Get bytes from std string in C

Question

I m working in a C   unmanaged project   I need to know how can I take a string like this  some data to encrypt  and get a byte   array which I m gonna use as the source for Encrypt   In C  I do    for  int i   0  i  lt  text Length  i        buffer i     byte text i     What I need to know is how to do the same but using unmanaged C     Thanks

User · Answer

Normally  encryption functions take   encrypt const void  ptr  size t bufferSize     as arguments  You can pass c str and length directly   encrypt strng c str    strng length       This way  extra space is allocated or wasted

User · Answer

If this is just plain vanilla C  then   strcpy buffer  text c str       Assuming that buffer is allocated and large enough to hold the contents of  text   which is the assumption in your original code   If encrypt   takes a  const char    then you can use   encrypt text c str      and you do not need to copy the string

User · Answer

If you just need read-only access  then c str   will do it   char const  c   myString c str      If you need read write access  then you can copy the string into a vector  vectors manage dynamic memory for you  You don t have to mess with allocation deallocation then    std  vector lt char gt  bytes myString begin    myString end     bytes push back   0    char  c    amp bytes 0

User · Answer

If this is just plain vanilla C  then   strcpy buffer  text c str       Assuming that buffer is allocated and large enough to hold the contents of  text   which is the assumption in your original code   If encrypt   takes a  const char    then you can use   encrypt text c str      and you do not need to copy the string

User · Answer

If you just need to read the data   encrypt str data   str size       If you need a read write copy of the data put it into a vector   Don t dynamically allocate space that s the job of vector    std  vector lt byte gt   source str begin   str end     encrypt  amp source 0  source size       Of course we are all assuming that byte is a char

User · Answer

If you just need read-only access  then c str   will do it   char const  c   myString c str      If you need read write access  then you can copy the string into a vector  vectors manage dynamic memory for you  You don t have to mess with allocation deallocation then    std  vector lt char gt  bytes myString begin    myString end     bytes push back   0    char  c    amp bytes 0

User · Answer

Normally  encryption functions take   encrypt const void  ptr  size t bufferSize     as arguments  You can pass c str and length directly   encrypt strng c str    strng length       This way  extra space is allocated or wasted

User · Answer

If this is just plain vanilla C  then   strcpy buffer  text c str       Assuming that buffer is allocated and large enough to hold the contents of  text   which is the assumption in your original code   If encrypt   takes a  const char    then you can use   encrypt text c str      and you do not need to copy the string

User · Answer

I dont think you want to use the c  code you have there  They provide System Text Encoding ASCII also UTF-     string str    some text  byte   bytes   System Text Encoding ASCII GetBytes str     your problems stem from ignoring the encoding in c  not your c   code

User · Answer

std  string  data would seem to be sufficient and most efficient  If you want to have non-const memory to manipulate  strange for encryption  you can copy the data to a buffer using memcpy   unsigned char buffer mystring length     memcpy buffer  mystring data    mystring length       STL fanboys would encourage you to use std  copy instead   std  copy mystring begin    mystring end    buffer     but there really isn t much of an upside to this  If you need null termination use std  string  c str   and the various string duplication techniques others have provided  but I d generally avoid that and just query for the length  Particularly with cryptography you just know somebody is going to try to break it by shoving nulls in to it  and using std  string  data   discourages you from lazily making assumptions about the underlying bits in the string

User · Answer

If this is just plain vanilla C  then   strcpy buffer  text c str       Assuming that buffer is allocated and large enough to hold the contents of  text   which is the assumption in your original code   If encrypt   takes a  const char    then you can use   encrypt text c str      and you do not need to copy the string

User · Answer

If you just need to read the data   encrypt str data   str size       If you need a read write copy of the data put it into a vector   Don t dynamically allocate space that s the job of vector    std  vector lt byte gt   source str begin   str end     encrypt  amp source 0  source size       Of course we are all assuming that byte is a char

User · Answer

I dont think you want to use the c  code you have there  They provide System Text Encoding ASCII also UTF-     string str    some text  byte   bytes   System Text Encoding ASCII GetBytes str     your problems stem from ignoring the encoding in c  not your c   code

User · Answer

If you just need to read the data   encrypt str data   str size       If you need a read write copy of the data put it into a vector   Don t dynamically allocate space that s the job of vector    std  vector lt byte gt   source str begin   str end     encrypt  amp source 0  source size       Of course we are all assuming that byte is a char

User · Answer

std  string  data would seem to be sufficient and most efficient  If you want to have non-const memory to manipulate  strange for encryption  you can copy the data to a buffer using memcpy   unsigned char buffer mystring length     memcpy buffer  mystring data    mystring length       STL fanboys would encourage you to use std  copy instead   std  copy mystring begin    mystring end    buffer     but there really isn t much of an upside to this  If you need null termination use std  string  c str   and the various string duplication techniques others have provided  but I d generally avoid that and just query for the length  Particularly with cryptography you just know somebody is going to try to break it by shoving nulls in to it  and using std  string  data   discourages you from lazily making assumptions about the underlying bits in the string

User · Answer

std  string  data would seem to be sufficient and most efficient  If you want to have non-const memory to manipulate  strange for encryption  you can copy the data to a buffer using memcpy   unsigned char buffer mystring length     memcpy buffer  mystring data    mystring length       STL fanboys would encourage you to use std  copy instead   std  copy mystring begin    mystring end    buffer     but there really isn t much of an upside to this  If you need null termination use std  string  c str   and the various string duplication techniques others have provided  but I d generally avoid that and just query for the length  Particularly with cryptography you just know somebody is going to try to break it by shoving nulls in to it  and using std  string  data   discourages you from lazily making assumptions about the underlying bits in the string

User · Answer

From a std  string you can use the c ptr   method if you want to get at the char t buffer pointer     It looks like you just want copy the characters of the string into a new buffer   I would simply use the std  string  copy function   length   str copy  buffer  str size

User · Answer

I dont think you want to use the c  code you have there  They provide System Text Encoding ASCII also UTF-     string str    some text  byte   bytes   System Text Encoding ASCII GetBytes str     your problems stem from ignoring the encoding in c  not your c   code

User · Answer

std  string  data would seem to be sufficient and most efficient  If you want to have non-const memory to manipulate  strange for encryption  you can copy the data to a buffer using memcpy   unsigned char buffer mystring length     memcpy buffer  mystring data    mystring length       STL fanboys would encourage you to use std  copy instead   std  copy mystring begin    mystring end    buffer     but there really isn t much of an upside to this  If you need null termination use std  string  c str   and the various string duplication techniques others have provided  but I d generally avoid that and just query for the length  Particularly with cryptography you just know somebody is going to try to break it by shoving nulls in to it  and using std  string  data   discourages you from lazily making assumptions about the underlying bits in the string

User · Answer

From a std  string you can use the c ptr   method if you want to get at the char t buffer pointer     It looks like you just want copy the characters of the string into a new buffer   I would simply use the std  string  copy function   length   str copy  buffer  str size

User · Answer

I dont think you want to use the c  code you have there  They provide System Text Encoding ASCII also UTF-     string str    some text  byte   bytes   System Text Encoding ASCII GetBytes str     your problems stem from ignoring the encoding in c  not your c   code

User · Answer

Normally  encryption functions take   encrypt const void  ptr  size t bufferSize     as arguments  You can pass c str and length directly   encrypt strng c str    strng length       This way  extra space is allocated or wasted

User · Answer

From a std  string you can use the c ptr   method if you want to get at the char t buffer pointer     It looks like you just want copy the characters of the string into a new buffer   I would simply use the std  string  copy function   length   str copy  buffer  str size

User · Answer

If you just need read-only access  then c str   will do it   char const  c   myString c str      If you need read write access  then you can copy the string into a vector  vectors manage dynamic memory for you  You don t have to mess with allocation deallocation then    std  vector lt char gt  bytes myString begin    myString end     bytes push back   0    char  c    amp bytes 0

User · Answer

If you just need read-only access  then c str   will do it   char const  c   myString c str      If you need read write access  then you can copy the string into a vector  vectors manage dynamic memory for you  You don t have to mess with allocation deallocation then    std  vector lt char gt  bytes myString begin    myString end     bytes push back   0    char  c    amp bytes 0

User · Answer

From a std  string you can use the c ptr   method if you want to get at the char t buffer pointer     It looks like you just want copy the characters of the string into a new buffer   I would simply use the std  string  copy function   length   str copy  buffer  str size

User · Answer

Normally  encryption functions take   encrypt const void  ptr  size t bufferSize     as arguments  You can pass c str and length directly   encrypt strng c str    strng length       This way  extra space is allocated or wasted

User · Answer

If you just need to read the data   encrypt str data   str size       If you need a read write copy of the data put it into a vector   Don t dynamically allocate space that s the job of vector    std  vector lt byte gt   source str begin   str end     encrypt  amp source 0  source size       Of course we are all assuming that byte is a char

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