Buffering

2. Storing collection of records.
Reading collection of records.
Writing collection of records.
Buffering Algorithm.
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Sharaf
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3. Company info class only
represents single record.
A collection of records
needs to be stored into a
dynamic array.
The collection of records
can be encapsulated into a
class that maps to a file.
Dr. Hussien M.
Sharaf
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Company1
Company2
…..
Company N

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Sharaf
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CompanyInfoCollection
Structure
Record 3 Record 4Record 1 Record 2210 250 180 190
1. Store collection of records in a dynamic array
2. Store file full path name.
3. Store and manage the indexing of records.

5. Dr. Hussien M.
Sharaf
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CompanyInfoCollection
Functionalities
Record 3 Record 4Record 1 Record 2210 250 180 190
1. Responsible for opening and closing of the file
stream.
2. Calling read or write of companyInfo without
knowing the details of read/write single line.
3. Manage the buffering of records while reading or
writing.
4. Count the number of records in a file.

6. Dr. Hussien M.
Sharaf
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Algorithm#1 Writing collection of
records
Record 3 Record 4Record 1 Record 2210 250 180 190
While (len(Buffer) < bufferingSize)
{
companyInfo[i].writeIntoStream( stringStream)
stringStream<<recordDelimiter
i++
}
Stringstream>>Buffer
FileStream.write(Buffer)

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Algorithm#2 Reading collection
of records
Record 3 Record 4Record 1 Record 2210 250 180 190
FileStream.read(Buffer, BufferingSize+1)
Stringstream<<Buffer;
While (! Stringstream.EOF)
{
companyInfo[i].ReadFromStream(Stringstream)
i++
}

8. 1. Read x MB into memory buffer (i.e.
char array).
2. Make sure to stop reading at the end of
a record. How can this be done?
3. Put the buffered data into a string
stream.
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9. 4. Pass the string stream to an instance of
companyInfo which extracts fields.
5. Add the new companyInfo to the array
of records.
6. Manage the index by adding an entry
with the correct offset.
7. Repeat steps 1-6 until EOF
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Sharaf
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11. Store the byte offset of each record into a list stored in
another file.
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Remember Indexing
Problems:
1. Two files are used: one for the data and another for
CompanyName offset
IBM 0Record1
n
n
Google 211Record2 n
Microsoft 462Record3 n
ITE 643Record4 n

12. Dr. Hussien M.
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class CompanyInfoCollection
{
private:
vector<CompanyInfo> Records;
RecordIndex recordIndexes;
public:
//read delimited fields
bool WriteDelimRecords(ostream& ,char);
//read delimited fields
bool readDelimRecords(istream&);
};

13. Dr. Hussien M.
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Read/write from
streamBuffer
Single
companyInfo
RecordsCollection
File stream
Read/write from
streamBuffer
Single
companyInfo
Records Indexes
Record 2211 Record 3462

14. Continue using the CompanyInfo program:
1) Where would you put the following
functionalities:
a. Read the multiple records into a buffer.
b. Split a single record into fields.
c. Append a single record into a collection of
records.
d. Search for a record given a company
name.
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15. Continue using the CompanyInfo program:
2) Implement Algorithm#1 into the
CompanyInfo program.
3) Implement Algorithm#2 into the
CompanyInfo program.
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Sharaf
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