Version 5.0 The LEDA User Manual

string C.get description( ) provides a description for C.
Additional Operations
uint32 C.get block size( ) returns the current block size.
void
C.set block size(uint32 block size)
sets the block size.
Coder∗ C.get coder( ) returns the instance of Coder which is actually used
for encoding and decoding.
4. Example
The following example shows how BlockCoder can be used to speed up seek operations. We
encode a file of about 3.85 MB, once with A0Coder and once with BlockCoder.
We feed each encoded file into an autodecoding ifstream and perform random seeks. The
file encoded with BlockCoder is slightly longer but seek operations become much faster.
#include
#include
#include
#include
using namespace LEDA;
void test_random_seek(istream& is)
{
const int buffer_sz = 100; char buffer[buffer_sz];
is.seekg(0, ios::end); streamoff size = (streamoff) is.tellg();
// yields the size of the original file
random_source rs;
rs.set_seed(0); rs.set_range(0, size - buffer_sz - 1);
}
timer t("seek"); t.start();
for (int i = 0; i < 100; ++i) {
is.seekg(rs()); is.read(buffer, buffer_sz); // random seek
}
t.stop();
int main()
{
typedef A0Coder Coder;
string in_file = "D:\\ctemp\\bible.txt"; // 3,85MB