mirror of
https://github.com/moparisthebest/curl
synced 2024-12-22 08:08:50 -05:00
railsnewbie257
Daniel Stenberg
parent
d8a3aa702a
commit
77350cef00
@ -56,7 +56,7 @@ git
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All changes to the sources are committed to the git repository as soon as
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they're somewhat verified to work. Changes shall be committed as independently
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as possible so that individual changes can be easier spotted and tracked
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as possible so that individual changes can be easily spotted and tracked
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afterwards.
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Tagging shall be used extensively, and by the time we release new archives we
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@ -98,7 +98,7 @@ Operating Systems
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On systems where configure runs, we aim at working on them all - if they have
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a suitable C compiler. On systems that don't run configure, we strive to keep
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curl running fine on:
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curl running correctly on:
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- Windows 98
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- AS/400 V5R3M0
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@ -126,13 +126,13 @@ Build tools
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Windows vs Unix
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===============
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There are a few differences in how to program curl the unix way compared to
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the Windows way. The four perhaps most notable details are:
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There are a few differences in how to program curl the Unix way compared to
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the Windows way. Perhaps the four most notable details are:
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1. Different function names for socket operations.
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In curl, this is solved with defines and macros, so that the source looks
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the same at all places except for the header file that defines them. The
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the same in all places except for the header file that defines them. The
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macros in use are sclose(), sread() and swrite().
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2. Windows requires a couple of init calls for the socket stuff.
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@ -142,7 +142,7 @@ Windows vs Unix
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behaviour.
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3. The file descriptors for network communication and file operations are
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not easily interchangeable as in unix.
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not as easily interchangeable as in Unix.
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We avoid this by not trying any funny tricks on file descriptors.
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@ -156,11 +156,11 @@ Windows vs Unix
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conditionals that deal with features *should* instead be in the format
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`#ifdef HAVE_THAT_WEIRD_FUNCTION`. Since Windows can't run configure scripts,
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we maintain a `curl_config-win32.h` file in lib directory that is supposed to
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look exactly as a `curl_config.h` file would have looked like on a Windows
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look exactly like a `curl_config.h` file would have looked like on a Windows
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machine!
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Generally speaking: always remember that this will be compiled on dozens of
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operating systems. Don't walk on the edge.
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operating systems. Don't walk on the edge!
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<a name="Library"></a>
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Library
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@ -250,8 +250,8 @@ Curl_readwrite()
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Called during the transfer of the actual protocol payload.
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During transfer, the progress functions in lib/progress.c are called at a
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frequent interval (or at the user's choice, a specified callback might get
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During transfer, the progress functions in lib/progress.c are called at
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frequent intervals (or at the user's choice, a specified callback might get
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called). The speedcheck functions in lib/speedcheck.c are also used to
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verify that the transfer is as fast as required.
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@ -272,7 +272,7 @@ Curl_disconnect()
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When doing normal connections and transfers, no one ever tries to close any
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connections so this is not normally called when `curl_easy_perform()` is
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used. This function is only used when we are certain that no more transfers
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is going to be made on the connection. It can be also closed by force, or
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are going to be made on the connection. It can be also closed by force, or
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it can be called to make sure that libcurl doesn't keep too many
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connections alive at the same time.
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@ -290,7 +290,7 @@ HTTP(S)
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base64-functions for user+password stuff (and more) is in (lib/base64.c) and
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all functions for parsing and sending cookies are found in (lib/cookie.c).
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HTTPS uses in almost every means the same procedure as HTTP, with only two
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HTTPS uses in almost every case the same procedure as HTTP, with only two
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exceptions: the connect procedure is different and the function used to read
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or write from the socket is different, although the latter fact is hidden in
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the source by the use of `Curl_read()` for reading and `Curl_write()` for
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@ -301,8 +301,7 @@ HTTP(S)
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An interesting detail with the HTTP(S) request, is the `Curl_add_buffer()`
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series of functions we use. They append data to one single buffer, and when
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the building is done the entire request is sent off in one single write. This
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is done this way to overcome problems with flawed firewalls and lame servers.
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the building is finished the entire request is sent off in one single write. This is done this way to overcome problems with flawed firewalls and lame servers.
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<a name="ftp"></a>
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FTP
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@ -396,12 +395,12 @@ Persistent Connections
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- When libcurl is told to perform a transfer, it first checks for an already
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existing connection in the cache that we can use. Otherwise it creates a
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new one and adds that the cache. If the cache is full already when a new
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connection is added added, it will first close the oldest unused one.
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new one and adds that to the cache. If the cache is full already when a new
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connection is added, it will first close the oldest unused one.
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- When the transfer operation is complete, the connection is left
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open. Particular options may tell libcurl not to, and protocols may signal
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closure on connections and then they won't be kept open of course.
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closure on connections and then they won't be kept open, of course.
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- When `curl_easy_cleanup()` is called, we close all still opened connections,
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unless of course the multi interface "owns" the connections.
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@ -414,7 +413,7 @@ multi interface/non-blocking
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============================
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The multi interface is a non-blocking interface to the library. To make that
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interface work as good as possible, no low-level functions within libcurl
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interface work as well as possible, no low-level functions within libcurl
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must be written to work in a blocking manner. (There are still a few spots
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violating this rule.)
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@ -465,7 +464,7 @@ Return Codes and Informationals
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description.
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In aiding the user to understand what's happening and to debug curl usage, we
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must supply a fair amount of informational messages by using the
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must supply a fair number of informational messages by using the
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`Curl_infof()` function. Those messages are only displayed when the user
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explicitly asks for them. They are best used when revealing information that
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isn't otherwise obvious.
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@ -489,7 +488,7 @@ Client
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functions used for the URL-"globbing" support. Globbing in the sense that the
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{} and [] expansion stuff is there.
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The client mostly messes around to setup its 'config' struct properly, then
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The client mostly sets up its 'config' struct properly, then
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it calls the `curl_easy_*()` functions of the library and when it gets back
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control after the `curl_easy_perform()` it cleans up the library, checks
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status and exits.
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@ -542,13 +541,13 @@ Test Suite
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The main test script is runtests.pl that will invoke test servers like
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httpserver.pl and ftpserver.pl before all the test cases are performed. The
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test suite currently only runs on unix-like platforms.
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test suite currently only runs on Unix-like platforms.
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You'll find a description of the test suite in the tests/README file, and the
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test case data files in the tests/FILEFORMAT file.
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The test suite automatically detects if curl was built with the memory
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debugging enabled, and if it was it will detect memory leaks, too.
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debugging enabled, and if it was, it will detect memory leaks, too.
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<a name="asyncdns"></a>
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Asynchronous name resolves
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@ -633,8 +632,8 @@ Future
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Several functions will be removed from the public `curl_` name space in a
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future libcurl release. They will then only become available as `curlx_`
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functions instead. To make the transition easier, we already today provide
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these functions with the `curlx_` prefix to allow sources to get built
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properly with the new function names. The functions this concerns are:
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these functions with the `curlx_` prefix to allow sources to be built
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properly with the new function names. The concerned functions are:
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- `curlx_getenv`
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- `curlx_strequal`
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@ -659,7 +658,7 @@ Content Encoding
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[HTTP/1.1][4] specifies that a client may request that a server encode its
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response. This is usually used to compress a response using one of a set of
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commonly available compression techniques. These schemes are 'deflate' (the
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zlib algorithm), 'gzip' and 'compress'. A client requests that the sever
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zlib algorithm), 'gzip' and 'compress'. A client requests that the server
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perform an encoding by including an Accept-Encoding header in the request
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document. The value of the header should be one of the recognized tokens
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'deflate', ... (there's a way to register new schemes/tokens, see sec 3.5 of
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@ -767,7 +766,7 @@ Track Down Memory Leaks
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Rebuild libcurl with -DCURLDEBUG (usually, rerunning configure with
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--enable-debug fixes this). 'make clean' first, then 'make' so that all
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files actually are rebuilt properly. It will also make sense to build
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files are actually rebuilt properly. It will also make sense to build
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libcurl with the debug option (usually -g to the compiler) so that debugging
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it will be easier if you actually do find a leak in the library.
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@ -828,16 +827,16 @@ Track Down Memory Leaks
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We also added a timer callback that makes libcurl call the application when
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the timeout value changes, and you set that with [`curl_multi_setopt()`][9]
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and the [`CURLMOPT_TIMERFUNCTION`][10] option. To get this to work,
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Internally, there's an added a struct to each easy handle in which we store
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Internally, there's an added struct to each easy handle in which we store
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an "expire time" (if any). The structs are then "splay sorted" so that we
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can add and remove times from the linked list and yet somewhat swiftly
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figure out both how long time there is until the next nearest timer expires
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figure out both how long there is until the next nearest timer expires
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and which timer (handle) we should take care of now. Of course, the upside
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of all this is that we get a [`curl_multi_timeout()`][8] that should also
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work with old-style applications that use [`curl_multi_perform()`][11].
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We created an internal "socket to easy handles" hash table that given
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a socket (file descriptor) return the easy handle that waits for action on
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a socket (file descriptor) returns the easy handle that waits for action on
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that socket. This hash is made using the already existing hash code
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(previously only used for the DNS cache).
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@ -949,8 +948,8 @@ for older and later versions as things don't change drastically that often.
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until it should be checked - normally some sort of timeout. Each `Curl_easy`
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has one node in the tree.
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`->sockhash` is a hash table to allow fast lookups of socket descriptor to
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which `Curl_easy` that uses that descriptor. This is necessary for the
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`->sockhash` is a hash table to allow fast lookups of socket descriptor for
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which `Curl_easy` uses that descriptor. This is necessary for the
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`multi_socket` API.
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`->conn_cache` points to the connection cache. It keeps track of all
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@ -973,8 +972,7 @@ for older and later versions as things don't change drastically that often.
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to work with.
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`->scheme` is the URL scheme name, usually spelled out in uppercase. That's
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"HTTP" or "FTP" etc. SSL versions of the protocol need its own `Curl_handler`
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setup so HTTPS separate from HTTP.
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"HTTP" or "FTP" etc. SSL versions of the protocol need their own `Curl_handler` setup so HTTPS separate from HTTP.
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`->setup_connection` is called to allow the protocol code to allocate
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protocol specific data that then gets associated with that `Curl_easy` for
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@ -1035,11 +1033,11 @@ for older and later versions as things don't change drastically that often.
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- `PROTOPT_CLOSEACTION` - this protocol has actions to do before closing the
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connection. This flag is no longer used by code, yet still set for a bunch
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protocol handlers.
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of protocol handlers.
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- `PROTOPT_DIRLOCK` - "direction lock". The SSH protocols set this bit to
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limit which "direction" of socket actions that the main engine will
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concern itself about.
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concern itself with.
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- `PROTOPT_NONETWORK` - a protocol that doesn't use network (read file:)
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@ -1060,7 +1058,7 @@ for older and later versions as things don't change drastically that often.
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The libcurl share API allocates a `Curl_share` struct, exposed to the
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external API as "CURLSH *".
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The idea is that the struct can have a set of own versions of caches and
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The idea is that the struct can have a set of its own versions of caches and
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pools and then by providing this struct in the `CURLOPT_SHARE` option, those
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specific `Curl_easy`s will use the caches/pools that this share handle
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holds.
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