value_log.h File Reference

Log file of the key-value pairs. More...

#include <stdio.h>

Include dependency graph for value_log.h:

Go to the source code of this file.

Data Structures
struct	ValueLog
	Value Log of the Database. More...

Functions
struct ValueLog *	ValueLog_new (const char *path, size_t head, size_t tail)
	Creates a new ValueLog or loads an existing one from disk.
int	ValueLog_append (struct ValueLog *log, size_t *pos, const char *key, size_t key_len, const char *value, size_t value_len)
	Appends a new key-value pair to the ValueLog.
int	ValueLog_get (const struct ValueLog *log, char **value, size_t *value_len, size_t value_loc)
	Fetches a value from the ValueLog at a given position.
int	ValueLog_sync (const struct ValueLog *log)
	Syncs the ValueLog to the disk.
void	ValueLog_free (struct ValueLog *log)
	Frees the ValueLog.

Detailed Description

Log file of the key-value pairs.

Author

Adam Comer adamb.nosp@m.come.nosp@m.r@gma.nosp@m.il.c.nosp@m.om

Date

May 15, 2020

Copyright

Apache-2.0 License

Function Documentation

ValueLog_append()

int ValueLog_append	(	struct ValueLog *	log,
		size_t *	pos,
		const char *	key,
		size_t	key_len,
		const char *	value,
		size_t	value_len )

Appends a new key-value pair to the ValueLog.

In the event that the write was unsuccessful, the ValueLog won't shift the head forward. Therefore, writes can be retried without the risk of polluting the ValueLog or corrupting past entries.

Parameters

log	The ValueLog to write to.
pos	A pointer that is assigned to the location on the where the key-value pair was written to.
key	The key being written.
key_len	The length of the key.
value	The value that is being written.
value_len	The length of the value.

Returns

This function returns 0 if the entry was written successfully and -1 if there was an error.

ValueLog_free()

void ValueLog_free

(

struct ValueLog *

log

)

Frees the ValueLog.

Note: This function won't delete the file or the underlying data in the ValueLog. This function only frees the memory allocated to a ValueLog.

Parameters

log	The ValueLog to free.

ValueLog_get()

int ValueLog_get	(	const struct ValueLog *	log,
		char **	value,
		size_t *	value_len,
		size_t	value_loc )

Fetches a value from the ValueLog at a given position.

Note: The value pointer will allocate memory to hold the value that is being requested. The caller is responsible for freeing the memory.

Parameters

log	The ValueLog to read from.
value	A double-pointer for the value. This pointer will set with a newly allocated block of memory with the value that the caller can access.
value_len	A pointer that is assigned to the the length of the value pointer.
value_loc	The location on the ValueLog that this value resides in.

Returns

This function returns 0 if the value was retrieved successfully and -1 if there was an error.

ValueLog_new()

struct ValueLog * ValueLog_new	(	const char *	path,
		size_t	head,
		size_t	tail )

Creates a new ValueLog or loads an existing one from disk.

If the ValueLog file already exists, this function will only open the file without scanning it. This function doesn't check if file has been corrupted.

Note: Free this ValueLog with ValueLog_free.

Parameters

path	Path to the ValueLog. The path must be be null-terminated.
head	The head of the ValueLog. Set to 0 for a new ValueLog.
tail	The tail of the ValueLog. Set to 0 for a new ValueLog.

Returns

A pointer to a ValueLog.

ValueLog_sync()

int ValueLog_sync

(

const struct ValueLog *

log

)

Syncs the ValueLog to the disk.

This function forcefully flushes the changes to the ValueLog to disk. Use this function sparingly as is will heavily reduce the write throughput of the ValueLog.

Parameters

log	The ValueLog to flush to disk.

Returns

This function returns 0 if the ValueLog successfully synced to the disk and -1 if there was an error.