clarified and updated
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Daniel Stenberg
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103
docs/INTERNALS
103
docs/INTERNALS
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@ -1,4 +1,4 @@
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Updated for curl 7.7 on March 13, 2001
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Updated for curl 7.7.2 on April 26, 2001
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_ _ ____ _
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___| | | | _ \| |
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/ __| | | | |_) | |
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@ -73,7 +73,7 @@ Library
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makes sure we stay absolutely platform independent.
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curl_easy_init() allocates an internal struct and makes some initializations.
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The returned handle does not revail internals.
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The returned handle does not reveal internals.
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curl_easy_setopt() takes a three arguments, where the option stuff must be
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passed in pairs, the parameter-ID and the parameter-value. The list of
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@ -81,33 +81,68 @@ Library
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curl_easy_perform() does a whole lot of things:
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It starts off in the lib/easy.c file by calling curl_transfer(), but the main
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work is lib/url.c. The function first analyzes the URL, it separates the
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different components and connects to the remote host. This may involve using
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a proxy and/or using SSL. The Curl_gethost() function in lib/hostip.c is used
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for looking up host names.
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It starts off in the lib/easy.c file by calling Curl_perform() and the main
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work then continues lib/url.c. The flow continues with a call to
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Curl_connect() to connect to the remote site.
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When connected, the proper protocol-specific function is called. The
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functions are named after the protocols they handle. Curl_ftp(), Curl_http(),
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Curl_dict(), etc. They all reside in their respective files (ftp.c, http.c
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and dict.c).
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o Curl_connect()
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The protocol-specific functions of course deal with protocol-specific
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negotiations and setup. They have access to the Curl_sendf() (from
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lib/sendf.c) function to send printf-style formatted data to the remote host
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and when they're ready to make the actual file transfer they call the
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Curl_Transfer() function (in lib/transfer.c) to setup the transfer and
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returns. Curl_perform() then calls Transfer() in lib/transfer.c that performs
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the entire file transfer. Curl_perform() is what does the main "connect - do
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- transfer - done" loop. It loops if there's a Location: to follow.
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... analyzes the URL, it separates the different components and connects to
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the remote host. This may involve using a proxy and/or using SSL. The
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Curl_gethost() function in lib/hostip.c is used for looking up host names.
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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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called). The speedcheck functions in lib/speedcheck.c are also used to verify
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that the transfer is as fast as required.
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When Curl_connect is done, we are connected to the remote site. Then it is
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time to tell the server to get a document/file. Curl_do() arranges this.
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o Curl_do()
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Curl_do() makes sure the proper protocol-specific function is called. The
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functions are named after the protocols they handle. Curl_ftp(),
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Curl_http(), Curl_dict(), etc. They all reside in their respective files
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(ftp.c, http.c and dict.c).
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The protocol-specific functions of course deal with protocol-specific
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negotiations and setup. They have access to the Curl_sendf() (from
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lib/sendf.c) function to send printf-style formatted data to the remote
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host and when they're ready to make the actual file transfer they call the
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Curl_Transfer() function (in lib/transfer.c) to setup the transfer and
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returns.
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o Transfer()
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Curl_perform() then calls Transfer() in lib/transfer.c that performs
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the entire file transfer.
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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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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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o Curl_done()
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Called after a transfer is done. This function takes care of everything
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that has to be done after a transfer. This function attempts to leave
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matters in a state so that Curl_do() should be possible to call again on
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the same connection (in a persistent connection case). It may also soon be
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closed with Curl_disconnect().
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o Curl_disconnect()
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During normal connection and transfers, no one ever tries to close any
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connection 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
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force). This function can also be called at times to make sure that libcurl
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doesn't keep too many connections alive at the same time.
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This function cleans up all resources that are associated with a single
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connection.
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Curl_perform() is the function that does the main "connect - do - transfer -
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done" loop. It loops if there's a Location: to follow.
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When completed, the curl_easy_cleanup() should be called to free up used
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resources.
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resources. It runs Curl_disconnect() on all open connectons.
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A quick roundup on internal function sequences (many of these call
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protocol-specific function-pointers):
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@ -257,6 +292,7 @@ Client
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======
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main() resides in src/main.c together with most of the client code.
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src/hugehelp.c is automatically generated by the mkhelp.pl perl script to
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display the complete "manual" and the src/urlglob.c file holds the functions
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used for the URL-"globbing" support. Globbing in the sense that the {} and []
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@ -272,25 +308,26 @@ Client
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curl_easy_getinfo() function to extract useful information from the curl
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session.
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Recent versions may loop and do all that several times if many URLs were
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Recent versions may loop and do all this several times if many URLs were
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specified on the command line or config file.
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Memory Debugging
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================
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The file named lib/memdebug.c contains debug-versions of a few
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functions. Functions such as malloc, free, fopen, fclose, etc that somehow
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deal with resources that might give us problems if we "leak" them. The
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functions in the memdebug system do nothing fancy, they do their normal
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function and then log information about what they just did. The logged data
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can then be analyzed after a complete session,
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The file lib/memdebug.c contains debug-versions of a few functions. Functions
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such as malloc, free, fopen, fclose, etc that somehow deal with resources
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that might give us problems if we "leak" them. The functions in the memdebug
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system do nothing fancy, they do their normal function and then log
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information about what they just did. The logged data can then be analyzed
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after a complete session,
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memanalyze.pl is a perl script present only present in CVS (not part of the
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memanalyze.pl is the perl script present only present in CVS (not part of the
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release archives) that analyzes a log file generated by the memdebug
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system. It detects if resources are allocated but never freed and other kinds
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of errors related to resource management.
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Use -DMALLOCDEBUG when compiling to enable memory debugging.
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Use -DMALLOCDEBUG when compiling to enable memory debugging, this is also
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switched on by running configure with --enable-debug.
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Test Suite
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==========
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