vector<char> -> file advice

[JackC]

Hi,

If i have a vector<charmaybe 15mb in size, whats the most efficient
way to write out all the elements to an output file?

I have tried this:

for(int z = 0; z < Output_Buffer.size(); z++)
{
write(ostr, (char *) Output_Buffer[z], 1);
}

But with 15mb in the buffer, that takes a good 30 seconds to write
out :(, any ideas on how i can speed it up? If i could use a
vector<stringi would do, but my preceding code processes lots of
individual chars so i just ended up adding them to a vector<charand
now need a fast way to output the buffer.

Thanks for any help.
Jack

[BobR]

JackC <je******@gmail.comwrote in message...

Hi,
If i have a vector<charmaybe 15mb in size, whats the most efficient
way to write out all the elements to an output file?
I have tried this:

for(int z = 0; z < Output_Buffer.size(); z++){
write(ostr, (char *) Output_Buffer[z], 1);
}

But with 15mb in the buffer, that takes a good 30 seconds to write
out :(, any ideas on how i can speed it up? If i could use a
vector<stringi would do, but my preceding code processes lots of
individual chars so i just ended up adding them to a vector<charand
now need a fast way to output the buffer.
Thanks for any help. Jack

A simple solution could be:

// includes here

int main(){
std::ofstream MyFile( "somefile.txt" );

std::vector<charBuffer( 50, 'Z' ); // for test

std::copy( Buffer.begin(), Buffer.end(),
std::ostream_iterator<char>( MyFile, "" ) );

return 0;
} // main()

--
Bob R
POVrookie

[JackC]

On 13 Aug, 19:13, "BobR" <[e-mail]:

JackC <[e-mail] in message...

Hi,
If i have a vector<charmaybe 15mb in size, whats the most efficient
way to write out all the elements to an output file?
I have tried this:

for(int z = 0; z < Output_Buffer.size(); z++){
write(ostr, (char *) Output_Buffer[z], 1);
}

But with 15mb in the buffer, that takes a good 30 seconds to write
out :(, any ideas on how i can speed it up? If i could use a
vector<stringi would do, but my preceding code processes lots of
individual chars so i just ended up adding them to a vector<charand
now need a fast way to output the buffer.
Thanks for any help. Jack

A simple solution could be:

// includes here

int main(){
std::ofstream MyFile( "somefile.txt" );

std::vector<charBuffer( 50, 'Z' ); // for test

std::copy( Buffer.begin(), Buffer.end(),
std::ostream_iterator<char>( MyFile, "" ) );

return 0;
} // main()

--
Bob R
POVrookie

Thanks Bob, exactly what i was after.

[BobR]

JackC <je******@gmail.comwrote in message...

On 13 Aug, 19:13, "BobR" <[e-mail]:

JackC <[e-mail] in message...

Hi,
If i have a vector<charmaybe 15mb in size, whats the most efficient
way to write out all the elements to an output file?

A simple solution could be:

// includes here
int main(){
std::ofstream MyFile( "somefile.txt" );
std::vector<charBuffer( 50, 'Z' ); // for test
std::copy( Buffer.begin(), Buffer.end(),
std::ostream_iterator<char>( MyFile, "" ) );
return 0;
} // main()

Thanks Bob, exactly what i was after.

Another thing you could try:

// note: only for std::vector<char(and array[]).
MyFile.write( &Buffer.at(0), Buffer.size() );

--
Bob R
POVrookie

[Gianni Mariani]

BobR wrote:

JackC <je******@gmail.comwrote in message...

>On 13 Aug, 19:13, "BobR" <[e-mail]:

>>JackC <[e-mail] in message...
Hi,
If i have a vector<charmaybe 15mb in size, whats the most efficient
way to write out all the elements to an output file?
A simple solution could be:

// includes here
int main(){
std::ofstream MyFile( "somefile.txt" );
std::vector<charBuffer( 50, 'Z' ); // for test
std::copy( Buffer.begin(), Buffer.end(),
std::ostream_iterator<char>( MyFile, "" ) );
return 0;
} // main()

Thanks Bob, exactly what i was after.

Another thing you could try:

// note: only for std::vector<char(and array[]).
MyFile.write( &Buffer.at(0), Buffer.size() );

Why not accomodate zero sized vectors ?

MyFile.write( &Buffer.front(), Buffer.size() );

- I'm not sure what front() does for zero sized vectors... probably UB

[Jim Langston]

"JackC" <je******@gmail.comwrote in message
news:11**********************@g4g2000hsf.googlegro ups.com...

Hi,

If i have a vector<charmaybe 15mb in size, whats the most efficient
way to write out all the elements to an output file?

I have tried this:

for(int z = 0; z < Output_Buffer.size(); z++)
{
write(ostr, (char *) Output_Buffer[z], 1);
}

But with 15mb in the buffer, that takes a good 30 seconds to write
out :(, any ideas on how i can speed it up? If i could use a
vector<stringi would do, but my preceding code processes lots of
individual chars so i just ended up adding them to a vector<charand
now need a fast way to output the buffer.

Why are you writing one character at a time? Why not just write the whole
1.5m? I.E.

write( ostr, &Output_Buffer[0], Output_Buffer.size() );

[Frank Birbacher]

Hi!

Gianni Mariani schrieb:

Why not accomodate zero sized vectors ?

MyFile.write( &Buffer.front(), Buffer.size() );

- I'm not sure what front() does for zero sized vectors... probably UB

Right, UB. I cannot think of a portable, legal way, but sometimes the
iterator is just a regular pointer. So begin() would suffice.

Frank