[sqlite] How can I change big-endian to little-endian in the database file
Dear all, in an upcoming project, it is required to store all integer values as little endian instead of big endian (don't ask why). Nevertheless, I would like to use SQLite in that project. What do we have to change in the sqlite library, if we store the integers as little endian. I came across some functions in B-tree.c and pager.c. In B-tree.c /* Read or write a two- and four-byte big-endian integer values.*/ get2byte, get4byte, put2byte, put4byte /* pager.c*/ ** All values are stored on disk as big-endian. */ read32bits, write32bits Is that enough. Another question, what do we have to change if we would also store the utf-chars as little endian? I appreciate your help. Martin ___ Der frühe Vogel fängt den Wurm. Hier gelangen Sie zum neuen Yahoo! Mail: http://mail.yahoo.de
Re: [sqlite] How can I change big-endian to little-endian in the database file
Martin Pfeifle [EMAIL PROTECTED] wrote: Dear all, in an upcoming project, it is required to store all integer values as little endian instead of big endian (don't ask why). Nevertheless, I would like to use SQLite in that project. What do we have to change in the sqlite library, if we store the integers as little endian. I came across some functions in B-tree.c and pager.c. In B-tree.c /* Read or write a two- and four-byte big-endian integer values.*/ get2byte, get4byte, put2byte, put4byte /* pager.c*/ ** All values are stored on disk as big-endian. */ read32bits, write32bits Is that enough. I think so. Big-endian numbers have the nice property that memcmp() compares positive integers in numerical order. I don't think we are using that property anywhere, but I might be mistaken. So if you do come up with a little-endian version of SQLite, you will want to test it very carefully. Another question, what do we have to change if we would also store the utf-chars as little endian? PRAGMA encoding=utf-16le; The le at the end is the important part. -- D. Richard Hipp [EMAIL PROTECTED] - To unsubscribe, send email to [EMAIL PROTECTED] -
Re: [sqlite] How can I change big-endian to little-endian in the database file
Martin Pfeifle [EMAIL PROTECTED] wrote: in an upcoming project, it is required to store all integer values as little endian instead of big endian... Does that mean you are not allowed to use TCP/IP which stores everything big-endian? ;-) -- D. Richard Hipp [EMAIL PROTECTED] - To unsubscribe, send email to [EMAIL PROTECTED] -
Re: [sqlite] How can I change big-endian to little-endian in the database file
I think there is no need to change endianess.
Sqlite is shadowing out this and similar low level aspects.
If you need to get data from database and use it in something what needs it in
other endianess, you may use something like this.
int change_endianess(unsigned char *data, int length)
{
unsigned char *buffer;
int i;
buffer = malloc(length);
for(i=0;ilength;i++)
{
buffer[i] = data[length - i];
}
memcpy(data, buffer, length);
free(buffer);
return length;
}
For example, i have whole system with big endian, but only ferroelectric ram
connected via i2c bus needs addresses in little endian, address is an 16bit
number, so i must to swap the two bytes.
*((unsigned char *)(buffer[0])) = addr 8;
*((unsigned char *)(buffer[1])) = addr 0xff;
If i understand it correctly, changing physical representation of data in the
database conflicts with SQL and relational databases principle.
Jakub
Dne úterý 03 duben 2007 09:49 Martin Pfeifle napsal(a):
Dear all,
in an upcoming project, it is required to store all integer values as
little endian instead of big endian (don't ask why).
Nevertheless, I would like to use SQLite in that project.
What do we have to change in the sqlite library,
if we store the integers as little endian.
I came across some functions in B-tree.c and pager.c.
In B-tree.c
/* Read or write a two- and four-byte big-endian integer values.*/
get2byte,
get4byte,
put2byte,
put4byte
/* pager.c*/
** All values are stored on disk as big-endian.
*/
read32bits,
write32bits
Is that enough.
Another question, what do we have to change if we would
also store the utf-chars as little endian?
I appreciate your help.
Martin
___
Der frühe Vogel fängt den Wurm. Hier gelangen Sie zum neuen Yahoo! Mail:
http://mail.yahoo.de
-
To unsubscribe, send email to [EMAIL PROTECTED]
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Re: [sqlite] How can I change big-endian to little-endian in the database file
A very efficient way to re-arrange the byte ordering is to use a free
union. No function calls involved or tests.
Jakub Ladman wrote:
I think there is no need to change endianess.
Sqlite is shadowing out this and similar low level aspects.
If you need to get data from database and use it in something what needs it in
other endianess, you may use something like this.
int change_endianess(unsigned char *data, int length)
{
unsigned char *buffer;
int i;
buffer = malloc(length);
for(i=0;ilength;i++)
{
buffer[i] = data[length - i];
}
memcpy(data, buffer, length);
free(buffer);
return length;
}
For example, i have whole system with big endian, but only ferroelectric ram
connected via i2c bus needs addresses in little endian, address is an 16bit
number, so i must to swap the two bytes.
*((unsigned char *)(buffer[0])) = addr 8;
*((unsigned char *)(buffer[1])) = addr 0xff;
If i understand it correctly, changing physical representation of data in the
database conflicts with SQL and relational databases principle.
Jakub
Dne úterý 03 duben 2007 09:49 Martin Pfeifle napsal(a):
Dear all,
in an upcoming project, it is required to store all integer values as
little endian instead of big endian (don't ask why).
Nevertheless, I would like to use SQLite in that project.
What do we have to change in the sqlite library,
if we store the integers as little endian.
I came across some functions in B-tree.c and pager.c.
In B-tree.c
/* Read or write a two- and four-byte big-endian integer values.*/
get2byte,
get4byte,
put2byte,
put4byte
/* pager.c*/
** All values are stored on disk as big-endian.
*/
read32bits,
write32bits
Is that enough.
Another question, what do we have to change if we would
also store the utf-chars as little endian?
I appreciate your help.
Martin
___
Der frühe Vogel fängt den Wurm. Hier gelangen Sie zum neuen Yahoo! Mail:
http://mail.yahoo.de
-
To unsubscribe, send email to [EMAIL PROTECTED]
-
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To unsubscribe, send email to [EMAIL PROTECTED]
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