2017-10-20

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ELF-32

Algorithm creator(s)

A variant of Peter J. Weinberger's HashPJW.


PB author(s)

Wayne Diamond, Dave Navarro


Description

Outputs a 32-bit unsigned hash that is the modulo generated by dividing the returned integer by the size of the table.


Note

Used in UNIX object files that use the ELF format.


Source

https://forum.powerbasic.com/forum/user-to-user-discussions/programming/19721-elfhash-c-translation?t=19192


See also

n/a


Source Code

Download source code file elf32.bas (Right-click -> "Save as ...")

FUNCTION Elf32(sKey AS STRING) AS LONG
'// by Dave Navarro, November 30 2000 
'// Bugfix by Wayne Diamond, 24 July 2002
  LOCAL key AS BYTE PTR
  LOCAL h AS LONG
  LOCAL g AS LONG
  LOCAL i AS LONG
  key = STRPTR(sKey)
  h = 0
  WHILE @key
    SHIFT LEFT h, 4
    h = h + @key
    key = key + 1
    g = h AND &HF0000000???
    IF g THEN
      i = g
      SHIFT RIGHT i, 24
      h = h XOR i
    END IF
    h = h AND (NOT g)
  WEND
  FUNCTION = h
END FUNCTION
 
 
FUNCTION Elf32(sKey AS STRING) AS DWORD
'// by Wayne Diamond, 24 July 2002
#REGISTER NONE
LOCAL lLen AS DWORD, ptrStr AS DWORD, H AS DWORD
lLen = LEN(sKey)
ptrStr = STRPTR(sKey)
       ! xor ebx, ebx      ; ebx = result holder (H)
       ! mov edx, lLen     ; edx = Length
       ! mov ecx, ptrStr   ; ecx = Ptr to string
       ! xor esi, esi      ; esi = temp holder
    Elf1:
       ! xor eax, eax
       ! shl ebx, 4
       ! mov al, [ecx]
       ! add ebx, eax
       ! inc ecx
       ! mov eax, ebx
       ! and eax, &HF0000000???
       ! cmp eax, 0
       ! je Elf2
       ! mov esi, eax
       ! shr esi, 24
       ! xor ebx, esi
    Elf2:
       ! not eax
       ! and ebx,eax
       ! dec edx
       ! cmp edx, 0
       ! jne Elf1
       ! mov H,ebx
    FUNCTION = H
END FUNCTION

Mirror provided by Knuth Konrad