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README.md: Some minor improvements.

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@ -24,15 +24,17 @@ The following resources can explain more if you are unfamiliar with it:
## What is MD4C ## What is MD4C
MD4C is C Markdown parser with the following features: MD4C is Markdown parser implementation in C, with the following features:
* **Compliance:** Generally MD4C aims to be compliant to the latest version of * **Compliance:** Generally, MD4C aims to be compliant to the latest version of
[CommonMark specification](http://spec.commonmark.org/). Currently, we are [CommonMark specification](http://spec.commonmark.org/). Currently, we are
fully compliant to CommonMark 0.29. fully compliant to CommonMark 0.29.
* **Extensions:** MD4C supports some commonly requested and accepted extensions. * **Extensions:** MD4C supports some commonly requested and accepted extensions.
See below. See below.
* **Performance:** MD4C is [very fast](https://talk.commonmark.org/t/2520).
* **Compactness:** MD4C parser is implemented in one source file and one header * **Compactness:** MD4C parser is implemented in one source file and one header
file. There are no dependencies other than standard C library. file. There are no dependencies other than standard C library.
@ -48,13 +50,12 @@ MD4C is C Markdown parser with the following features:
long as the platform provides C standard library, including a heap memory long as the platform provides C standard library, including a heap memory
management.) management.)
* **Encoding:** MD4C can be compiled to recognize ASCII-only control characters, * **Encoding:** MD4C by default expects UTF-8 encoding of the input document.
UTF-8 and, on Windows, also UTF-16 (i.e. what is on Windows commonly called But it can be compiled to recognize ASCII-only control characters (i.e. to
just "Unicode"). See more details below. disable all Unicode-specific code), or (on Windows) to expect UTF-16 (i.e.
what is on Windows commonly called just "Unicode"). See more details below.
* **Permissive license:** MD4C is available under the MIT license. * **Permissive license:** MD4C is available under the [MIT license](LICENSE.md).
* **Performance:** MD4C is [very fast](https://talk.commonmark.org/t/2520).
## Using MD4C ## Using MD4C
@ -93,8 +94,8 @@ chunks into a buffer or writes them to a file.
The default behavior is to recognize only Markdown syntax defined by the The default behavior is to recognize only Markdown syntax defined by the
[CommonMark specification](http://spec.commonmark.org/). [CommonMark specification](http://spec.commonmark.org/).
However with appropriate flags, the behavior can be tuned to enable some However, with appropriate flags, the behavior can be tuned to enable some
additional extensions: extensions:
* With the flag `MD_FLAG_COLLAPSEWHITESPACE`, a non-trivial whitespace is * With the flag `MD_FLAG_COLLAPSEWHITESPACE`, a non-trivial whitespace is
collapsed into a single space. collapsed into a single space.
@ -128,7 +129,7 @@ additional extensions:
instead of an ordinary emphasis or strong emphasis. instead of an ordinary emphasis or strong emphasis.
Few features of CommonMark (those some people see as mis-features) may be Few features of CommonMark (those some people see as mis-features) may be
disabled: disabled with the following flags:
* With the flag `MD_FLAG_NOHTMLSPANS` or `MD_FLAG_NOHTMLBLOCKS`, raw inline * With the flag `MD_FLAG_NOHTMLSPANS` or `MD_FLAG_NOHTMLBLOCKS`, raw inline
HTML or raw HTML blocks respectively are disabled. HTML or raw HTML blocks respectively are disabled.
@ -139,9 +140,11 @@ disabled:
## Input/Output Encoding ## Input/Output Encoding
The CommonMark specification generally assumes UTF-8 input, but under closer The CommonMark specification declares that any sequence of Unicode code points
inspection, Unicode plays any role in few very specific situations when parsing is a valid CommonMark document.
Markdown documents:
But, under a closer inspection, Unicode plays any role in few very specific
situations when parsing Markdown documents:
1. For detection of word boundaries when processing emphasis and strong 1. For detection of word boundaries when processing emphasis and strong
emphasis, some classification of Unicode characters (whether it is emphasis, some classification of Unicode characters (whether it is
@ -153,22 +156,23 @@ Markdown documents:
3. For translating HTML entities (e.g. `&`) and numeric character 3. For translating HTML entities (e.g. `&`) and numeric character
references (e.g. `#` or `ಫ`) into their Unicode equivalents. references (e.g. `#` or `ಫ`) into their Unicode equivalents.
However MD4C leaves this translation on the renderer/application; as the However note MD4C leaves this translation on the renderer/application; as
renderer is supposed to really know output encoding and whether it really the renderer is supposed to really know output encoding and whether it
needs to perform this kind of translation. (For example, when the renderer really needs to perform this kind of translation. (For example, when the
outputs HTML, it may leave the entities untranslated and defer the work to renderer outputs HTML, it may leave the entities untranslated and defer the
a web browser.) work to a web browser.)
MD4C relies on this property of the CommonMark and the implementation is, to MD4C relies on this property of the CommonMark and the implementation is, to
a large degree, encoding-agnostic. Most of MD4C code only assumes that the a large degree, encoding-agnostic. Most of MD4C code only assumes that the
encoding of your choice is compatible with ASCII, i.e. that the codepoints encoding of your choice is compatible with ASCII. I.e. that the codepoints
below 128 have the same numeric values as ASCII. below 128 have the same numeric values as ASCII.
Any input MD4C does not understand is simply seen as part of the document text Any input MD4C does not understand is simply seen as part of the document text
and sent to the renderer's callback functions unchanged. and sent to the renderer's callback functions unchanged.
The two situations (word boundary detection and link reference matching) where The two situations (word boundary detection and link reference matching) where
MD4C has to understand Unicode are handled as specified by the following rules: MD4C has to understand Unicode are handled as specified by the following
preprocessor macros (as specified at the time MD4C is being built):
* If preprocessor macro `MD4C_USE_UTF8` is defined, MD4C assumes UTF-8 for the * If preprocessor macro `MD4C_USE_UTF8` is defined, MD4C assumes UTF-8 for the
word boundary detection and for the case-insensitive matching of link labels. word boundary detection and for the case-insensitive matching of link labels.
@ -199,11 +203,11 @@ MD4C has to understand Unicode are handled as specified by the following rules:
## Documentation ## Documentation
The API of the parser is quite well documented in the comments in the `md4c.h`. The API of the parser is quite well documented in the comments in the `md4c.h`.
The markdown-to-html API is described in its header `md4c-html.h`. Similarly, the markdown-to-html API is described in its header `md4c-html.h`.
There is also [project wiki](http://github.com/mity/md4c/wiki) which provides There is also [project wiki](http://github.com/mity/md4c/wiki) which provides
some more comprehensive documentation. However note it is incomplete and some some more comprehensive documentation. However note it is incomplete and some
details may be little-bit outdated. details may be somewhat outdated.
## FAQ ## FAQ
@ -212,8 +216,8 @@ details may be little-bit outdated.
**A:** Some other implementations combine Markdown parser and HTML generator **A:** Some other implementations combine Markdown parser and HTML generator
into a single entangled code hidden behind an interface which just allows the into a single entangled code hidden behind an interface which just allows the
conversion from Markdown to HTML, and they are unusable if you want to process conversion from Markdown to HTML. They are often unusable if you want to
the input in any other way. process the input in any other way.
Even when the parsing is available as a standalone feature, most parsers (if Even when the parsing is available as a standalone feature, most parsers (if
not all of them; at least within the scope of C/C++ language) are full DOM-like not all of them; at least within the scope of C/C++ language) are full DOM-like
@ -221,8 +225,8 @@ parsers: They construct abstract syntax tree (AST) representation of the whole
Markdown document. That takes time and it leads to bigger memory footprint. Markdown document. That takes time and it leads to bigger memory footprint.
It's completely fine as long as you really need it. If you don't need the full It's completely fine as long as you really need it. If you don't need the full
AST, there is very high chance that using MD4C will be faster and much less AST, there is a very high chance that using MD4C will be substantially faster
memory-hungry. and less hungry in terms of memory consumption.
Last but not least, some Markdown parsers are implemented in a naive way. When Last but not least, some Markdown parsers are implemented in a naive way. When
fed with a [smartly crafted input pattern](test/pathological_tests.py), they fed with a [smartly crafted input pattern](test/pathological_tests.py), they
@ -238,11 +242,11 @@ as a bug.)
**Q: Does MD4C perform any input validation?** **Q: Does MD4C perform any input validation?**
**A:** No. **A:** No. And we are proud of it. :-)
CommonMark specification states that any sequence of Unicode characters is CommonMark specification states that any sequence of Unicode characters is
a valid Markdown document. (In practice, this more or less always means UTF-8 a valid Markdown document. (In practice, this more or less always means UTF-8
encoding is assumed.) encoding.)
In other words, according to the specification, it does not matter whether some In other words, according to the specification, it does not matter whether some
Markdown syntax construction is in some way broken or not. If it is broken, it Markdown syntax construction is in some way broken or not. If it is broken, it
@ -256,7 +260,7 @@ a part of the text.
If you need to validate that the input is, say, a well-formed UTF-8 document, If you need to validate that the input is, say, a well-formed UTF-8 document,
you have to do it on your own. The easiest way how to do this is to simply you have to do it on your own. The easiest way how to do this is to simply
validate the whole Markdown document before passing it to the MD4C parser. validate the whole document before passing it to the MD4C parser.
## License ## License
@ -272,7 +276,7 @@ Ports and bindings to other languages:
Port of MD4C to D language. Port of MD4C to D language.
* [markdown-wasm](https://github.com/rsms/markdown-wasm): * [markdown-wasm](https://github.com/rsms/markdown-wasm):
Markdown parser and HTML generator for WebAssembly, based on MD4C. Port of MD4C to WebAssembly.
* [PyMD4C](https://github.com/dominickpastore/pymd4c): * [PyMD4C](https://github.com/dominickpastore/pymd4c):
Python bindings for MD4C Python bindings for MD4C