text: /*
   * copyright (c) 2001 Fabrice Bellard
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  #ifndef AVFORMAT_AVIO_H
  #define AVFORMAT_AVIO_H
  
  /**
   * @file libavformat/avio.h
   * unbuffered I/O operations
   *
   * @warning This file has to be considered an internal but installed
   * header, so it should not be directly included in your projects.
   */
  
  #include <stdint.h>
  
  #include "libavutil/common.h"
  
  /* unbuffered I/O */
  
  /**
   * URL Context.
   * New fields can be added to the end with minor version bumps.
   * Removal, reordering and changes to existing fields require a major
   * version bump.
   * sizeof(URLContext) must not be used outside libav*.
   */
  typedef struct URLContext {
  #if LIBAVFORMAT_VERSION_MAJOR >= 53
      const AVClass *av_class; ///< information for av_log(). Set by url_open().
  #endif
      struct URLProtocol *prot;
      int flags;
      int is_streamed;  /**< true if streamed (no seek possible), default = false */
      int max_packet_size;  /**< if non zero, the stream is packetized with this max packet size */
      void *priv_data;
      char *filename; /**< specified URL */
  } URLContext;
  
  typedef struct URLPollEntry {
      URLContext *handle;
      int events;
      int revents;
  } URLPollEntry;
  
  #define URL_RDONLY 0
  #define URL_WRONLY 1
  #define URL_RDWR   2
  
  typedef int URLInterruptCB(void);
  
  /**
   * Creates an URLContext for accessing to the resource indicated by
   * url, and opens it using the URLProtocol up.
   *
   * @param puc pointer to the location where, in case of success, the
   * function puts the pointer to the created URLContext
   * @param flags flags which control how the resource indicated by url
   * is to be opened
   * @return 0 in case of success, a negative value corresponding to an
   * AVERROR code in case of failure
   */
  int url_open_protocol (URLContext **puc, struct URLProtocol *up,
                         const char *url, int flags);
  
  /**
   * Creates an URLContext for accessing to the resource indicated by
   * url, and opens it.
   *
   * @param puc pointer to the location where, in case of success, the
   * function puts the pointer to the created URLContext
   * @param flags flags which control how the resource indicated by url
   * is to be opened
   * @return 0 in case of success, a negative value corresponding to an
   * AVERROR code in case of failure
   */
  int url_open(URLContext **h, const char *url, int flags);
  
  /**
   * Reads up to size bytes from the resource accessed by h, and stores
   * the read bytes in buf.
   *
   * @return The number of bytes actually read, or a negative value
   * corresponding to an AVERROR code in case of error. A value of zero
   * indicates that it is not possible to read more from the accessed
   * resource (except if the value of the size argument is also zero).
   */
  int url_read(URLContext *h, unsigned char *buf, int size);
  
  /**
   * Read as many bytes as possible (up to size), calling the
   * read function multiple times if necessary.
   * Will also retry if the read function returns AVERROR(EAGAIN).
   * This makes special short-read handling in applications
   * unnecessary, if the return value is < size then it is
   * certain there was either an error or the end of file was reached.
   */
  int url_read_complete(URLContext *h, unsigned char *buf, int size);
  int url_write(URLContext *h, unsigned char *buf, int size);
  
  /**
   * Changes the position that will be used by the next read/write
   * operation on the resource accessed by h.
   *
   * @param pos specifies the new position to set
   * @param whence specifies how pos should be interpreted, it must be
   * one of SEEK_SET (seek from the beginning), SEEK_CUR (seek from the
   * current position), SEEK_END (seek from the end), or AVSEEK_SIZE
   * (return the filesize of the requested resource, pos is ignored).
   * @return a negative value corresponding to an AVERROR code in case
   * of failure, or the resulting file position, measured in bytes from
   * the beginning of the file. You can use this feature together with
   * SEEK_CUR to read the current file position.
   */
  int64_t url_seek(URLContext *h, int64_t pos, int whence);
  
  /**
   * Closes the resource accessed by the URLContext h, and frees the
   * memory used by it.
   *
   * @return a negative value if an error condition occurred, 0
   * otherwise
   */
  int url_close(URLContext *h);
  
  /**
   * Returns a non-zero value if the resource indicated by url
   * exists, 0 otherwise.
   */
  int url_exist(const char *url);
  
  int64_t url_filesize(URLContext *h);
  
  /**
   * Return the file descriptor associated with this URL. For RTP, this
   * will return only the RTP file descriptor, not the RTCP file descriptor.
   * To get both, use rtp_get_file_handles().
   *
   * @return the file descriptor associated with this URL, or <0 on error.
   */
  int url_get_file_handle(URLContext *h);
  
  /**
   * Return the maximum packet size associated to packetized file
   * handle. If the file is not packetized (stream like HTTP or file on
   * disk), then 0 is returned.
   *
   * @param h file handle
   * @return maximum packet size in bytes
   */
  int url_get_max_packet_size(URLContext *h);
  void url_get_filename(URLContext *h, char *buf, int buf_size);
  
  /**
   * The callback is called in blocking functions to test regulary if
   * asynchronous interruption is needed. AVERROR(EINTR) is returned
   * in this case by the interrupted function. 'NULL' means no interrupt
   * callback is given.
   */
  void url_set_interrupt_cb(URLInterruptCB *interrupt_cb);
  
  /* not implemented */
  int url_poll(URLPollEntry *poll_table, int n, int timeout);
  
  /**
   * Pause and resume playing - only meaningful if using a network streaming
   * protocol (e.g. MMS).
   * @param pause 1 for pause, 0 for resume
   */
  int av_url_read_pause(URLContext *h, int pause);
  
  /**
   * Seek to a given timestamp relative to some component stream.
   * Only meaningful if using a network streaming protocol (e.g. MMS.).
   * @param stream_index The stream index that the timestamp is relative to.
   *        If stream_index is (-1) the timestamp should be in AV_TIME_BASE
   *        units from the beginning of the presentation.
   *        If a stream_index >= 0 is used and the protocol does not support
   *        seeking based on component streams, the call will fail with ENOTSUP.
   * @param timestamp timestamp in AVStream.time_base units
   *        or if there is no stream specified then in AV_TIME_BASE units.
   * @param flags Optional combination of AVSEEK_FLAG_BACKWARD, AVSEEK_FLAG_BYTE
   *        and AVSEEK_FLAG_ANY. The protocol may silently ignore
   *        AVSEEK_FLAG_BACKWARD and AVSEEK_FLAG_ANY, but AVSEEK_FLAG_BYTE will
   *        fail with ENOTSUP if used and not supported.
   * @return >= 0 on success
   * @see AVInputFormat::read_seek
   */
  int64_t av_url_read_seek(URLContext *h, int stream_index,
                           int64_t timestamp, int flags);
  
  /**
   * Passing this as the "whence" parameter to a seek function causes it to
   * return the filesize without seeking anywhere. Supporting this is optional.
   * If it is not supported then the seek function will return <0.
   */
  #define AVSEEK_SIZE 0x10000
  
  /**
   * Oring this flag as into the "whence" parameter to a seek function causes it to
   * seek by any means (like reopening and linear reading) or other normally unreasonble
   * means that can be extreemly slow.
   * This may be ignored by the seek code.
   */
  #define AVSEEK_FORCE 0x20000
  
  typedef struct URLProtocol {
      const char *name;
      int (*url_open)(URLContext *h, const char *url, int flags);
      int (*url_read)(URLContext *h, unsigned char *buf, int size);
      int (*url_write)(URLContext *h, unsigned char *buf, int size);
      int64_t (*url_seek)(URLContext *h, int64_t pos, int whence);
      int (*url_close)(URLContext *h);
      struct URLProtocol *next;
      int (*url_read_pause)(URLContext *h, int pause);
      int64_t (*url_read_seek)(URLContext *h, int stream_index,
                               int64_t timestamp, int flags);
      int (*url_get_file_handle)(URLContext *h);
  } URLProtocol;
  
  #if LIBAVFORMAT_VERSION_MAJOR < 53
  extern URLProtocol *first_protocol;
  #endif
  
  extern URLInterruptCB *url_interrupt_cb;
  
  /**
   * If protocol is NULL, returns the first registered protocol,
   * if protocol is non-NULL, returns the next registered protocol after protocol,
   * or NULL if protocol is the last one.
   */
  URLProtocol *av_protocol_next(URLProtocol *p);
  
  #if LIBAVFORMAT_VERSION_MAJOR < 53
  /**
   * @deprecated Use av_register_protocol() instead.
   */
  attribute_deprecated int register_protocol(URLProtocol *protocol);
  #endif
  
  /**
   * Registers the URLProtocol protocol.
   */
  int av_register_protocol(URLProtocol *protocol);
  
  /**
   * Bytestream IO Context.
   * New fields can be added to the end with minor version bumps.
   * Removal, reordering and changes to existing fields require a major
   * version bump.
   * sizeof(ByteIOContext) must not be used outside libav*.
   */
  typedef struct {
      unsigned char *buffer;
      int buffer_size;
      unsigned char *buf_ptr, *buf_end;
      void *opaque;
      int (*read_packet)(void *opaque, uint8_t *buf, int buf_size);
      int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
      int64_t (*seek)(void *opaque, int64_t offset, int whence);
      int64_t pos; /**< position in the file of the current buffer */
      int must_flush; /**< true if the next seek should flush */
      int eof_reached; /**< true if eof reached */
      int write_flag;  /**< true if open for writing */
      int is_streamed;
      int max_packet_size;
      unsigned long checksum;
      unsigned char *checksum_ptr;
      unsigned long (*update_checksum)(unsigned long checksum, const uint8_t *buf, unsigned int size);
      int error;         ///< contains the error code or 0 if no error happened
      int (*read_pause)(void *opaque, int pause);
      int64_t (*read_seek)(void *opaque, int stream_index,
                           int64_t timestamp, int flags);
  } ByteIOContext;
  
  int init_put_byte(ByteIOContext *s,
                    unsigned char *buffer,
                    int buffer_size,
                    int write_flag,
                    void *opaque,
                    int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
                    int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
                    int64_t (*seek)(void *opaque, int64_t offset, int whence));
  ByteIOContext *av_alloc_put_byte(
                    unsigned char *buffer,
                    int buffer_size,
                    int write_flag,
                    void *opaque,
                    int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
                    int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
                    int64_t (*seek)(void *opaque, int64_t offset, int whence));
  
  void put_byte(ByteIOContext *s, int b);
  void put_buffer(ByteIOContext *s, const unsigned char *buf, int size);
  void put_le64(ByteIOContext *s, uint64_t val);
  void put_be64(ByteIOContext *s, uint64_t val);
  void put_le32(ByteIOContext *s, unsigned int val);
  void put_be32(ByteIOContext *s, unsigned int val);
  void put_le24(ByteIOContext *s, unsigned int val);
  void put_be24(ByteIOContext *s, unsigned int val);
  void put_le16(ByteIOContext *s, unsigned int val);
  void put_be16(ByteIOContext *s, unsigned int val);
  void put_tag(ByteIOContext *s, const char *tag);
  
  void put_strz(ByteIOContext *s, const char *buf);
  
  /**
   * fseek() equivalent for ByteIOContext.
   * @return new position or AVERROR.
   */
  int64_t url_fseek(ByteIOContext *s, int64_t offset, int whence);
  
  /**
   * Skip given number of bytes forward.
   * @param offset number of bytes
   */
  void url_fskip(ByteIOContext *s, int64_t offset);
  
  /**
   * ftell() equivalent for ByteIOContext.
   * @return position or AVERROR.
   */
  int64_t url_ftell(ByteIOContext *s);
  
  /**
   * Gets the filesize.
   * @return filesize or AVERROR
   */
  int64_t url_fsize(ByteIOContext *s);
  
  /**
   * feof() equivalent for ByteIOContext.
   * @return non zero if and only if end of file
   */
  int url_feof(ByteIOContext *s);
  
  int url_ferror(ByteIOContext *s);
  
  int av_url_read_fpause(ByteIOContext *h, int pause);
  int64_t av_url_read_fseek(ByteIOContext *h, int stream_index,
                            int64_t timestamp, int flags);
  
  #define URL_EOF (-1)
  /** @note return URL_EOF (-1) if EOF */
  int url_fgetc(ByteIOContext *s);
  
  /** @warning currently size is limited */
  #ifdef __GNUC__
  int url_fprintf(ByteIOContext *s, const char *fmt, ...) __attribute__ ((__format__ (__printf__, 2, 3)));
  #else
  int url_fprintf(ByteIOContext *s, const char *fmt, ...);
  #endif
  
  /** @note unlike fgets, the EOL character is not returned and a whole
      line is parsed. return NULL if first char read was EOF */
  char *url_fgets(ByteIOContext *s, char *buf, int buf_size);
  
  void put_flush_packet(ByteIOContext *s);
  
  
  /**
   * Reads size bytes from ByteIOContext into buf.
   * @return number of bytes read or AVERROR
   */
  int get_buffer(ByteIOContext *s, unsigned char *buf, int size);
  
  /**
   * Reads size bytes from ByteIOContext into buf.
   * This reads at most 1 packet. If that is not enough fewer bytes will be
   * returned.
   * @return number of bytes read or AVERROR
   */
  int get_partial_buffer(ByteIOContext *s, unsigned char *buf, int size);
  
  /** @note return 0 if EOF, so you cannot use it if EOF handling is
      necessary */
  int get_byte(ByteIOContext *s);
  unsigned int get_le24(ByteIOContext *s);
  unsigned int get_le32(ByteIOContext *s);
  uint64_t get_le64(ByteIOContext *s);
  unsigned int get_le16(ByteIOContext *s);
  
  char *get_strz(ByteIOContext *s, char *buf, int maxlen);
  unsigned int get_be16(ByteIOContext *s);
  unsigned int get_be24(ByteIOContext *s);
  unsigned int get_be32(ByteIOContext *s);
  uint64_t get_be64(ByteIOContext *s);
  
  uint64_t ff_get_v(ByteIOContext *bc);
  
  static inline int url_is_streamed(ByteIOContext *s)
  {
      return s->is_streamed;
  }
  
  /**
   * Creates and initializes a ByteIOContext for accessing the
   * resource referenced by the URLContext h.
   * @note When the URLContext h has been opened in read+write mode, the
   * ByteIOContext can be used only for writing.
   *
   * @param s Used to return the pointer to the created ByteIOContext.
   * In case of failure the pointed to value is set to NULL.
   * @return 0 in case of success, a negative value corresponding to an
   * AVERROR code in case of failure
   */
  int url_fdopen(ByteIOContext **s, URLContext *h);
  
  /** @warning must be called before any I/O */
  int url_setbufsize(ByteIOContext *s, int buf_size);
  #if LIBAVFORMAT_VERSION_MAJOR < 53
  /** Reset the buffer for reading or writing.
   * @note Will drop any data currently in the buffer without transmitting it.
   * @param flags URL_RDONLY to set up the buffer for reading, or URL_WRONLY
   *        to set up the buffer for writing. */
  int url_resetbuf(ByteIOContext *s, int flags);
  #endif
  
  /**
   * Rewinds the ByteIOContext using the specified buffer containing the first buf_size bytes of the file.
   * Used after probing to avoid seeking.
   * Joins buf and s->buffer, taking any overlap into consideration.
   * @note s->buffer must overlap with buf or they can't be joined and the function fails
   * @note This function is NOT part of the public API
   *
   * @param s The read-only ByteIOContext to rewind
   * @param buf The probe buffer containing the first buf_size bytes of the file
   * @param buf_size The size of buf
   * @return 0 in case of success, a negative value corresponding to an
   * AVERROR code in case of failure
   */
  int ff_rewind_with_probe_data(ByteIOContext *s, unsigned char *buf, int buf_size);
  
  /**
   * Creates and initializes a ByteIOContext for accessing the
   * resource indicated by url.
   * @note When the resource indicated by url has been opened in
   * read+write mode, the ByteIOContext can be used only for writing.
   *
   * @param s Used to return the pointer to the created ByteIOContext.
   * In case of failure the pointed to value is set to NULL.
   * @param flags flags which control how the resource indicated by url
   * is to be opened
   * @return 0 in case of success, a negative value corresponding to an
   * AVERROR code in case of failure
   */
  int url_fopen(ByteIOContext **s, const char *url, int flags);
  
  int url_fclose(ByteIOContext *s);
  URLContext *url_fileno(ByteIOContext *s);
  
  /**
   * Return the maximum packet size associated to packetized buffered file
   * handle. If the file is not packetized (stream like http or file on
   * disk), then 0 is returned.
   *
   * @param s buffered file handle
   * @return maximum packet size in bytes
   */
  int url_fget_max_packet_size(ByteIOContext *s);
  
  int url_open_buf(ByteIOContext **s, uint8_t *buf, int buf_size, int flags);
  
  /** return the written or read size */
  int url_close_buf(ByteIOContext *s);
  
  /**
   * Open a write only memory stream.
   *
   * @param s new IO context
   * @return zero if no error.
   */
  int url_open_dyn_buf(ByteIOContext **s);
  
  /**
   * Open a write only packetized memory stream with a maximum packet
   * size of 'max_packet_size'.  The stream is stored in a memory buffer
   * with a big endian 4 byte header giving the packet size in bytes.
   *
   * @param s new IO context
   * @param max_packet_size maximum packet size (must be > 0)
   * @return zero if no error.
   */
  int url_open_dyn_packet_buf(ByteIOContext **s, int max_packet_size);
  
  /**
   * Return the written size and a pointer to the buffer. The buffer
   *  must be freed with av_free().
   * @param s IO context
   * @param pbuffer pointer to a byte buffer
   * @return the length of the byte buffer
   */
  int url_close_dyn_buf(ByteIOContext *s, uint8_t **pbuffer);
  
  unsigned long ff_crc04C11DB7_update(unsigned long checksum, const uint8_t *buf,
                                      unsigned int len);
  unsigned long get_checksum(ByteIOContext *s);
  void init_checksum(ByteIOContext *s,
                     unsigned long (*update_checksum)(unsigned long c, const uint8_t *p, unsigned int len),
                     unsigned long checksum);
  
  /* udp.c */
  int udp_set_remote_url(URLContext *h, const char *uri);
  int udp_get_local_port(URLContext *h);
  #if (LIBAVFORMAT_VERSION_MAJOR <= 52)
  int udp_get_file_handle(URLContext *h);
  #endif
  
  #endif /* AVFORMAT_AVIO_H */
  