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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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/*
** 2011-08-10
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file defines the LSM API.
*/
#ifndef _LSM_H
#define _LSM_H
#include <stddef.h>
#ifdef __cplusplus
extern "C" {
#endif

/*
** Opaque handle types.
*/
typedef struct lsm_compress lsm_compress;   /* Compression library functions */
typedef struct lsm_compress_factory lsm_compress_factory;
typedef struct lsm_cursor lsm_cursor;       /* Database cursor handle */
typedef struct lsm_db lsm_db;               /* Database connection handle */
typedef struct lsm_env lsm_env;             /* Runtime environment */
typedef struct lsm_file lsm_file;           /* OS file handle */
typedef struct lsm_mutex lsm_mutex;         /* Mutex handle */

/* 64-bit integer type used for file offsets. */
typedef long long int lsm_i64;              /* 64-bit signed integer type */

/* Candidate values for the 3rd argument to lsm_env.xLock() */
#define LSM_LOCK_UNLOCK 0
#define LSM_LOCK_SHARED 1
#define LSM_LOCK_EXCL   2

/* Flags for lsm_env.xOpen() */
#define LSM_OPEN_READONLY 0x0001

/*
** CAPI: Database Runtime Environment
**
** Run-time environment used by LSM
*/
struct lsm_env {
  int nByte;                 /* Size of this structure in bytes */
  int iVersion;              /* Version number of this structure (1) */
  /****** file i/o ***********************************************/
  void *pVfsCtx;
  int (*xFullpath)(lsm_env*, const char *, char *, int *);
  int (*xOpen)(lsm_env*, const char *, int flags, lsm_file **);
  int (*xRead)(lsm_file *, lsm_i64, void *, int);
  int (*xWrite)(lsm_file *, lsm_i64, void *, int);
  int (*xTruncate)(lsm_file *, lsm_i64);
  int (*xSync)(lsm_file *);
  int (*xSectorSize)(lsm_file *);
  int (*xRemap)(lsm_file *, lsm_i64, void **, lsm_i64*);
  int (*xFileid)(lsm_file *, void *pBuf, int *pnBuf);
  int (*xClose)(lsm_file *);
  int (*xUnlink)(lsm_env*, const char *);
  int (*xLock)(lsm_file*, int, int);
  int (*xTestLock)(lsm_file*, int, int, int);
  int (*xShmMap)(lsm_file*, int, int, void **);
  void (*xShmBarrier)(void);
  int (*xShmUnmap)(lsm_file*, int);
  /****** memory allocation ****************************************/
  void *pMemCtx;
  void *(*xMalloc)(lsm_env*, size_t);            /* malloc(3) function */
  void *(*xRealloc)(lsm_env*, void *, size_t);   /* realloc(3) function */
  void (*xFree)(lsm_env*, void *);               /* free(3) function */
  size_t (*xSize)(lsm_env*, void *);             /* xSize function */
  /****** mutexes ****************************************************/
  void *pMutexCtx;
  int (*xMutexStatic)(lsm_env*,int,lsm_mutex**); /* Obtain a static mutex */
  int (*xMutexNew)(lsm_env*, lsm_mutex**);       /* Get a new dynamic mutex */
  void (*xMutexDel)(lsm_mutex *);           /* Delete an allocated mutex */
  void (*xMutexEnter)(lsm_mutex *);         /* Grab a mutex */
  int (*xMutexTry)(lsm_mutex *);            /* Attempt to obtain a mutex */
  void (*xMutexLeave)(lsm_mutex *);         /* Leave a mutex */
  int (*xMutexHeld)(lsm_mutex *);           /* Return true if mutex is held */
  int (*xMutexNotHeld)(lsm_mutex *);        /* Return true if mutex not held */
  /****** other ****************************************************/
  int (*xSleep)(lsm_env*, int microseconds);

  /* New fields may be added in future releases, in which case the
  ** iVersion value will increase. */
};

/* 
** Values that may be passed as the second argument to xMutexStatic. 
*/
#define LSM_MUTEX_GLOBAL 1
#define LSM_MUTEX_HEAP   2

/*
** CAPI: LSM Error Codes
*/
#define LSM_OK         0
#define LSM_ERROR      1
#define LSM_BUSY       5
#define LSM_NOMEM      7
#define LSM_READONLY   8
#define LSM_IOERR     10
#define LSM_CORRUPT   11
#define LSM_FULL      13
#define LSM_CANTOPEN  14
#define LSM_PROTOCOL  15
#define LSM_MISUSE    21

#define LSM_MISMATCH  50


#define LSM_IOERR_NOENT (LSM_IOERR | (1<<8))

/* 
** CAPI: Creating and Destroying Database Connection Handles
**
** Open and close a database connection handle.
*/
int lsm_new(lsm_env*, lsm_db **ppDb);
int lsm_close(lsm_db *pDb);

/* 
** CAPI: Connecting to a Database
*/
int lsm_open(lsm_db *pDb, const char *zFilename);

/*
** CAPI: Obtaining pointers to database environments
**
** Return a pointer to the environment used by the database connection 
** passed as the first argument. Assuming the argument is valid, this 
** function always returns a valid environment pointer - it cannot fail.
*/
lsm_env *lsm_get_env(lsm_db *pDb);

/*
** The lsm_default_env() function returns a pointer to the default LSM
** environment for the current platform.
*/
lsm_env *lsm_default_env(void);


/*
** CAPI: Configuring a database connection.
**
** The lsm_config() function is used to configure a database connection.
*/
int lsm_config(lsm_db *, int, ...);

/*
** The following values may be passed as the second argument to lsm_config().
**
** LSM_CONFIG_AUTOFLUSH:
**   A read/write integer parameter. 
**
**   This value determines the amount of data allowed to accumulate in a
**   live in-memory tree before it is marked as old. After committing a
**   transaction, a connection checks if the size of the live in-memory tree,
**   including data structure overhead, is greater than the value of this
**   option in KB. If it is, and there is not already an old in-memory tree,
**   the live in-memory tree is marked as old.
**
**   The maximum allowable value is 1048576 (1GB). There is no minimum 
**   value. If this parameter is set to zero, then an attempt is made to
**   mark the live in-memory tree as old after each transaction is committed.
**
**   The default value is 1024 (1MB).
**
** LSM_CONFIG_PAGE_SIZE:
**   A read/write integer parameter. This parameter may only be set before
**   lsm_open() has been called.
**
** LSM_CONFIG_BLOCK_SIZE:
**   A read/write integer parameter. 
**
**   This parameter may only be set before lsm_open() has been called. It
**   must be set to a power of two between 64 and 65536, inclusive (block 
**   sizes between 64KB and 64MB).
**
**   If the connection creates a new database, the block size of the new
**   database is set to the value of this option in KB. After lsm_open()
**   has been called, querying this parameter returns the actual block
**   size of the opened database.
**
**   The default value is 1024 (1MB blocks).
**
** LSM_CONFIG_SAFETY:
**   A read/write integer parameter. Valid values are 0, 1 (the default) 
**   and 2. This parameter determines how robust the database is in the
**   face of a system crash (e.g. a power failure or operating system 
**   crash). As follows:
**
**     0 (off):    No robustness. A system crash may corrupt the database.
**
**     1 (normal): Some robustness. A system crash may not corrupt the
**                 database file, but recently committed transactions may
**                 be lost following recovery.
**
**     2 (full):   Full robustness. A system crash may not corrupt the
**                 database file. Following recovery the database file
**                 contains all successfully committed transactions.
**
** LSM_CONFIG_AUTOWORK:
**   A read/write integer parameter.
**
** LSM_CONFIG_AUTOCHECKPOINT:
**   A read/write integer parameter.
**
**   If this option is set to non-zero value N, then a checkpoint is
**   automatically attempted after each N KB of data have been written to 
**   the database file.
**
**   The amount of uncheckpointed data already written to the database file
**   is a global parameter. After performing database work (writing to the
**   database file), the process checks if the total amount of uncheckpointed 
**   data exceeds the value of this paramter. If so, a checkpoint is performed.
**   This means that this option may cause the connection to perform a 
**   checkpoint even if the current connection has itself written very little
**   data into the database file.
**
**   The default value is 2048 (checkpoint every 2MB).
**
** LSM_CONFIG_MMAP:
**   A read/write integer parameter. If this value is set to 0, then the 
**   database file is accessed using ordinary read/write IO functions. Or,
**   if it is set to 1, then the database file is memory mapped and accessed
**   that way. If this parameter is set to any value N greater than 1, then
**   up to the first N KB of the file are memory mapped, and any remainder
**   accessed using read/write IO.
**
**   The default value is 1 on 64-bit platforms and 32768 on 32-bit platforms.
**   
**
** LSM_CONFIG_USE_LOG:
**   A read/write boolean parameter. True (the default) to use the log
**   file normally. False otherwise.
**
** LSM_CONFIG_AUTOMERGE:
**   A read/write integer parameter. The minimum number of segments to
**   merge together at a time. Default value 4.
**
** LSM_CONFIG_MAX_FREELIST:
**   A read/write integer parameter. The maximum number of free-list 
**   entries that are stored in a database checkpoint (the others are
**   stored elsewhere in the database).
**
**   There is no reason for an application to configure or query this
**   parameter. It is only present because configuring a small value
**   makes certain parts of the lsm code easier to test.
**
** LSM_CONFIG_MULTIPLE_PROCESSES:
**   A read/write boolean parameter. This parameter may only be set before
**   lsm_open() has been called. If true, the library uses shared-memory
**   and posix advisory locks to co-ordinate access by clients from within
**   multiple processes. Otherwise, if false, all database clients must be 
**   located in the same process. The default value is true.
**
** LSM_CONFIG_SET_COMPRESSION:
**   Set the compression methods used to compress and decompress database
**   content. The argument to this option should be a pointer to a structure
**   of type lsm_compress. The lsm_config() method takes a copy of the 
**   structures contents.
**
**   This option may only be used before lsm_open() is called. Invoking it
**   after lsm_open() has been called results in an LSM_MISUSE error.
**
** LSM_CONFIG_GET_COMPRESSION:
**   Query the compression methods used to compress and decompress database
**   content.
**
** LSM_CONFIG_SET_COMPRESSION_FACTORY:
**   Configure a factory method to be invoked in case of an LSM_MISMATCH
**   error.
**
** LSM_CONFIG_READONLY:
**   A read/write boolean parameter. This parameter may only be set before
**   lsm_open() is called.
*/
#define LSM_CONFIG_AUTOFLUSH                1
#define LSM_CONFIG_PAGE_SIZE                2
#define LSM_CONFIG_SAFETY                   3
#define LSM_CONFIG_BLOCK_SIZE               4
#define LSM_CONFIG_AUTOWORK                 5
#define LSM_CONFIG_MMAP                     7
#define LSM_CONFIG_USE_LOG                  8
#define LSM_CONFIG_AUTOMERGE                9
#define LSM_CONFIG_MAX_FREELIST            10
#define LSM_CONFIG_MULTIPLE_PROCESSES      11
#define LSM_CONFIG_AUTOCHECKPOINT          12
#define LSM_CONFIG_SET_COMPRESSION         13
#define LSM_CONFIG_GET_COMPRESSION         14
#define LSM_CONFIG_SET_COMPRESSION_FACTORY 15
#define LSM_CONFIG_READONLY                16

#define LSM_SAFETY_OFF    0
#define LSM_SAFETY_NORMAL 1
#define LSM_SAFETY_FULL   2

/*
** CAPI: Compression and/or Encryption Hooks
*/
struct lsm_compress {
  void *pCtx;
  unsigned int iId;
  int (*xBound)(void *, int nSrc);
  int (*xCompress)(void *, char *, int *, const char *, int);
  int (*xUncompress)(void *, char *, int *, const char *, int);
  void (*xFree)(void *pCtx);
};

struct lsm_compress_factory {
  void *pCtx;
  int (*xFactory)(void *, lsm_db *, unsigned int);
  void (*xFree)(void *pCtx);
};

#define LSM_COMPRESSION_EMPTY 0
#define LSM_COMPRESSION_NONE  1

/*
** CAPI: Allocating and Freeing Memory
**
** Invoke the memory allocation functions that belong to environment
** pEnv. Or the system defaults if no memory allocation functions have 
** been registered.
*/
void *lsm_malloc(lsm_env*, size_t);
void *lsm_realloc(lsm_env*, void *, size_t);
void lsm_free(lsm_env*, void *);

/*
** CAPI: Querying a Connection For Operational Data
**
** Query a database connection for operational statistics or data.
*/
int lsm_info(lsm_db *, int, ...);

int lsm_get_user_version(lsm_db *, unsigned int *);
int lsm_set_user_version(lsm_db *, unsigned int);

/*
** The following values may be passed as the second argument to lsm_info().
**
** LSM_INFO_NWRITE:
**   The third parameter should be of type (int *). The location pointed
**   to by the third parameter is set to the number of 4KB pages written to
**   the database file during the lifetime of this connection. 
**
** LSM_INFO_NREAD:
**   The third parameter should be of type (int *). The location pointed
**   to by the third parameter is set to the number of 4KB pages read from
**   the database file during the lifetime of this connection.
**
** LSM_INFO_DB_STRUCTURE:
**   The third argument should be of type (char **). The location pointed
**   to is populated with a pointer to a nul-terminated string containing
**   the string representation of a Tcl data-structure reflecting the 
**   current structure of the database file. Specifically, the current state
**   of the worker snapshot. The returned string should be eventually freed 
**   by the caller using lsm_free().
**
**   The returned list contains one element for each level in the database,
**   in order from most to least recent. Each element contains a 
**   single element for each segment comprising the corresponding level,
**   starting with the lhs segment, then each of the rhs segments (if any)
**   in order from most to least recent.
**
**   Each segment element is itself a list of 4 integer values, as follows:
**
**   <ol><li> First page of segment
**       <li> Last page of segment
**       <li> Root page of segment (if applicable)
**       <li> Total number of pages in segment
**   </ol>
**
** LSM_INFO_ARRAY_STRUCTURE:
**   There should be two arguments passed following this option (i.e. a 
**   total of four arguments passed to lsm_info()). The first argument 
**   should be the page number of the first page in a database array 
**   (perhaps obtained from an earlier INFO_DB_STRUCTURE call). The second 
**   trailing argument should be of type (char **). The location pointed 
**   to is populated with a pointer to a nul-terminated string that must 
**   be eventually freed using lsm_free() by the caller.
**
**   The output string contains the text representation of a Tcl list of
**   integers. Each pair of integers represent a range of pages used by
**   the identified array. For example, if the array occupies database
**   pages 993 to 1024, then pages 2048 to 2777, then the returned string
**   will be "993 1024 2048 2777".
**
**   If the specified integer argument does not correspond to the first
**   page of any database array, LSM_ERROR is returned and the output
**   pointer is set to a NULL value.
**
** LSM_INFO_LOG_STRUCTURE:
**   The third argument should be of type (char **). The location pointed
**   to is populated with a pointer to a nul-terminated string containing
**   the string representation of a Tcl data-structure. The returned 
**   string should be eventually freed by the caller using lsm_free().
**
**   The Tcl structure returned is a list of six integers that describe
**   the current structure of the log file.
**
** LSM_INFO_ARRAY_PAGES:
**
** LSM_INFO_PAGE_ASCII_DUMP:
**   As with LSM_INFO_ARRAY_STRUCTURE, there should be two arguments passed
**   with calls that specify this option - an integer page number and a
**   (char **) used to return a nul-terminated string that must be later
**   freed using lsm_free(). In this case the output string is populated
**   with a human-readable description of the page content.
**
**   If the page cannot be decoded, it is not an error. In this case the
**   human-readable output message will report the systems failure to 
**   interpret the page data.
**
** LSM_INFO_PAGE_HEX_DUMP:
**   This argument is similar to PAGE_ASCII_DUMP, except that keys and
**   values are represented using hexadecimal notation instead of ascii.
**
** LSM_INFO_FREELIST:
**   The third argument should be of type (char **). The location pointed
**   to is populated with a pointer to a nul-terminated string containing
**   the string representation of a Tcl data-structure. The returned 
**   string should be eventually freed by the caller using lsm_free().
**
**   The Tcl structure returned is a list containing one element for each
**   free block in the database. The element itself consists of two 
**   integers - the block number and the id of the snapshot that freed it.
**
** LSM_INFO_CHECKPOINT_SIZE:
**   The third argument should be of type (int *). The location pointed to
**   by this argument is populated with the number of KB written to the
**   database file since the most recent checkpoint.
**
** LSM_INFO_TREE_SIZE:
**   If this value is passed as the second argument to an lsm_info() call, it
**   should be followed by two arguments of type (int *) (for a total of four
**   arguments).
**
**   At any time, there are either one or two tree structures held in shared
**   memory that new database clients will access (there may also be additional
**   tree structures being used by older clients - this API does not provide
**   information on them). One tree structure - the current tree - is used to
**   accumulate new data written to the database. The other tree structure -
**   the old tree - is a read-only tree holding older data and may be flushed 
**   to disk at any time.
** 
**   Assuming no error occurs, the location pointed to by the first of the two
**   (int *) arguments is set to the size of the old in-memory tree in KB.
**   The second is set to the size of the current, or live in-memory tree.
**
** LSM_INFO_COMPRESSION_ID:
**   This value should be followed by a single argument of type 
**   (unsigned int *). If successful, the location pointed to is populated 
**   with the database compression id before returning.
*/
#define LSM_INFO_NWRITE           1
#define LSM_INFO_NREAD            2
#define LSM_INFO_DB_STRUCTURE     3
#define LSM_INFO_LOG_STRUCTURE    4
#define LSM_INFO_ARRAY_STRUCTURE  5
#define LSM_INFO_PAGE_ASCII_DUMP  6
#define LSM_INFO_PAGE_HEX_DUMP    7
#define LSM_INFO_FREELIST         8
#define LSM_INFO_ARRAY_PAGES      9
#define LSM_INFO_CHECKPOINT_SIZE 10
#define LSM_INFO_TREE_SIZE       11
#define LSM_INFO_FREELIST_SIZE   12
#define LSM_INFO_COMPRESSION_ID  13


/* 
** CAPI: Opening and Closing Write Transactions
**
** These functions are used to open and close transactions and nested 
** sub-transactions.
**
** The lsm_begin() function is used to open transactions and sub-transactions. 
** A successful call to lsm_begin() ensures that there are at least iLevel 
** nested transactions open. To open a top-level transaction, pass iLevel=1. 
** To open a sub-transaction within the top-level transaction, iLevel=2. 
** Passing iLevel=0 is a no-op.
**
** lsm_commit() is used to commit transactions and sub-transactions. A
** successful call to lsm_commit() ensures that there are at most iLevel 
** nested transactions open. To commit a top-level transaction, pass iLevel=0. 
** To commit all sub-transactions inside the main transaction, pass iLevel=1.
**
** Function lsm_rollback() is used to roll back transactions and
** sub-transactions. A successful call to lsm_rollback() restores the database 
** to the state it was in when the iLevel'th nested sub-transaction (if any) 
** was first opened. And then closes transactions to ensure that there are 
** at most iLevel nested transactions open. Passing iLevel=0 rolls back and 
** closes the top-level transaction. iLevel=1 also rolls back the top-level 
** transaction, but leaves it open. iLevel=2 rolls back the sub-transaction 
** nested directly inside the top-level transaction (and leaves it open).
*/
int lsm_begin(lsm_db *pDb, int iLevel);
int lsm_commit(lsm_db *pDb, int iLevel);
int lsm_rollback(lsm_db *pDb, int iLevel);

/* 
** CAPI: Writing to a Database
**
** Write a new value into the database. If a value with a duplicate key 
** already exists it is replaced.
*/
int lsm_insert(lsm_db*, const void *pKey, int nKey, const void *pVal, int nVal);

/*
** Delete a value from the database. No error is returned if the specified
** key value does not exist in the database.
*/
int lsm_delete(lsm_db *, const void *pKey, int nKey);

/*
** Delete all database entries with keys that are greater than (pKey1/nKey1) 
** and smaller than (pKey2/nKey2). Note that keys (pKey1/nKey1) and
** (pKey2/nKey2) themselves, if they exist in the database, are not deleted.
**
** Return LSM_OK if successful, or an LSM error code otherwise.
*/
int lsm_delete_range(lsm_db *, 
    const void *pKey1, int nKey1, const void *pKey2, int nKey2
);

/*
** CAPI: Explicit Database Work and Checkpointing
**
** This function is called by a thread to work on the database structure.
*/
int lsm_work(lsm_db *pDb, int nMerge, int nKB, int *pnWrite);

int lsm_flush(lsm_db *pDb);

/*
** Attempt to checkpoint the current database snapshot. Return an LSM
** error code if an error occurs or LSM_OK otherwise.
**
** If the current snapshot has already been checkpointed, calling this 
** function is a no-op. In this case if pnKB is not NULL, *pnKB is
** set to 0. Or, if the current snapshot is successfully checkpointed
** by this function and pbKB is not NULL, *pnKB is set to the number
** of bytes written to the database file since the previous checkpoint
** (the same measure as returned by the LSM_INFO_CHECKPOINT_SIZE query).
*/
int lsm_checkpoint(lsm_db *pDb, int *pnKB);

/*
** CAPI: Opening and Closing Database Cursors
**
** Open and close a database cursor.
*/
int lsm_csr_open(lsm_db *pDb, lsm_cursor **ppCsr);
int lsm_csr_close(lsm_cursor *pCsr);

/* 
** CAPI: Positioning Database Cursors
**
** If the fourth parameter is LSM_SEEK_EQ, LSM_SEEK_GE or LSM_SEEK_LE,
** this function searches the database for an entry with key (pKey/nKey). 
** If an error occurs, an LSM error code is returned. Otherwise, LSM_OK.
**
** If no error occurs and the requested key is present in the database, the
** cursor is left pointing to the entry with the specified key. Or, if the 
** specified key is not present in the database the state of the cursor 
** depends on the value passed as the final parameter, as follows:
**
** LSM_SEEK_EQ:
**   The cursor is left at EOF (invalidated). A call to lsm_csr_valid()
**   returns non-zero.
**
** LSM_SEEK_LE:
**   The cursor is left pointing to the largest key in the database that
**   is smaller than (pKey/nKey). If the database contains no keys smaller
**   than (pKey/nKey), the cursor is left at EOF.
**
** LSM_SEEK_GE:
**   The cursor is left pointing to the smallest key in the database that
**   is larger than (pKey/nKey). If the database contains no keys larger
**   than (pKey/nKey), the cursor is left at EOF.
**
** If the fourth parameter is LSM_SEEK_LEFAST, this function searches the
** database in a similar manner to LSM_SEEK_LE, with two differences:
**
** <ol><li>Even if a key can be found (the cursor is not left at EOF), the
** lsm_csr_value() function may not be used (attempts to do so return
** LSM_MISUSE).
**
** <li>The key that the cursor is left pointing to may be one that has 
** been recently deleted from the database. In this case it is
** guaranteed that the returned key is larger than any key currently 
** in the database that is less than or equal to (pKey/nKey).
** </ol>
**
** LSM_SEEK_LEFAST requests are intended to be used to allocate database
** keys.
*/
int lsm_csr_seek(lsm_cursor *pCsr, const void *pKey, int nKey, int eSeek);

int lsm_csr_first(lsm_cursor *pCsr);
int lsm_csr_last(lsm_cursor *pCsr);

/*
** Advance the specified cursor to the next or previous key in the database.
** Return LSM_OK if successful, or an LSM error code otherwise.
**
** Functions lsm_csr_seek(), lsm_csr_first() and lsm_csr_last() are "seek"
** functions. Whether or not lsm_csr_next and lsm_csr_prev may be called
** successfully also depends on the most recent seek function called on
** the cursor. Specifically:
**
** <ul>
** <li> At least one seek function must have been called on the cursor.
** <li> To call lsm_csr_next(), the most recent call to a seek function must
** have been either lsm_csr_first() or a call to lsm_csr_seek() specifying
** LSM_SEEK_GE.
** <li> To call lsm_csr_prev(), the most recent call to a seek function must
** have been either lsm_csr_last() or a call to lsm_csr_seek() specifying
** LSM_SEEK_LE.
** </ul>
**
** Otherwise, if the above conditions are not met when lsm_csr_next or 
** lsm_csr_prev is called, LSM_MISUSE is returned and the cursor position
** remains unchanged.
*/
int lsm_csr_next(lsm_cursor *pCsr);
int lsm_csr_prev(lsm_cursor *pCsr);

/*
** Values that may be passed as the fourth argument to lsm_csr_seek().
*/
#define LSM_SEEK_LEFAST   -2
#define LSM_SEEK_LE       -1
#define LSM_SEEK_EQ        0
#define LSM_SEEK_GE        1

/* 
** CAPI: Extracting Data From Database Cursors
**
** Retrieve data from a database cursor.
*/
int lsm_csr_valid(lsm_cursor *pCsr);
int lsm_csr_key(lsm_cursor *pCsr, const void **ppKey, int *pnKey);
int lsm_csr_value(lsm_cursor *pCsr, const void **ppVal, int *pnVal);

/*
** If no error occurs, this function compares the database key passed via
** the pKey/nKey arguments with the key that the cursor passed as the first
** argument currently points to. If the cursors key is less than, equal to
** or greater than pKey/nKey, *piRes is set to less than, equal to or greater
** than zero before returning. LSM_OK is returned in this case.
**
** Or, if an error occurs, an LSM error code is returned and the final 
** value of *piRes is undefined. If the cursor does not point to a valid
** key when this function is called, LSM_MISUSE is returned.
*/
int lsm_csr_cmp(lsm_cursor *pCsr, const void *pKey, int nKey, int *piRes);

/*
** CAPI: Change these!!
**
** Configure a callback to which debugging and other messages should 
** be directed. Only useful for debugging lsm.
*/
void lsm_config_log(lsm_db *, void (*)(void *, int, const char *), void *);

/*
** Configure a callback that is invoked if the database connection ever
** writes to the database file.
*/
void lsm_config_work_hook(lsm_db *, void (*)(lsm_db *, void *), void *);

/* ENDOFAPI */
#ifdef __cplusplus
}  /* End of the 'extern "C"' block */
#endif
#endif /* ifndef _LSM_H */