/**

 * hdr_histogram_log.h

 * Written by Michael Barker and released to the public domain,

 * as explained at http://creativecommons.org/publicdomain/zero/1.0/

 *

 * The implementation makes use of zlib to provide compression.  You will need

 * to link against -lz in order to link applications that include this header.

 */

#ifndef HDR_HISTOGRAM_H_LOG

#define HDR_HISTOGRAM_H_LOG 1

#define HDR_COMPRESSION_COOKIE_MISMATCH -29999

#define HDR_ENCODING_COOKIE_MISMATCH -29998

#define HDR_DEFLATE_INIT_FAIL -29997

#define HDR_DEFLATE_FAIL -29996

#define HDR_INFLATE_INIT_FAIL -29995

#define HDR_INFLATE_FAIL -29994

#define HDR_LOG_INVALID_VERSION -29993

#define HDR_TRAILING_ZEROS_INVALID -29992

#define HDR_VALUE_TRUNCATED -29991

#define HDR_ENCODED_INPUT_TOO_LONG -29990

#include <stdint.h>

#include <stdbool.h>

#include <stdio.h>

#include "hdr_time.h"

#include "hdr_histogram.h"

#ifdef __cplusplus

extern "C" {

#endif

/**

 * Encode and compress the histogram with gzip.

 */

int hdr_log_encode(struct hdr_histogram* histogram, char** encoded_histogram);

/**

 * Decode and decompress the histogram with gzip.

 */

int hdr_log_decode(struct hdr_histogram** histogram, char* base64_histogram, size_t base64_len);

struct hdr_log_writer

{

    uint32_t nonce;

};

/**

 * Initialise the log writer.

 *

 * @param writer 'This' pointer

 * @return 0 on success.

 */

int hdr_log_writer_init(struct hdr_log_writer* writer);

/**

 * Write the header to the log, this will constist of a user defined string,

 * the current timestamp, version information and the CSV header.

 *

 * @param writer 'This' pointer

 * @param file The stream to output the log header to.

 * @param user_prefix User defined string to include in the header.

 * @param timestamp The start time that the histogram started recording from.

 * @return Will return 0 if it successfully completed or an error number if there

 * was a failure.  EIO if the write failed.

 */

int hdr_log_write_header(

    struct hdr_log_writer* writer,

    FILE* file,

    const char* user_prefix,

    hdr_timespec* timestamp);

/**

 * Write an hdr_histogram entry to the log.  It will be encoded in a similar

 * fashion to the approach used by the Java version of the HdrHistogram.  It will

 * be a CSV line consisting of <start timestamp>,<end timestamp>,<max>,<histogram>

 * where <histogram> is the binary histogram gzip compressed and base64 encoded.

 *

 * Timestamp is a bit of misnomer for the start_timestamp and end_timestamp values

 * these could be offsets, e.g. start_timestamp could be offset from process start

 * time and end_timestamp could actually be the length of the recorded interval.

 *

 * @param writer 'This' pointer

 * @param file The stream to write the entry to.

 * @param start_timestamp The start timestamp to include in the logged entry.

 * @param end_timestamp The end timestamp to include in the logged entry.

 * @param histogram The histogram to encode and log.

 * @return Will return 0 if it successfully completed or an error number if there

 * was a failure.  Errors include HDR_DEFLATE_INIT_FAIL, HDR_DEFLATE_FAIL if

 * something when wrong during gzip compression.  ENOMEM if we failed to allocate

 * or reallocate the buffer used for encoding (out of memory problem).  EIO if

 * write failed.

 */

int hdr_log_write(

    struct hdr_log_writer* writer,

    FILE* file,

    const hdr_timespec* start_timestamp,

    const hdr_timespec* end_timestamp,

    struct hdr_histogram* histogram);

struct hdr_log_reader

{

    int major_version;

    int minor_version;

    hdr_timespec start_timestamp;

};

/**

 * Initialise the log reader.

 *

 * @param reader 'This' pointer

 * @return 0 on success

 */

int hdr_log_reader_init(struct hdr_log_reader* reader);

/**

 * Reads the the header information from the log.  Will capure information

 * such as version number and start timestamp from the header.

 *

 * @param hdr_log_reader 'This' pointer

 * @param file The data stream to read from.

 * @return 0 on success.  An error number on failure.

 */

int hdr_log_read_header(struct hdr_log_reader* reader, FILE* file);

/**

 * Reads an entry from the log filling in the specified histogram, timestamp and

 * interval values.  If the supplied pointer to the histogram for this method is

 * NULL then a new histogram will be allocated for the caller, however it will

 * become the callers responsibility to free it later.  If the pointer is non-null

 * the histogram read from the log will be merged with the supplied histogram.

 *

 * @param reader 'This' pointer

 * @param file The stream to read the histogram from.

 * @param histogram Pointer to allocate a histogram to or merge into.

 * @param timestamp The first timestamp from the CSV entry.

 * @param interval The second timestamp from the CSV entry

 * @return Will return 0 on success or an error number if there was some wrong

 * when reading in the histogram.  EOF (-1) will indicate that there are no more

 * histograms left to be read from 'file'.

 * HDR_INFLATE_INIT_FAIL or HDR_INFLATE_FAIL if

 * there was a problem with Gzip.  HDR_COMPRESSION_COOKIE_MISMATCH or

 * HDR_ENCODING_COOKIE_MISMATCH if the cookie values are incorrect.

 * HDR_LOG_INVALID_VERSION if the log can not be parsed.  ENOMEM if buffer space

 * or the histogram can not be allocated.  EIO if there was an error during

 * the read.  EINVAL in any input values are incorrect.

 */

int hdr_log_read(

    struct hdr_log_reader* reader, FILE* file, struct hdr_histogram** histogram,

    hdr_timespec* timestamp, hdr_timespec* interval);

/**

 * Returns a string representation of the error number.

 *

 * @param errnum The error response from a previous call.

 * @return The user readable representation of the error.

 */

const char* hdr_strerror(int errnum);

#ifdef __cplusplus

}

#endif

#endif