/** \file mp4.h Public API of the mp4 parser. */

/**
 * Callbacks provided by the user of the mp4 parsing API.
 *
 * A pointer to this structure is passed to the two public open functions. If
 * the file is opened in read-only mode, the ->write() and ->truncate() methods
 * won't be called and may thus be NULL. The ->read() and ->seek() methods
 * must be supplied for either open type.
 *
 * All methods are supposed to work like their corresponding system calls.
 * That is, they should return non-negative for success and -1 on failure. In
 * the error case errno is expected to be set accordingly.
 *
 * \sa \ref mp4_open(), \ref mp4_open_meta().
 */
struct mp4_callback {
	/** This pointer is propagated to each call of all methods. */
	void *user_data;
	/**
	 * This should return the number of bytes read on success. Short reads
	 * are OK: the function may return less than length.
	 */
	ssize_t (*read)(void *user_data, void *buffer, size_t length);
	/**
	 * This method is assumed to succeed. The implementation should simply
	 * abort on errors. Note that offsets beyond EOF must not be regarded
	 * as invalid arguments.
	 */
	off_t (*seek)(void *user_data, off_t offset, int whence);
	/**
	 * Like the write() system call, this should return the number of bytes
	 * written. Short writes are OK: the function may return less than
	 * count.
	 */
	ssize_t (*write)(void *user_data, void *buffer, size_t count);
	/**
	 * Unlike the truncate system call, this function does not receive an
	 * offset. The method is expected to truncate the file to the offset
	 * given by the current file position instead.
	 */
	int (*truncate)(void *user_data);
};

/** Specifies one metadata tag. Both fields are 0-terminated strings. */
struct mp4_tag {
	/** The item name: "artist", "title", "album", "comment", or "date". */
	char *item;
	/** An arbitrary string value. */
	char *value;
};

/**
 * An array of name/value pairs.
 *
 * This structure is initialized when the mp4 file is opened in either mode.
 * If the file contains metadata items other than the standard five, those
 * non-standard items are not included in the array. After a successful open, a
 * pointer to the metadata structure can be obtained via \ref mp4_get_meta().
 */
struct mp4_metadata {
	/** It's OK to change this, for example by calling realloc(). */
	struct mp4_tag *tags;
	/** The number of entries of the array. */
	unsigned count;
};

/**
 * The mp4 file handle.
 *
 * A pointer to this opaque structure is returned by the two open functions.
 * All other functions of the mp4 API receive a pointer of this type.
 */
struct mp4;

int mp4_set_sample_position(struct mp4 *f, uint32_t sample);
int mp4_open(const struct mp4_callback *cb, struct mp4 **result);
void mp4_close(struct mp4 *f);
int mp4_get_sample_size(const struct mp4 *f, uint32_t sample, uint32_t *result);
uint16_t mp4_get_sample_rate(const struct mp4 *f);
uint16_t mp4_get_channel_count(const struct mp4 *f);
uint32_t mp4_num_samples(const struct mp4 *f);
uint64_t mp4_get_duration(const struct mp4 *f);
int mp4_open_meta(const struct mp4_callback *cb, struct mp4 **result);
struct mp4_metadata *mp4_get_meta(struct mp4 *f);
int mp4_update_meta(struct mp4 *f);
__malloc char *mp4_get_tag_value(const struct mp4 *f, const char *item);