Reading binary data - firemonkey

Question

I am trying to read data from a binary file. One block of data is 76 bytes long (this varies with the number of the 2-byte "main data items" in the middle of the block). The first datum is 4 bytes, second is 4 bytes, and then there are a bunch of 2 byte main data items, and at the end are 2 more 2-byte pieces of data.
Based on this Delphi sample I've learned how to read the file with the code below:
short AShortInt; // 16 bits
int AInteger; // 32 bits
try
{
infile=new TFileStream(myfile,fmOpenRead); // myfile is binary
BR = new TBinaryReader(infile, TEncoding::Unicode, false);
for (int rows = 0; rows < 5; rows++) { // just read the first 5 blocks of data for testing
AInteger = BR->ReadInt32(); // read first two 4 byte integers for this block
AInteger = BR->ReadInt32();
for (int i = 0; i < 32; i++) { // now read the 32 2-byte integers from this block
AShortInt = BR->ReadInt16();
}
AShortInt = BR->ReadInt16(); // read next to last 2-byte int
AShortInt = BR->ReadInt16(); // read the last 2-byte int
}
delete infile;
delete BR;
Close();
}
catch(...)
{
delete infile; // closes the file, doesn't delete it.
delete BR;
ShowMessage("Can't open file!");
Close();
}
But, what i would like to do is use a 76-byte wide buffer to read the entire block, and then pick the various datum out of that buffer. I put together the following code based on this question and i can read a whole block of data into the buffer.
UnicodeString myfile = System::Ioutils::TPath::Combine(System::Ioutils::TPath::GetDocumentsPath(), "binaryCOM.dat");
TFileStream*infile=0;
try
{
infile=new TFileStream(myfile,fmOpenRead);
const int bufsize=76;
char*buf=new char[bufsize];
int a = 0;
while(int bytesread=infile->Read(buf,bufsize)) {
a++; // just a place to break on Run to Cursor
}
delete[]buf;
}
catch(...)
{
delete infile;
ShowMessage("Can't open file!");
Close();
}
But i can't figure out how to piece together subsets out of the bytes in the buffer. Is there a way to concatenate bytes? So i could read a block of data into a 76 byte buffer and then do something like this below?
unsigned int FirstDatum = buf[0]+buf[1]+buf[2]+buf[3]; // concatenate the 4 bytes for the first piece of data
This will be an FMX app for Win32, iOS, and Android built in C++Builder 10.3.2.

Answer 1

Here is my modified code using Remy's suggestion of TMemoryStream.
UnicodeString myfile = System::Ioutils::TPath::Combine(System::Ioutils::TPath::GetDocumentsPath(), "binaryCOM.dat");
TMemoryStream *MS=0;
TBinaryReader *BR=0;
std::vector<short> myArray;
short AShortInt;
int AInteger;
int NumDatums = 32; // the variable number of 2-byte main datums
try
{
MS = new TMemoryStream();
MS->LoadFromFile(myfile);
BR = new TBinaryReader(MS, TEncoding::Unicode, false);
for (int rows = 0; rows < 5; rows++) { // testing with first 5 blocks of data
AInteger = BR->ReadInt32(); // read first two 4 byte integers
AInteger = BR->ReadInt32(); // here
for (int i = 0; i < NumDatums; i++) { // read the main 2-byte data
AShortInt = BR->ReadInt16();
myArray.push_back(AShortInt); // push it into vector
}
AShortInt = BR->ReadInt16(); // read next to last 2-byte int
AShortInt = BR->ReadInt16(); // read the last 2-byte int
// code here to do something with this block of data just read from file
}
}
delete MS;
delete BR;
}
catch(...)
{
delete MS;
delete BR;
ShowMessage("Can't open file.");
}