#ifndef FILE_CACHE_H__
#define FILE_CACHE_H__

struct BlockId
{
	const char* atom_fn;
	u32 block_num;
};

extern bool block_eq(BlockId b1, BlockId b2);

// create an id for use with the cache that uniquely identifies
// the block from the file <atom_fn> starting at <ofs>.
extern BlockId block_cache_make_id(const char* atom_fn, const off_t ofs);

extern void* block_cache_alloc(BlockId id);

extern void block_cache_mark_completed(BlockId id);

extern void* block_cache_find(BlockId id);
extern void block_cache_release(BlockId id);




enum FileCacheFlags
{
	// indicates the buffer will not be freed immediately
	// (i.e. before the next buffer alloc) as it normally should.
	// this flag serves to suppress a warning and better avoid fragmentation.
	// caller sets this when FILE_LONG_LIVED is specified.
	//
	// also used by file_cache_retrieve because it may have to
	// 'reactivate' the buffer (transfer from cache to extant list),
	// which requires knowing whether the buffer is long-lived or not.
	FC_LONG_LIVED    = 1,

	// statistics (e.g. # buffer allocs) should not be updated.
	// (useful for simulation, e.g. trace_entry_causes_io)
	FC_NO_STATS      = 2,

	// file_cache_retrieve should not update item credit.
	// (useful when just looking up buffer given atom_fn)
	FC_NO_ACCOUNTING = 4
};

// allocate a new buffer of <size> bytes (possibly more due to internal
// fragmentation). never returns 0.
// <atom_fn>: owner filename (buffer is intended to be used for data from
//   this file).
extern FileIOBuf file_buf_alloc(size_t size, const char* atom_fn, uint fc_flags = 0);

// mark <buf> as no longer needed. if its reference count drops to 0,
// it will be removed from the extant list. if it had been added to the
// cache, it remains there until evicted in favor of another buffer.
extern LibError file_buf_free(FileIOBuf buf, uint fc_flags = 0);

// interpret file_io parameters (pbuf, size, flags, cb) and allocate a
// file buffer if necessary.
// called by file_io and afile_read.
extern LibError file_buf_get(FileIOBuf* pbuf, size_t size,
	const char* atom_fn, uint flags, FileIOCB cb);

// inform us that the buffer address will be increased by <padding>-bytes.
// this happens when reading uncompressed files from archive: they
// start at unaligned offsets and file_io rounds offset down to
// next block boundary. the buffer therefore starts with padding, which
// is skipped so the user only sees their data.
// we make note of the new buffer address so that it can be freed correctly
// by passing the new padded buffer.
extern void file_buf_add_padding(FileIOBuf exact_buf, size_t exact_size, size_t padding);

// if buf is not in extant list, complain; otherwise, mark it as
// coming from the file <atom_fn>.
// this is needed in the following case: uncompressed reads from archive
// boil down to a file_io of the archive file. the buffer is therefore
// tagged with the archive filename instead of the desired filename.
// afile_read sets things right by calling this.
extern LibError file_buf_set_real_fn(FileIOBuf buf, const char* atom_fn);

// "give" <buf> to the cache, specifying its size and owner filename.
// since this data may be shared among users of the cache, it is made
// read-only (via MMU) to make sure no one can corrupt/change it.
//
// note: the reference added by file_buf_alloc still exists! it must
// still be file_buf_free-d after calling this.
extern LibError file_cache_add(FileIOBuf buf, size_t size, const char* atom_fn);



// check if the contents of the file <atom_fn> are in file cache.
// if not, return 0; otherwise, return buffer address and optionally
// pass back its size.
//
// note: does not call stats_cache because it does not know the file size
// in case of cache miss! doing so is left to the caller.
extern FileIOBuf file_cache_retrieve(const char* atom_fn, size_t* psize, uint fc_flags = 0);

// invalidate all data loaded from the file <fn>. this ensures the next
// load of this file gets the (presumably new) contents of the file,
// not previous stale cache contents.
// call after hotloading code detects file has been changed.
extern LibError file_cache_invalidate(const char* P_fn);

// reset entire state of the file cache to what it was after initialization.
// that means completely emptying the extant list and cache.
// used after simulating cache operation, which fills the cache with
// invalid data.
extern void file_cache_reset();

extern void file_cache_init();
extern void file_cache_shutdown();

#endif	// #ifndef FILE_CACHE_H__