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JudySL_funcs(3) Library Functions Manual JudySL_funcs(3)


JudySL - C library for creating and accessing a dynamic array, using a null-terminated string as an index (associative array)


PPvoid_t JudySLIns(      PPvoid_t PPJSLArray, const uint8_t * Index, PJError_t PJError);
int      JudySLDel(      PPvoid_t PPJSLArray, const uint8_t * Index, PJError_t PJError);
PPvoid_t JudySLGet(      Pcvoid_t  PJSLArray, const uint8_t * Index, PJError_t PJError);
Word_t   JudySLFreeArray(PPvoid_t PPJSLArray, PJError_t PJError);
PPvoid_t JudySLFirst(    Pcvoid_t  PJSLArray,       uint8_t * Index, PJError_t PJError);
PPvoid_t JudySLNext(     Pcvoid_t  PJSLArray,       uint8_t * Index, PJError_t PJError);
PPvoid_t JudySLLast(     Pcvoid_t  PJSLArray,       uint8_t * Index, PJError_t PJError);
PPvoid_t JudySLPrev(     Pcvoid_t  PJSLArray,       uint8_t * Index, PJError_t PJError);


A macro equivalent exists for each function call. Because the macro forms are sometimes faster and have a simpler error handling interface than the equivalent functions, they are the preferred way of calling the JudySL functions. See JudySL(3) for more information. The function call definitions are included here for completeness.

One of the difficulties in using the JudySL function calls lies in determining whether to pass a pointer or the address of a pointer. Since the functions that modify the JudySL array must also modify the pointer to the JudySL array, you must pass the address of the pointer rather than the pointer itself. This often leads to hard-to-debug programmatic errors. In practice, the macros allow the compiler to catch programming errors when pointers instead of addresses of pointers are passed.

The JudySL function calls have an additional parameter beyond those specified in the macro calls. This parameter is either a pointer to an error structure, or NULL (in which case the detailed error information is not returned).

In the following descriptions, the functions are described in terms of how the macros use them (only in the case of #define JUDYERROR_NOTEST 1). This is the suggested use of the macros after your program has been fully debugged. When the JUDYERROR_NOTEST macro is not specified, an error structure is declared to store error information returned from the JudySL functions when an error occurs.

Notice the placement of the & in the different functions.

#define JSLI(PValue, PJSLArray, Index) \

PValue = JudyLIns(&PJSLArray, Index, PJE0)

#define JSLD(Rc_int, PJSLArray, Index) \

Rc_int = JudySLDel(&PJSLArray, Index, PJE0)

#define JSLG(PValue, PJSLArray, Index) \

PValue = JudySLIns(PJSLArray, Index, PJE0)

#define JSLFA(Rc_word, PJSLArray) \

Rc_word = JudySLFreeArray(&PJSLArray, PJE0)

#define JSLF(PValue, PJSLArray, Index) \

PValue = JudySLFirst(PJSLArray, Index, PJE0)

#define JSLN(PValue, PJSLArray, Index) \

PValue = JudySLNext(PJSLArray, Index, PJE0)

#define JSLL(PValue, PJSLArray, Index) \

PValue = JudySLLast(PJSLArray, Index, PJE0)

#define JSLP(PValue, PJSLArray, Index) \

PValue = JudySLPrev(PJSLArray, Index, PJE0)


Definitions for all the Judy functions, the types Pvoid_t, Pcvoid_t, PPvoid_t, Word_t , JError_t, and PJError_t, the constants NULL, JU_ERRNO_*, JERR, PPJERR, and PJE0 are provided in the Judy.h header file (/usr/include/Judy.h). Note: Callers should define JudySL arrays as type Pvoid_t, which can be passed by value to functions that take Pcvoid_t (constant Pvoid_t), and also by address to functions that take PPvoid_t.

The return type from most JudySL functions is PPvoid_t so that the values stored in the array can be pointers to other objects, which is a typical usage, or cast to a Word_t * when a pointer to a value is required instead of a pointer to a pointer.


Judy was invented by Doug Baskins and implemented -Packard.


Judy(3), Judy1(3), JudyL(3), JudySL(3), JudyHS(3),
the Judy website,, for more information and Application Notes.