mirror of
https://github.com/klzgrad/naiveproxy.git
synced 2024-11-28 08:16:09 +03:00
76 lines
3.2 KiB
Markdown
76 lines
3.2 KiB
Markdown
|
# Chrome's URL library
|
||
|
|
|
||
|
|
## Layers
|
||
|
|
|
||
|
|
There are several conceptual layers in this directory. Going from the lowest
|
||
|
|
level up, they are:
|
||
|
|
|
||
|
|
### Parsing
|
||
|
|
|
||
|
|
The `url_parse.*` files are the parser. This code does no string
|
||
|
|
transformations. Its only job is to take an input string and splits out the
|
||
|
|
components of the URL as best as it can deduce them, for a given type of URL.
|
||
|
|
Parsing can never fail, it will take its best guess. This layer does not
|
||
|
|
have logic for determining the type of URL parsing to apply, that needs to
|
||
|
|
be applied at a higher layer (the "util" layer below).
|
||
|
|
|
||
|
|
Because the parser code is derived (_very_ distantly) from some code in
|
||
|
|
Mozilla, some of the parser files are in `url/third_party/mozilla/`.
|
||
|
|
|
||
|
|
The main header to include for calling the parser is
|
||
|
|
`url/third_party/mozilla/url_parse.h`.
|
||
|
|
|
||
|
|
### Canonicalization
|
||
|
|
|
||
|
|
The `url_canon*` files are the canonicalizer. This code will transform specific
|
||
|
|
URL components or specific types of URLs into a standard form. For some
|
||
|
|
dangerous or invalid data, the canonicalizer will report that a URL is invalid,
|
||
|
|
although it will always try its best to produce output (so the calling code
|
||
|
|
can, for example, show the user an error that the URL is invalid). The
|
||
|
|
canonicalizer attempts to provide as consistent a representation as possible
|
||
|
|
without changing the meaning of a URL.
|
||
|
|
|
||
|
|
The canonicalizer layer is designed to be independent of the string type of
|
||
|
|
the embedder, so all string output is done through a `CanonOutput` wrapper
|
||
|
|
object. An implementation for `std::string` output is provided in
|
||
|
|
`url_canon_stdstring.h`.
|
||
|
|
|
||
|
|
The main header to include for calling the canonicalizer is
|
||
|
|
`url/url_canon.h`.
|
||
|
|
|
||
|
|
### Utility
|
||
|
|
|
||
|
|
The `url_util*` files provide a higher-level wrapper around the parser and
|
||
|
|
canonicalizer. While it can be called directly, it is designed to be the
|
||
|
|
foundation for writing URL wrapper objects (The GURL later and Blink's KURL
|
||
|
|
object use the Utility layer to implement the low-level logic).
|
||
|
|
|
||
|
|
The Utility code makes decisions about URL types and calls the correct parsing
|
||
|
|
and canonicalzation functions for those types. It provides an interface to
|
||
|
|
register application-specific schemes that have specific requirements.
|
||
|
|
Sharing this loigic between KURL and GURL is important so that URLs are
|
||
|
|
handled consistently across the application.
|
||
|
|
|
||
|
|
The main header to include is `url/url_util.h`.
|
||
|
|
|
||
|
|
### GURL and Origin
|
||
|
|
|
||
|
|
At the highest layer, a C++ object for representing URLs is provided. This
|
||
|
|
object uses STL. Most uses need only this layer. Include `url/gurl.h`.
|
||
|
|
|
||
|
|
Also at this layer is also the Origin object which exists to make security
|
||
|
|
decisions on the web. Include `url/origin.h`.
|
||
|
|
|
||
|
|
## Historical background
|
||
|
|
|
||
|
|
This code was originally a separate library that was designed to be embedded
|
||
|
|
into both Chrome (which uses STL) and WebKit (which didn't use any STL at the
|
||
|
|
time). As a result, the parsing, canonicalization, and utility code could
|
||
|
|
not use STL, or any other common code in Chromium like base.
|
||
|
|
|
||
|
|
When WebKit was forked into the Chromium repo and renamed Blink, this
|
||
|
|
restriction has been relaxed somewhat. Blink still provides its own URL object
|
||
|
|
using its own string type, so the insulation that the Utility layer provides is
|
||
|
|
still useful. But some STL strings and calls to base functions have gradually
|
||
|
|
been added in places where doing so is possible.
|