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chase: update outdated comment about result path

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This commit is contained in:
Yu Watanabe 2023-04-17 05:47:25 +09:00
parent 24be89ebd8
commit b3ef56bc8e
1 changed files with 20 additions and 6 deletions
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26
src/basic/chase.c
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@ -111,12 +111,26 @@ int chaseat(int dir_fd, const char *path, ChaseFlags flags, char **ret_path, int
* given directory file descriptor, even if it is absolute. If the given directory file descriptor is
* AT_FDCWD and "path" is absolute, it is interpreted relative to the root directory of the host.
*
* If "dir_fd" is a valid directory fd, "path" is an absolute path and "ret_path" is not NULL, this
* functions returns a relative path in "ret_path" because openat() like functions generally ignore
* the directory fd if they are provided with an absolute path. On the other hand, if "dir_fd" is
* AT_FDCWD and "path" is an absolute path, we return an absolute path in "ret_path" because
* otherwise, if the caller passes the returned relative path to another openat() like function, it
* would be resolved relative to the current working directory instead of to "/".
* When "dir_fd" points to a non-root directory and CHASE_AT_RESOLVE_IN_ROOT is set, this function
* always returns a relative path in "ret_path", even if "path" is an absolute path, because openat()
* like functions generally ignore the directory fd if they are provided with an absolute path. When
* CHASE_AT_RESOLVE_IN_ROOT is not set, then this returns relative path to the specified file
* descriptor if all resolved symlinks are relative, otherwise absolute path will be returned. When
* "dir_fd" is AT_FDCWD and "path" is an absolute path, we return an absolute path in "ret_path"
* because otherwise, if the caller passes the returned relative path to another openat() like
* function, it would be resolved relative to the current working directory instead of to "/".
*
* Summary about the result path:
* - "dir_fd" points to the root directory
* → result will be absolute
* - "dir_fd" points to a non-root directory, and CHASE_AT_RESOLVE_IN_ROOT is set
* → relative
* - "dir_fd" points to a non-root directory, and CHASE_AT_RESOLVE_IN_ROOT is not set
* → relative when all resolved symlinks are relative, otherwise absolute
* - "dir_fd" is AT_FDCWD, and "path" is absolute
* → absolute
* - "dir_fd" is AT_FDCWD, and "path" is relative
* → relative when all resolved symlinks are relative, otherwise absolute
*
* Algorithmically this operates on two path buffers: "done" are the components of the path we
* already processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we