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+While some other iconv(3) implementations - like FreeBSD iconv(3) - choose
+the "many small shared libraries" and dlopen(3) approach, this implementation
+packs everything into a single shared library. Here is a comparison of the
+two designs.
+* Run-time efficiency
+ 1. A dlopen() based approach needs a cache of loaded shared libraries.
+ Otherwise, every iconv_open() call will result in a call to dlopen()
+ and thus to file system related system calls - which is prohibitive
+ because some applications use the iconv_open/iconv/iconv_close sequence
+ for every single filename, string, or piece of text.
+ 2. In terms of virtual memory use, both approaches are on par. Being shared
+ libraries, the tables are shared between any processes that use them.
+ And because of the demand loading used by Unix systems (and because libiconv
+ does not have initialization functions), only those parts of the tables
+ which are needed (typically very few kilobytes) will be read from disk and
+ paged into main memory.
+ 3. Even with a cache of loaded shared libraries, the dlopen() based approach
+ makes more system calls, because it has to load one or two shared libraries
+ for every encoding in use.
+* Total size
+ In the dlopen(3) approach, every shared library has a symbol table and
+ relocation offset. All together, FreeBSD iconv installs more than 200 shared
+ libraries with a total size of 2.3 MB. Whereas libiconv installs 0.45 MB.
+* Extensibility
+ The dlopen(3) approach is good for guaranteeing extensibility if the iconv
+ implementation is distributed without source. (Or when, as in glibc, you
+ cannot rebuild iconv without rebuilding your libc, thus possibly
+ destabilizing your system.)
+ The libiconv package achieves extensibility through the LGPL license:
+ Every user has access to the source of the package and can extend and
+ replace just
+ The places which have to be modified when a new encoding is added are as
+ follows: add an #include statement in iconv.c, add an entry in the table in
+ iconv.c, and of course, update the README and iconv_open.3 manual page.
+* Use within other packages
+ If you want to incorporate an iconv implementation into another package
+ (such as a mail user agent or web browser), the single library approach
+ is easier, because:
+ 1. In the shared library approach you have to provide the right directory
+ prefix which will be used at run time.
+ 2. Incorporating iconv as a static library into the executable is easy -
+ it won't need dynamic loading. (This assumes that your package is under
+ the LGPL or GPL license.)
+All conversions go through Unicode. This is possible because most of the
+world's characters have already been allocated in the Unicode standard.
+Therefore we have for each encoding two functions:
+- For conversion from the encoding to Unicode, a function called xxx_mbtowc.
+- For conversion from Unicode to the encoding, a function called xxx_wctomb,
+ and for stateful encodings, a function called xxx_reset which returns to
+ the initial shift state.
+All our functions operate on a single Unicode character at a time. This is
+obviously less efficient than operating on an entire buffer of characters at
+a time, but it makes the coding considerably easier and less bug-prone. Those
+who wish best performance should install the Real Thing (TM): GNU libc 2.1
+or newer.