/*++

    Copyright (c) 1989-2000  Microsoft Corporation

    Module Name:

        hash.c

    Abstract:

        BUGBUG: comment.

    Author:

        vadimb     created     sometime in 2000

    Revision History:
--*/

#include "sdbp.h"

#define DEFAULT_STR_HASH_SIZE 8147

#if defined(KERNEL_MODE) && defined(ALLOC_DATA_PRAGMA)
#pragma  data_seg()
#endif // KERNEL_MODE && ALLOC_DATA_PRAGMA


//
// Table used to calculate CRC32. This is used to generate
// the hash index for strings.
//

static DWORD rgdwCrc[] =
{
  0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL,
  0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L,
  0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L,
  0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L,

  0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
  0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L,
  0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL,
  0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L,

  0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 0xa2677172L,
  0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
  0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L,
  0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L,

  0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L,
  0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 0xb8bda50fL,
  0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
  0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL,

  0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL,
  0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L,
  0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 0xe10e9818L,
  0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,

  0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL,
  0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L,
  0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL,
  0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L,

  0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
  0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL,
  0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L,
  0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L,

  0x5005713cL, 0x270241aaL, 0xbe0b1010L, 0xc90c2086L,
  0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
  0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L,
  0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL,

  0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL,
  0xead54739L, 0x9dd277afL, 0x04db2615L, 0x73dc1683L,
  0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
  0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L,

  0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL,
  0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L,
  0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 0x67dd4accL,
  0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,

  0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L,
  0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL,
  0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L,
  0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 0x4669be79L,

  0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
  0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL,
  0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L,
  0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL,

  0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 0x026d930aL,
  0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
  0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L,
  0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L,

  0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL,
  0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 0x18b74777L,
  0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
  0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L,

  0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L,
  0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL,
  0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L,
  0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,

  0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L,
  0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL,
  0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L,
  0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL

};

#if defined(KERNEL_MODE) && defined(ALLOC_PRAGMA)
#pragma alloc_text(PAGE, HashCreate)
#pragma alloc_text(PAGE, HashFree)
#pragma alloc_text(PAGE, HashStringRef)
#pragma alloc_text(PAGE, HashString)
#pragma alloc_text(PAGE, HashFindString)
#pragma alloc_text(PAGE, HashFindStringByRef)
#pragma alloc_text(PAGE, HashAddString)
#pragma alloc_text(PAGE, HashAddStringByRef)
#endif // KERNEL_MODE && ALLOC_PRAGMA


PVOID
HashCreate(
    void
    )
/*++
    Return: The hash.

    Desc:   Creates and initializes the hash.
--*/
{
    PSTRHASH pHash;

    pHash = (PSTRHASH)SdbAlloc(sizeof(STRHASH));

    if (pHash == NULL) {
        DBGPRINT((sdlError,
                  "HashCreate",
                  "Failed to allocate %d bytes.\n",
                  sizeof(STRHASH)));
        return NULL;
    }

    pHash->dwHashSize = DEFAULT_STR_HASH_SIZE;

    pHash->pTable = (PSTRHASHELEMENT*)SdbAlloc(sizeof(PSTRHASHELEMENT) * DEFAULT_STR_HASH_SIZE);

    if (pHash->pTable == NULL) {
        DBGPRINT((sdlError,
                  "HashCreate",
                  "Failed to allocate %d bytes for the table.\n",
                  sizeof(PSTRHASHELEMENT) * DEFAULT_STR_HASH_SIZE));
        
        SdbFree(pHash);
        return NULL;
    }
    
    return pHash;
}

void
HashFree(
    IN  PVOID pStringHash       // the hash to be freed.
    )
/*++
    Return: void

    Desc:   BUGBUG: comments ?
--*/
{
    PSTRHASHELEMENT phe, pheNext;
    PSTRHASH        pHash = (PSTRHASH)pStringHash;
    int             i;

    if (pHash == NULL) {
        DBGPRINT((sdlError, "HashFree", "Invalid argument.\n"));
        return;
    }

    if (pHash->pTable != NULL) {

        for (i = 0; i < (int)pHash->dwHashSize; i++) {

            for (phe = pHash->pTable[i]; phe != NULL; ) {
                pheNext = phe->pNext;
                SdbFree(phe);
                phe = pheNext;
            }
        }

        SdbFree(pHash->pTable);
    }

    SdbFree(pHash);
}


DWORD
HashStringRef(
    IN  PSTRHASH  pHash,        // pointer to the string hash structure.
    IN  STRINGREF srString      // string-reference (a dword) that is used to
                                // identify the string in an sdb file.
    )
/*++
    Return: Hash index for the string

    Desc:   BUGBUG: comments ?
--*/
{
    //
    // really simple for now
    //

    return (srString % pHash->dwHashSize);
}


DWORD
HashString(
    IN  PSTRHASH pHash,         // pointer to the string hash structure.
    IN  LPCTSTR  szString       // the string to be hashed
    )
/*++
    Return: The string reference in the hash.

    Desc:   BUGBUG: comments ?
--*/
{
    DWORD dwHash = 0;

    while (*szString) {
        dwHash += (dwHash << 5) + dwHash + *szString++;
    }
    
    dwHash %= pHash->dwHashSize;

    return dwHash;
}

STRINGREF
HashFindString(
    IN  PSTRHASH pHash,         // pointer to the string hash structure.
    IN  LPCTSTR  szString       // string to search for.
    )
/*++
    Return: The string ref if the string is found in the hash, 0 otherwise.

    Desc:   Searches for the specified string in the hash table.
--*/
{
    DWORD           dwHash;
    PSTRHASHELEMENT phe;
    int             iCmp;
    STRINGREF       srReturn = STRINGREF_NULL;

    dwHash = HashString(pHash, szString);

    phe = pHash->pTable[dwHash];

    for (; phe != NULL; phe = phe->pNext) {

        iCmp = _tcsicmp(szString, phe->szStr);

        //
        // The list of items related to the entry dwHash in the table
        // is sorted in ascending order by the "add" routine
        // therefore we compare until we find an item that is greater or equal
        // to the search string.
        //

        if (iCmp <= 0) {
            //
            // Found or failure, stop the search.
            //
            srReturn = (iCmp == 0 ? phe->srStr : STRINGREF_NULL);
            break;
        }
    }

    return srReturn;
}

LPTSTR
HashFindStringByRef(
    IN  PSTRHASH  pHash,        // pointer to the string hash structure.
    IN  STRINGREF srString      // stringref of the string to search for.
    )
/*++
    Return: The pointer to the found string or NULL.

    Desc:   Searches for the specified string in the hash table.
--*/
{
    DWORD           dwHash;
    PSTRHASHELEMENT phe;
    LPTSTR          pStr = NULL;

    dwHash = HashStringRef(pHash, srString);

    phe = pHash->pTable[dwHash];

    for (; phe != NULL; phe = phe->pNext) {
        if (phe->srStr >= srString) {
            pStr = ((phe->srStr == srString) ? phe->szStr : NULL);
            break;
        }
    }

    return pStr;
}


BOOL
HashAddString(
    IN  PSTRHASH  pHash,        // pointer to the string hash structure.
    IN  LPCTSTR   szString,     // the string to be added
    IN  STRINGREF srString      // the string ref for the string to be added
    )
/*++
    Return: TRUE on success, FALSE otherwise.

    Desc:   BUGBUG: comments ?
--*/
{
    DWORD           dwHash;
    PSTRHASHELEMENT phe;
    PSTRHASHELEMENT pheLast;
    PSTRHASHELEMENT pheNew;
    DWORD           dwStrSize;

    dwHash = HashString(pHash, szString);

    phe = pHash->pTable[dwHash];

    dwStrSize = (DWORD)(_tcslen(szString) + 1) * sizeof(TCHAR);

    //
    // Now check where to insert the string.
    //
    for (pheLast = NULL;
         phe != NULL && _tcsicmp(szString, phe->szStr) > 0;
         pheLast = phe, phe = phe->pNext) {
        ;
    }

    //
    // Insert it.
    //
    pheNew = (PSTRHASHELEMENT)SdbAlloc(sizeof(STRHASHELEMENT) + dwStrSize);

    if (pheNew == NULL) {
        DBGPRINT((sdlError,
                  "HashAddString",
                  "Failed to allocate %d bytes.\n",
                  sizeof(STRHASHELEMENT) + dwStrSize));
        return FALSE;
    }

    pheNew->szStr = (LPTSTR)(pheNew + 1);
    pheNew->srStr = srString;

    RtlMoveMemory(pheNew->szStr, szString, dwStrSize);

    pheNew->pNext = phe;

    if (pheLast == NULL) {
        pHash->pTable[dwHash] = pheNew;
    } else {
        pheLast->pNext = pheNew;
    }

    return TRUE;
}

LPTSTR
HashAddStringByRef(
    IN  PSTRHASH  pHash,
    IN  LPCTSTR   szString,
    IN  STRINGREF srString
    )
/*++
    Return: The pointer to the string added in the hash table.

    Desc:   BUGBUG: comments ?
--*/
{
    DWORD           dwHash;
    PSTRHASHELEMENT phe;
    PSTRHASHELEMENT pheLast;
    PSTRHASHELEMENT pheNew;
    DWORD           dwStrSize;
    LPTSTR          lpszCachedString = NULL;

    dwHash = HashStringRef(pHash, srString);

    phe = pHash->pTable[dwHash];

    dwStrSize = (DWORD)(_tcslen(szString) + 1) * sizeof(TCHAR);

    //
    // Check where to insert the string.
    //
    for (pheLast = NULL;
         phe != NULL && srString > phe->srStr;
         pheLast = phe, phe = phe->pNext);

    //
    // Insert it.
    //
    pheNew = (PSTRHASHELEMENT)SdbAlloc(sizeof(STRHASHELEMENT) + dwStrSize);

    if (pheNew == NULL) {
        DBGPRINT((sdlError,
                  "HashAddStringByRef",
                  "Failed to allocate %d bytes.\n",
                  sizeof(STRHASHELEMENT) + dwStrSize));

        return NULL;
    }

    pheNew->szStr = (LPTSTR)(pheNew + 1);
    pheNew->srStr = srString;

    RtlMoveMemory(pheNew->szStr, szString, dwStrSize);

    pheNew->pNext = phe;

    if (pheLast == NULL) {
        pHash->pTable[dwHash] = pheNew;
    } else {
        pheLast->pNext = pheNew;
    }

    lpszCachedString = pheNew->szStr;

    return lpszCachedString;
}