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Revision 935015fc

Added by dsorber almost 9 years ago

Adding example "lowercase util" that tests multiple approaches to lowercasing an entire buffer.

View differences:

software/lowercase_util/Makefile
CXXFLAGS= -std=c++11 -O3
all: main
main: lowercase_util.cc
g++ $(CXXFLAGS) lowercase_util.cc -o lowercase_util
#%.o : %.c %.h
# g++ $(CXXFLAGS) -c $<
clean:
rm -f lowercase_util
software/lowercase_util/lowercase_util.cc
#include <cctype>
#include <chrono>
#include <cstdint>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
#include <sys/types.h>
#include <sys/stat.h>
// https://stackoverflow.com/questions/3883993/how-could-these-case-conversion-functions-be-improved
// g++ -std=c++11 -O3 lowercase_util.cc -o lowercase_util
int main(const int argc, char** argv)
{
if (argc < 2)
{
std::cerr << "USAGE: " << argv[0] << " <filename>" << std::endl;
return -1;
}
std::cout << "Lowercase Test Util\n" << std::endl;
std::string filePath(argv[1]);
// Stat the file path to get its size
struct stat fs_stat;
const int gotStatOK(stat(filePath.c_str(), &fs_stat));
if (gotStatOK < 0)
{
perror("stat()");
return -1;
}
uint32_t fileSize = fs_stat.st_size;
std::cout << "File size: " << fileSize << "\n" << std::endl;
// Read in file
std::ifstream inFileStream(filePath, std::ios::in | std::ios::binary);
if (! inFileStream)
{
std::cerr << "Unable to open specified file." << std::endl;
return -1;
}
// Read file in then close stream
std::vector<char> contents;
contents.resize(fileSize);
inFileStream.read(contents.data(), fileSize);
inFileStream.close();
// TEST1: regular tolower() -----------------------------------------------
std::vector<char> copy1(contents);
auto start = std::chrono::system_clock::now();
for (uint32_t idx = 0; idx < fileSize; ++idx)
{
copy1[idx] = tolower(copy1[idx]);
}
auto end = std::chrono::system_clock::now();
auto diff = end - start;
std::cout << "Test 1 -- duration: "
<< std::chrono::duration<double, std::milli>(diff).count()
<< " ms" << std::endl;
// TEST2: technique 1 -----------------------------------------------------
std::vector<char> copy2(contents);
start = std::chrono::system_clock::now();
for (uint32_t idx = 0; idx < fileSize; ++idx)
{
// *c += (*c - 'A' < 26U) << 5;
copy2[idx] += (copy2[idx] - 'A' < 26U) << 5;
}
end = std::chrono::system_clock::now();
diff = end - start;
std::cout << "Test 2 -- duration: "
<< std::chrono::duration<double, std::milli>(diff).count()
<< " ms" << std::endl;
#if 0
// Verify copy2
std::ofstream outStream1("output_copy2.txt", std::ios::out | std::ios::binary);
outStream1.write(copy2.data(), fileSize);
outStream1.close();
#endif
// TEST3: technque 2 ------------------------------------------------------
std::vector<char> copy3(contents);
start = std::chrono::system_clock::now();
for (uint32_t idx = 0; idx < fileSize; ++idx)
{
// *c += (64U - *c & *c - 91U) >> CHAR_BIT * sizeof(unsigned) - 1 << 5;
// *c += ((64U - *c & *c - 91U) >> 31) << 5;
copy3[idx] += ((64U - copy3[idx] & copy3[idx] - 91U) >> 31) << 5;
}
end = std::chrono::system_clock::now();
diff = end - start;
std::cout << "Test 3 -- duration: "
<< std::chrono::duration<double, std::milli>(diff).count()
<< " ms" << std::endl;
#if 0
// Verify copy3
std::ofstream outStream2("output_copy3.txt", std::ios::out | std::ios::binary);
outStream2.write(copy3.data(), fileSize);
outStream2.close();
#endif
// TEST 4: technique 3 ----------------------------------------------------
std::vector<char> copy4(contents);
start = std::chrono::system_clock::now();
for (uint32_t idx = 0; idx < fileSize; ++idx)
{
// c += (((96-(int)c)&((int)c-123))>>9)&(-32);
copy4[idx] += (((96 - (int)copy4[idx]) & ((int)copy4[idx] - 123)) >> 9) & (-32);
}
end = std::chrono::system_clock::now();
diff = end - start;
std::cout << "Test 4 -- duration: "
<< std::chrono::duration<double, std::milli>(diff).count()
<< " ms" << std::endl;
return 0;
}

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