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C++ (DOS) and Dbase files

Posted on 2000-03-08
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Can anyone tell me how to access a Dbase III file using C++ for DOS? Any help will be appreciated.
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Question by:vicki9991
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by:AlexVirochovsky
ID: 2599234
Viki, i wrote C++ programme, that
creates, reads and saves records in
DBF files. But for Windows! For Dos
i must rewrite and test it. Add PTS
and i'll make it. And write you EMail.
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by:vicki9991
ID: 2603335
thank you Alex. I am waiting...
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LVL 14

Expert Comment

by:AlexVirochovsky
ID: 2603369
Viki, you's EMail??  
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Accepted Solution

by:
AlexVirochovsky earned 100 total points
ID: 2609604
#include <dos.h>
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
#include <io.h>
#include <string.h>
#include <sys\stat.h>
#include <fcntl.h>
typedef enum                              // Field Val Check type
   {
      fldvNOCHECKS     = 0,                  // Does not have explicit val checks
      fldvHASCHECKS    = 1,                  // One or more val checks on the field
      fldvUNKNOWN      = 2                   // Dont know at this time
   } FLDVchk;
typedef enum                              // Field Rights
   {
      fldrREADWRITE     = 0,                 // Field can be Read/Written
      fldrREADONLY      = 1,                 // Field is Read only
      fldrNONE          = 2,                 // No Rights on this field
      fldrUNKNOWN       = 3                  // Dont know at this time
   } FLDRights;

typedef struct {                        // Field Descriptor
      int            iFldNum;                // Field number (1..n)
      char           szName[41];             // Field name
      unsigned int   iFldType;               // Field type
      unsigned int   iSubType;               // Field subtype (if applicable)
      unsigned int   iUnits1;                // Number of Chars, digits etc
      unsigned int   iUnits2;                // Decimal places etc.
      unsigned int   iOffset;                // Offset in the record (computed)
      unsigned int   iCol;                   // Column on the Screen
   } FLDDesc;


typedef struct DIRELEMENTtag{                          // Field Descriptor
      char szName[11];             // Field name
      char iFldType;               // Field type
      long lOffset;               // Offset in the record
      unsigned char iUnits1;         // Number of Chars, digits etc
      unsigned char iUnits2;       // Decimal places etc.
      char szReserv[14];         //reserve
   } DIRELEMENT;
#define fldUNKNOWN      0
#define fldZSTRING      1                 // Null terminated string
#define fldDATE         2                 // Date     (32 bit)
#define fldFLOAT        7                 // 64 bit floating point
int CreateTable(char *szTable,FLDDesc *fldDesc,int uNumFields);

void main()
{
  FLDDesc fldDesc[] =
      {
        { 1, "Field1", fldZSTRING, fldUNKNOWN,15,0, 0, 0},
        { 2, "Field2", fldZSTRING, fldUNKNOWN, 1,0, 0, 0},
        { 3, "Field3", fldZSTRING, fldUNKNOWN,20,0, 0, 0},
        { 4, "Field4", fldZSTRING, fldUNKNOWN,20,0, 0, 0},
        { 5, "Field5", fldFLOAT,   fldUNKNOWN, 4,0, 0, 0},
        { 6, "Field6", fldDATE,    fldUNKNOWN, 8,0, 0, 0}
      };

  CreateTable("test.dbf",fldDesc,6);
}
/*================================================================*/
/*  Name       : ReadFldDesc                                */
/*  Descript   : Read Description of Fields                    */
/*  Parameters : Name of File                                */
/*  Return     : Number of Field (0: No)                    */
/*================================================================*/
void ReadFldDesc(char *szTable,FLDDesc *fldDesc, int uNumFields)
{
  FILE *hFile = fopen (szTable, "rb");      //open Table
  if (hFile)            //OK
    {
      int i;
      lseek(hFile->fd, 32l, 0);                 //begin of Fields
      for (i = 0; i < uNumFields; i++)       //for all filds
      {
        DIRELEMENT dir;                        //element of directory
        read(hFile->fd, &dir, sizeof(DIRELEMENT) );      //read
        strcpy(fldDesc[i].szName,dir.szName);            //name
        fldDesc[i].iUnits1 = dir.iUnits1;      //len of field
        fldDesc[i].iUnits2 = dir.iUnits2;      //decimal point
        fldDesc[i].iFldNum = i+1;                  //decimal point

        switch (dir.iFldType)                        //find type
          {
            case 'C': fldDesc[i].iFldType = fldZSTRING; break;
            case 'D': fldDesc[i].iFldType = fldDATE;    break;
            case 'N': fldDesc[i].iFldType = fldFLOAT;   break;
          }
      }
      for (i = 0; i < uNumFields; i++)
      fldDesc[i].iOffset = i == 0 ? 1 :      //place in Record
             fldDesc[i-1].iOffset + fldDesc[i-1].iUnits1;
    }
  fclose (hFile);
}
/*================================================================*/
/*  Name       : FindNumFields                                */
/*  Descript   : Find Number of Field                            */
/*  Parameters : Name of File                                */
/*  Return     : Number of Field (0: No)                    */
/*================================================================*/
int FindNumFields(char *szTable)
{
  FILE *hFile = fopen (szTable, "r+b");      //File of Index
  int uNumFields = 0;
  if (hFile)                              //ok
    {
      int nBegin;
      lseek(hFile->fd, 8l, 0);           //place of Num
      read(hFile->fd, &nBegin, sizeof(int));   //read

      uNumFields = (nBegin - 1 - 32)/32;   //number of fields
      fclose(hFile);
    }
   return uNumFields;
}
/*=============================================================*/
/* Name      : CreateTable()                                   */
/* Desciprion: This function creates a table by name and table */
/* Parameters: Number of File                                */
/*  Return   : -1: Error, 0: OK                               */
/*=============================================================*/
int CreateTable(char *szTable,FLDDesc *fldDesc,int uNumFields)
{
  long lTest = 0,lNum;
  char c = 3;
  int  Year,nBegin,nLen,i;
  struct date dDate;

  int hFile = creat(szTable, S_IREAD |S_IWRITE);          //open Table
  if (hFile == -1)                //no file: Error!
    return -1;
  lseek(hFile, 0l, 0);                     //begin
  write(hFile, &c, sizeof(char));            //save 3: Db3!

  getdate(&dDate);
  Year = dDate.da_year%100;
  write(hFile, &Year, sizeof(char));          //save Year
  write(hFile, &dDate.da_mon, sizeof(char));  //same mon
  write(hFile, &dDate.da_day, sizeof(char));  //save day
  write(hFile, &lTest, sizeof(long));        //save 0
  nBegin = 32 + 32*uNumFields + 1;   //begin of Data
  write(hFile, &nBegin, sizeof(int));        //save
  nLen = 1;                                 //len of record
  for (i = 0;i < uNumFields; nLen += fldDesc[i++].iUnits1);
  write(hFile, &nLen, sizeof(int));              //save Record len
  c = 0;                              //reserve
  for (i = 0; i < 20;i++)
    write(hFile, &c, sizeof(char));              //save 0
  for (i = 0; i < uNumFields; i++)             //for all filds
    {
      DIRELEMENT dir;                        //element of directory
      memset(&dir, 0, sizeof(DIRELEMENT));      //clear
      strcpy(dir.szName,fldDesc[i].szName);      //name
      strupr(dir.szName);                  //to Up case
      switch (fldDesc[i].iFldType)            //find type
      {
        case fldZSTRING:    dir.iFldType = 'C'; break;
        case fldDATE:       dir.iFldType = 'D'; break;
        case fldFLOAT:      dir.iFldType = 'N'; break;
      }
      dir.iUnits1 = fldDesc[i].iUnits1;            //len of field
      dir.iUnits2 = fldDesc[i].iUnits2;            //decimal point
      write(hFile, &dir, sizeof(DIRELEMENT) );//save
    }
  c = 0x0d;                              //end of Dir Section
  write(hFile, &c, 1);       //save end of Dir Sectiopn of file

  lNum = 0;                  //number of records
  c = 0x1A;
  write(hFile, &c, 1);       //end of file
  lseek(hFile, 0x1d, 0);           //place of Date
  c = 0x1b;
  write(hFile, &c, 1);       //set 1b
  if (lNum)
    {
      lseek(hFile, 4l, 0);           //place of N rec.
      write(hFile, &lNum, sizeof(long));       //save N rec
    }
  close (hFile);
  return 0;
}
/*======================================================*/
/*  Name       : ReadRecord                          */
/*  Descript   : Get data from  file to Memory              */
/*  Parameters : name of file, buffer, index of record  */
/*  Return     : 0: ok, -1: error                  */
/*======================================================*/
int  ReadFile(char *szTable,char *buff,long iNumRec)
{
  int hFile = open (szTable,O_RDONLY | O_BINARY);      //open Table

  long l,lOff,lNum;
  int ind,ret = -1;

  lseek(hFile, 4l, 0);            //form lNum current

  read(hFile, &lNum, sizeof(long));
  if (lNum >= 0 && iNumRec < lNum)                  //no data
    {
      short int len, nYear, nBegin;                       //len of record
      read(hFile, &nBegin, sizeof(int));   //read
      read(hFile,&len, sizeof(int));   //read len of record
      lOff = (long)nBegin + iNumRec * (long)len;
      lseek(hFile, lOff, 0);
      read(hFile,buff,len);
      ret = 0;
    }
  close(hFile);
  return ret;
}

/*================================================================*/
/*  Name       : AddRecord                                */
/*  Descript   : Put data to file                             */
/*  Parameters : Name of File, record,                          */
/*             : Save = 0: New Record, 1: Change Old, 2: Delete   */
/*             :        3: UnDelete                          */
/*             : iNumRec:  index of Record(for Change/Delete)        */
/*  Return     : -1: Error                                  */
/*================================================================*/
int AddRecord (char *szTable,char *buff,int bSave, long iNumRec)
{
  int hFile = open (szTable,O_RDWR | O_BINARY);      //open Table
  int nRet = -1;
  long lNum,lOff;
  int len, nYear, nBegin;                       //len of record
  struct date dDate;
                           //lenght:last bait : 0x1A;
  lseek(hFile, 0x4l, 0);       //begin of # records
  read(hFile,&lNum, sizeof(long)); //read #
  read(hFile, &nBegin, sizeof(int));   //read
  read(hFile,&len, sizeof(int));   //read len of record
  lOff = (long)nBegin + (bSave == 0 ? lNum: iNumRec) * (long)len;
  lseek(hFile, lOff, 0);
  if (bSave == 0 || bSave == 1)
    {
      *buff = ' ';
      if (write(hFile, buff, len) == len )
      nRet = 0;
    }
  else if (bSave == 2 &&
       write(hFile, "*", sizeof(char)) == sizeof(char))//delete!
    nRet = 0;
  else if (bSave == 3 &&
       write(hFile, " ", sizeof(char)) == sizeof(char))//UnDelete!
    nRet = 0;

  if (bSave == 0) //not exists Record
    write(hFile, "\0x1A", 1);       //end of file

  if (bSave == 0)        //new N of Record
    {
      lNum++;
      lseek(hFile, 0x4l, 0);       //begin of # records
      write(hFile,&lNum, sizeof(long)); //write back
    }
                                   //change date
  getdate(&dDate);
  lseek(hFile, 1l, 0);           //place of Date
  nYear = dDate.da_year%100;
  write(hFile, &nYear, sizeof(char));   //save Year
  write(hFile, &dDate.da_mon, sizeof(char));  //same mon
  write(hFile, &dDate.da_day, sizeof(char));  //save day
  close(hFile);
  return nRet;
}
If you have some Q about text,ask!
Alex
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