Liblognorm 1.1.2 documentation

Library API

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Library API

To use the library, include liblognorm.h (which is quoted below) into your code. The API is fairly simple and hardly needs further explanations.

#include <stdlib.h>	/* we need size_t */
#include <json.h>

/* error codes */
#define LN_NOMEM -1
#define LN_INVLDFDESCR -1
#define LN_BADCONFIG -250
#define LN_BADPARSERSTATE -500
#define LN_WRONGPARSER -1000

#define LN_RB_LINE_TOO_LONG -1001
#define LN_OVER_SIZE_LIMIT -1002

/**
 * The library context descriptor.
 * This is used to permit multiple independent instances of the
 * library to be called within a single program. This is most
 * useful for plugin-based architectures.
 */
typedef struct ln_ctx_s* ln_ctx;

/* API */
/**
 * Return library version string.
 *
 * Returns the version of the currently used library.
 *
 * @return Zero-Terminated library version string.
 */
/* Note: this MUST NOT be inline to make sure the actual library
 * has the right version, not just what was used to compile!
 */
const char *ln_version(void);

/**
 * Return if library is build with advanced statistics
 * activated.
 *
 * @return 1 if advanced stats are active, 0 if not
 */
int ln_hasAdvancedStats(void);

/**
 * Initialize a library context.
 *
 * To prevent memory leaks, ln_exitCtx() must be called on a library
 * context that is no longer needed.
 *
 * @return new library context or NULL if an error occured
 */
ln_ctx ln_initCtx(void);

/**
 * Inherit control attributes from a library context.
 *
 * This does not copy the parse-tree, but does copy
 * behaviour-controling attributes such as enableRegex.
 *
 * Just as with ln_initCtx, ln_exitCtx() must be called on a library
 * context that is no longer needed.
 *
 * @return new library context or NULL if an error occured
 */
ln_ctx ln_inherittedCtx(ln_ctx parent);

/**
 * Discard a library context.
 *
 * Free's the ressources associated with the given library context. It
 * MUST NOT be accessed after calling this function.
 *
 * @param ctx The context to be discarded.
 *
 * @return Returns zero on success, something else otherwise.
 */
int ln_exitCtx(ln_ctx ctx);


/* binary values, so that we can "or" them together */
#define LN_CTXOPT_ALLOW_REGEX		0x01 /**< permit regex matching */
#define LN_CTXOPT_ADD_EXEC_PATH		0x02 /**< add exec_path attribute (time-consuming!) */
#define LN_CTXOPT_ADD_ORIGINALMSG	0x04 /**< always add original message to output
					          (not just in error case) */
#define LN_CTXOPT_ADD_RULE		0x08 /**< add mockup rule */
#define LN_CTXOPT_ADD_RULE_LOCATION	0x10 /**< add rule location (file, lineno) to metadata */
/**
 * Set options on ctx.
 *
 * @param ctx The context to be modified.
 * @param opts a potentially or-ed list of options, see LN_CTXOPT_*
 */
void
ln_setCtxOpts(ln_ctx ctx, unsigned opts);


/**
 * Set a debug message handler (callback).
 *
 * Liblognorm can provide helpful information for debugging
 * - it's internal processing
 * - the way a log message is being normalized
 *
 * It does so by emiting "interesting" information about its processing
 * at various stages. A caller can obtain this information by registering
 * an entry point. When done so, liblognorm will call the entry point
 * whenever it has something to emit. Note that debugging can be rather
 * verbose.
 *
 * The callback will be called with the following three parameters in that order:
 * - the caller-provided cookie
 * - a zero-terminated string buffer
 * - the length of the string buffer, without the trailing NUL byte
 *
 * @note
 * The provided callback function <b>must not</b> call any liblognorm
 * APIs except when specifically flagged as safe for calling by a debug
 * callback handler.
 *
 * @param[in] ctx The library context to apply callback to.
 * @param[in] cb The function to be called for debugging
 * @param[in] cookie Opaque cookie to be passed down to debug handler. Can be
 *                   used for some state tracking by the caller. This is defined as
 *                   void* to support pointers. To play it safe, a pointer should be
 *                   passed (but advantorous folks may also use an unsigned).
 *
 * @return Returns zero on success, something else otherwise.
 */
int ln_setDebugCB(ln_ctx ctx, void (*cb)(void*, const char*, size_t), void *cookie);

/**
 * Set a error message handler (callback).
 *
 * If set, this is used to emit error messages of interest to the user, e.g.
 * on failures during rulebase load. It is suggested that a caller uses this
 * feedback to aid its users in resolving issues.
 * Its semantics are otherwise exactly the same like ln_setDebugCB().
 */
int ln_setErrMsgCB(ln_ctx ctx, void (*cb)(void*, const char*, size_t), void *cookie);


/**
 * enable or disable debug mode.
 *
 * @param[in] ctx context
 * @param[in] b boolean 0 - disable debug mode, 1 - enable debug mode
 */
void ln_enableDebug(ln_ctx ctx, int i);


/**
 * Load a (log) sample file.
 *
 * The file must contain log samples in syntactically correct format. Samples are added
 * to set already loaded in the current context. If there is a sample with duplicate
 * semantics, this sample will be ignored. Most importantly, this can \b not be used
 * to change tag assignments for a given sample.
 *
 * @param[in] ctx The library context to apply callback to.
 * @param[in] file Name of file to be loaded.
 *
 * @return Returns zero on success, something else otherwise.
 */
int ln_loadSamples(ln_ctx ctx, const char *file);

/**
 * Load a rulebase via a string.
 *
 * Note: this can only load v2 samples, v1 is NOT supported.
 *
 * @param[in] ctx The library context to apply callback to.
 * @param[in] string The string with the actual rulebase.
 *
 * @return Returns zero on success, something else otherwise.
 */
int ln_loadSamplesFromString(ln_ctx ctx, const char *string);

/**
 * Normalize a message.
 *
 * This is the main library entry point. It is called with a message
 * to normalize and will return a normalized in-memory representation
 * of it.
 *
 * If an error occurs, the function returns -1. In that case, an
 * in-memory event representation has been generated if event is
 * non-NULL. In that case, the event contains further error details in
 * normalized form.
 *
 * @note
 * This function works on byte-counted strings and as such is able to
 * process NUL bytes if they occur inside the message. On the other hand,
 * this means the the correct messages size, \b excluding the NUL byte,
 * must be provided.
 *
 * @param[in] ctx The library context to use.
 * @param[in] str The message string (see note above).
 * @param[in] strLen The length of the message in bytes.
 * @param[out] json_p A new event record or NULL if an error occured. <b>Must be
 *                   destructed if no longer needed.</b>
 *
 * @return Returns zero on success, something else otherwise.
 */
int ln_normalize(ln_ctx ctx, const char *str, const size_t strLen, struct json_object **json_p);

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