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Table of contents
  1. 1. Syntax
  2. 2. Description

JS_PushArguments

Table of contents
  1. 1. Syntax
  2. 2. Description

Main Page > SpiderMonkey > JSAPI Reference > JS_PushArguments

Convert any number of arguments to jsvals and store the resulting jsvals in an array.

Syntax 

jsval * JS_PushArguments(JSContext *cx, void **markp, const char *format, ...);

jsval * JS_PushArgumentsVA(JSContext *cx, void **markp, const char *format, va_list ap);
Name Type Description
cx JSContext * The context in which to perform any necessary conversions.

cx also affects the interpretation of format, if JS_AddArgumentFormatter has been called.

Requires request. (In a JS_THREADSAFE build, the caller must be in a request on this JSContext.)
markp void ** Out parameter. On success, *markp receives the internally allocated stack mark which should be passed to JS_PopArguments.
format const char * Null-terminated string holding a list of format types to convert the following arguments to.
... various (in JS_PushArguments) A variable number of arguments to be converted to jsvals. There must be one argument for each argument described in format.
ap va_list (in JS_PushArgumentsVA) The list of arguments to be converted to jsvals. There must be one argument for each argument described in format. The type va_list is a standard feature of the C programming language. It is defined in <stdarg.h>.

Description

JS_PushArguments provides a convenient way to translate a series of native C/C++ values to jsvals with a single function call.

cx is the context for the call. markp points to a void * to hold the internally allocated stack frame pointer to pass back to JS_PopArguments.

format is a sequential character array, where each element of the array indicates the JS type into which to convert the next C/C++ argument. format can contain one or more instances of the following characters, as appropriate:

Character Argument type
b JSBool
c uint16 (16-bit, unsigned integer)
i int32 (32-bit, ECMA-compliant signed integer)
u uint32 (32-bit, ECMA-compliant, unsigned integer)
j int32 (32-bit, signed integer)
d jsdouble
I jsdouble (converted to an integer value)
s char * (C string)
S JSString * (Unicode string)
W jschar * (Unicode null-terminated string)
o JSObject *
f JSFunction *
* None. Any asterisks (*) in format are ignored.

This function also takes in consideration any additional custom types defined in cx using JS_AddArgumentFormatter.

For example, if format is "bIob", then there must be four arguments after format. Their types must be JSBool, jsdouble, JSObject *, and JSBool. If successful, JS_PushArguments would return a pointer to an array of four jsvals: a boolean, a number, an object (or null), and a boolean.

On success, JS_PushArguments fills in the supplied markp pointer and returns a pointer to the first element of an array of jsval which are automatically rooted as necessary (protected from the GC temporarily). The application must call JS_PopArguments using the supplied markp stack pointer when done with this stack frame, to free the memory and unroot the jsvals.

On error or exception, JS_PushArguments returns NULL.

To perform the opposite conversion, converting an array of jsvals to various native C types, use JS_ConvertArguments.

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Page last modified 20:12, 21 Aug 2008 by Jorend

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