ssc/extensions.md

Extending the compiler

Custom import resolvers

The import resolver's job is to load scripts identified by name. It is used to find both the main script (passed to the sunCompiler.Compile method) and scripts referenced by import statements. The resolver used by a compiler is the one passed through the resolver parameter. In order to create a custom import resolver, simply inherit from the abstract class sunImportResolver.

There are three primary methods in the import-resolver API:

Method	Description
Enter	Called when the compiler begins compiling a script. The script about to be compiled is passed through the file parameter.
Exit	Similar to Enter, but is called when the compiler finishes compiling a script.
Resolve	This is where the actual import resolver logic is implemented. The name of the script is passed through the name parameter. The method initializes a new sunScriptFile instance and passes it to the file out parameter.

Import results

The enum sunImportResult defines the result of the import:

Value	Description
Loaded	Script successfully loaded and is ready to be compiled.
Missing	Script could not be found. This is flagged as a compiler error.
Skipped	Script was found, but is not flagged for compilation. Instead, the compiler will silently ignore the import.
FailedToLoad	Script was found, but initializing the sunScriptFile instance failed. This is flagged as a compiler error.

Script files

The sunScriptFile class has various properties:

Property	Description
Name	The name of the script. May be the original name passed to sunImportResolver.Resolve, or some other value. Does not have to be unique.
Stream	The read-enabled stream containing the script's contents. This is used by the compiler to parse the script.
Id	An unsigned, 64-bit number used to uniquely identify this script. Every script successfully resolved by an import resolver must have a unique value for this property.

Custom binary formats

In the API, the sunBinary class manages writing the compiled binary. It receives instructions from the compiler to write commands, symbols, and data strings to the binary. The default implementation uses the standard SPC binary format used by Super Mario Sunshine. By inheriting from the sunBinary class, you may create your own output formats.

Almost all the methods in the base sunBinary class are either abstract or virtual. Thus, there is quite a bit of overhead in creating a custom binary formatter.

Method	Description
Open	Called when the compiler begins compiling. Useful for initialization.
Close	Called when the compiler finishes compiling. Useful for finalization.

Writing a binary is split into several sections:

.text

The .text section contains all the executable instructions that the interpreter will then run. To signal when the compiler begins and ends writing .text, there are the following virtual methods:

Method	Description
BeginText	Called when the compiler begins writing the .text section.
EndText	Called when the compiler finishes writing the .text section.

There is also a method for each of the standard commands defined by TSpcInterp. Their job is to simply write the specified command, with the following exceptions:

• It is the responsibility of the WriteINT method to redirect to WriteINT0 or WriteINT1, if that functionality is desired. WriteINT0 and WriteINT1 are never called by the compiler directly.

The API defines several methods and properties for navigating the .text section:

Name	Description
Offset	Specifies the current offset into the .text section, as an unsigned, 32-bit integer.
Goto	Seeks to the specified offset into the .text section.
Keep	Pushes the current offset into the .text section onto the stack.
Back	Pops the element off the top of the stack and seeks to that offset in the .text section.

.data

The .data section contains a table of all the strings used in scripts. These entries are referenced by the str instruction. Data entries are automatically interned by ssc, so your implementation need not check for duplicate entries.

The API has the following methods for writing the .data section:

Method	Description
BeginData	Called when the compiler begins writing the .data section.
WriteData	Writes a data entry to the section, specified by the data parameter.
EndData	Called when the compiler finishes writing the .data section.

.sym

The .sym section contains a table of all the symbols (imported and exported) used by the scripts. If the clean-symbols option is specified when building ssc, then only symbols which are detected as being used will be written to the symbol table.

The API has the following methods for writing the .sym section:

Method	Description
BeginSymbol	Called when the compiler begins writing the .sym section.
WriteSymbol	Writes a symbol entry to the section. The type, name, and data parameters specify the properties of the symbol being written. This method must manually implement string interning, if that is a requirement.
EndSymbol	Called when the compiler finishes writing the .sym section.