Hands-off reading for FLAC.

[disorder] / lib / hreader.h

/*
 * This file is part of DisOrder
 * Copyright (C) 2010 Richard Kettlewell
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/** @file lib/hreader.h
 * @brief Hands-off reader - read files without keeping them open
 */
#ifndef HREADER_H
#define HREADER_H

#include <unistd.h>

/** @brief A hands-off reader
 *
 * Allows files to be read without holding them open.
 */
struct hreader {
  const char *path;		/* file to read */
  off_t size;                   /* file size */
  off_t read_offset;            /* for next hreader_read() */
  off_t buf_offset;             /* offset of start of buffer */
  char *buffer;			/* input buffer */
  size_t bufsize;		/* buffer size */
  size_t bytes;			/* size of last read */
};

/** @brief Initialize a hands-off reader
 * @param path File to read
 * @param h Reader to initialize
 * @return 0 on success, -1 on error
 */
int hreader_init(const char *path, struct hreader *h);

/** @brief Read some bytes
 * @param h Reader to read from
 * @param buffer Where to store bytes
 * @param n Maximum bytes to read
 * @return Bytes read, or 0 at EOF, or -1 on error
 */
int hreader_read(struct hreader *h, void *buffer, size_t n);

/** @brief Read some bytes at a given offset
 * @param h Reader to read from
 * @param offset Offset to read at
 * @param buffer Where to store bytes
 * @param n Maximum bytes to read
 * @return Bytes read, or 0 at EOF, or -1 on error
 */
int hreader_pread(struct hreader *h, void *buffer, size_t n, off_t offset);

/** @brief Seek within a file
 * @param h Reader to seek
 * @param offset Offset
 * @param whence SEEK_*
 * @return Result offset
 */
off_t hreader_seek(struct hreader *h, off_t offset, int whence);

/** @brief Return file size
 * @param h Reader to find size of
 * @return Size in bytes
 */
static inline off_t hreader_size(const struct hreader *h) {
  return h->size;
}

/** @brief Test for end of file
 * @param h Reader to test
 * @return 1 at eof, 0 otherwise
 *
 * This tells you whether the next read will return 0 bytes, rather than
 * whether the last read reached end of file.  So it is slightly different to
 * feof().
 */
static inline int hreader_eof(const struct hreader *h) {
  return h->read_offset == h->size;
}

#endif /* HREADER_H */

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