a cross-behavior should be optimal for MicroPython needs. --- py/modio.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'py/modio.c') diff --git a/py/modio.c b/py/modio.c index 423315081f..2fbe6bc1e1 100644 --- a/py/modio.c +++ b/py/modio.c @@ -78,10 +78,13 @@ STATIC mp_uint_t bufwriter_write(mp_obj_t self_in, const void *buf, mp_uint_t si memcpy(self->buf + self->len, buf, rem); buf = (byte*)buf + rem; size -= rem; - mp_uint_t out_sz = mp_stream_writeall(self->stream, self->buf, self->alloc, errcode); - if (out_sz == MP_STREAM_ERROR) { + mp_uint_t out_sz = mp_stream_write_exactly(self->stream, self->buf, self->alloc, errcode); + if (*errcode != 0) { return MP_STREAM_ERROR; } + // TODO: try to recover from a case of non-blocking stream, e.g. move + // remaining chunk to the beginning of buffer. + assert(out_sz == self->alloc); self->len = 0; } @@ -93,9 +96,12 @@ STATIC mp_obj_t bufwriter_flush(mp_obj_t self_in) { if (self->len != 0) { int err; - mp_uint_t out_sz = mp_stream_writeall(self->stream, self->buf, self->len, &err); + mp_uint_t out_sz = mp_stream_write_exactly(self->stream, self->buf, self->len, &err); + // TODO: try to recover from a case of non-blocking stream, e.g. move + // remaining chunk to the beginning of buffer. + assert(out_sz == self->len); self->len = 0; - if (out_sz == MP_STREAM_ERROR) { + if (err != 0) { nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(err))); } } -- cgit v1.2.3