SQLite

/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.125 2004/05/11 00:58:56 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.

    if( !pPage->zeroData ){
      while( (0x80&*(cell++))!=0 ){}  /* Skip the data size number */
    }
    getVarint(cell, pSize);
  }
  return SQLITE_OK;
}

/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
  MemPage *pPage;
  unsigned char *cell;
  u64 size;

  if( !pCur->isValid ){
    return pCur->status ? pCur->status : SQLITE_INTERNAL;
  }
  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( pPage->isInit );
  pageIntegrity(pPage);
  if( pPage->zeroData ){
    *pSize = 0;
  }else{
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( !pPage->leaf ){
      cell += 4;  /* Skip the child pointer */
    }
    getVarint(cell, &size);
    assert( (size & 0x00000000ffffffff)==size );
    *pSize = (u32)size;
  }
  return SQLITE_OK;
}

/*
** Read payload information from the entry that the pCur cursor is
** pointing to.  Begin reading the payload at "offset" and read
** a total of "amt" bytes.  Put the result in zBuf.
**
** This routine does not make a distinction between key and data.

  }
  assert( pCur->pPage!=0 );
  assert( pCur->pPage->intKey==0 );
  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  return getPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
}
























































































/*
** Read part of the data associated with cursor pCur.  Exactly
** "amt" bytes will be transfered into pBuf[].  The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong.  An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
  if( !pCur->isValid ){
    return pCur->status ? pCur->status : SQLITE_INTERNAL;
  }
  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  return getPayload(pCur, offset, amt, pBuf, 1);
}

/*
** Return a pointer to payload information from the entry that the 
** pCur cursor is pointing to.  The pointer is to the beginning of
** the key if skipKey==0 and it points to the beginning of data if
** skipKey==1.
**
** At least amt bytes of information must be available on the local
** page or else this routine returns NULL.  If amt<0 then the entire
** key/data must be available.
**
** This routine is an optimization.  It is common for the entire key
** and data to fit on the local page and for there to be no overflow
** pages.  When that is so, this routine can be used to access the
** key and data without making a copy.  If the key and/or data spills
** onto overflow pages, then getPayload() must be used to reassembly
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached
** page of the database.  The data might change or move the next time
** any btree routine is called.
*/
static const unsigned char *fetchPayload(
  BtCursor *pCur,      /* Cursor pointing to entry to read from */
  int amt,             /* Amount requested */
  int skipKey          /* read beginning at data if this is true */
){
  unsigned char *aPayload;
  MemPage *pPage;
  Btree *pBt;
  u64 nData, nKey;
  int maxLocal;

  assert( pCur!=0 && pCur->pPage!=0 );
  assert( pCur->isValid );
  pBt = pCur->pBt;
  pPage = pCur->pPage;
  pageIntegrity(pPage);
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  aPayload = pPage->aCell[pCur->idx];
  aPayload += 2;  /* Skip the next cell index */
  if( !pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
  if( pPage->zeroData ){
    nData = 0;
  }else{
    aPayload += getVarint(aPayload, &nData);
  }
  aPayload += getVarint(aPayload, &nKey);
  if( pPage->intKey ){
    nKey = 0;
  }
  maxLocal = pBt->maxLocal;
  if( skipKey ){
    aPayload += nKey;
    maxLocal -= nKey;
    if( amt<0 ) amt = nData;
    assert( amt<=nData );
  }else{
    if( amt<0 ) amt = nKey;
    assert( amt<=nKey );
  }
  if( amt>maxLocal ){
    return 0;  /* If any of the data is not local, return nothing */
  }
  return aPayload;
}


/*
** Return a pointer to the first amt bytes of the key or data
** for record that cursor pCur is point to if the entire request
** exists in contiguous memory on the main tree page.  If any
** any part of the request is on an overflow page, return 0.
** If pCur is not pointing to a valid entry return 0.
**
** If amt<0 then return the entire key or data.
**
** The pointer returned is ephemeral.  The key/data may move
** or be destroyed on the next call to any Btree routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
**
** It is a fatal error to call these routines with amt values that
** are larger than the key/data size.
*/
const void *sqlite3BtreeKeyFetch(BtCursor *pCur, int amt){
  return (const void*)fetchPayload(pCur, amt, 0);
}
const void *sqlite3BtreeDataFetch(BtCursor *pCur, int amt){
  return (const void*)fetchPayload(pCur, amt, 1);
}


/*
** Move the cursor down to a new child page.  The newPgno argument is the
** page number of the child page in the byte order of the disk image.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;

    Pgno chldPg;
    MemPage *pPage = pCur->pPage;
    int c = -1;  /* pRes return if table is empty must be -1 */
    lwr = 0;
    upr = pPage->nCell-1;
    pageIntegrity(pPage);
    while( lwr<=upr ){
      const void *pCellKey;
      u64 nCellKey;
      pCur->idx = (lwr+upr)/2;
      sqlite3BtreeKeySize(pCur, &nCellKey);
      if( pPage->intKey ){
        if( nCellKey<nKey ){
          c = -1;
        }else if( nCellKey>nKey ){
          c = +1;
        }else{
          c = 0;
        }
      }else if( (pCellKey = sqlite3BtreeKeyFetch(pCur, nCellKey))!=0 ){
        c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
      }else{
        u8 *pCellKey = sqliteMalloc( nCellKey );
        if( pCellKey==0 ) return SQLITE_NOMEM;
        rc = sqlite3BtreeKey(pCur, 0, nCellKey, pCellKey);
        c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
        sqliteFree(pCellKey);
        if( rc ) return rc;
      }
      if( c==0 ){

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
**
** @(#) $Id: btree.h,v 1.45 2004/05/11 00:58:56 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/

int sqlite3BtreeLast(BtCursor*, int *pRes);
int sqlite3BtreeNext(BtCursor*, int *pRes);
int sqlite3BtreeEof(BtCursor*);
int sqlite3BtreeFlags(BtCursor*);
int sqlite3BtreePrevious(BtCursor*, int *pRes);
int sqlite3BtreeKeySize(BtCursor*, u64 *pSize);
int sqlite3BtreeKey(BtCursor*, u32 offset, u32 amt, void*);
const void *sqlite3BtreeKeyFetch(BtCursor*, int amt);
const void *sqlite3BtreeDataFetch(BtCursor*, int amt);
int sqlite3BtreeDataSize(BtCursor*, u32 *pSize);
int sqlite3BtreeData(BtCursor*, u32 offset, u32 amt, void*);

char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot);
struct Pager *sqlite3BtreePager(Btree*);

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the btree.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test3.c,v 1.35 2004/05/11 00:58:56 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

  Tcl_AppendResult(interp, zBuf, 0);
  return SQLITE_OK;
}

/*
** Usage:   btree_keysize ID
**
** Return the number of bytes of key.  For an INTKEY table, this
** returns the key itself.
*/
static int btree_keysize(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){

    return TCL_ERROR;
  }
  zBuf[n] = 0;
  Tcl_AppendResult(interp, zBuf, 0);
  free(zBuf);
  return SQLITE_OK;
}

/*
** Usage:   btree_fetch_key ID AMT
**
** Use the sqlite3BtreeKeyFetch() routine to get AMT bytes of the key.
** If sqlite3BtreeKeyFetch() fails, return an empty string.
*/
static int btree_fetch_key(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  BtCursor *pCur;
  int n;
  u64 nKey;
  const char *zBuf;
  char zStatic[1000];

  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID AMT\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
  sqlite3BtreeKeySize(pCur, &nKey);
  zBuf = sqlite3BtreeKeyFetch(pCur, n);
  if( zBuf ){
    assert( nKey<sizeof(zStatic) );
    if( n>0 ) nKey = n;
    memcpy(zStatic, zBuf, (int)nKey); 
    zStatic[nKey] = 0;
    Tcl_AppendResult(interp, zStatic, 0);
  }
  return TCL_OK;
}

/*
** Usage:   btree_fetch_data ID AMT
**
** Use the sqlite3BtreeDataFetch() routine to get AMT bytes of the key.
** If sqlite3BtreeDataFetch() fails, return an empty string.
*/
static int btree_fetch_data(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  BtCursor *pCur;
  int n;
  u32 nData;
  const char *zBuf;
  char zStatic[1000];

  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID AMT \"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pCur) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
  sqlite3BtreeDataSize(pCur, &nData);
  zBuf = sqlite3BtreeDataFetch(pCur, n);
  if( zBuf ){
    assert( nData<sizeof(zStatic) );
    if( n>0 ) nData = n;
    memcpy(zStatic, zBuf, (int)nData); 
    zStatic[nData] = 0;
    Tcl_AppendResult(interp, zStatic, 0);
  }
  return TCL_OK;
}

/*
** Usage:   btree_payload_size ID
**
** Return the number of bytes of payload
*/
static int btree_payload_size(

     { "btree_insert",             (Tcl_CmdProc*)btree_insert             },
     { "btree_next",               (Tcl_CmdProc*)btree_next               },
     { "btree_prev",               (Tcl_CmdProc*)btree_prev               },
     { "btree_eof",                (Tcl_CmdProc*)btree_eof                },
     { "btree_keysize",            (Tcl_CmdProc*)btree_keysize            },
     { "btree_key",                (Tcl_CmdProc*)btree_key                },
     { "btree_data",               (Tcl_CmdProc*)btree_data               },
     { "btree_fetch_key",          (Tcl_CmdProc*)btree_fetch_key          },
     { "btree_fetch_data",         (Tcl_CmdProc*)btree_fetch_data         },
     { "btree_payload_size",       (Tcl_CmdProc*)btree_payload_size       },
     { "btree_first",              (Tcl_CmdProc*)btree_first              },
     { "btree_last",               (Tcl_CmdProc*)btree_last               },
     { "btree_cursor_info",        (Tcl_CmdProc*)btree_cursor_info        },
     { "btree_cursor_list",        (Tcl_CmdProc*)btree_cursor_list        },
     { "btree_integrity_check",    (Tcl_CmdProc*)btree_integrity_check    },
     { "btree_breakpoint",         (Tcl_CmdProc*)btree_breakpoint         },

int sqlite2BtreeKeyCompare(
  BtCursor *pCur,       /* Pointer to entry to compare against */
  const void *pKey,     /* Key to compare against entry that pCur points to */
  int nKey,             /* Number of bytes in pKey */
  int nIgnore,          /* Ignore this many bytes at the end of pCur */
  int *pResult          /* Write the result here */
){
  const void *pCellKey;
  void *pMallocedKey;
  u64 nCellKey;
  int rc;

  sqlite3BtreeKeySize(pCur, &nCellKey);
  nCellKey = nCellKey - nIgnore;
  if( nCellKey<=0 ){
    *pResult = 0;
    return SQLITE_OK;
  }

  pCellKey = sqlite3BtreeKeyFetch(pCur, nCellKey);
  if( pCellKey ){
    *pResult = memcmp(pCellKey, pKey, nKey>nCellKey?nCellKey:nKey);
    return SQLITE_OK;
  }

  pMallocedKey = sqliteMalloc( nCellKey );
  if( pMallocedKey==0 ) return SQLITE_NOMEM;

  rc = sqlite3BtreeKey(pCur, 0, nCellKey, pMallocedKey);
  *pResult = memcmp(pMallocedKey, pKey, nKey>nCellKey?nCellKey:nKey);
  sqliteFree(pMallocedKey);

  return rc;
}

/*
** The following three functions:
**

    int ii;
    int bytes = 1 << (data_type-1);

    pMem->flags = MEM_Int;
    pMem->i = 0;

    for(ii=0; ii<bytes; ii++){
      pMem->i = (pMem->i<<8) + zBuf[ii+ret];
    }

    /* If this is a 1, 2 or 4 byte integer, extend the sign-bit if need be. */
    if( bytes<8 && pMem->i & (1<<(bytes*8-1)) ){
      pMem->i = pMem->i - (1<<(bytes*8));
    }

# 2004 May 10
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is btree database backend
#
# $Id: btree5.test,v 1.2 2004/05/11 00:58:56 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Attempting to read table 1 of an empty file gives an SQLITE_EMPTY
# error.

# each entry agrees with its key.
#
proc check_table {N} {
  global c1
  btree_first $c1
  set cnt 0
  while {![btree_eof $c1]} {
    if {[set data [btree_data $c1]] ne "data-for-[btree_key $c1]"} {
      return "wrong data for entry $cnt"
    }
    set n [string length $data]
    set fdata1 [btree_fetch_data $c1 $n]
    set fdata2 [btree_fetch_data $c1 -1]
    if {$fdata1 ne "" && $fdata1 ne $data} {
puts "fdata1=[list $fdata1] data=[list $data]"
      return "DataFetch returned the wrong value with amt=$n"
    }
    if {$fdata1 ne $fdata2} {
      return "DataFetch returned the wrong value when amt=-1"
    }
    if {$n>10} {
      set fdata3 [btree_fetch_data $c1 10]
      if {$fdata3 ne [string range $data 0 9]} {
        return "DataFetch returned the wrong value when amt=10"
      }
    }
    incr cnt
    btree_next $c1
  }
  if {$cnt!=$N} {
    return "wrong number of entries"
  }