Unified engines for stream I/O
Buffers that can be attached to a device to get buffered I/O
Currently supported devices for input:
`Polldescr(st,fd,esys): The poll system call is used with file
descriptor fd to wait for incoming data. The
event system esys is the underlying event queue. This works
well for pipes, sockets etc. but not for normal files. The
style st can be obtained from fd via
Netsys.get_fd_style.`Multiplex mplex: The multiplex controller mplex is
used as device.`Buffer buf: Data comes from the buffer buf (which in turn
is connected with a second device)`Count_in(f,d): Data is read from d, and every time a few
bytes n are read the function f n is called (which may raise
an exception)Generally, it is not well supported to read in parallel several times from the same device.
Currently supported devices for output:
`Polldescr(fd,esys): The poll system call is used with file
descriptor fd to wait until data can be output. The
event system esys is the underlying event queue. This works
well for pipes, sockets etc. but not for normal files.`Multiplex mplex: The multiplex controller mplex is
used as device.`Buffer buf: Data is written to the buffer buf (which in turn
is connected with a second device)`Count_out(f,d): Data is written to d, and every time a few
bytes n are written the function f n is called (which may raise
an exception)Generally, it is not well supported to write in parallel several times to the same device.
The user can pass data buffers that base either on strings or on
bigarrays of char (memory). Note that `Memory is not supported
for all devices or device configurations.
Returns whether `Memory buffers are supported
May be raised by Uq_io.input_line_e
let e = input_e d s pos len: Reads data from d and puts it into
the string s starting at pos and with maximum length len.
When data is available, the engine e transitions to `Done n
where n is the number of actually read bytes.
If len>0 and no bytes can be read because the end is reached, the engine
transitions to `Error End_of_file.
let e = input_e d s pos len: Reads data from d and puts it into
the string s starting at pos and with length len.
Exactly len bytes are read, and when done,
the engine e transitions to `Done ().
If the end of the file is reached before len bytes are read,
the engine transitions to `Error End_of_file.
let e = input_line_e d: Reads the next line from d and transitions
to `Done line when done. Note that this is only supported for a
buffered device!
If the end of the file is already reached when this function is
called, the engine transitions to `Error End_of_file.
If max_len is set, this is the maximum length of the line
(including LF). If exceeded, the engine transitions to
`Error Line_too_long.
let e = input_lines_e d: Reads as many lines from d as can be
found in the buffer of d, and transitions to `Done lines. If
no complete line is in the buffer, the function extends the buffer and
waits until at least one line is added to the buffer (if necessary,
this process is repeated).
If the end of the file is already reached when this function is
called, the engine transitions to `Error End_of_file.
The function never returns an empty list of lines.
input_lines_e is just an optimized version of input_line_e that
requires fewer and cheaper blitting operations.
If max_len is set, this is the maximum length of the line
(including LF). If exceeded, the engine transitions to
`Error Line_too_long.
Represents EOF as None. Useful in the combination
input_e d s p l >> eof_as_noneand
input_line_e d >> eof_as_none
where >> is from Uq_engines.Operators
let e = output_e d s pos len: Outputs data to d and takes it
from the string s starting at pos and with maximum length
len. When data is written, the engine e transitions to `Done n
where n is the number of actually written bytes.
let e = really_output_e d s pos len: Outputs data to d and takes it
from the string s starting at pos and with length
len. When all data is written, the engine e transitions to
`Done ().
let e = output_string_e d s: Outputs the string s to d,
and transitions to `Done() when done.
let e = output_string_e d m: Outputs the bigarray m to d,
and transitions to `Done() when done.
let e = output_string_e d b: Outputs the contents of b to d,
and transitions to `Done() when done.
let e = write_eof_e d: For devices supporting half-open connections,
this engine writes the EOF marker and transitions to
`Done true. For other devices nothing happens, and the engine
transitions to `Done false. (In the latter case, the only way to
signal EOF is to shut down the device, see below.)
Note that the effect of write_eof_e cannot be buffered. Because
of this, the io_buffer flushes all data first (i.e. write_eof_e
implies the effect of flush_e).
let e = copy_e d_in d_out: Copies data from d_in to d_out,
and transitions to `Done n when all data is copied (where
n are the number of copied bytes).
By default, d_in is read until end of file. If len is passed,
at most this number of bytes are copied. The length can also be given
as int64 in len64.
By setting small_buffer, the copy buffer consists only of a
single page. Normally, a bigger buffer is allocated.
let e = flush_e d: If d has an internal buffer, all data is
written out to d. If there is no such buffer, this is a no-op.
When done, the engine transitions to `Done().
The shutdown is the last part of the protocol. Although it is often done autonomously by the kernel, this interface supports user-implemented shutdowns (e.g. for SSL).
The shutdown can be skipped, and the device can be inactivated immediately. For some devices, the other side of the I/O stream will then see an error, though.
The shutdown is always for both the input and the output circuit of the device.
Performs a regular shutdown of the device. The linger argument
may be used to configure a non-default linger timeout.
The engine transitions to `Done() when done.
The shutdown also releases the OS resources (closes the descriptor etc.), but only if successful.
Note that the effect of shutdown_e cannot be buffered. Because
of this, the io_buffer flushes all data first (i.e. shutdown_e
implies the effect of flush_e). Input data available in the
buffer can still be read after the shutdown.
Releases the OS resources immediately. This is the right thing to do when aborting the communication, or for cleanup after an I/O error. It is wrong to inactivate after a successful shutdown, because the shutdown already includes the inactivation.
Blit to a string or memory buffer
Requests that the buffer is filled more than currently, and
transitions to `Done eof when there is more data, or the
EOF is reached (eof=true).
Provides a buffered version of the out_device. The argument
max is the maximum number of bytes to buffer. This can also be
set to None meaning no limit.
By setting small_buffer, the initial output buffer consists only of a
single page. Normally, a bigger buffer is allocated.
filter_out_buffer ~max p d: The data written to this device is
redirected via pipe p and finally written to d.