Author: Jonas Bilinkevicius

How to parse a line from a comma-separated file into a record

Answer:

1   { ... }
2   type
3     TRec = record
4       lastname, firstname: string[30];
5       age: Integer;
6       position: string[40];
7       salary: Single;
8     end;
9   
10  procedure ParseLine(const Line: string; var rec: TRec);
11  var
12    i, start, field: Integer;
13  
14    procedure CopyField(currPos: Integer);
15    var
16      len, err: Integer;
17      temp: string;
18    begin
19      len := currpos - start;
20      if len > 0 then
21      begin
22        temp := Copy(Line, start, len);
23        err := 0;
24        with rec do
25          case field of
26            0: lastname := temp;
27            1: firstname := temp;
28            2: Val(temp, age, err);
29            3: position := temp;
30            4: Val(temp, salary, err)
31          else
32            { too much data in this line, issue error message }
33          end;
34        if err <> 0 then
35        begin
36          {issue error message}
37        end;
38      end
39      else
40        {no data in this field, issue error message or leave the default }
41    end;
42  
43  begin
44    {set defaults for the fields, init variables}
45    FillChar(rec, sizeof(rec), 0);
46    field := 0; {fields keeps track of which field to fill next}
47    start := 1; {fencepost for start of field data}
48    for i := 1 to Succ(Length(Line)) do
49    begin
50      if i > Length(Line) then
51      begin
52        {copy the last section of the line to the last field}
53        CopyField(i);
54      end
55      else
56        {test for separator character} if Line[i] = ',' then
57        begin
58          {found one, copy data from current fencepost to this separator}
59          CopyField(i);
60          {advance fencepost to position after separator}
61          start := i + 1;
62          {next field}
63          Inc(field);
64        end;
65    end;
66  end;