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JudyHS(3) DragonFly Library Functions Manual JudyHS(3)
JudyHS macros - C library for creating and accessing a dynamic array,
using an array-of-bytes of Length as an Index and a word as a Value.
cc [flags] sourcefiles -lJudy
Word_t * PValue; // JudyHS array element
int Rc_int; // return flag
Word_t Rc_word; // full word return value
Pvoid_t PJHSArray = (Pvoid_t) NULL; // initialize JudyHS array
uint8_t * Index; // array-of-bytes pointer
Word_t Length; // number of bytes in Index
JHSI( PValue, PJHSArray, Index, Length); // JudyHSIns()
JHSD( Rc_int, PJHSArray, Index, Length); // JudyHSDel()
JHSG( PValue, PJHSArray, Index, Length); // JudyHSGet()
JHSFA(Rc_word, PJHSArray); // JudyHSFreeArray()
A JudyHS array is the equivalent of an array of word-sized
value/pointers. An Index is a pointer to an array-of-bytes of
specified length: Length. Rather than using a null terminated string,
this difference from JudySL(3) allows strings to contain all bits
(specifically the null character). This new addition (May 2004) to
Judy arrays is a hybird using the best capabilities of hashing and Judy
methods. JudyHS does not have a poor performance case where knowledge
of the hash algorithm can be used to degrade the performance.
Since JudyHS is based on a hash method, Indexes are not stored in any
particular order. Therefore the JudyHSFirst(), JudyHSNext(),
JudyHSPrev() and JudyHSLast() neighbor search functions are not
practical. The Length of each array-of-bytes can be from 0 to the
limits of malloc() (about 2GB).
The hallmark of JudyHS is speed with scalability, but memory efficiency
is excellent. The speed is very competitive with the best hashing
methods. The memory efficiency is similar to a linked list of the same
Indexes and Values. JudyHS is designed to scale from 0 to billions of
A JudyHS array is allocated with a NULL pointer
Pvoid_t PJHSArray = (Pvoid_t) NULL;
Because the macro forms of the API have a simpler error handling
interface than the equivalent functions, they are the preferred way to
JHSI(PValue, PJHSArray, Index, Length) // JudyHSIns()
Given a pointer to a JudyHS array (PJHSArray), insert an Index string
of length: Length and a Value into the JudyHS array: PJHSArray. If
the Index is successfully inserted, the Value is initialized to 0. If
the Index was already present, the Value is not modified.
Return PValue pointing to Value. Your program should use this pointer
to read or modify the Value, for example:
Value = *PValue;
*PValue = 1234;
Note: JHSI() and JHSD can reorganize the JudyHS array. Therefore,
pointers returned from previous JudyHS calls become invalid and must be
re-acquired (using JHSG()).
JHSD(Rc_int, PJHSArray, Index, Length) // JudyHSDel()
Given a pointer to a JudyHS array (PJHSArray), delete the specified
Index along with the Value from the JudyHS array.
Return Rc_int set to 1 if successfully removed from the array. Return
Rc_int set to 0 if Index was not present.
JHSG(PValue, PJHSArray, Index, Length) // JudyHSGet()
Given a pointer to a JudyHS array (PJHSArray), find Value associated
Return PValue pointing to Index's Value. Return PValue set to NULL if
the Index was not present.
JHSFA(Rc_word, PJHSArray) // JudyHSFreeArray()
Given a pointer to a JudyHS array (PJHSArray), free the entire array.
Return Rc_word set to the number of bytes freed and PJHSArray set to
ERRORS: See: Judy_3.htm#ERRORS
Show how to program with the JudyHS macros. This program will print
duplicate lines and their line number from stdin.
// cc -O PrintDupLines.c -lJudy -o PrintDupLines
#define MAXLINE 1000000 /* max fgets length of line */
uint8_t Index[MAXLINE]; // string to check
int // Usage: PrintDupLines < file
Pvoid_t PJArray = (PWord_t)NULL; // Judy array.
PWord_t PValue; // Judy array element pointer.
Word_t Bytes; // size of JudyHS array.
Word_t LineNumb = 0; // current line number
Word_t Dups = 0; // number of duplicate lines
while (fgets(Index, MAXLINE, stdin) != (char *)NULL)
LineNumb++; // line number
// store string into array
JHSI(PValue, PJArray, Index, strlen(Index));
if (PValue == PJERR) // See ERRORS section
fprintf(stderr, "Out of memory -- exit\n");
if (*PValue == 0) // check if duplicate
printf("Duplicate lines %lu:%lu:%s", *PValue, LineNumb, Index);
*PValue = LineNumb; // store Line number
printf("%lu Duplicates, free JudyHS array of %lu Lines\n",
Dups, LineNumb - Dups);
JHSFA(Bytes, PJArray); // free JudyHS array
printf("JudyHSFreeArray() free'ed %lu bytes of memory\n", Bytes);
JudyHS was invented and implemented by Doug Baskins after retiring from
Judy(3), Judy1(3), JudyL(3), JudySL(3),
the Judy website, http://judy.sourceforge.net, for further information
and Application Notes.