Optimizing code for reading some VLVs in a file? - function

Question

I'm trying to read some variable-length-values from a file I created.
The file contains the following:
81 7F 81 01 2F F3 FF
There are two VLVs there, 81 7F and 81 01 which are 255 and 129 in decimal.
I also created some file-reader functions that go like this:
void read_byte_from_file_to(std::fstream& file, uint8_t& to) {
file.read((char*)&to, 1);
}
unsigned long readVLV(std::fstream& t_midi_file) {
unsigned long result = 0;
static unsigned long sum = 0, depth = 0, count = 0;
uint8_t c;
read_byte_from_file_to(t_midi_file, c);
++count;
if (c & 0x80) {
readVLV(t_midi_file);
}
sum += (c & 0x7F) << (7 * depth++);
if (count == depth) {
result = sum;
sum = 0;
depth = 0;
count = 0;
}
return result;
};
While running readVLV n times gives correct answers for the first n VLVs when reading from a file, I absolutely hate how I wrote it, which so much statics parameters and that ugly parameter reset. SO if someone could head me in the right direction I'd be very pleased.

Answer 1

A basic _readVLV which takes the positional state of the function could be done by writing
unsigned long _readVLV(
std::fstream& t_midi_file,
unsigned long sum,
unsigned long depth) {
uint8_t c;
read_byte_from_file_to(t_midi_file, c);
if (c & 0x80) {
sum += _readVLV(t_midi_file, sum, depth);
++depth;
}
return (c & 0x7F) << (7 * depth);
}
and creating a global readVLV function that takes the positional information and the file like so
unsigned long readVLV(std::fstream& t_midi_file) {
unsigned long sum = 0, depth = 0, count = 0;
return _readVLV(t_midi_file, sum, depth, count);
}