py/stream.c - lite/micropython - Linaro Git Browser

 /*
  * This file is part of the Micro Python project, http://micropython.org/
  *
  * The MIT License (MIT)
  *
  * Copyright (c) 2013, 2014 Damien P. George
  * Copyright (c) 2014 Paul Sokolovsky
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 #include <string.h>

 #include "py/nlr.h"
 #include "py/objstr.h"
 #include "py/stream.h"

 #if MICROPY_STREAMS_NON_BLOCK
 #include <errno.h>
 #if defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR)
 #define EWOULDBLOCK 140
 #endif
 #endif

 // This file defines generic Python stream read/write methods which
 // dispatch to the underlying stream interface of an object.

 // TODO: should be in mpconfig.h
 #define DEFAULT_BUFFER_SIZE 256

 STATIC mp_obj_t stream_readall(mp_obj_t self_in);

 #if MICROPY_STREAMS_NON_BLOCK
 // 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)
 #else
 #define is_nonblocking_error(errno) (0)
 #endif

 #define STREAM_CONTENT_TYPE(stream) (((stream)->is_text) ? &mp_type_str : &mp_type_bytes)

 STATIC mp_obj_t stream_read(mp_uint_t 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) {
         // CPython: io.UnsupportedOperation, OSError subclass
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
     }

     // What to do if sz < -1?  Python docs don't specify this case.
     // CPython does a readall, but here we silently let negatives through,
     // and they will cause a MemoryError.
     mp_int_t sz;
     if (n_args == 1 || ((sz = mp_obj_get_int(args[1])) == -1)) {
         return stream_readall(args[0]);
     }

     #if MICROPY_PY_BUILTINS_STR_UNICODE
     if (o->type->stream_p->is_text) {
         // We need to read sz number of unicode characters.  Because we don't have any
         // buffering, and because the stream API can only read bytes, we must read here
         // in units of bytes and must never over read.  If we want sz chars, then reading
         // sz bytes will never over-read, so we follow this approach, in a loop to keep
         // reading until we have exactly enough chars.  This will be 1 read for text
         // with ASCII-only chars, and about 2 reads for text with a couple of non-ASCII
         // chars.  For text with lots of non-ASCII chars, it'll be pretty inefficient
         // in time and memory.

         vstr_t vstr;
         vstr_init(&vstr, sz);
         mp_uint_t more_bytes = sz;
         mp_uint_t last_buf_offset = 0;
         while (more_bytes > 0) {
             char *p = vstr_add_len(&vstr, more_bytes);
             if (p == NULL) {
                 nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_MemoryError, "out of memory"));
             }
             int error;
             mp_uint_t out_sz = o->type->stream_p->read(o, p, more_bytes, &error);
             if (out_sz == MP_STREAM_ERROR) {
                 vstr_cut_tail_bytes(&vstr, more_bytes);
                 if (is_nonblocking_error(error)) {
                     // With non-blocking streams, we read as much as we can.
                     // If we read nothing, return None, just like read().
                     // Otherwise, return data read so far.
                     // TODO what if we have read only half a non-ASCII char?
                     if (vstr.len == 0) {
                         vstr_clear(&vstr);
                         return mp_const_none;
                     }
                     break;
                 }
                 nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
             }

             if (out_sz < more_bytes) {
                 // Finish reading.
                 // TODO what if we have read only half a non-ASCII char?
                 vstr_cut_tail_bytes(&vstr, more_bytes - out_sz);
                 if (out_sz == 0) {
                     break;
                 }
             }

             // count chars from bytes just read
             for (mp_uint_t off = last_buf_offset;;) {
                 byte b = vstr.buf[off];
                 int n;
                 if (!UTF8_IS_NONASCII(b)) {
                     // 1-byte ASCII char
                     n = 1;
                 } else if ((b & 0xe0) == 0xc0) {
                     // 2-byte char
                     n = 2;
                 } else if ((b & 0xf0) == 0xe0) {
                     // 3-byte char
                     n = 3;
                 } else if ((b & 0xf8) == 0xf0) {
                     // 4-byte char
                     n = 4;
                 } else {
                     // TODO
                     n = 5;
                 }
                 if (off + n <= vstr.len) {
                     // got a whole char in n bytes
                     off += n;
                     sz -= 1;
                     last_buf_offset = off;
                     if (off >= vstr.len) {
                         more_bytes = sz;
                         break;
                     }
                 } else {
                     // didn't get a whole char, so work out how many extra bytes are needed for
                     // this partial char, plus bytes for additional chars that we want
                     more_bytes = (off + n - vstr.len) + (sz - 1);
                     break;
                 }
             }
         }

         return mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
     }
     #endif

     vstr_t vstr;
     vstr_init_len(&vstr, sz);
     int error;
     mp_uint_t out_sz = o->type->stream_p->read(o, vstr.buf, sz, &error);
     if (out_sz == MP_STREAM_ERROR) {
         vstr_clear(&vstr);
         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_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
     } else {
         vstr.len = out_sz;
         return mp_obj_new_str_from_vstr(STREAM_CONTENT_TYPE(o->type->stream_p), &vstr);
     }
 }

 mp_obj_t mp_stream_write(mp_obj_t self_in, const void *buf, mp_uint_t len) {
     struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)self_in;
     if (o->type->stream_p == NULL || o->type->stream_p->write == NULL) {
         // CPython: io.UnsupportedOperation, OSError subclass
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
     }

     int error;
     mp_uint_t out_sz = o->type->stream_p->write(self_in, buf, len, &error);
     if (out_sz == MP_STREAM_ERROR) {
         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_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
     } else {
         return MP_OBJ_NEW_SMALL_INT(out_sz);
     }
 }

 STATIC mp_obj_t stream_write_method(mp_obj_t self_in, mp_obj_t arg) {
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(arg, &bufinfo, MP_BUFFER_READ);
     return mp_stream_write(self_in, bufinfo.buf, bufinfo.len);
 }

 STATIC mp_obj_t stream_readinto(mp_uint_t 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) {
         // CPython: io.UnsupportedOperation, OSError subclass
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
     }
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);

     // CPython extension: if 2nd arg is provided, that's max len to read,
     // instead of full buffer. Similar to
     // https://docs.python.org/3/library/socket.html#socket.socket.recv_into
     mp_uint_t len = bufinfo.len;
     if (n_args > 2) {
         len = mp_obj_int_get_truncated(args[2]);
         if (len > bufinfo.len) {
             len = bufinfo.len;
         }
     }

     int error;
     mp_uint_t out_sz = o->type->stream_p->read(o, bufinfo.buf, len, &error);
     if (out_sz == MP_STREAM_ERROR) {
         if (is_nonblocking_error(error)) {
             return mp_const_none;
         }
         nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
     } else {
         return MP_OBJ_NEW_SMALL_INT(out_sz);
     }
 }

 STATIC mp_obj_t stream_readall(mp_obj_t self_in) {
     struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)self_in;
     if (o->type->stream_p == NULL || o->type->stream_p->read == NULL) {
         // CPython: io.UnsupportedOperation, OSError subclass
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
     }

     mp_uint_t total_size = 0;
     vstr_t vstr;
     vstr_init(&vstr, DEFAULT_BUFFER_SIZE);
     char *p = vstr.buf;
     mp_uint_t current_read = DEFAULT_BUFFER_SIZE;
     while (true) {
         int error;
         mp_uint_t out_sz = o->type->stream_p->read(self_in, p, current_read, &error);
         if (out_sz == MP_STREAM_ERROR) {
             if (is_nonblocking_error(error)) {
                 // With non-blocking streams, we read as much as we can.
                 // If we read nothing, return None, just like read().
                 // Otherwise, return data read so far.
                 if (total_size == 0) {
                     return mp_const_none;
                 }
                 break;
             }
             nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
         }
         if (out_sz == 0) {
             break;
         }
         total_size += out_sz;
         if (out_sz < current_read) {
             current_read -= out_sz;
             p += out_sz;
         } else {
             p = vstr_extend(&vstr, DEFAULT_BUFFER_SIZE);
             current_read = DEFAULT_BUFFER_SIZE;
             if (p == NULL) {
                 // TODO
                 nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError/*&mp_type_RuntimeError*/, "Out of memory"));
             }
         }
     }

     vstr.len = total_size;
     return mp_obj_new_str_from_vstr(STREAM_CONTENT_TYPE(o->type->stream_p), &vstr);
 }

 // Unbuffered, inefficient implementation of readline() for raw I/O files.
 STATIC mp_obj_t stream_unbuffered_readline(mp_uint_t 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) {
         // CPython: io.UnsupportedOperation, OSError subclass
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
     }

     mp_int_t max_size = -1;
     if (n_args > 1) {
         max_size = MP_OBJ_SMALL_INT_VALUE(args[1]);
     }

     vstr_t vstr;
     if (max_size != -1) {
         vstr_init(&vstr, max_size);
     } else {
         vstr_init(&vstr, 16);
     }

     while (max_size == -1 || max_size-- != 0) {
         char *p = vstr_add_len(&vstr, 1);
         if (p == NULL) {
             nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_MemoryError, "out of memory"));
         }

         int error;
         mp_uint_t out_sz = o->type->stream_p->read(o, p, 1, &error);
         if (out_sz == MP_STREAM_ERROR) {
             if (is_nonblocking_error(error)) {
                 if (vstr.len == 1) {
                     // We just incremented it, but otherwise we read nothing
                     // and immediately got EAGAIN. This is case is not well
                     // specified in
                     // https://docs.python.org/3/library/io.html#io.IOBase.readline
                     // unlike similar case for read(). But we follow the latter's
                     // behavior - return None.
                     vstr_clear(&vstr);
                     return mp_const_none;
                 } else {
                     goto done;
                 }
             }
             nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
         }
         if (out_sz == 0) {
 done:
             // Back out previously added byte
             // Consider, what's better - read a char and get OutOfMemory (so read
             // char is lost), or allocate first as we do.
             vstr_cut_tail_bytes(&vstr, 1);
             break;
         }
         if (*p == '\n') {
             break;
         }
     }

     return mp_obj_new_str_from_vstr(STREAM_CONTENT_TYPE(o->type->stream_p), &vstr);
 }

 // TODO take an optional extra argument (what does it do exactly?)
 STATIC mp_obj_t stream_unbuffered_readlines(mp_obj_t self) {
     mp_obj_t lines = mp_obj_new_list(0, NULL);
     for (;;) {
         mp_obj_t line = stream_unbuffered_readline(1, &self);
         if (!mp_obj_is_true(line)) {
             break;
         }
         mp_obj_list_append(lines, line);
     }
     return lines;
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_stream_unbuffered_readlines_obj, stream_unbuffered_readlines);

 mp_obj_t mp_stream_unbuffered_iter(mp_obj_t self) {
     mp_obj_t l_in = stream_unbuffered_readline(1, &self);
     if (mp_obj_is_true(l_in)) {
         return l_in;
     }
     return MP_OBJ_STOP_ITERATION;
 }

 STATIC mp_obj_t stream_seek(mp_uint_t 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->ioctl == NULL) {
         // CPython: io.UnsupportedOperation, OSError subclass
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
     }

     struct mp_stream_seek_t seek_s;
     // TODO: Could be uint64
     seek_s.offset = mp_obj_get_int(args[1]);
     seek_s.whence = 0;
     if (n_args == 3) {
         seek_s.whence = mp_obj_get_int(args[2]);
     }

     int error;
     mp_uint_t res = o->type->stream_p->ioctl(o, MP_STREAM_SEEK, (mp_uint_t)&seek_s, &error);
     if (res == MP_STREAM_ERROR) {
         nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
     }

     // TODO: Could be uint64
     return mp_obj_new_int_from_uint(seek_s.offset);
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_seek_obj, 2, 3, stream_seek);

 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_read_obj, 1, 2, stream_read);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_readinto_obj, 2, 3, stream_readinto);
 MP_DEFINE_CONST_FUN_OBJ_1(mp_stream_readall_obj, stream_readall);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_unbuffered_readline_obj, 1, 2, stream_unbuffered_readline);
 MP_DEFINE_CONST_FUN_OBJ_2(mp_stream_write_obj, stream_write_method);
	/*
	* This file is part of the Micro Python project, http://micropython.org/
	*
	* The MIT License (MIT)
	*
	* Copyright (c) 2013, 2014 Damien P. George
	* Copyright (c) 2014 Paul Sokolovsky
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	#include <string.h>

	#include "py/nlr.h"
	#include "py/objstr.h"
	#include "py/stream.h"

	#if MICROPY_STREAMS_NON_BLOCK
	#include <errno.h>
	#if defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR)
	#define EWOULDBLOCK 140
	#endif
	#endif

	// This file defines generic Python stream read/write methods which
	// dispatch to the underlying stream interface of an object.

	// TODO: should be in mpconfig.h
	#define DEFAULT_BUFFER_SIZE 256

	STATIC mp_obj_t stream_readall(mp_obj_t self_in);

	#if MICROPY_STREAMS_NON_BLOCK
	// 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)
	#else
	#define is_nonblocking_error(errno) (0)
	#endif

	#define STREAM_CONTENT_TYPE(stream) (((stream)->is_text) ? &mp_type_str : &mp_type_bytes)

	STATIC mp_obj_t stream_read(mp_uint_t 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) {
	// CPython: io.UnsupportedOperation, OSError subclass
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
	}

	// What to do if sz < -1? Python docs don't specify this case.
	// CPython does a readall, but here we silently let negatives through,
	// and they will cause a MemoryError.
	mp_int_t sz;
	if (n_args == 1 \|\| ((sz = mp_obj_get_int(args[1])) == -1)) {
	return stream_readall(args[0]);
	}

	#if MICROPY_PY_BUILTINS_STR_UNICODE
	if (o->type->stream_p->is_text) {
	// We need to read sz number of unicode characters. Because we don't have any
	// buffering, and because the stream API can only read bytes, we must read here
	// in units of bytes and must never over read. If we want sz chars, then reading
	// sz bytes will never over-read, so we follow this approach, in a loop to keep
	// reading until we have exactly enough chars. This will be 1 read for text
	// with ASCII-only chars, and about 2 reads for text with a couple of non-ASCII
	// chars. For text with lots of non-ASCII chars, it'll be pretty inefficient
	// in time and memory.

	vstr_t vstr;
	vstr_init(&vstr, sz);
	mp_uint_t more_bytes = sz;
	mp_uint_t last_buf_offset = 0;
	while (more_bytes > 0) {
	char *p = vstr_add_len(&vstr, more_bytes);
	if (p == NULL) {
	nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_MemoryError, "out of memory"));
	}
	int error;
	mp_uint_t out_sz = o->type->stream_p->read(o, p, more_bytes, &error);
	if (out_sz == MP_STREAM_ERROR) {
	vstr_cut_tail_bytes(&vstr, more_bytes);
	if (is_nonblocking_error(error)) {
	// With non-blocking streams, we read as much as we can.
	// If we read nothing, return None, just like read().
	// Otherwise, return data read so far.
	// TODO what if we have read only half a non-ASCII char?
	if (vstr.len == 0) {
	vstr_clear(&vstr);
	return mp_const_none;
	}
	break;
	}
	nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
	}

	if (out_sz < more_bytes) {
	// Finish reading.
	// TODO what if we have read only half a non-ASCII char?
	vstr_cut_tail_bytes(&vstr, more_bytes - out_sz);
	if (out_sz == 0) {
	break;
	}
	}

	// count chars from bytes just read
	for (mp_uint_t off = last_buf_offset;;) {
	byte b = vstr.buf[off];
	int n;
	if (!UTF8_IS_NONASCII(b)) {
	// 1-byte ASCII char
	n = 1;
	} else if ((b & 0xe0) == 0xc0) {
	// 2-byte char
	n = 2;
	} else if ((b & 0xf0) == 0xe0) {
	// 3-byte char
	n = 3;
	} else if ((b & 0xf8) == 0xf0) {
	// 4-byte char
	n = 4;
	} else {
	// TODO
	n = 5;
	}
	if (off + n <= vstr.len) {
	// got a whole char in n bytes
	off += n;
	sz -= 1;
	last_buf_offset = off;
	if (off >= vstr.len) {
	more_bytes = sz;
	break;
	}
	} else {
	// didn't get a whole char, so work out how many extra bytes are needed for
	// this partial char, plus bytes for additional chars that we want
	more_bytes = (off + n - vstr.len) + (sz - 1);
	break;
	}
	}
	}

	return mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
	}
	#endif

	vstr_t vstr;
	vstr_init_len(&vstr, sz);
	int error;
	mp_uint_t out_sz = o->type->stream_p->read(o, vstr.buf, sz, &error);
	if (out_sz == MP_STREAM_ERROR) {
	vstr_clear(&vstr);
	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_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
	} else {
	vstr.len = out_sz;
	return mp_obj_new_str_from_vstr(STREAM_CONTENT_TYPE(o->type->stream_p), &vstr);
	}
	}

	mp_obj_t mp_stream_write(mp_obj_t self_in, const void *buf, mp_uint_t len) {
	struct _mp_obj_base_t o = (struct _mp_obj_base_t )self_in;
	if (o->type->stream_p == NULL \|\| o->type->stream_p->write == NULL) {
	// CPython: io.UnsupportedOperation, OSError subclass
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
	}

	int error;
	mp_uint_t out_sz = o->type->stream_p->write(self_in, buf, len, &error);
	if (out_sz == MP_STREAM_ERROR) {
	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_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
	} else {
	return MP_OBJ_NEW_SMALL_INT(out_sz);
	}
	}

	STATIC mp_obj_t stream_write_method(mp_obj_t self_in, mp_obj_t arg) {
	mp_buffer_info_t bufinfo;
	mp_get_buffer_raise(arg, &bufinfo, MP_BUFFER_READ);
	return mp_stream_write(self_in, bufinfo.buf, bufinfo.len);
	}

	STATIC mp_obj_t stream_readinto(mp_uint_t 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) {
	// CPython: io.UnsupportedOperation, OSError subclass
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
	}
	mp_buffer_info_t bufinfo;
	mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);

	// CPython extension: if 2nd arg is provided, that's max len to read,
	// instead of full buffer. Similar to
	// https://docs.python.org/3/library/socket.html#socket.socket.recv_into
	mp_uint_t len = bufinfo.len;
	if (n_args > 2) {
	len = mp_obj_int_get_truncated(args[2]);
	if (len > bufinfo.len) {
	len = bufinfo.len;
	}
	}

	int error;
	mp_uint_t out_sz = o->type->stream_p->read(o, bufinfo.buf, len, &error);
	if (out_sz == MP_STREAM_ERROR) {
	if (is_nonblocking_error(error)) {
	return mp_const_none;
	}
	nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
	} else {
	return MP_OBJ_NEW_SMALL_INT(out_sz);
	}
	}

	STATIC mp_obj_t stream_readall(mp_obj_t self_in) {
	struct _mp_obj_base_t o = (struct _mp_obj_base_t )self_in;
	if (o->type->stream_p == NULL \|\| o->type->stream_p->read == NULL) {
	// CPython: io.UnsupportedOperation, OSError subclass
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
	}

	mp_uint_t total_size = 0;
	vstr_t vstr;
	vstr_init(&vstr, DEFAULT_BUFFER_SIZE);
	char *p = vstr.buf;
	mp_uint_t current_read = DEFAULT_BUFFER_SIZE;
	while (true) {
	int error;
	mp_uint_t out_sz = o->type->stream_p->read(self_in, p, current_read, &error);
	if (out_sz == MP_STREAM_ERROR) {
	if (is_nonblocking_error(error)) {
	// With non-blocking streams, we read as much as we can.
	// If we read nothing, return None, just like read().
	// Otherwise, return data read so far.
	if (total_size == 0) {
	return mp_const_none;
	}
	break;
	}
	nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
	}
	if (out_sz == 0) {
	break;
	}
	total_size += out_sz;
	if (out_sz < current_read) {
	current_read -= out_sz;
	p += out_sz;
	} else {
	p = vstr_extend(&vstr, DEFAULT_BUFFER_SIZE);
	current_read = DEFAULT_BUFFER_SIZE;
	if (p == NULL) {
	// TODO
	nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_OSError/&mp_type_RuntimeError/, "Out of memory"));
	}
	}
	}

	vstr.len = total_size;
	return mp_obj_new_str_from_vstr(STREAM_CONTENT_TYPE(o->type->stream_p), &vstr);
	}

	// Unbuffered, inefficient implementation of readline() for raw I/O files.
	STATIC mp_obj_t stream_unbuffered_readline(mp_uint_t 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) {
	// CPython: io.UnsupportedOperation, OSError subclass
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
	}

	mp_int_t max_size = -1;
	if (n_args > 1) {
	max_size = MP_OBJ_SMALL_INT_VALUE(args[1]);
	}

	vstr_t vstr;
	if (max_size != -1) {
	vstr_init(&vstr, max_size);
	} else {
	vstr_init(&vstr, 16);
	}

	while (max_size == -1 \|\| max_size-- != 0) {
	char *p = vstr_add_len(&vstr, 1);
	if (p == NULL) {
	nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_MemoryError, "out of memory"));
	}

	int error;
	mp_uint_t out_sz = o->type->stream_p->read(o, p, 1, &error);
	if (out_sz == MP_STREAM_ERROR) {
	if (is_nonblocking_error(error)) {
	if (vstr.len == 1) {
	// We just incremented it, but otherwise we read nothing
	// and immediately got EAGAIN. This is case is not well
	// specified in
	// https://docs.python.org/3/library/io.html#io.IOBase.readline
	// unlike similar case for read(). But we follow the latter's
	// behavior - return None.
	vstr_clear(&vstr);
	return mp_const_none;
	} else {
	goto done;
	}
	}
	nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
	}
	if (out_sz == 0) {
	done:
	// Back out previously added byte
	// Consider, what's better - read a char and get OutOfMemory (so read
	// char is lost), or allocate first as we do.
	vstr_cut_tail_bytes(&vstr, 1);
	break;
	}
	if (*p == '\n') {
	break;
	}
	}

	return mp_obj_new_str_from_vstr(STREAM_CONTENT_TYPE(o->type->stream_p), &vstr);
	}

	// TODO take an optional extra argument (what does it do exactly?)
	STATIC mp_obj_t stream_unbuffered_readlines(mp_obj_t self) {
	mp_obj_t lines = mp_obj_new_list(0, NULL);
	for (;;) {
	mp_obj_t line = stream_unbuffered_readline(1, &self);
	if (!mp_obj_is_true(line)) {
	break;
	}
	mp_obj_list_append(lines, line);
	}
	return lines;
	}
	MP_DEFINE_CONST_FUN_OBJ_1(mp_stream_unbuffered_readlines_obj, stream_unbuffered_readlines);

	mp_obj_t mp_stream_unbuffered_iter(mp_obj_t self) {
	mp_obj_t l_in = stream_unbuffered_readline(1, &self);
	if (mp_obj_is_true(l_in)) {
	return l_in;
	}
	return MP_OBJ_STOP_ITERATION;
	}

	STATIC mp_obj_t stream_seek(mp_uint_t 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->ioctl == NULL) {
	// CPython: io.UnsupportedOperation, OSError subclass
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
	}

	struct mp_stream_seek_t seek_s;
	// TODO: Could be uint64
	seek_s.offset = mp_obj_get_int(args[1]);
	seek_s.whence = 0;
	if (n_args == 3) {
	seek_s.whence = mp_obj_get_int(args[2]);
	}

	int error;
	mp_uint_t res = o->type->stream_p->ioctl(o, MP_STREAM_SEEK, (mp_uint_t)&seek_s, &error);
	if (res == MP_STREAM_ERROR) {
	nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
	}

	// TODO: Could be uint64
	return mp_obj_new_int_from_uint(seek_s.offset);
	}
	MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_seek_obj, 2, 3, stream_seek);

	MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_read_obj, 1, 2, stream_read);
	MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_readinto_obj, 2, 3, stream_readinto);
	MP_DEFINE_CONST_FUN_OBJ_1(mp_stream_readall_obj, stream_readall);
	MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_unbuffered_readline_obj, 1, 2, stream_unbuffered_readline);
	MP_DEFINE_CONST_FUN_OBJ_2(mp_stream_write_obj, stream_write_method);