notes to UPGRADING.INTERNALS

Author: weltling

UPGRADING.INTERNALS

@@ -2,6 +2,8 @@ PHP 7.1 INTERNALS UPGRADE NOTES
 
 0. Wiki Examples
 1. Internal API changes
+  e. Codepage handling on Windows
+  f. Path handling on Windows
 
 2. Build system changes
   a. Unix build system changes
@@ -21,6 +23,51 @@ changes. See: https://wiki.php.net/phpng-upgrading
 1. Internal API changes
 ========================
 
+  e. Codepage handling on Windows
+     
+    A set of new APIs was introduced, which allows to handle codepage
+    conversions. The corresponding prototypes and macros are contained
+    in win32/codepage.h.
+
+    Functions with php_win32_cp_* signatures provide handling for various
+    codepage aspects. Primarily they are in use at various places in the
+    I/O utils code and directly in the core where necessary, providing
+    conversions to/from UTF-16. Arbitrary conversions between codepages
+    are possible as well, whereby UTF-16 will be always an intermediate
+    state in this case.
+
+    For input length arguments, the macro PHP_WIN32_CP_IGNORE_LEN can be
+    passed, then the API will calculate the length.  For output length
+    arguments, the macro PHP_WIN32_CP_IGNORE_LEN_P can be passed, then
+    the API won't set the output length.
+
+    The mapping between encodings and codepages is provided by the predefined
+    array of data contained in win32/cp_enc_map.c. To change the data,
+    a generator win32/cp_enc_map_gen.c needs to be edited and run.
+
+  f. Path handling on Windows
+
+    A set of new APIs was introduced, which allows to handle UTF-8 paths. The
+    corresponding prototypes and macros are contained in win32/ioutil.h.
+
+    Functions with php_win32_ioutil_* signatures provide POSIX I/O analogues.
+    These functions are integrated in various places across the code base to
+    support Unicode filenames. While accepting char * arguments, internally 
+    the conversion to wchar_t * happens. Internally almost no ANSI APIs are
+    used, but directly their wide equivalents. The string conversion rules
+    correspond to those already present in the core and depend on the current
+    encoding settings. Doing so allows to move away from the ANSI Windows API
+    with its dependency on the system OEM/ANSI codepage.
+
+    Thanks to the wide API usage, the long paths are now supported as well. The
+    PHP_WIN32_IOUTIL_MAXPATHLEN macro is defined to 2048 bytes and will override
+    the MAXPATHLEN in files where the header is included.
+
+    The most optimal use case for scripts is utilizing UTF-8 for any I/O
+    related functions. UTF-8 filenames are supported on any system disregarding
+    the system OEM/ANSI codepage.
+
+
 ========================
 2. Build system changes
 ========================