IPhone programming: How to Use APIs to operate BLOB fields in SQLite

IPhoneProgramming:SQLiteHow to Use API operations?BLOBType fields are the content to be introduced in this article. In actual programming and development, we often need to deal with storage of large-capacity binary data, such as slices or music. For these binary dataBlobFields ).SQLiteA set of functions are provided to process suchBLOBField type.

The following code demonstrates how to use these API functions.

First, we need to create a database:

 
 

  
  
Sqlite3_exec (db, "create table list (fliename varchar (128) UNIQUE, fzip blob);", 0, 0, & zErrMsg );
  
  
 
  
  
/Since mmmm.rar is a binary file, do you need to use the insert statement first? No.
  
  
Sqlite3_prepare (db, "insert into list values ('mmmm.rar ',?); ",-1, & stat, 0 );
  
  
FILE * fp;
  
  
Long filesize = 0;
  
  
Char * ffile;
  
  
Fp = fopen ("mmmm.rar", "rb ");
  
  
If (fp! = NULL)
  
  
{
  
  
// Calculate the file size
  
  
Fseek (fp, 0, SEEK_END );
  
  
Filesize = ftell (fp );
  
  
Fseek (fp, 0, SEEK_SET );
  
  
// Read the file
  
  
Ffile = new char [filesize + 1];
  
  
Size_t sz = fread (ffile, sizeof (char), filesize + 1, fp );
  
  
Fclose (fp );
  
  
}
  
  
// Bind the file data to the insert statement and replace "?" Part
  
  
Sqlite3_bind_blob (stat, 1, ffile, filesize, NULL );
  
  
// Execute the bound SQL statement
  
  
Sqlite3_step (stat );
 
 

At this time, the database already has a piece of data containing the BLOB field. Next we will read this data:

 
 

  
  
// Select the data.
  
  
Sqlite3_prepare (db, "select * from list;",-1, & stat, 0 );
  
  
Sqlite3_step (stat );
  
  
// Obtain the BLOB field in the record
  
  
Const void * test = sqlite3_column_blob (stat, 1 );
  
  
// Obtain the data length in the field
  
  
Int size = sqlite3_column_bytes (stat, 1 );
  
  
// Copy this field
  
  
Sprintf (buffer2, "% s", test );
 
 

At this time, buffer2 can be written to the file, so that BLOB data processing is complete.

Summary:IPhoneProgramming:SQLiteHow to Use API operations?BLOBThe content of the type field has been introduced. I hope this article will help you!