CringeDB/File-Page Abstraction/cdb_file-page.c

#include "cdb_file-page.h"
#include "../System Abstraction/cdb_sustem.h"

struct fp_File_impl{
    sys_File file;
    unsigned long pageSize;
};

//Creates a new file, opens it, and resizes it to the specified page size
fp_File fp_fileNew(char * fileName, unsigned long pageSize){ //there shouldn't be a page, longer than 4gb
    sys_File currentFile = sys_fileOpenInMem(fileName, SYS_FILE_NEW);
    if(currentFile == NULL){
        return NULL;
    }

    fp_File returnable = sys_heapAlloc(sizeof(struct fp_File_impl));
    returnable->pageSize = pageSize;
    returnable->file = currentFile;

    //The new File will be initialized with one memory Unit (Byte), so this code resizes it to the pageSize
    if(sys_fileResize(returnable->file, pageSize - 1) == NULL){
        sys_heapFree(returnable);
        return NULL;
    }

    return returnable;
}

fp_File fp_fileTemp(char * fileName, unsigned long pageSize){
    sys_File currentFile = sys_fileOpenInMem(fileName, SYS_FILE_TEMP);
    if(currentFile == NULL){
        return NULL;
    }

    fp_File returnable = sys_heapAlloc(sizeof(struct fp_File_impl));
    returnable->pageSize = pageSize;
    returnable->file = currentFile;

    //The new File will be initialized with one memory Unit (Byte), so this code resizes it to the pageSize
    if(sys_fileResize(returnable->file, pageSize - 1) == NULL){
        sys_heapFree(returnable);
        return NULL;
    }

    return returnable;
}

fp_File fp_fileOpen(char * fileName){
    sys_File currentFile = sys_fileOpenInMem(fileName, SYS_FILE_NOTHING);
    if(currentFile == NULL){
        return NULL;
    }

    fp_File returnable = sys_heapAlloc(sizeof(struct fp_File_impl));
    //returnable->pageSize = pageSize;
    returnable->file = currentFile;

    //since this function does not read the header, there is no way of knowing, what the page size is. Somebody else has to call the fp_fileInit function for this

    return returnable;
}

//Since someone else has to read the header, this function sets the read page size after fp_fileOpen has been called
void fp_fileInit(fp_File file, unsigned long pageSize){
    file->pageSize = pageSize;
}

//negative values indicate the removable of the latest pages; so this library doesn't need more functions
void * fp_fileAppendPages(fp_File file, long numberOfPages){
    void *newMem = sys_fileResize(file->file, file->pageSize * numberOfPages);
    if(newMem == NULL) {
        sys_fileClose(file->file);
        file->file = NULL;
        file->pageSize = 0;
        return NULL;
    }

    return newMem;
}

void * fp_fileToMemory(fp_File file){
    return sys_fileFileToMemory(file->file);
}

void fp_fileFlush(fp_File file) {
    sys_fileFlush(file->file);
}

void fp_fileClose(fp_File file){
    if(file->file != NULL) {
        sys_fileClose(file->file);
    }

    sys_heapFree(file);
}