multi: add xfer_buf to multi handle

- can be borrowed by transfer during recv-write operation
- needs to be released before borrowing again
- adjustis size to `data->set.buffer_size`

multi: add xfer_buf to multi handle

- can be borrowed by transfer during recv-write operation
- needs to be released before borrowing again
- adjustis size to `data->set.buffer_size`
- used in transfer.c readwrite_data()

Closes #12805

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transfer: make the select_bits_paused condition check both directions

If there is activity in a direction that is not paused, return false.

Reported-by: Sergey Bronnikov
Bug: ht

transfer: make the select_bits_paused condition check both directions

If there is activity in a direction that is not paused, return false.

Reported-by: Sergey Bronnikov
Bug: https://curl.se/mail/lib-2024-01/0049.html
Closes #12740

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transfer: remove warning: Value stored to 'blen' is never read

Detected by scan-build

Follow-up from 1cd2f0072f

Closes #12693

lib: replace readwrite with write_resp

This clarifies the handling of server responses by folding the code for
the complicated protocols into their protocol handlers. This concerns
m

lib: replace readwrite with write_resp

This clarifies the handling of server responses by folding the code for
the complicated protocols into their protocol handlers. This concerns
mainly HTTP and its bastard sibling RTSP.

The terms "read" and "write" are often used without clear context if
they refer to the connect or the client/application side of a
transfer. This PR uses "read/write" for operations on the client side
and "send/receive" for the connection, e.g. server side. If this is
considered useful, we can revisit renaming of further methods in another
PR.

Curl's protocol handler `readwrite()` method been changed:

```diff
- CURLcode (*readwrite)(struct Curl_easy *data, struct connectdata *conn,
- const char *buf, size_t blen,
- size_t *pconsumed, bool *readmore);
+ CURLcode (*write_resp)(struct Curl_easy *data, const char *buf, size_t blen,
+ bool is_eos, bool *done);
```

The name was changed to clarify that this writes reponse data to the
client side. The parameter changes are:

* `conn` removed as it always operates on `data->conn`
* `pconsumed` removed as the method needs to handle all data on success
* `readmore` removed as no longer necessary
* `is_eos` as indicator that this is the last call for the transfer
response (end-of-stream).
* `done` TRUE on return iff the transfer response is to be treated as
finished

This change affects many files only because of updated comments in
handlers that provide no implementation. The real change is that the
HTTP protocol handlers now provide an implementation.

The HTTP protocol handlers `write_resp()` implementation will get passed
**all** raw data of a server response for the transfer. The HTTP/1.x
formatted status and headers, as well as the undecoded response
body. `Curl_http_write_resp_hds()` is used internally to parse the
response headers and pass them on. This method is public as the RTSP
protocol handler also uses it.

HTTP/1.1 "chunked" transport encoding is now part of the general
*content encoding* writer stack, just like other encodings. A new flag
`CLIENTWRITE_EOS` was added for the last client write. This allows
writers to verify that they are in a valid end state. The chunked
decoder will check if it indeed has seen the last chunk.

The general response handling in `transfer.c:466` happens in function
`readwrite_data()`. This mainly operates now like:

```
static CURLcode readwrite_data(data, ...)
{
do {
Curl_xfer_recv_resp(data, buf)
...
Curl_xfer_write_resp(data, buf)
...
} while(interested);
...
}
```

All the response data handling is implemented in
`Curl_xfer_write_resp()`. It calls the protocol handler's `write_resp()`
implementation if available, or does the default behaviour.

All raw response data needs to pass through this function. Which also
means that anyone in possession of such data may call
`Curl_xfer_write_resp()`.

Closes #12480

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transfer: adjust_pollset improvements

- let `multi_getsock()` initialize the pollset in what the
transfer state requires in regards to SEND/RECV
- change connection filters `adjust

transfer: adjust_pollset improvements

- let `multi_getsock()` initialize the pollset in what the
transfer state requires in regards to SEND/RECV
- change connection filters `adjust_pollset()` implementation
to react on the presence of POLLIN/-OUT in the pollset and
no longer check CURL_WANT_SEND/CURL_WANT_RECV
- cf-socket will no longer add POLLIN on its own
- http2 and http/3 filters will only do adjustments if the
passed pollset wants to POLLIN/OUT for the transfer on
the socket. This is similar to the HTTP/2 proxy filter
and works in stacked filters.

Closes #12640

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transfer: fix upload rate limiting, add test cases

- add test cases for rate limiting uploads for all
http versions
- fix transfer loop handling of limits. Signal a re-receive

transfer: fix upload rate limiting, add test cases

- add test cases for rate limiting uploads for all
http versions
- fix transfer loop handling of limits. Signal a re-receive
attempt only on exhausting maxloops without an EAGAIN
- fix `data->state.selectbits` forcing re-receive to also
set re-sending when transfer is doing this.

Reported-by: Karthikdasari0423 on github
Fixes #12559
Closes #12586

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readwrite_data: loop less

This function is made to loop in order to drain incoming data
faster. Completely removing the loop has a measerably negative impact on
transfer speeds.

readwrite_data: loop less

This function is made to loop in order to drain incoming data
faster. Completely removing the loop has a measerably negative impact on
transfer speeds.

Downsides with the looping include

- it might call the progress callback much more seldom. Especially if
the write callback is slow.

- rate limiting becomes less exact

- a single transfer might "starve out" other parallel transfers

- QUIC timers for other connections can't be maintained correctly

The long term fix should be to remove the loop and optimize coming back
to avoid the transfer speed penalty.

This fix lower the max loop count to reduce the starvation problem, and
avoids the loop completely for when rate-limiting is in progress.

Ref: #12488
Ref: https://curl.se/mail/lib-2023-12/0012.html
Closes #12504

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lib: eliminate `conn->cselect_bits`

- use `data->state.dselect_bits` everywhere instead
- remove `bool *comeback` parameter as non-zero
`data->state.dselect_bits` will indicate tha

lib: eliminate `conn->cselect_bits`

- use `data->state.dselect_bits` everywhere instead
- remove `bool *comeback` parameter as non-zero
`data->state.dselect_bits` will indicate that IO is
incomplete.

Closes #12512

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transfer: abort pause send when connection is marked for closing

This handles cases of some bi-directional "upgrade" scenarios
(i.e. WebSockets) where sending is paused until some "upgra

transfer: abort pause send when connection is marked for closing

This handles cases of some bi-directional "upgrade" scenarios
(i.e. WebSockets) where sending is paused until some "upgrade" handshake
is completed, but server rejects the handshake and closes the
connection.

Closes #12428

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transfer: cleanup done+excess handling

- add `SingleRequest->download_done` as indicator that
all download bytes have been received
- remove `stop_reading` bool from readwrite func

transfer: cleanup done+excess handling

- add `SingleRequest->download_done` as indicator that
all download bytes have been received
- remove `stop_reading` bool from readwrite functions
- move excess body handling into client download writer

Closes #12371

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windows: use built-in `_WIN32` macro to detect Windows

Windows compilers define `_WIN32` automatically. Windows SDK headers
or build env defines `WIN32`, or we have to take care of it. T

windows: use built-in `_WIN32` macro to detect Windows

Windows compilers define `_WIN32` automatically. Windows SDK headers
or build env defines `WIN32`, or we have to take care of it. The
agreement seems to be that `_WIN32` is the preferred practice here.
Make the source code rely on that to detect we're building for Windows.

Public `curl.h` was using `WIN32`, `__WIN32__` and `CURL_WIN32` for
Windows detection, next to the official `_WIN32`. After this patch it
only uses `_WIN32` for this. Also, make it stop defining `CURL_WIN32`.

There is a slight chance these break compatibility with Windows
compilers that fail to define `_WIN32`. I'm not aware of any obsolete
or modern compiler affected, but in case there is one, one possible
solution is to define this macro manually.

grepping for `WIN32` remains useful to discover Windows-specific code.

Also:

- extend `checksrc` to ensure we're not using `WIN32` anymore.

- apply minor formatting here and there.

- delete unnecessary checks for `!MSDOS` when `_WIN32` is present.

Co-authored-by: Jay Satiro
Reviewed-by: Daniel Stenberg

Closes #12376

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transfer: avoid unreachable expression

If curl_off_t and size_t have the same size (which is common on modern
64 bit systems), a condition cannot occur which Coverity pointed
out. Av

transfer: avoid unreachable expression

If curl_off_t and size_t have the same size (which is common on modern
64 bit systems), a condition cannot occur which Coverity pointed
out. Avoid the warning by having the code conditionally only used if
curl_off_t actually is larger.

Follow-up to 1cd2f0072fa482e25baa2

Closes #12370

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transfer: readwrite improvements

- changed header/chunk/handler->readwrite prototypes to accept `buf`,
`blen` and a `pconsumed` pointer. They now get the buffer to work on
and re

transfer: readwrite improvements

- changed header/chunk/handler->readwrite prototypes to accept `buf`,
`blen` and a `pconsumed` pointer. They now get the buffer to work on
and report back how many bytes they consumed
- eliminated `k->str` in SingleRequest
- improved excess data handling to properly calculate with any body data
left in the headerb buffer
- eliminated `k->badheader` enum to only be a bool

Closes #12283

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transfer: avoid calling the read callback again after EOF

Regression since 7f43f3dc5994d01b12 (7.84.0)

Bug: https://curl.se/mail/lib-2023-11/0017.html

Closes #12363

lib: client writer, part 2, accounting + logging

This PR has these changes:

Renaming of unencode_* to cwriter, e.g. client writers
- documentation of sendf.h functions
- mov

lib: client writer, part 2, accounting + logging

This PR has these changes:

Renaming of unencode_* to cwriter, e.g. client writers
- documentation of sendf.h functions
- move max decode stack checks back to content_encoding.c
- define writer phase which was used as order before
- introduce phases for monitoring inbetween decode phases
- offering default implementations for init/write/close

Add type paramter to client writer's do_write()
- always pass all writes through the writer stack
- writers who only care about BODY data will pass other writes unchanged

add RAW and PROTOCOL client writers
- RAW used for Curl_debug() logging of CURLINFO_DATA_IN
- PROTOCOL used for updates to data->req.bytecount, max_filesize checks and
Curl_pgrsSetDownloadCounter()
- remove all updates of data->req.bytecount and calls to
Curl_pgrsSetDownloadCounter() and Curl_debug() from other code
- adjust test457 expected output to no longer see the excess write

Closes #12184

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url: protocol handler lookup tidy-up

- rename lookup to what it does
- use ARRAYSIZE instead of NULL check for end
- offer alternate lookup for 0-terminated strings

Closes #

url: protocol handler lookup tidy-up

- rename lookup to what it does
- use ARRAYSIZE instead of NULL check for end
- offer alternate lookup for 0-terminated strings

Closes #12216

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RTSP: improved RTP parser

- fix HTTP header parsing to report incomplete
lines it buffers as consumed!
- re-implement the RTP parser for interleave RTP
messages for robustnes

RTSP: improved RTP parser

- fix HTTP header parsing to report incomplete
lines it buffers as consumed!
- re-implement the RTP parser for interleave RTP
messages for robustness. It is now keeping its
state at the connection
- RTSP protocol handler "readwrite" implementation
now tracks if the response is before/in/after
header parsing or "in" a bod by calling
"Curl_http_readwrite_headers()" itself. This
allows it to know when non-RTP bytes are "junk"
or HEADER or BODY.
- tested with #12035 and various small receive
sizes where current master fails

Closes #12052

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transfer: only reset the FTP wildcard engine in CLEAR state

To avoid the state machine to start over and redownload all the files
*again*.

Reported-by: lkordos on github
Reg

transfer: only reset the FTP wildcard engine in CLEAR state

To avoid the state machine to start over and redownload all the files
*again*.

Reported-by: lkordos on github
Regression from 843b3baa3e3cb228 (shipped in 8.1.0)
Bisect-by: Dan Fandrich
Fixes #11775
Closes #12156

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h2: testcase and fix for pausing h2 streams

- refs #11982 where it was noted that paused transfers may
close successfully without delivering the complete data
- made sample poc int

h2: testcase and fix for pausing h2 streams

- refs #11982 where it was noted that paused transfers may
close successfully without delivering the complete data
- made sample poc into tests/http/client/h2-pausing.c and
added test_02_27 to reproduce

Closes #11989
Fixes #11982
Reported-by: Harry Sintonen

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lib: move handling of `data->req.writer_stack` into Curl_client_write()

- move definitions from content_encoding.h to sendf.h
- move create/cleanup/add code into sendf.c
- installed

lib: move handling of `data->req.writer_stack` into Curl_client_write()

- move definitions from content_encoding.h to sendf.h
- move create/cleanup/add code into sendf.c
- installed content_encoding writers will always be called
on Curl_client_write(CLIENTWRITE_BODY)
- Curl_client_cleanup() frees writers and tempbuffers from
paused transfers, irregardless of protocol

Closes #11908

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build: delete checks for C89 standard headers

Delete checks and guards for standard C89 headers and assume these are
available: `stdio.h`, `string.h`, `time.h`, `setjmp.h`, `stdlib.h`,

build: delete checks for C89 standard headers

Delete checks and guards for standard C89 headers and assume these are
available: `stdio.h`, `string.h`, `time.h`, `setjmp.h`, `stdlib.h`,
`stddef.h`, `signal.h`.

Some of these we already used unconditionally, some others we only used
for feature checks.

Follow-up to 9c7165e96a3a9a2d0b7059c87c699b5ca8cdae93 #11918 (for `stdio.h` in CMake)

Closes #11940

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lib: let the max filesize option stop too big transfers too

Previously it would only stop them from getting started if the size is
known to be too big then.

Update the libcurl a

lib: let the max filesize option stop too big transfers too

Previously it would only stop them from getting started if the size is
known to be too big then.

Update the libcurl and curl docs accordingly.

Fixes #11810
Reported-by: Elliot Killick
Assisted-by: Jay Satiro
Closes #11820

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transfer: also stop the sending on closed connection

Previously this cleared the receiving bit only but in some cases it is
also still sending (like a request-body) when disconnected and

transfer: also stop the sending on closed connection

Previously this cleared the receiving bit only but in some cases it is
also still sending (like a request-body) when disconnected and neither
direction can continue then.

Fixes #11769
Reported-by: Oleg Jukovec
Closes #11795

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http2: polish things around POST

- added test cases for various code paths
- fixed handling of blocked write when stream had
been closed inbetween attempts
- re-enabled DEBUGAS

http2: polish things around POST

- added test cases for various code paths
- fixed handling of blocked write when stream had
been closed inbetween attempts
- re-enabled DEBUGASSERT on send with smaller data size

- in debug builds, environment variables can be set to simulate a slow
network when sending data. cf-socket.c and vquic.c support
* CURL_DBG_SOCK_WBLOCK: percentage of send() calls that should be
answered with a EAGAIN. TCP/UNIX sockets.
This is chosen randomly.
* CURL_DBG_SOCK_WPARTIAL: percentage of data that shall be written
to the network. TCP/UNIX sockets.
Example: 80 means a send with 1000 bytes would only send 800
This is applied to every send.
* CURL_DBG_QUIC_WBLOCK: percentage of send() calls that should be
answered with EAGAIN. QUIC only.
This is chosen randomly.

Closes #11756

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spelling: use 'reuse' not 're-use' in code and elsewhere

Unify the spelling as both versions were previously used intermittently

Closes #11717