Mixing
How to read hex values into integer with fstream (C++)
up vote
0
down vote
favorite
I am trying to read a little-endian hex string from a binary file, and put that value into an integer to work with it. When I try to read, instead of getting a number I get ascii symbols. I've tried casts and atoi and nothing seems to work. What is the best way to use fstream to read a hex string into an integer from a file?
This is essentially my program:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(int argc, char* argv) {
fstream input;
fstream output;
char cbuffer[4];
char revbuffer[8];
input.open(argv[1], fstream::binary | fstream::in);
output.open("output.txt", ios::out | ios::app);
input.seekg(16, input.beg);
input.read(cbuffer, 4);
cout << sizeof(revbuffer) << endl;
cout << cbuffer[0] << cbuffer[1] << cbuffer[2] << cbuffer[3] << endl;
}
c++ input hex fstream atoi
edited 3 hours ago
dwalter
5,35912233
asked 4 hours ago
Kasper
1
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
up vote
0
down vote
favorite
I am trying to read a little-endian hex string from a binary file, and put that value into an integer to work with it. When I try to read, instead of getting a number I get ascii symbols. I've tried casts and atoi and nothing seems to work. What is the best way to use fstream to read a hex string into an integer from a file?
This is essentially my program:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(int argc, char* argv) {
fstream input;
fstream output;
char cbuffer[4];
char revbuffer[8];
input.open(argv[1], fstream::binary | fstream::in);
output.open("output.txt", ios::out | ios::app);
input.seekg(16, input.beg);
input.read(cbuffer, 4);
cout << sizeof(revbuffer) << endl;
cout << cbuffer[0] << cbuffer[1] << cbuffer[2] << cbuffer[3] << endl;
}
c++ input hex fstream atoi
edited 3 hours ago
dwalter
5,35912233
asked 4 hours ago
Kasper
1
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
is the value really stored as a hex string in the file? You mentioned the byte order and you read 4 chars from the file so a hex string seems improbable.
– Ted Lyngmo
1 hour ago
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I am trying to read a little-endian hex string from a binary file, and put that value into an integer to work with it. When I try to read, instead of getting a number I get ascii symbols. I've tried casts and atoi and nothing seems to work. What is the best way to use fstream to read a hex string into an integer from a file?
This is essentially my program:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(int argc, char* argv) {
fstream input;
fstream output;
char cbuffer[4];
char revbuffer[8];
input.open(argv[1], fstream::binary | fstream::in);
output.open("output.txt", ios::out | ios::app);
input.seekg(16, input.beg);
input.read(cbuffer, 4);
cout << sizeof(revbuffer) << endl;
cout << cbuffer[0] << cbuffer[1] << cbuffer[2] << cbuffer[3] << endl;
}
c++ input hex fstream atoi
edited 3 hours ago
dwalter
5,35912233
asked 4 hours ago
Kasper
1
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I am trying to read a little-endian hex string from a binary file, and put that value into an integer to work with it. When I try to read, instead of getting a number I get ascii symbols. I've tried casts and atoi and nothing seems to work. What is the best way to use fstream to read a hex string into an integer from a file?
This is essentially my program:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(int argc, char* argv) {
fstream input;
fstream output;
char cbuffer[4];
char revbuffer[8];
input.open(argv[1], fstream::binary | fstream::in);
output.open("output.txt", ios::out | ios::app);
input.seekg(16, input.beg);
input.read(cbuffer, 4);
cout << sizeof(revbuffer) << endl;
cout << cbuffer[0] << cbuffer[1] << cbuffer[2] << cbuffer[3] << endl;
}
c++ input hex fstream atoi
c++ input hex fstream atoi
edited 3 hours ago
dwalter
5,35912233
asked 4 hours ago
Kasper
1
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 3 hours ago
dwalter
5,35912233
asked 4 hours ago
Kasper
1
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 3 hours ago
dwalter
5,35912233
edited 3 hours ago
dwalter
5,35912233
edited 3 hours ago
dwalter
5,35912233
5,35912233
asked 4 hours ago
Kasper
1
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
Kasper
1
asked 4 hours ago
Kasper
1
1
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Kasper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
is the value really stored as a hex string in the file? You mentioned the byte order and you read 4 chars from the file so a hex string seems improbable.
– Ted Lyngmo
1 hour ago
add a comment |
is the value really stored as a hex string in the file? You mentioned the byte order and you read 4 chars from the file so a hex string seems improbable.
– Ted Lyngmo
1 hour ago
is the value really stored as a hex string in the file? You mentioned the byte order and you read 4 chars from the file so a hex string seems improbable.
– Ted Lyngmo
1 hour ago
is the value really stored as a hex string in the file? You mentioned the byte order and you read 4 chars from the file so a hex string seems improbable.
– Ted Lyngmo
1 hour ago
add a comment |
1 Answer
1
active
oldest
votes
up vote
0
down vote
If it's an integer value stored in binary format, I guess it's either a int32_t or a uint32_t. Since you mention that the value is stored in little-endian byte order, I guess you want to make sure that the host running your program converts it (if it needs to). C++20 has std::endian. If that's not available to you, there are usually macros for detecting endianness at compiletime that you can use instead of the std::endian tests I've used. I've assumed that the value is a uint32_t below.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <type_traits> // std::endian
// little endian unsigned 32 bit to host byte order
inline uint32_t Le32toh(uint32_t le) {
static_assert(std::endian::native == std::endian::little || std::endian::native == std::endian::big);
if constexpr (std::endian::native == std::endian::little) return le;
const uint8_t* c=reinterpret_cast<const uint8_t*>(&le);
return // little-to-big endian conversion
(static_cast<uint32_t>(c[0])<<24) |
(static_cast<uint32_t>(c[1])<<16) |
(static_cast<uint32_t>(c[2])<<8) |
(static_cast<uint32_t>(c[3]));
return le;
}
int main(int argc, char* argv) {
std::vector<std::string> args(argv+1, argv+argc);
std::fstream output("output.txt", std::ios::out | std::ios::app);
uint32_t cbuffer;
for(const auto& file : args) {
std::fstream input(file, std::fstream::binary | std::fstream::in);
input.seekg(16, input.beg);
// read directly into the varibles memory
input.read(reinterpret_cast<char*>(&cbuffer), 4);
// output the value unconverted
std::cout << std::hex << cbuffer << "n";
// convert if needed
cbuffer = Le32toh(cbuffer);
// output the value converted
std::cout << std::hex << cbuffer << "n";
}
}
answered 4 hours ago
Ted Lyngmo
838112
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
If it's an integer value stored in binary format, I guess it's either a int32_t or a uint32_t. Since you mention that the value is stored in little-endian byte order, I guess you want to make sure that the host running your program converts it (if it needs to). C++20 has std::endian. If that's not available to you, there are usually macros for detecting endianness at compiletime that you can use instead of the std::endian tests I've used. I've assumed that the value is a uint32_t below.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <type_traits> // std::endian
// little endian unsigned 32 bit to host byte order
inline uint32_t Le32toh(uint32_t le) {
static_assert(std::endian::native == std::endian::little || std::endian::native == std::endian::big);
if constexpr (std::endian::native == std::endian::little) return le;
const uint8_t* c=reinterpret_cast<const uint8_t*>(&le);
return // little-to-big endian conversion
(static_cast<uint32_t>(c[0])<<24) |
(static_cast<uint32_t>(c[1])<<16) |
(static_cast<uint32_t>(c[2])<<8) |
(static_cast<uint32_t>(c[3]));
return le;
}
int main(int argc, char* argv) {
std::vector<std::string> args(argv+1, argv+argc);
std::fstream output("output.txt", std::ios::out | std::ios::app);
uint32_t cbuffer;
for(const auto& file : args) {
std::fstream input(file, std::fstream::binary | std::fstream::in);
input.seekg(16, input.beg);
// read directly into the varibles memory
input.read(reinterpret_cast<char*>(&cbuffer), 4);
// output the value unconverted
std::cout << std::hex << cbuffer << "n";
// convert if needed
cbuffer = Le32toh(cbuffer);
// output the value converted
std::cout << std::hex << cbuffer << "n";
}
}
answered 4 hours ago
Ted Lyngmo
838112
add a comment |
up vote
0
down vote
If it's an integer value stored in binary format, I guess it's either a int32_t or a uint32_t. Since you mention that the value is stored in little-endian byte order, I guess you want to make sure that the host running your program converts it (if it needs to). C++20 has std::endian. If that's not available to you, there are usually macros for detecting endianness at compiletime that you can use instead of the std::endian tests I've used. I've assumed that the value is a uint32_t below.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <type_traits> // std::endian
// little endian unsigned 32 bit to host byte order
inline uint32_t Le32toh(uint32_t le) {
static_assert(std::endian::native == std::endian::little || std::endian::native == std::endian::big);
if constexpr (std::endian::native == std::endian::little) return le;
const uint8_t* c=reinterpret_cast<const uint8_t*>(&le);
return // little-to-big endian conversion
(static_cast<uint32_t>(c[0])<<24) |
(static_cast<uint32_t>(c[1])<<16) |
(static_cast<uint32_t>(c[2])<<8) |
(static_cast<uint32_t>(c[3]));
return le;
}
int main(int argc, char* argv) {
std::vector<std::string> args(argv+1, argv+argc);
std::fstream output("output.txt", std::ios::out | std::ios::app);
uint32_t cbuffer;
for(const auto& file : args) {
std::fstream input(file, std::fstream::binary | std::fstream::in);
input.seekg(16, input.beg);
// read directly into the varibles memory
input.read(reinterpret_cast<char*>(&cbuffer), 4);
// output the value unconverted
std::cout << std::hex << cbuffer << "n";
// convert if needed
cbuffer = Le32toh(cbuffer);
// output the value converted
std::cout << std::hex << cbuffer << "n";
}
}
answered 4 hours ago
Ted Lyngmo
838112
add a comment |
up vote
0
down vote
up vote
0
down vote
If it's an integer value stored in binary format, I guess it's either a int32_t or a uint32_t. Since you mention that the value is stored in little-endian byte order, I guess you want to make sure that the host running your program converts it (if it needs to). C++20 has std::endian. If that's not available to you, there are usually macros for detecting endianness at compiletime that you can use instead of the std::endian tests I've used. I've assumed that the value is a uint32_t below.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <type_traits> // std::endian
// little endian unsigned 32 bit to host byte order
inline uint32_t Le32toh(uint32_t le) {
static_assert(std::endian::native == std::endian::little || std::endian::native == std::endian::big);
if constexpr (std::endian::native == std::endian::little) return le;
const uint8_t* c=reinterpret_cast<const uint8_t*>(&le);
return // little-to-big endian conversion
(static_cast<uint32_t>(c[0])<<24) |
(static_cast<uint32_t>(c[1])<<16) |
(static_cast<uint32_t>(c[2])<<8) |
(static_cast<uint32_t>(c[3]));
return le;
}
int main(int argc, char* argv) {
std::vector<std::string> args(argv+1, argv+argc);
std::fstream output("output.txt", std::ios::out | std::ios::app);
uint32_t cbuffer;
for(const auto& file : args) {
std::fstream input(file, std::fstream::binary | std::fstream::in);
input.seekg(16, input.beg);
// read directly into the varibles memory
input.read(reinterpret_cast<char*>(&cbuffer), 4);
// output the value unconverted
std::cout << std::hex << cbuffer << "n";
// convert if needed
cbuffer = Le32toh(cbuffer);
// output the value converted
std::cout << std::hex << cbuffer << "n";
}
}
answered 4 hours ago
Ted Lyngmo
838112
If it's an integer value stored in binary format, I guess it's either a int32_t or a uint32_t. Since you mention that the value is stored in little-endian byte order, I guess you want to make sure that the host running your program converts it (if it needs to). C++20 has std::endian. If that's not available to you, there are usually macros for detecting endianness at compiletime that you can use instead of the std::endian tests I've used. I've assumed that the value is a uint32_t below.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <type_traits> // std::endian
// little endian unsigned 32 bit to host byte order
inline uint32_t Le32toh(uint32_t le) {
static_assert(std::endian::native == std::endian::little || std::endian::native == std::endian::big);
if constexpr (std::endian::native == std::endian::little) return le;
const uint8_t* c=reinterpret_cast<const uint8_t*>(&le);
return // little-to-big endian conversion
(static_cast<uint32_t>(c[0])<<24) |
(static_cast<uint32_t>(c[1])<<16) |
(static_cast<uint32_t>(c[2])<<8) |
(static_cast<uint32_t>(c[3]));
return le;
}
int main(int argc, char* argv) {
std::vector<std::string> args(argv+1, argv+argc);
std::fstream output("output.txt", std::ios::out | std::ios::app);
uint32_t cbuffer;
for(const auto& file : args) {
std::fstream input(file, std::fstream::binary | std::fstream::in);
input.seekg(16, input.beg);
// read directly into the varibles memory
input.read(reinterpret_cast<char*>(&cbuffer), 4);
// output the value unconverted
std::cout << std::hex << cbuffer << "n";
// convert if needed
cbuffer = Le32toh(cbuffer);
// output the value converted
std::cout << std::hex << cbuffer << "n";
}
}
answered 4 hours ago
Ted Lyngmo
838112
edited 2 hours ago
answered 4 hours ago
Ted Lyngmo
838112
answered 4 hours ago
Ted Lyngmo
838112
answered 4 hours ago
Ted Lyngmo
838112
838112
add a comment |
add a comment |
Kasper is a new contributor. Be nice, and check out our Code of Conduct.
Kasper is a new contributor. Be nice, and check out our Code of Conduct.
Kasper is a new contributor. Be nice, and check out our Code of Conduct.
Kasper is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53371469%2fhow-to-read-hex-values-into-integer-with-fstream-c%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
is the value really stored as a hex string in the file? You mentioned the byte order and you read 4 chars from the file so a hex string seems improbable.
– Ted Lyngmo
1 hour ago