BufferFile.c

#include <stdio.h>
#include <windows.h>

FILE *midi;
char *buffer;
size_t bufRange = 0;
unsigned long int bufSize = 0;
long long bufPos = 0;
long long filePos = 0;
long long curSeek = 0;
char *pathSave;
BOOL fileEnded = FALSE;

void BufferInit(char path[], unsigned long seek, unsigned int bufSizee)
{
    bufSize = bufSizee;
    pathSave = path;
    midi = fopen(path, "rb");
    if (midi == NULL)
    {
        perror("Could not open file path");
        return;
    }
    buffer = malloc(bufSize);
    bufRange = fread(buffer, 1, bufSize, midi);
    curSeek += filePos + bufRange;
    fileEnded = (bufRange != bufSize);
}
void UpdateBuffer()
{
    if (!fileEnded)
    {
        filePos += bufPos;
        fseeko(midi, filePos - curSeek, SEEK_CUR);
        bufRange = fread(buffer, 1, bufSize, midi);
        curSeek = filePos + bufRange;
        fileEnded = (bufRange != bufSize);
        bufPos = 0;
    }
}
void Seek(long long pos)
{
    int cond = pos - filePos >= bufRange;
    bufPos = pos - filePos;
    if (cond)
    {
        UpdateBuffer();
    }
}
int Pushback = -1;
void Skip(unsigned long int count)
{
    for (unsigned long int i = 0; i < count; i++)
    {
        if (Pushback != -1)
        {
            Pushback = -1;
        }
        if (bufPos >= bufRange)
        {
            UpdateBuffer();
        }
        bufPos++;
    }
}
void ResizeBuffer(unsigned long int size)
{
    bufSize = size;
    free(buffer);
    buffer = malloc(size);
    UpdateBuffer();
}
unsigned char ReadFast()
{
    if (bufPos >= bufRange)
    {
        UpdateBuffer();
    }
    bufPos++;
    return buffer[bufPos - 1];
}
unsigned char *ReadRange(int size)
{
    if (bufPos + size >= bufRange)
    {
        UpdateBuffer();
    }
    unsigned char *range = malloc(size + 1);
    for (int i = 0; i < size; i++)
    {
        *(range + i) = *(buffer + bufPos + i);
    }
    range[size] = '\0';
    bufPos += size;
    return range;
}
void Copy(unsigned char *target, unsigned long int offset, unsigned long int size)
{
    if (bufPos + size >= bufRange)
    {
        UpdateBuffer();
    }
    if (size == 0)
    {
        size = bufSize;
    }
    memcpy(target + offset, buffer + bufPos, size);
    bufPos += size;
}