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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
| commit | c0b7206652b2852bc574694e7ba07ba1c2acdc00 (patch) | |
| tree | 5cb95cb0e19e03610525903df46279df2c3b7eb1 /rubbos/app/httpd-2.0.64/srclib/apr/docs/canonical_filenames.html | |
| parent | b6d3d6e668b793220f2d3af1bc3e828553dc3fe6 (diff) | |
delete app
Change-Id: Id4c572809969ebe89e946e88063eaed262cff3f2
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
Diffstat (limited to 'rubbos/app/httpd-2.0.64/srclib/apr/docs/canonical_filenames.html')
| -rw-r--r-- | rubbos/app/httpd-2.0.64/srclib/apr/docs/canonical_filenames.html | 156 |
1 files changed, 0 insertions, 156 deletions
diff --git a/rubbos/app/httpd-2.0.64/srclib/apr/docs/canonical_filenames.html b/rubbos/app/httpd-2.0.64/srclib/apr/docs/canonical_filenames.html deleted file mode 100644 index 10867d37..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/apr/docs/canonical_filenames.html +++ /dev/null @@ -1,156 +0,0 @@ -<HTML> -<HEAD><TITLE>APR Canonical Filenames</TITLE></HEAD> -<BODY> -<h1>APR Canonical Filename</h1> - -<h2>Requirements</h2> - -<p>APR porters need to address the underlying discrepancies between -file systems. To achieve a reasonable degree of security, the -program depending upon APR needs to know that two paths may be -compared, and that a mismatch is guarenteed to reflect that the -two paths do not return the same resource</p>. - -<p>The first discrepancy is in volume roots. Unix and pure deriviates -have only one root path, "/". Win32 and OS2 share root paths of -the form "D:/", D: is the volume designation. However, this can -be specified as "//./D:/" as well, indicating D: volume of the -'this' machine. Win32 and OS2 also may employ a UNC root path, -of the form "//server/share/" where share is a share-point of the -specified network server. Finally, NetWare root paths are of the -form "server/volume:/", or the simpler "volume:/" syntax for 'this' -machine. All these non-Unix file systems accept volume:path, -without a slash following the colon, as a path relative to the -current working directory, which APR will treat as ambigious, that -is, neither an absolute nor a relative path per se.</p> - -<p>The second discrepancy is in the meaning of the 'this' directory. -In general, 'this' must be eliminated from the path where it occurs. -The syntax "path/./" and "path/" are both aliases to path. However, -this isn't file system independent, since the double slash "//" has -a special meaning on OS2 and Win32 at the start of the path name, -and is invalid on those platforms before the "//server/share/" UNC -root path is completed. Finally, as noted above, "//./volume/" is -legal root syntax on WinNT, and perhaps others.</p> - -<p>The third discrepancy is in the context of the 'parent' directory. -When "parent/path/.." occurs, the path must be unwound to "parent". -It's also critical to simply truncate leading "/../" paths to "/", -since the parent of the root is root. This gets tricky on the -Win32 and OS2 platforms, since the ".." element is invalid before -the "//server/share/" is complete, and the "//server/share/../" -seqence is the complete UNC root "//server/share/". In relative -paths, leading ".." elements are significant, until they are merged -with an absolute path. The relative form must only retain the ".." -segments as leading segments, to be resolved once merged to another -relative or an absolute path.</p> - -<p>The fourth discrepancy occurs with acceptance of alternate character -codes for the same element. Path seperators are not retained within -the APR canonical forms. The OS filesystem and APR (slashed) forms -can both be returned as strings, to be used in the proper context. -Unix, Win32 and Netware all accept slashes and backslashes as the -same path seperator symbol, although unix strictly accepts slashes. -While the APR form of the name strictly uses slashes, always consider -that there could be a platform that actually accepts slashes as a -character within a segment name.</p> - -<p>The fifth and worst discrepancy plauges Win32, OS2, Netware, and some -filesystems mounted in Unix. Case insensitivity can permit the same -file to slip through in both it's proper case and alternate cases. -Simply changing the case is insufficient for any character set beyond -ASCII, since various dilectic forms of characters suffer from one to -many or many to one translations. An example would be u-umlaut, which -might be accepted as a single character u-umlaut, a two character -sequence u and the zero-width umlaut, the upper case form of the same, -or perhaps even a captial U alone. This can be handled in different -ways depending on the purposes of the APR based program, but the one -requirement is that the path must be absolute in order to resolve these -ambiguities. Methods employed include comparison of device and inode -file uniqifiers, which is a fairly fast operation, or quering the OS -for the true form of the name, which can be much slower. Only the -acknowledgement of the file names by the OS can validate the equality -of two different cases of the same filename.</p> - -<p>The sixth discrepancy, illegal or insignificant characters, is especially -significant in non-unix file systems. Trailing periods are accepted -but never stored, therefore trailing periods must be ignored for any -form of comparison. And all OS's have certain expectations of what -characters are illegal (or undesireable due to confusion.)</p> - -<p>A final warning, canonical functions don't transform or resolve case -or character ambiguity issues until they are resolved into an absolute -path. The relative canonical path, while useful, while useful for URL -or similar identifiers, cannot be used for testing or comparison of file -system objects.</p> - -<hr> - -<h2>Canonical API</h2> - -Functions to manipulate the apr_canon_file_t (an opaque type) include: - -<ul> -<li>Create canon_file_t (from char* path and canon_file_t parent path) -<li>Merged canon_file_t (from path and parent, both canon_file_t) -<li>Get char* path of all or some segments -<li>Get path flags of IsRelative, IsVirtualRoot, and IsAbsolute -<li>Compare two canon_file_t structures for file equality -</ul> - -<p>The path is corrected to the file system case only if is in absolute -form. The apr_canon_file_t should be preserved as long as possible and -used as the parent to create child entries to reduce the number of expensive -stat and case canonicalization calls to the OS.</p> - -<p>The comparison operation provides that the APR can postpone correction -of case by simply relying upon the device and inode for equivilance. The -stat implementation provides that two files are the same, while their -strings are not equivilant, and eliminates the need for the operating -system to return the proper form of the name.</p> - -<p>In any case, returning the char* path, with a flag to request the proper -case, forces the OS calls to resolve the true names of each segment. Where -there is a penality for this operation and the stat device and inode test -is faster, case correction is postponed until the char* result is requested. -On platforms that identify the inode, device, or proper name interchangably -with no penalities, this may occur when the name is initially processed.</p> - -<hr> - -<h2>Unix Example</h2> - -<p>First the simplest case:</p> - -<pre> -Parse Canonical Name -accepts parent path as canonical_t - this path as string - -Split this path Segments on '/' - -For each of this path Segments - If first Segment - If this Segment is Empty ([nothing]/) - Append this Root Segment (don't merge) - Continue to next Segment - Else is relative - Append parent Segments (to merge) - Continue with this Segment - If Segment is '.' or empty (2 slashes) - Discard this Segment - Continue with next Segment - If Segment is '..' - If no previous Segment or previous Segment is '..' - Append this Segment - Continue with next Segment - If previous Segment and previous is not Root Segment - Discard previous Segment - Discard this Segment - Continue with next Segment - Append this Relative Segment - Continue with next Segment -</pre> - -</BODY> -</HTML>
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