LibSass wouldn't be much good without a way to interface with it. These interface documentations describe the various functions and data structures available to implementers. They are split up over three major components, which have all their own source files (plus some common functionality).
- Sass Context - Trigger and handle the main Sass compilation
- Sass Value - Exchange values and its format with LibSass
- Sass Function - Get invoked by LibSass for function statments
- Sass Importer - Get invoked by LibSass for @import statments
First you will need to include the header file! This will automatically load all other headers too!
#include "sass/context.h"
#include <stdio.h>
#include "sass/context.h"
int main() {
puts(libsass_version());
return 0;
}
gcc -Wall version.c -lsass -o version && ./version
- Sample code for Sass Context
- Sample code for Sass Value
- Sample code for Sass Function
- Sample code for Sass Importer
The most important is your sass file (or string of sass code). With this, you
will want to start a LibSass compiler. Here is some pseudocode describing the
process. The compiler has two different modes: direct input as a string with
Sass_Data_Context
or LibSass will do file reading for you by using
Sass_File_Context
. See the code for a list of options available
Sass_Options
The general rule is if the API takes const char*
it will make a copy,
but where the API is char*
it will take over memory ownership, so make sure to pass
in memory that is allocated via sass_copy_c_string
or sass_alloc_memory
.
Building a file compiler
context = sass_make_file_context("file.scss")
options = sass_file_context_get_options(context)
sass_option_set_precision(options, 1)
sass_option_set_source_comments(options, true)
sass_file_context_set_options(context, options)
compiler = sass_make_file_compiler(sass_context)
sass_compiler_parse(compiler)
sass_compiler_execute(compiler)
output = sass_context_get_output_string(context)
// Retrieve errors during compilation
error_status = sass_context_get_error_status(context)
json_error = sass_context_get_error_json(context)
// Release memory dedicated to the C compiler
sass_delete_compiler(compiler)
Building a data compiler
// LibSass takes over memory owenership, make sure to allocate
// a buffer via `sass_alloc_memory` or `sass_copy_c_string`.
buffer = sass_copy_c_string("div { a { color: blue; } }")
context = sass_make_data_context(buffer)
options = sass_data_context_get_options(context)
sass_option_set_precision(options, 1)
sass_option_set_source_comments(options, true)
sass_data_context_set_options(context, options)
compiler = sass_make_data_compiler(context)
sass_compiler_parse(compiler)
sass_compiler_execute(compiler)
output = sass_context_get_output_string(context)
// div a { color: blue; }
// Retrieve errors during compilation
error_status = sass_context_get_error_status(context)
json_error = sass_context_get_error_json(context)
// Release memory dedicated to the C compiler
sass_delete_compiler(compiler)
Everything is stored in structs:
struct Sass_Options;
struct Sass_Context : Sass_Options;
struct Sass_File_context : Sass_Context;
struct Sass_Data_context : Sass_Context;
This mirrors very well how libsass
uses these structures.
Sass_Options
holds everything you feed in before the compilation. It also hostsinput_path
andoutput_path
options, because they are used to generate/calculate relative links in source-maps. Theinput_path
is shared withSass_File_Context
.Sass_Context
holds all the data returned by the compilation step.Sass_File_Context
is a specific implementation that requires no additional fieldsSass_Data_Context
is a specific implementation that adds theinput_source
field
Structs can be down-casted to access context
or options
!
We keep memory around for as long as the main context object
is not destroyed (sass_delete_context
). LibSass will create copies of most
inputs/options beside the main sass code. You need to allocate and fill that
buffer before passing it to LibSass. You may also overtake memory management
from libsass for certain return values (i.e. sass_context_take_output_string
).
Make sure to free it via sass_free_memory
.
// to allocate buffer to be filled
void* sass_alloc_memory(size_t size);
// to allocate a buffer from existing string
char* sass_copy_c_string(const char* str);
// to free overtaken memory when done
void sass_free_memory(void* ptr);
// Some convenient string helper function
char* sass_string_unquote (const char* str);
char* sass_string_quote (const char* str, const char quote_mark);
// Get compiled libsass version
const char* libsass_version(void);
// Implemented sass language version
// Hardcoded version 3.4 for time being
const char* libsass_language_version(void);
input_path
The input_path
is part of Sass_Options
, but it also is the main option for
Sass_File_Context
. It is also used to generate relative file links in source-
maps. Therefore it is pretty useful to pass this information if you have a
Sass_Data_Context
and know the original path.
output_path
Be aware that libsass
does not write the output file itself. This option
merely exists to give libsass
the proper information to generate links in
source-maps. The file has to be written to the disk by the
binding/implementation. If the output_path
is omitted, libsass
tries to
extrapolate one from the input_path
by replacing (or adding) the file ending
with .css
.
The error_code
is integer value which indicates the type of error that
occurred inside the LibSass process. Following is the list of error codes along
with the short description:
- 1: normal errors like parsing or
eval
errors - 2: bad allocation error (memory error)
- 3: "untranslated" C++ exception (
throw std::exception
) - 4: legacy string exceptions (
throw const char*
orstd::string
) - 5: Some other unknown exception
Although for the API consumer, error codes do not offer much value except indicating whether any error occurred during the compilation, it helps debugging the LibSass internal code paths.
The proof is in the pudding, so we have highlighted a few implementations that should be on par with the latest LibSass interface version. Some of them may not have all features implemented!
We use a functional API to make dynamic linking more robust and future compatible. The API is not yet 100% stable, so we do not yet guarantee ABI forward compatibility.
LibSass can load plugins from directories. Just define plugin_path
on context
options to load all plugins from the directories. To implement plugins, please
consult the following example implementations.