User Guide

356 Chapter 21: C-Level Extensibility
The C-level API
The C-level extensibility API consists of the following functions:
typedef JSBool (*JSNative)(JSContext *cx, JSObject *obj, unsigned int
argc, jsval *argv, jsval *rval)
Description
This function signature describes C-level implementations of JavaScript functions in the
following situations:
• The cx pointer is a pointer to an opaque JSContext structure, which must be passed to some
of the functions in the JavaScript API. This variable holds the interpreter’s execution context.
• The obj pointer is a pointer to the object in whose context the script executes. While the script
is running, the
this keyword is equal to this object.
• The argc integer is the number of arguments being passed to the function.
• The argv pointer is a pointer to an array of jsval structures. The array is argc elements
in length.
• The rval pointer is a pointer to a single jsval structure. The function’s return value should
be written to
*rval.
The function returns
JS_TRUE if successful; JS_FALSE otherwise. If the function returns
JS_FALSE, the current script stops executing and an error message appears.
JSBool JS_DefineFunction()
Description
This function registers a C-level function with the JavaScript interpreter in Dreamweaver. After
the
JS_DefineFunction() function registers the C-level function that you specify in the call
argument, you can invoke it in a JavaScript script by referring to it with the name that you specify
in the
name argument. The name is case-sensitive.
Typically, this function is called from the
MM_Init() function, which Dreamweaver calls
during startup.
Arguments
char *name
, JSNative call, unsigned int nargs
• The name argument is the name of the function as it is exposed to JavaScript.
• The call argument is a pointer to a C-level function. The function must accept the same
arguments as readContentsOfFile, and it must return a JSBool, which indicates success or
failure.
• The nargs argument is the number of arguments that the function expects to receive.
Returns
A Boolean value: JS_TRUE indicates success; JS_FALSE indicates failure.