#include "segmentsFile.h"
#include "../common/platform.h"

void fileSegmentInit(file_segment_t *segment, int fd, int pos, int len, char access) {
	//set basic information
	segment->fd=fd;
	segment->access=access;
	segment->filePos=pos;
	
	//enable caching one PC
	#if defined(PC)
	segment->cacheOff=-1;
	segment->cacheLen=0;
	segment->cacheWritten=0;
	#endif
	
	//enlarge the file if needed
	int fileSize=File_length(fd);
	if(fileSize+pos<len&&(access&MMU_ACCESS_w)) {
		if(File_truncate(fd, len+pos)) fileSize=len+pos;
	}
	segment->fileSize=fileSize;
}

//enable cache on PC
#if defined(PC)
void fileSegmentRead(int pos, char* value, void *opaque) {
	//get the segment information
	file_segment_t *segment=(file_segment_t*) opaque;
	
	//make sure we have cache for this
	if(!fileSegmentLoad(segment, pos)) return;
	if(pos<segment->cacheOff||pos>=segment->cacheOff+segment->cacheLen) return;
	
	//read from cache
	*value=segment->cache[pos-segment->cacheOff];
}

void fileSegmentWrite(int pos, char value, void *opaque) {
	//get the segment information
	file_segment_t *segment=(file_segment_t*) opaque;
	
	//make sure we have cache for this
	if(!fileSegmentLoad(segment, pos)) return;
	if(pos<segment->cacheOff||pos>=segment->cacheOff+segment->cacheLen) return;
	
	//write to cache
	segment->cache[pos-segment->cacheOff]=value;
	segment->cacheWritten=1;
}

int fileSegmentFlush(file_segment_t *segment) {
	//check if we have write access and we have an actual cache
	if(!(segment->access&MMU_ACCESS_w)) return 0;
	if(segment->cacheOff==-1||segment->cacheLen==0) return 1;
	
	//check if we have written
	if(!segment->cacheWritten) return 1;
	
	//flush to disk
	return File_write(segment->fd, segment->cacheOff+segment->filePos, segment->cache, segment->cacheLen);
}

int fileSegmentLoad(file_segment_t *segment, int pos) {
	//determine the aligned offset, and don't load if it's already loaded
	pos-=pos/CACHE_LEN;
	if(segment->cacheOff==pos) return 1;
	
	//determine length to cache
	int len=CACHE_LEN;
	if(pos+len+segment->filePos>segment->fileSize) len=segment->fileSize-pos;
	
	//flush if we need to
	if(segment->access&MMU_ACCESS_w) {
		if(!fileSegmentFlush(segment)) return 0;
	}
	
	//invalidate the cache
	segment->cacheOff=-1;
	segment->cacheLen=0;
	
	//read the file
	len=File_read(segment->fd, pos+segment->filePos, segment->cache, len);
	
	//update the cache
	segment->cacheOff=pos;
	segment->cacheLen=len;
	segment->cacheWritten=0;
	
	return 1;
}

//direct access to underlying file cache on casio
#else
void fileSegmentRead(int pos, char* value, void *opaque) {
	//get the segment information
	file_segment_t *segment=(file_segment_t*) opaque;
	
	//get offset into disk
	int offset=pos+segment->filePos;
	
	//read from file, the file will check for access itself
	File_read(segment->fd, offset, value, 1);
}

void fileSegmentWrite(int pos, char value, void *opaque) {
	//get the segment information
	file_segment_t *segment=(file_segment_t*) opaque;
	
	//get offset into disk
	int offset=pos+segment->filePos;
	
	//write into file, the file will check for access itself
	File_write(segment->fd, offset, &value, 1);
}

#endif