An integer is always 64 bits.
Jerry Krinock wrote:
I need to read an sqlite database generated by others. So I wrote an
outer loop which steps through the rows of a table using sqlite3_step,
and an inner loop which steps through the columns. The inner loop finds
the type using sqlite3_column_type(), then 'switches' to get the value
using the appropriate sqlite3_column_XXXXX() function.
It works fine if, when encountering an SQLITE_INTEGER type, I use
sqlite_column_int64() to get the data.
I don't know whether or not I'm just "lucky" that the application which
wrote the database uses 64 bit for all of its integers? If so, what if
someone throws a 32-bit integer at me someday? How can I tell whether
integer data objects in a table are 32 or 64 bit? The column
specifications I get from pragma_table_info() are likewise
uninformative, saying simply type=INTEGER.
Thanks again,
Jerry Krinock
// Method Implementation (Objective-C for Mac OS X)
- (NSArray*)dicsOfRowsInTable:(NSString*)table {
// Will return nil if fails, empty array if no rows
void* db = [self db] ;
//char* errMsg = NULL ;
int result ;
NSString* statement = [[NSString alloc] initWithFormat:@"SELECT *
FROM '%@'", table] ;
// Compile the statement into a virtual machine
sqlite3_stmt* preparedStatement ;
result = sqlite3_prepare(db, [statement UTF8String], -1,
&preparedStatement, NULL) ;
[statement release] ;
NSArray* output = nil ;
if (result != SQLITE_OK) {
[self showError:"prepare" from:11 code:result] ;
}
else {
NSMutableArray* rowDics = [[NSMutableArray alloc] init] ;
NSArray* keys = [self keysInTable:table] ;
int nColumns = [keys count] ;
while (result = sqlite3_step(preparedStatement) == SQLITE_ROW) {
NSMutableDictionary* rowDic = [[NSMutableDictionary alloc]
init] ;
int iColumn ;
for (iColumn= 0; iColumn<nColumns; iColumn++) {
int type = sqlite3_column_type(preparedStatement,
iColumn) ;
// The sqlite3_column_type() routine returns datatype code
// for the initial data type of the result column.
// The returned value is one of SQLITE_INTEGER,
// SQLITE_FLOAT, SQLITE_TEXT, SQLITE_BLOB, or SQLITE_NULL
// Initialize to null in case object is not found
const void* pFirstByte = NULL ;
int nBytes = 0 ;
id object = nil ;
long long int intValue ;
const unsigned char* utf8String ;
double doubleValue ;
switch(type) {
case SQLITE_BLOB:
nBytes = sqlite3_column_bytes(preparedStatement,
iColumn) ;
// "The return value from sqlite3_column_blob()
for a zero-length
// blob is an arbitrary pointer, possibly even a
NULL pointer."
// Therefore, we qualify...
if (nBytes > 0) {
pFirstByte =
sqlite3_column_blob(preparedStatement, iColumn) ;
object = [[NSData alloc]
initWithBytes:pFirstByte length:nBytes] ;
}
break ;
case SQLITE_INTEGER:
intValue =
sqlite3_column_int64(preparedStatement, iColumn) ;
object = [NSNumber numberWithLongLong:intValue] ;
break ;
case SQLITE_TEXT:
// "Strings returned by sqlite3_column_text()
and sqlite3_column_text16(),
// even zero-length strings, are always zero
terminated."
// So, we ignore the length and just convert it
utf8String =
sqlite3_column_text(preparedStatement, iColumn) ;
object = [NSString
stringWithUTF8String:(char*)utf8String] ;
break ;
case SQLITE_FLOAT:
doubleValue =
sqlite3_column_double(preparedStatement, iColumn) ;
object = [NSNumber numberWithDouble:doubleValue] ;
break ;
case SQLITE_NULL:
default:
// Just leave object nil, will replace with
[NSNull null] soon.
;
}
if (object == nil) {
object = [NSNull null] ;
}
[rowDic setObject:object forKey:[keys
objectAtIndex:iColumn]] ;
}
NSDictionary* rowDicCopy = [rowDic copy] ;
[rowDics addObject:rowDicCopy] ;
[rowDicCopy release] ;
}
output = [rowDics copy] ;
[rowDics release] ;
}
// Finalize the statement (this releases resources allocated by
sqlite3_prepare()
result = sqlite3_finalize(preparedStatement) ;
if (result != SQLITE_OK) {
[self showError:"finalize" from:13 code:result] ;
}
return [output autorelease] ;
}
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